International Journal of Power Electronics (76 papers in press)
Response of Electron-irradiated Silicon Carbide Schottky Power Diodes at Elevated Temperature
by Nurul Fadzlin Hasbullah, Mohamad Azim Mohd Khairi, Yusof Abdullah
Abstract: Thermal dependence experiments have been carried out on silicon carbide Schottky power diodes. The devices were exposed to 3 MeV electrons with 10 MGy dose. Current density-voltage (~300 K to ~490 K) characterization have been used for the investigation. The results show that, at the highest tested temperature, the forward current density at 0.3 V increased approximately 7 orders of magnitude for unirradiated devices and approximately 8 orders of magnitude for the irradiated devices. The increase is believed due to the generation of free carriers which obtained the energy from the temperature. The series resistance of unirradiated increased with increasing temperature which may be due to the decrease in the free carrier mobility, whilst the series resistance of irradiated devices decreased with increasing temperature which indicates that more free carriers have acquired enough energy to be released from the traps introduced by the irradiation. The reverse current density shows that the current increased with increasing temperature due to the radiation-induced defects that act as generation-recombination centres. The activation energies of the irradiated devices were derived, and it is higher than the unirradiated devices. On top of that, there are two slopes in the plot of the activation energy versus voltage which suggests that the reverse leakage current is probably due to two different type of mechanisms.
Keywords: electron radiation; SiC; Schottky diode; high voltage; temperature dependent; electrical characterization; activation energy; leakage current mechanism.
Bi-directional Power Flow Control with Improved Power Quality using Intelligent Controller for AC-DC Coupled Hybrid Micro-Grid System
by C. Nagaraj, K. Manjunatha Sharma
Abstract: At the level of the distribution system, the intermittent solar-wind renewable sources and non-linear power electronic loads connected to the mains grid causes harmonics, which distorts its current. Also, many DC loads are connected to the AC distribution system and thereby increases the power conversion stages. These issues can be adequately addressed by introducing the smart micro-grid system. In an individual AC or DC micro-grid, the more number of AC-DC-AC/DC-AC-DC power conversion stages lead to the losses. Therefore, in this paper, the AC-DC coupled hybrid micro-grid system is presented in which AC renewable sources and AC loads are connected to AC sub-grid as well as DC renewable sources, and DC loads are connected to DC sub-grid thereby reducing the power conversion stages. Further, the generalized power conversion loss calculation is also discussed. The shunt active power filter based 3ϕ 4-leg bi-directional intermediate converter using d-q load current technique without phase locked loop is proposed to achieve the inverter-based and rectifier-based power flow between AC and DC sub-grids with acceptable power quality as per IEEE 519 standards at a common coupling point. The hysteresis based current technique is used to compare the actual filter current with a reference filter current to generate the switching pulses for the bi-directional intermediate converter. The MATLAB simulation is carried out, and the performance of the proposed system is analyzed using the d-q load current technique based fuzzy logic and PI controller. To validate the proposed control technique, different case studies are performed by considering balanced and unbalanced grid and load conditions with variation in renewable sources. The obtained results demonstrate that the overall system performance is improved with the d-q load current technique based fuzzy logic controller.
Keywords: bidirectional intermediate converter; common coupling point; coupled hybrid micro-grid; hysteresis based current technique; shunt active power filter.
Comparative Study of FCS-MPC and PWM Control Techniques for Autonomous Four-Leg VSI
by Raef Aboelsaud, Alexander Garganeev, Ahmed Ibrahim
Abstract: Finite control set model predictive control (FCS-MPC) is considered as a new control technique in the power electronics fields which dont require modulation stage. The absence of modulation stage results in operating under variable switching frequency which can affect the harmonic distortion of the output signal, the switching losses, filters design, and so on. On the other hand, the linear controllers control the power converters with constant switching frequency by using modulators. In this paper, the overall performance of FCS-MPC is assessed by performing a comparative study with a linear controller based on scalar pulse width modulation (PWM). The control systems are applied on an autonomous 4-Leg voltage source inverter (VSI) with LC filter as part of an autonomous power supply system. The main purpose of the two control techniques is to control 4-Leg VSI to provide balanced load voltage with lower total harmonic distortion. The steady state performance of the two control techniques is tested under balanced, unbalanced, linear and nonlinear load conditions. Moreover, the effect of the load variations on the switching frequency of the FCS-MPC is discussed. Finally, the performances of the two control methods in tracking the reference voltage under transient conditions are analyzed.
Keywords: Control; FCS-MPC; PWM; PID; Four-Leg Inverter.
Droop Control Method based on Fuzzy Adaptive Virtual Resistance for DC Microgrids
by Hossein Khoramikia, Seyed Mohammad Dehghan, Saeed Hasanzadeh
Abstract: DC microgrid is a high-efficiency and high-reliability solution for integrating energy sources, energy storage units and loads. Droop control method based on the virtual resistance is the most popular control method for DC MGs. However, this method has two limitations: 1- Unequal load sharing in case of unequal line resistances of converters, 2- DC bus voltage deviation with increasing the load. In this paper, in order to solve these limitations, a new control method based on fuzzy controller is proposed to determine instantaneous virtual resistance considering current sharing error and DC bus voltage deviation. In the proposed method, a low bandwidth communication network is used for current sharing of converters and DC bus voltage regulation. The performance of the proposed method has been investigated for difference line resistances and load changes. The simulation results show that the proposed control method leads to increasing load sharing accuracy and DC bus voltage restoration improvement.
Keywords: DC microgrid; fuzzy controller; voltage restore; load sharing.
Model Predictive Current Control with Duty Ratio Optimization for a Three-phase Grid-Tied Inverter based on Runge-Kutta Approximation
by Shahrouz Ebrahimpanah, Qihong Chen, Liyan Zhang
Abstract: This paper proposes a model predictive current control for a three-phase inverter connected to the grid by using a duty cycle optimization based on Runge-Kutta approximation. In this method each of 7 possible switching states are checked to find one that minimizes the cost function. It is a fact that the current ripples cannot decrease to a minimum value because there is only one voltage vector during one control period, thus the sampling frequency should be selected high for a sufficient performance. In order to find a solution to this problem, a duty ratio optimization technique based on Runge-Kutta approximation is introduced by using a non-zero and a zero voltage vector. Moreover, the duration of the two voltage vectors are selected according to the current error minimization. Simulation and experimental results verify that the proposed method obtains reduced current ripples and lower total harmonic distortions compared to the conventional method.
Keywords: model predictive current control; THD; total harmonic distortions; cost function; three phase-grid tied inverter.
Multi-function Control of Small-scaled Grid-connected PV Systems
by Esmaeil Zangeneh Bighash, Seyed Mohammad Sadeghzadeh, Esmaeil Ebrahimzadeh, Frede Blaabjerg
Abstract: One of the most important fields in distributions grid is the power quality issue. In this regards, voltage drop and harmonic distortions are two important challenges in the power quality. Some custom power devices like Resistive-Active Power Filter (R-APF), Dynamic Voltage Restorer (DVR), and The Static Synchronous Compensator (STATCOM) are used in order to fix these challenges. However, due to the high cost, these devices cannot be dispersed overall distribution grid. On the other hand, the installation capacity of the grid-connected small-scaled PV systems in distribution grids is remarkable. Therefore, the capacity of these systems can play an important role in distribution grids. By applying a proper control, these systems can, in addition to their energy source, be used as a harmonic and voltage compensators at the point of common coupling (PCC). This paper presents a multi-functions control scheme for small-scaled PV systems. In the presented approach, the control system, in addition to delivering the energy of the panels to the grid, will put the solar system in the harmonic and voltage compensation process at the PCC. Both the voltage and harmonic compensation strategies are implemented by on-line analyzing the PCC voltage. The structure in the proposed approach is a single-phase transformerless HERIC inverter with the LCL filter at the output. Finally, the results will be evaluated by MATLAB simulator and verified by experimental prototype.
Keywords: Resistive-Active Power Filter (R-APF); Active Power Filter (APF); Dynamic Voltage Restore (DVR); Static Synchronous Compensator (STATCOM); Photovoltaic (PV); Uninterruptible Power Supply (UPS); and Low-Voltage Ride-Through (LVRT).
A Comprehensive Review on BLDC Motor and Its Control Techniques
by Dileep Kumar, R.A. Gupta
Abstract: Brushless direct current (BLDC) motor drives have gained more popularity and emerged as the latest research area due to their ability to offer salient features such as compact size, higher efficiency, less maintenance, rugged operation, more reliable, and high torque to weight ratio. Recently, BLDC motor drives are widely adopted in numerous fields of industries and household applications such as robotics, electric vehicle, defense, aviation, industry, ventilation, dryer, and air conditioner. Most of the BLDC motors are consist of three hall sensors which are commonly employed for generating the gate pulses for the inverter to achieve a successful commutation sequence. It is worth mentioning that, proper commutation sequence is essential in order to effectively control the phase winding current. Moreover, rectangular shaped phase currents are required to produce a constant torque. However, practically ideal rectangular current shape cannot be obtained due to the phase winding inductance. Therefore, BLDC motor drives are facing the great challenge of current ripples due to the unequal rate of incoming and outgoing phase current during the commutation process which results in torque ripples. In view of these aspects, this paper presents a comprehensive review of the BLDC motor drive. Different converter topologies and current/torque control techniques have been carried out thoroughly to verify the potential of BLDC motor drives.
Keywords: BLDC motor; Inverter; DC-DC Converter; Torque ripple; Current ripple.
Universal Inverters for Flexible Power Electronic Test-Bed Implementation
by Lei Shao, Hanze Liu, Jiucang Sun, Ji Li, Hongli Liu, Xiaoqi Chen
Abstract: As the rapid development of electric grids, power electronic equipment has been widely deployed in modern power systems. The flexible operation of power electronic equipment has significantly complicated the grid operation, which enables different types of grid operation conditions that need to be emulated in the lab to facilitate the testing and development of advanced control diagram. Note that the fully controllable power electronic converters make it feasible to establish and simulate different operation conditions, which greatly diversifies the flexibility of conventional test-beds used for power electronics and power system research. In this paper, a generic three-leg converter is used and further functional expansion is implemented to make it a controllable unit for simulating different grid assets, including photovoltaics (PVs), batteries, etc. Hence, a universal inverter-based grid simulator is developed. Advanced control diagram is designed to achieve the flexible operation of the power-electronics-based grid simulators. Rather than relying on conventional synchronous-frame-based proportional-integral (PI) controllers, proportional-resonant (PR) controllers in stationary frame is used to avoid the coordinate transformation from a-b-c framework to d-q-0 framework. In other words, the coordinate transformation from stationary frame to rotational frame is eliminated. Test cases are established to test and validate the developed universal grid simulator.
Keywords: Grid simulator; stationary frame; synchronous frame; universal inverters.
Design of a Model Predictive Controller for Grid Connected Microgrids
by Sambit Kumar Panda, Arnab Ghosh
Abstract: Power electronics converter and inverter systems for microgrid operations are always stochastic in nature. When the system operates in grid tied mode the user always faces a steady state residual problem as the load connected to the grid varies and so the amount of current drawn from the microgrid varies which leads to a mismatch between the actual current and desired current. As a result, input current changes which creates a significant amount of voltage drop at the input. All the converters and inverters used in our system are controlled using Model Predictive Controller (MPC) except the boost converter for solar PV system which is operating in Incremental Conductance method (INC) and for the bi-directional converter a two loop continuous current control is implemented for controlling the output voltage as well as the inductor current reference. The inner loop forms the core of MPC whereas the outer loop keeps track of the voltage. The proposed control strategy gives very fast dynamics when subjected to different stochastic conditions and certainly the control strategy doesnt allow the DC voltage to fall below a certain voltage level. Presented simulation results justify the effectiveness of proposed strategy.
Keywords: Microgrids; Model Predictive Control (MPC); Incremental Conductance method (INC); Optimization technique; Microparks.
Simulation and Comparative Analysis of Single Phase H Bridge Micro Inverters with Conventional PI Control and Virtual Output Impedance Control: A Case Study
by Apoorva Saxena, Durg Singh Chauhan
Abstract: In this paper it has been proposed that Microgrids can form economical and technically viable option for the electrification in remote rural areas. It has been observed that inverters form the basic building blocks of these Micro grids. Proper selection of inverter design parameters along with suitable gain margins and phase margins of control loops, can help in the stable operation of inverters with improved voltage quality by reducing the Total Harmonic Distortion (THD). The dual voltage and current feedback loops are designed for the proposed inverter and closed loop performance analysis is performed for the corresponding transfer functions. The effect of voltage and current loop control parameters on the phase margin, cutoff frequency etc is analyzed in detail using industry recognized PSIM software. Introduction of a third virtual capacitive feedback loop changes the inverter output impedance nature and magnitude. The design of this virtual feedback loop is explained by controlling the time constant of the integrator circuit. The comparative analysis of the inverter performance is done for both with and without the virtual impedance feedback loop through a case study of 510 W, 220 V system. It has been observed that introduction of capacitive feedback loop can lead to reduction in higher order voltage harmonics, improvement in voltage regulation etc.
Keywords: Microgrid; Rural electrification; Inverter; Dual feedback loop; Virtual impedance loop; Inverter output impedance.
Constrained Discrete Mode Control of supercapacitor energy storage system for improved AGC of a multi-area power system with effects of wind power
by Sabah Un Nisa, Mairaj Ud Din Mufti
Abstract: For successful integration of renewables with the existing power systems, energy stor- age systems are increasingly being used. This paper proposes the development of a discrete mode control strategy for integrating a small rating supercapacitor energy storage(SCS) into a wind embedded multi-area power system for cost effective and improved AGC. Global optimization toolbox(MATLAB) is used to make the primary control loop of SCS to mimic a first order lag relation. This is purposely done for achieving a dual objec- tive. On one hand SCS is being forced to follow faithfully the command from the master controller and on the other hand discrete version of the representative model of inner con- trol loop is utilized for a control design procedure which while considerably reducing the frequency and tie-power deviations, ensures constrained operation of SCS. To virtually validate the proposed scheme, relevant modeling issues are addressed and a simulation platform is developed in MATLAB/Simulink environment.
Keywords: Automatic Generation control,Wind Energy; Energy Storage System,Controller Design; Power System.
FUZZY Logic Based Hybrid Active Filter for Compensating Harmonic and Reactive power in Distributed generation
by Buddhadeva Sahoo, Sangram Routray, Pravat Kumar Rout
Abstract: The increased infiltration of nonlinear loads and power electronics interfaced distribution generation systems degrade the power quality level. Active filtering of electric power is an emerging technology for mitigation of harmonic distortions and reactive power as a solution to this alarming issue. This study proposed a fuzzy logic control (FLC) approach for a single stage three-phase reduced switch cascaded solar inverter (RSCSI) having the hybrid active filter capability. With nonlinear load, the function objectives are to compensate the utility side current harmonic and offer the required amount of reactive power compensation to the system. The efficiency and reliability of power delivery is further improved by applying maximum power point tracking algorithm (MPPT) based on Perturb & Observe (P&O) method. A RSCSI approach is implemented as a shunt active filter, which reduce the harmonic distortion by its multiple voltage levels. In the proposed approach, the inverter provides similar features like a single stage multi-level operation with lesser dc-link voltage compared to the peak voltages (L-L), and less complexity in the circuit design. Secondly, the proposed single stage three-phase RSCSI also acts as a hybrid filter to enhance the overall performance of the test system. For the cascaded inverter to function for controlling active power and harmonics, d-q reference method and an improved wide-band control technique are implemented. Fuzzy logic controller (FLC) is used in the proposed single stage three phase RSCSI to avoid the limitation of the shunt active power filter containing the conventional inverter (VSI) with PI controller. A detailed comparative analysis has been done through MATLAB software and the simulation results of the test system verify the enhanced performance of the proposed approach.
Keywords: Photovoltaic (PV) system; reduced switch cascaded solar inverter (RSCSI); fuzzy logic controller (FLC); non-linear load; d-q control; hybrid active filter.
Space Vector Modulation of Multilevel Inverters with On-Line Vector Identification and Reduced Switching Losses for HEV/EV Applications
by Scott Cash, Oluremi Olatunbosun, Quan Zhou, Hongming Xu
Abstract: Multilevel inverters are used in a wide range of medium-high power applications including Hybrid and Electric Vehicles (HEV/EV). This paper investigates an on-line Reduced Intermediate Switching Space Vector Pulse Width Modulation (RIS-SVPWM) scheme to minimise switching losses without the need for large lookup tables or severely diminishing output harmonic quality. While previous on-line methods only calculate the switching patterns of a single enclosing voltage vector, this RIS-SVPWM method calculates all the switching patterns surrounding the reference voltage by incorporating only two more additional mapping iterations into the on-line algorithm regardless of the inverter level. The RIS-SVPWM method can operate in the sinusoidal, overmodulation mode-I and overmodulation mode-II regions of various inverter voltage levels and topologies. The performance of the RIS-SVPWM algorithm is examined over the entire driving range of an HEV/EV by controlling a MATLAB/Simulink model of a 3-phase 5-level Cascade H-Bridge inverter powering an induction motor model. The results of the simulation study show that there is a reduction in intermediate switching by up to 90% and a total switching reduction by 30% over a previous on-line SVPWM algorithm while maintaining acceptable voltage and current waveform harmonic quality.
Keywords: Space Vector Modulation; On-line SVPWM; Multilevel Inverter; Hybrid and Electric Vehicle; Reduced Switching.
Design and simulation of medium wave based RF energy harvesting system with feedforward controlled DC to DC boost converter.
by Tapashi Thakuria, Hidam Kumarjit Singh, Tulshi Bezboruah
Abstract: In this paper the design and simulation of a novel DC-DC boost converter is proposed which is used to enhance the output voltage of a Radio Frequency energy harvesting system from medium wave broadcasting at the near field. The Radio Frequency energy transmitted from the high power medium wave transmitters at the band of 750 KHz-2 MHz is received by a ferrite rod antenna and converted it to a DC signal by using 5th stage Dickson voltage multiplier. A DC to DC boost converter along with a Pulse Width Modulated controller having a switching frequency of 50 KHz is designed where the duty cycle can be adjusted. The circuit is designed for a fixed input Radio Frequency signal of 0.5 V which is tuned at 759 KHz of the medium wave frequency band. The maximum output voltage is observed to be 5.14 V at a duty cycle of 0.1 and load resistance of 1 Kohm. The output voltage can be changed by varying the duty cycle for different applications. The maximum power efficiency observed for the boost converter is 87.9% at load resistance of 100 ohm.
Keywords: Radio Frequency; Ferrite Antenna; Energy Harvesting; Boost converter.
Research on Power Quality Comprehensive Control Device under the Situation of Medium Voltage and High Power Based on H-Bridge Cascade Converter
by Zhiqiang Zhou, Yu SHEN, Chengkuan WAN, Wei HU, Tao WANG, Hao TANG
Abstract: This paper proposes a power quality control device based on H-Bridge cascade converter, to solve the problems in current decentralized power quality control, such as huge investment in equipment, expensive operation and maintenance cost, hard to coordinate, and low global technical-economic ratio. It provides a novel thought for the comprehensive control of power quality under the situation of medium voltage and high power. This paper has three parts. In the first part, the topology structure and working principle of the power quality comprehensive control device based on H-Bridge cascade converter are analyzed, and its key parameters are analyzed and designed. In the second part, corresponding coordinated control strategy is proposed according to the function of power quality comprehensive control device. Finally, a 10kV/1MVA medium-voltage and high-power power quality comprehensive control device is designed. The simulation through MATLAB Simulink proves that the parameter design is correct and the coordinated control strategy is effective.
Keywords: H-Bridge Cascade Converter; Comprehensive Control of Power Quality; Coordinated Control Strategy; Parameter Design.
Predictive Direct Power Control of Three-phase Three-level Four-leg Unified Power Quality Conditioner
by Mansour Bouzidi, Said Barkat
Abstract: In this paper, a predictive direct power control for three-phase three-level four-leg unified power quality conditioner (UPQC) has been proposed. The proposed three-level four-leg UPQC is capable of simultaneous compensation for supply voltage and load current disturbances. The predictive active and reactive power controllers were synthesized using a new predictive model of four-leg UPQC. In addition, a new algorithm of three-level three dimensional space vector modulation (3DSVM) was proposed to control a three-level four-leg inverter. The idea is to perform the different steps of 3DSVM in only one sector. Furthermore, the voltage-balancing control of common DC capacitors was achieved by controlling the shunt converter using a three-level 3DSVM equipped by a balancing strategy. Finally, the proposed control method of the three-level four-leg UPQC was verified and compared with direct power control (DPC) through simulation using MATLAB/Simulink under different operating conditions.
Keywords: Power quality enhancement; Predictive direct power control; Direct power control; Four-wire unified power quality conditioner; Three-level four-leg inverter; 3D-Space vector modulation.
Adaptive power sharing in Flexible frequency, Flexible voltage Hybrid power system
by Preeti Gupta, Pankaj Swarnkar
Abstract: Hybrid power systems (HPS) are small clusters of distributed generation, storage system along with load. Intertied hybrid systems have been anticipated the better interconnection of the various hybrid power systems and exploiting the major features of both AC and DC HPS. Being an independent module the flexible intertied hybrid power system (FIHPS) can operate at their own preferred voltage and frequency. In stand-alone mode of operation individual HPS of different voltage and frequency can be operated like self-controlled HPS and to provide back-up power can be exchanged between different HPS. Interfacing these AC and DC HPS necessitates appropriate control and power management strategy. Autonomous droop strategy is suitable for the FIHPS, where there is no possibility of fast communication links. This paper proposes a novel topology for control where different frequency AC HPS and different voltage DC HPS are connected to form a FIHPS. The paper focuses on the design of adaptive power sharing mechanism by introducing correction factor which changes its value as per the requirement of load automatically. Performance of an FIHPS under novel droop control with multiple AC and DC HPS is evaluated and analyzed under various operating conditions. This paper also considers the power management issues among different sources in both AC and DC HPS. The feasibility of proposed power management method is realized in MATLAB/Simulink platform which results in coordination among different HPS with maintaining the rated frequency and voltage.
Keywords: Intertied HPS; Interlinking power converter; Droop control.
Induction Motor Sliding Mode Estimators with Known Fluxes
by Mihai Comanescu
Abstract: Direct Field Orientation (DFO) is a widely-used method to control the induction motor (IM) drive. In DFO, the stationary frame fluxes are estimated using an observer and are fed in the ?tan?^(-1) function to obtain the field orientation angle. This angle affects the stability and performance of the drive and no computational effort should be spared to ensure the accuracy of the fluxes. A flux observer may be augmented with parameter estimation schemes; also, the fluxes may be corrected to reduce the errors caused by non-ideal integration. If the fluxes are fully accurate, they can be viewed as an extra set of measurements and can now be used as input quantities into observers that estimate the other quantities of interest in IM control: speed, load torque, inverse of the rotor time constant. This paper shows what IM quantities can be estimated when the fluxes are known and presents a series of observer designs. The estimation mathematics is validated with simulations and experiments.
Keywords: Voltage model observer; speed estimation; load torque estimation; rotor time constant estimation; sensorless control; sliding mode observers; model reference adaptive system.
HIL Implementation of an Islanding Detection and an Automatic Mode Switching for Droop Based Microgrid
by Shreeram Kulkarni, Dattatraya Gaonkar
Abstract: This paper presents the control schemes and performance study of parallel connected inverter-based distributed generation sources (DGs) in microgrid for grid-connected and stand-alone modes of operation. This stand-alone mode of operation of inverter based DG system is mainly based on the droop control scheme with the virtual complex impedance in the outer voltage loop. The microgrid load power is proportionally shared by the DGs according to their power ratings which feature good reliability and efficiency. Both the modes are switched automatically based on the Phase Locked Loop (PLL) phase error sin(gamma-theta). This phase error is used to detect the islanding during disturbances in the system and also helps in seamless transfer between the modes. The PLL phase error response, islanding detection and mode switching are presented for various fault conditions. The hardware-in-the-loop (HIL) based platform is used to evaluate the performance of the microgrid in both the modes with islanding detection and automatic mode switching operation.
Keywords: Microgrid; Inverter Parallel Operation; Droop Control; Phase Locked Loop; Islanding Detection; Automatic Mode Switching; Hardware In the Loop.
Stability Analysis of Parallel DC-DC Converters Controlled Over Communication Network
by Ashraf Kalil, Ang Swee Peng, Ali Asheibi
Abstract: Nowadays parallel converters are found in many industrial applications. In order to achieve the control tasks the control signals are exchanged through wires which increases the complexity and reduces the reliability. Communication networks are promoted to replace the conventional wiring system. In this paper we propose a method for computing the delay margin of parallel DC-DC converters controlled over communication network. The parallel converters implement Master-slave control strategy where the control signals are exchanged over communication network. The system is modeled as a general time delay system and the proposed method is used to compute the delay margin of the system. The transcendental time delay characteristics equation is transformed to frequency dependant equation. The spectral radius is used to find the frequencies at which the roots crosses the imaginary axis. The crossing frequencies are determined through the sweeping test and the binary iteration algorithm. The impact of the system and the controller parameters on the maximum delay margin is studied. It is found that the capacitance, the load resistance and the input voltage have strong effects on the delay margin, while for the controller parameters, the gains of the master voltage controller have the strong impacts where the delay margin decreases with the increasing of these gains.
Keywords: communication delay; delay margin; parallel DC-DC converters; stability; sweeping test.
Capabilities and Incapabilities of Unity Power Factor (UPF) Control Algorithm for DSTATCOM under abnormal grid and load conditions
by Yogesh Rohilla, Dinesh Kumar, Bharat Singh Rajpurohit
Abstract: Distribution Static Compensator (DSTATCOM) is an efficient custom power device to enhance the power quality of distribution network. To operate the DSTATCOM, a control strategy is must and the Unity Power Factor (UPF) is one such control strategy, which is used in DSTATCOM applications. The UPF algorithm has been developed in such a way that it operates as the reference supply current generator for DSTATCOM. To ensure the effective operation of DSTATCOM, it is important to analyse the performance of selected control algorithm at different disturbances either coming from source side or load side. Three-phase four-wire distribution system is considered for this study and performance of UPF based DSTATCOM system has been analysed for different disturbances such as unbalanced and harmonic distortion coming from source and load side. Exhaustive analysis is provided using the simulation tools (MATLAB/Simulink) to show the capabilities and incapabilities of UPF control algorithm under such disturbances. Each case is analysed thoroughly keeping the view of reactive power requirement, load balancing, total harmonic distortion levels as per IEEE-519 standard, and power factor improvement.
Keywords: Current distortion; DSTATCOM; power quality; unity power factor control algorithm; voltage distortion.
A Multi-Port Non-Isolated Bidirectional DC-DC Converter
by Sepideh Bahravar, Karim Abbaszadeh, Javad Olamaei
Abstract: In this paper, an extended topology for design of a high voltage gain n-port bidirectional dc-dc converter with decreased voltage stress on the switches is developed. First, dual-port and three-port conventional converters are investigated; afterward, the extended four and n-port bidirectional converters are analyzed based on the concept of these basic models. The advantages of the extended topology are its simple configuration with reduced number of the switches and small size thanks to use no transformer in the topology. In the results, the voltage stress on switches, minimum and maximum current values of the inductors and the voltage gain between the lower voltage source and the upper one are calculated for the extended n-port converter. As a typical case, a four-port converter is designed and simulated by the PSCAD software and by controlling the duty cycle of the converter, which is extracted from an incremental conduction algorithm, the maximum power of photovoltaic (PV) module is extracted in varying environmental conditions. In addition, to validate the operational performance of the four-port converter and evaluate the presented analysis, a prototype was fabricated and the experimental results were also presented
Keywords: Bidirectional dc-dc converter; photovoltaic module; maximum power point tracking (MPPT); multi-port dc-dc converter; non-isolated dc-dc converter.
Design of linear and non-linear controller for dc-dc boost converter with right-half plane zero
by Anitha Thiagarajan
Abstract: A major problem arises in the controller design when the transfer function of controlto- output voltage has right-half plane (RHP) zero. The effect of RHP zero predominates in the transfer functions of boost and buck-boost converters leading to a tedious controller design. Hence in this paper, the design of linear and nonlinear controllers for a dc-dc boost converter is discussed. Since the design of the linear controller(PI) strongly depends on the small signal transfer function of the converters, it leads to poor voltage regulation for wide variation in operating point. To overcome the above said difficulties and to achieve large signal stability, robustness, good dynamic response and simple implementation, an additional inner loop employing sliding mode control (SMC) with boundary layer is proposed in current mode control (CMC) scheme. Extensive simulation studies are carried out for dc-dc boost converter with RHP zero to verify the merits of SMC over PI controller using Matlab/SIMULINK software.
Keywords: DC-DC converter; Boost converter; RHP zero; Sliding mode controller; PI controller.
Adaptive Control Algorithm to Interface Fuel Cell and Photo Voltaic Energy Sources
by Shikha Gupta, RACHANA GARG, ALKA SINGH
Abstract: This paper presents the control algorithm for photovoltaic (PV) and fuel cell (FC) interfaced voltage-source converter (VSC). The control algorithm ensures uninterrupted power supply and reliable operation under variable power generation and load conditions. Hyperbolic tangent based least mean square (H-LMS) system is proposed to generate proper gating signal of the inverter. The basic function of generation sources is to meet the active power demand. Furthermore, the proposed system architecture has added features to balance the load, suppress the harmonics and compensate reactive power. These functionalities make sure that the supply current is sinusoidal even under nonlinear and unbalanced load conditions. The proposed algorithm provides fast computation and convergence rate. Comparison with conventional LMS is presented in terms of convergence rate and supply current harmonics under MATLAB/Simulink platform. The control algorithm is also examined for stability through Lyapunov stability criterion, thus, the error function of the algorithm converged to zero asymptotically.
Keywords: Solid oxide fuel cell; photovoltaic; renewable energy sources; voltage source converter; least mean square method; Lyapunov stability.
A New High Step-up Soft Switching Converter for Photovoltaic System
by Mahmood Vesali, Majid Delshad, Ali Khajeh Naeini
Abstract: In this paper, a new DC-DC boost converter with ZCS condition is presented. The ZCS condition of the proposed converter is established without adding any auxiliary switches and with minimum auxiliary elements, so the converter efficiency is high. The converter is controlled by pulse width modulation which design and implementation of the control circuit for the converter is very simple. The proposed converter has low current and voltage stress on the switch and the other advantage of the converter is high voltage gain due to existence of coupled inductors and voltage lifting in output, therefore the proposed converter is very suitable for photovoltaic systems. The experimental results verify the theoretical analysis and the converter efficiency at full load is approximately 96%.
Keywords: DC-DC converter; soft switching; zero voltage switching; zero current switching; photovoltaic systems.
Effect of PWM Schemes on the Performance and Common-Mode Current of the Proposed Modified 7- Level H-Bridge Inverter
by Uvais Mustafa, M. Saad Bin ARIF
Abstract: In this paper, modified H-Bridge Seven level inverter topology is proposed. The performance of the proposed topology is evaluated in terms of the THD and the fundamental component of the output voltage for open-loop operation and in terms of Common Mode Current for the connected grid system. Implementation feasibility of different PWM techniques and their effect on the performance of the topology has been performed. The PWM switching based on a high frequency is used; as high-frequency PWM technique reduces the THD in the output voltage. The analysis shows that the Alternate Phase Opposite Disposition (APOD-PWM) based on a triangular carrier scheme offers the minimum THD of 15.72% for the unity modulation index while operating in an open loop, and in Phase Disposition (IPD-PWM) triangular carrier scheme offers the minimum common mode current of 222mA. Also, the output voltage decreases and the fundamental component increases with increment in modulation index is observed. Results obtained show that the topology has low THD as well as common mode current is well within limits for grid-tied applications.
Keywords: Total Harmonic Distortion (THD); Multilevel Inverter (MLI); modulation index; Pulse Width Modulation (PWM); Common Mode Current (CMC).
Photoelectric Composite Cable Temperature Calculations and Correction of its Parameters
by Tabi Fouda Bernard Marie, Dezhi Han
Abstract: A method for correcting the thermal resistance of the insulation layer by using the current difference and the conductor temperature difference is proposed paper. The optical fiber temperature of the three-core photoelectric composite submarine cable is measured by BOTDA; and the corresponding relationship between the temperature variation of the optical fiber and the conductor is performed by finite element analysis, thereby obtaining the difference in temperature of the conductor. After finite element analysis, the corrected thermal resistance is therefore replaced in the calculation. It has been shown by comparison that, the correction of the thermal resistance of the insulation layer can effectively improve the transmission capacity requirements of the cable and the accuracy of the calculation of the transient temperature rise of the conductor.
Keywords: Transient temperature rise of conductor; thermal path method; high-voltage three-core photoelectric composite submarine cable; thermal resistance of insulation layer; finite element; BOTDA.
Multilevel Converter Topology Suitable for Separate and Variable Magnitude of DC Sources
by Bikram Das, Debashis Chatterjee, Aniruddha Bhattacharya
Abstract: A new configuration of multilevel inverter (MLI) has been presented in this paper requiring less number of power semiconductor switches and driver circuits. The proposed topology has better switch utilization ratio (SUR) with reduction in inverter price. The circuit functional performance of MLI is validated through suitable simulation and experimental results on a laboratory prototype.The MLI has been considered for 5, 11 and 13-level configurations with different resistive and inductive load combinations. Both equal and unequal dc sources are considered to justify the feasibility of the topology.
Keywords: Multilevel inverter; cascaded configuration; loss calculation; switch utilization;.
A Novel Switched Capacitor Based Multilevel Inverter Structure for Renewable Energy Convertion System
by Gashaw Ango, Tapas Roy, Pradip Kumar Sadhu
Abstract: Switched capacitor multilevel inverters (SCMLIs) are one of popular solutions to mitigate the different limitations of conventional multilevel inverters (MLIs). A large number of innovative SCMLIs have been reported in literature in recent years. However, the large requirement of power switches, capacitors and large voltage stress across the switches are the major limitations of SCMLIs. In this paper, a novel MLI structure using switched capacitor principle has been proposed. It does not require any H-bridge circuit which reduces the switch stress voltage of the structure. It has the ability to produce 13 output voltage levels. Further, the cascaded arrangement of proposed basic structure has been realized The structure requires lower number of components as compared to the other SCMLIs. The operating principle, capacitor selection procedure and power losses of proposed structure have been discussed. Extensive simulation and experimental studies have been conducted to validate the effectiveness of the proposed structure.
Keywords: boosting factor; multilevel inverters; switched capacitor; series-parallel; voltage balancing.
SOLAR POWER-DRIVEN PERMANENT MAGNET SYNCHRONOUS MOTOR COUPLED WITH PUMP LOAD: DESIGN, DEVELOPMENT AND CONTROL
by Menka Dubey, Shailendra Sharma, Rakesh Saxena
Abstract: This paper presents design, development and control of solar photo voltaic (SPV) supply system for permanent magnet synchronous motor (PMSM) driven pump load. The proposed system is very effective in curtailing power demand on existing grid supply on highly dense population areas. An Incremental conductance method followed by sliding mode control scheme is used to track SPV array maximum power point (MPP) and vary the speed of the PMSM accordingly under the change in atmospheric conditions. The direct torque controlled (DTC), voltage source inverter (VSI) is employed to control the PMSM speed and to achieve stable operating point. A prototype of single stage SPV supply based PMSM coupled with DC machine is developed in laboratory for emulating the centrifugal pump characteristics. Performances under different environmental and operating conditions, are obtained on the developed prototype to prove the efficacy of the proposed control
Keywords: photo voltaic system; sliding mode control; permanent magnet synchronous motor; water pumping system.
A Passivity based Controller for an Interleaved Boost PFC Converter
by Kumari Shipra, Rakesh Maurya, S.N. Sharma
Abstract: This paper reveals a passivity-based control technique for the interleaved boost PFC converter. First, an Euler-Lagrange (EL) mathematical formulation for the interleaved boost PFC converter is developed. Then, the passivity-based control methodology is implemented in the system. The output voltage can be maintained constant via the introduction of the notion of the energy modification in passive components. In the controller design, the energy of the system is made non-conservative by adding damping factor. That makes the system become passive against disturbances. This paper develops a polynomial function for the damping injection to keep the desired output voltage constant against the variation of load current and input supply. The proposed controller offers several features such as ease of implementation, no tuning of parameters like proportion integral controller, robustness against disturbances as well. A Simulink model with the proposed controller is developed using MATLAB/Simulink block and its performances are investigated under various operating conditions. Further, real-time implementation, the stability analysis for the proposed controller is also carried out.
Keywords: Mathematical Modelling; the Euler-Lagrange; Boost Converter; Interleaved Control techniques; Passivity based Control.
Design and Implementation of Constant Flux Controller for VSI Assisted SEIG Feeding Induction Motor Pump
by Sachin Angadi, Udaykumar R. Yaragatti, Yellasiri Suresh, A.B. Raju
Abstract: In small scale, stand-alone, wind-power generation employing self-excited induction generator (SEIG), water pumping using an induction motor is a typical application. In this paper, a simple voltage regulation scheme for the constant flux operation of the inverter assisted SEIG feeding three-phase induction motor pump is presented. The behaviour of DC-link voltage, frequency, amplitude modulation index (ma) and the shaft speed for load and speed perturbations are discussed in detail. Also, the overall active and reactive power flow for constant flux operation at the point of common coupling (PCC) is analysed. The proposed work presents a simple and reliable controller for SEIG based stand-alone system for frequency-dependent loads using only a DC-link voltage sensor. Detailed system simulations are performed using Matlab/Simulink and the results of a laboratory prototype are presented to validate the theoretical analysis and practical operability of the proposed system.
Keywords: active power; constant flux; induction motor; induction generator; reactive power; SEIG; stand alone SEIG; voltage regulation; water pumping.
Finite Element and Analytic Equivalent Circuit Models for MSIM feeded by MPI controled by SVPWM Strategy to minimize circulation harmonic current
by Thouraya Guenenna, Khaled Smida, Adel Khedher
Abstract: This article deals with the determination of the Multi Stars Induction Machine (MSIM) equivalent circuit parameters based on the geometrical and electrical data using two methods namely analytic and Finite Element Method (FEM). Additionally, this paper proposes a general dynamic study of MSIM. This latter is fed by a Multi-Phase Inverter (MPI) controlled by a Space Vector Pulse Width Modulation (SVPWM) and a Sinusoidal Pulse Width Modulation (SPWM). However, when this machine is fed by the voltage inverter for the case of 30
Keywords: multi-stars induction machine (MSIM); analytic method; finite element method (FEM); space vector PWM; sinusoidal PWM; multi-phase inverter (MPI).
Rooftop based Magnetically Levitated VAWT with Specially Designed Guide Vanes for Enhanced Efficiency in Distributed Generation
by Nitin Gupta, Sandeep Banerjee
Abstract: This work proposes a practically feasible and distinct method of harvesting wind energy for urban and rural rooftops. This technique is especially useful for distributed generation. A one-fourth scaled version of a new type of wind energy conversion system (WECS) has been presented. The novelty of the reported WECS lies in the usage of a magnetically levitated vertical axis wind turbine (VAWT) along with dynamic guide vanes system. The usage of magnetic levitation results in loss minimization and efficiency maximization. To tap maximum wind energy, the guide vanes are programmed to dynamically change their angle according to the wind speed. This paper also presents the utility of an axial flux permanent magnet (AFPM) generator for VAWT systems. An experimental model has been developed and its results have been presented. The experimental results have been put to use for developing a model of the VAWT system using Fuzzy Inference System (FIS).
Keywords: distributed generation; guide vanes; magnetic levitation; vertical axis wind turbine; Venturi effect.
Comparative Analysis Between Different Approaches for Single-Phase PLLs
by Luis Monteiro, J.G. Pinto, Vitor Monteiro, Carlos Couto, Joao Afonso
Abstract: This paper presents a comparative analysis between two distinct synchronizing circuits, which are usually applied as the core of control algorithms for single-phase power quality applications. One of these synchronizing circuits corresponds to a single-phase Phase-Locked Loop (PLL), implemented in ?-? coordinates (??-PLL), whereas the other one corresponds to the Enhanced PLL (E-PLL). The major contribution of this paper is to present a single-phase PLL oriented to power quality applications, with a very simple structure, capable to be synchronized with the fundamental component of an input signal (voltage or current), even considering substantial disturbances, such as, frequency deviations, phase shifts, harmonic components and amplitude variations. Simulation and experimental results, involving these two synchronizing circuits submitted to three different test cases, are provided in order to compare their transient and steady-state performance. Moreover, it is also presented a comparison involving the processing speed and memory requirements of these synchronizing circuits in the DSP TMS320F28335.
Keywords: Phase-Locked Loop (PLL); alpha-beta-PLL; Enhanced PLL (E-PLL); Digital Signal Processor (DSP); Power Quality.
Investigations on Variable and Constant Switching Frequency Hysteresis Controller for VSI fed IM drive
by Joseph Peter, Rijil Ramchand
Abstract: In various Current Controlled-Pulse Width Modulated(CC-PWM) techniques which are extensively employed in high performance drives, Hysteresis Current Controllers (HCC) offer significant simple implementation and good dynamic response. However, conventional HCC have drawbacks, such as, limit cycle oscillations ,overshoot in current error, generation of sub-harmonic components in the current, and non-optimum switching of inverter voltage vectors which can create variable switching frequency. This work proposes a new constant switching Current Error Space Phasor (CESP) based hysteresis controller with a simple online computation of the boundary and phase voltage harmonic spectrum similar to Voltage Controlled Bus Clamping PWM (VC-BCPWM) based VSI fed Induction Motor drive. The error boundary computed using voltage and current errors in the present sampling interval is used for identifying next vector to be switched. The current controller using CESP approach is simulated using MATLAB SIMULINK and experimentally verified on 2.2 kW I.M drive.
Keywords: hysteresis; switching frequency; current error space vector; bus clamping PWM.
Control of single phase photovoltaic H6 inverter in grid-connected and stand-alone modes of operation
by Majid Abadi Marzoni, Seyed Mohammad Sadeghzadeh
Abstract: this paper proposes a control strategy for single phase transformerless photovoltaic H6 inverter with capability of operation in both grid connected and stand-alone modes. This control strategy enables seamless transition between two modes without any reconfiguration of control structure and need of any external communication. A multi loop control structure including an inner voltage and current control with PR controller and outer power control with droop controller is utilized to make the inverter operate in both modes. In grid-connected mode, the power control loop regulates reference voltage and frequency for voltage control loop, to adjust power flow of inverter to the main grid while in islanded mode, reference voltage and frequency are determined according to droop characteristic of inverter to supply local load demand. The simulation and experimental result are used to verify the performance of the proposed control.
Keywords: single phase H6 inverter; grid connected; stand alone; seamless transition.
Design and simulation of a voltage mode controlled boost converter for low power RF energy harvesting system
by Tapashi Thakuria, Tulshi Bezboruah
Abstract: In this work, a voltage mode feedback controlled DC to DC boost converter is designed and simulated for a medium wave based radio frequency (RF) energy harvesting system. The RF signal with an input power of 4 mW is converted to a DC signal which is stepped up and regulated by the boost converter. The DC to DC boost converter is controlled by a pulse width modulated circuit which generates a switching signal of frequency 100 kHz. A type-III compensator circuit is designed to regulate the output voltage at 3.3 V and 5 V which is suitable for low power applications.
Keywords: Radio Frequency(RF); Energy Harvesting; Boost Converter; Compensator; Voltage Mode Control.
Evaluation and Minimization of Total Harmonic Distortion in Three-Phase Two-Level Voltage Source Inverter with Low Switching Frequency
by Neerparaj Rai, Sandeep Chakravorty
Abstract: In this paper, an optimal Pulse Width Modulated (PWM) waveform over complete modulation index range in terms of least total harmonic distortion (THD%) is determined for two-level three-phase inverter. Two types of pole voltage PWM
waveforms specifically typeA and typeB have been considered at low pulse number (P = 5) owing to switching loss limitation. The different types of waveform can be distinguished by the positive or negative voltage transition at the point where the fundamental voltage has maximum positive slope. The cost function is formulated for each PWM waveform and a combination of Genetic Algorithm (GA) and Newton-Raphson (NR) method is used to obtain a total of two solution sets corresponding to typeA and typeB namely solution set-A and solution set-B. Based on the four solution sets, an optimal PWM waveform is proposed to minimize the low order harmonics for the inverter output. The optimal PWM waveform is evaluated and compared with conventional Selective Harmonic Elimination (SHE-PWM) and Sine-Triangle (ST-PWM) methods. The optimal PWM results in notably improved performance over ST-PWM and SHE-PWM for complete modulation index (M) range and above M = 0.6 respectively. The theoretical analysis and results are validated
by MATLAB simulation and experimental studies for a two-level inverter.
Keywords: Selective harmonic elimination; PWM formulations; multilevel inverter; iterative techniques; optimization algorithms.
Superior Transient and Stability Performance of Voltage Regulation by Battery-fed Bidirectional Converter for Supporting Various Operational Modes of PMDC Machine
by Satyajit Saha, Pritam Gayen
Abstract: This paper presents systematic procedure to design voltage controller for achieving superior dynamic performance of battery-fed bidirectional converter for supporting operation of permanent magnet direct current (PMDC) machine. Nowadays, this system is extensively used in electric vehicle. Here, either motoring or regenerating mode of operation of the electrical machine is required. Therefore, voltage control action by bidirectional DC-DC converter plays an important role for supporting various operational modes of PMDC. In this respect, derivation of small signal model of overall system is given. At next, condition for absolute stability is calculated from the model on basis of Routh-Hurwitz criterion. Then, gains of proportional-integral (PI) controller have been tuned using Ziegler-Nichols tuning chart from derived values of ultimate gain and critical frequency as per conventional approach. But, the calculated gains from Ziegler-Nichols tuning chart do not provide satisfactory dynamic performance and sound stability margin under variable voltage conditions. Thus, performance of voltage regulation is deeply investigated and redesign of voltage controller is emphasized for achieving both superior dynamic performance and significantly stronger stability margin. Superior transient and stability performances of voltage control loop in proposed case are compared with that of conventional case. Proposed approach is verified in MATLAB-SIMULINK software based modelling of physical system and also, in experimental platform.
Keywords: Battery; bidirectional DC-DC converter; voltage controller; PMDC machine; motoring and regenerative mode; transient performance; relative stability.
Robust Control of Multi-phase Interleaved Boost Converters in the Presence of Perturbations and Open Phase Fault
by Sajjad Shoja-Majidabad, Sajed Derakhshani Pour
Abstract: In this paper, robust control of interleaved boost converters is studied under load and supply voltage perturbations and open phase fault. First, a new decentralized proportional-integral adaptive sliding mode control strategy is developed for the interleaved boost converters. In this status, each phase of the converter operates separately and the proportional-integral controller generates needed reference current from the voltage tracking error. Second, a novel proportional-integral adaptive sliding mode control method based on master-slave strategy is proposed. In this strategy, one phase of the converter acts as the master and the other phases act as the slaves. The master phase controls the voltage and others are responsible for their currents separately. However, the reference current is provided by average value of the converter phase currents. The adaptive gains of the proposed control methods are able to estimate the related perturbations without any prior knowledge. Comparative MATLAB/ Simpower simulations are carried out on a three-phase IBC to show the effectiveness of the proposed control strategies in the presence of load and supply voltage perturbations and open phase fault. Moreover, the tracking capability of both methods is verified by the simulations.
Keywords: Multi-phase interleaved boost converter; adaptive sliding mode control; decentralized control; master-slave control; open phase fault; load and supply voltage perturbations; equal current distribution.
Intelligent Adjustable-Speed Drive on an FPGA
by Azzouz Benzekri
Abstract: This paper addresses the design, simulation and implementation of a PI-like fuzzy controller to adjust the velocity of an armature-controlled DC motor using hardware/software co-design. Fuzzy control and digital pulse width modulation (PWM) techniques are used as computational solution, while the implementation is carried on a reconfigurable hardware platform. This controller is designed with four considerations in mind: design integration, robustness, reduced complexity and flexibility. Computationally intensive tasks are implemented as hardware accelerators using VHDL, data flow and control are implemented in software using system-on-programmable-chip (SoPC) approach. With this paradigm, we get the robustness of fuzzy control, the best of software programmability of Nios®-II and the hardware reconfigurability of the FPGA. The model was synthesised using Quartus®II and targeted at a Cyclone-II FPGA. Computer simulation results show the effectiveness and merit of this process. The real-time applicability of this controller is exemplified on a motor provided with a tachogenerator mounted on its shaft.
Keywords: FPGA; SoPC; Nios® II; VHDL; Hardware/Software Co-Design; Adjustable-speed drive; PWM; PI-like Fuzzy Controller; Armature-controlled; Quartus II.
Second order Sliding Mode Controller interlinked with DSTATCOM
For Mitigation of Total Harmonic Distortion
by Swetha K, Sivachidambaranathan V
Abstract: Power Quality (PQ) is demonstrated as any power crisis that consequence in the
misdirection of user devices. Electrical PQ is turning out to be widely concerned with both
electric appliances and customers. Voltage fluctuation remains as the most important PQ
crisis as it has a major effect on both the equipment and production environment.
DSTATSCOM is a significant device, which enhances the power factor and sustains stable
distribution voltage and alleviates harmonics in the distribution network. D-STATCOM
minimizes the voltage fluctuations and voltage instability of the power system that results in the speedy revival of system voltage after contingency occurrence. However, the THD
problem remains a major issue in D-STATCOM devices that affects system performance.
Hence, in this paper, efforts are made to minimize the THD problem in D-STATCOM
devices by connecting the Second-order Sliding Mode Controller (SoSMC) to D-STATCOM
linked system. The main objective of the proposed controlled model is to minimize the THD
so that the enhanced power quality can be attained. Moreover, the performance of the SoSMC
controller is evaluated over the traditional PI controllers, and the results are analyzed.
Keywords: Power Quality;D-STATCOM; Total Harmonic Distortion; Second Order Sliding Mode Controller.
Experimental Implementation of SEIG Based Wind Energy System Using Neural Network Controller
by Giribabu Dyanamina
Abstract: The paper presents a standalone self excited induction generator (SASEIG) based wind energy system (WES) connected with back to back power converter. It consists of a generator side converter (GSC) used to regulate variation of torque and flux, and load side converter (LSC) used to adjust variation of DC voltage. The indirect vector control (IVC) technique is employed to regulate the GSC and LSC separately. When a SASEIG operated at variable speed the voltage variation of controller is very critical. Therefore to enhance the voltage variation the proportional integral (PI) controller is replaced with NNC in indirect vector control of GSC. The proposed WES is simulated using MATLAB/SIMULINK software and is operated at variable speeds, to validate the proposed method experimentally the prototype model is developed and it is digitally implemented using DS-1104 R&D controller.
Keywords: Self Excited Induction Generator; Indirect Vector Control; Wind Energy System; Neural Network Controller.
Comparative Analysis of Unit Template, SRF and the Modified SRF Technique for DSTATCOM Based Distribution System
by Aaqib Ahmad Qureshi, Abdul Hamid Bhat
Abstract: This paper introduces a new hybrid control strategy called the Modified SRF theory which makes use of both SRF as well as unit template technique to generate the reference supply currents which are then compared with the sensed supply currents and fed to the hysteresis/PWM current controller to generate the necessary switching signals for switches of the VSC of the DSTATCOM for a three-phase three-wire system.. This proposed control algorithm is compared with the unit template or PI controller-based algorithm and the SRF theory to mitigate a variety of problems such as low power factor, voltage regulation, current unbalance and harmonics in the system. The proposed algorithm is proved better than conventional algorithms reported in the literature.
Keywords: DSTATCOM; control technique; power quality; unit template; SRF; Modified SRF; custom power device.
Short-Time Wind Power Prediction using Hybrid Kernel Extreme Learning Machine
by Sthita Prajna Mishra, Jyotirmayee Naik
Abstract: A hybrid short-time wind power forecasting technique based on Variational Mode Decomposition (VMD) and Kernel Extreme Learning Machine (KELM) is proposed in this paper. The non-stationary historical wind data is initially decomposed into various modes using VMD technique, which is subsequently passed through the proposed KELM (Gaussian and wavelet based) and conventional ELM (without weight optimization and with optimization (Chaotic firefly optimization algorithm(CFA)), respectively, in order to predict the thirty minutes and one hour ahead wind power, respectively. It is observed that, rather than optimizing the arbitrary input layer weights of VMD-ELM technique, the proposed Gaussian based EMD- KELM technique illustrates the most effective and accurate short-time wind power predictions for some diverse seasons. The overall results presented in the simulation (through MATLAB Simulation Platform) and result section are satisfactory and indicates the proposed Gaussian based EMD- KELM technique as a highly potential prediction technique for real time applications in power systems. The proposed model can be tested in the industry having wind generation or wind power plant where this can be applied in order to predict the future wind power to schedule the load profile in efficient manner. This can be also validated through wind test bench system.
Keywords: Variational Mode Decomposition; Kernel Extreme Learning Machine (KELM); Chaotic firefly optimization algorithm; wind power prediction.
An improved grid integration technique for SPV based CHB-MLI in distribution network
by Prabir Ranjan Kasari, Subhadeep Bhattacharjee
Abstract: The growing power electronics based nonlinear load increases harmonic contribution in the power system that leads to deterioration in the quality of power. The unbalance loading in three phase four wire (3P4W) system allows a neutral current flow which is an escalating concern for the utility. In this paper, the instantaneous power balance method is employed for Solar Photovoltaic (SPV) based nine-level Cascaded H-Bridge Multilevel Inverter (CHB-MLI). A modified instantaneous Power Balance Method (PBT) is proposed for integrating this SPV based CHB-MLI. The average and oscillating zero sequence power are incorporated in the proposed instantaneous power balance method to generate an appropriate reference for interfaced CHB-MLI. It is evident from the study that, the zero sequence components have a significant effect on an unbalance three phase four wire system, considered as a utility in this paper. The proposed controller provides CHB-MLI that feeds the average power of SPV and also supports the utility by supplying nonlinear, oscillating power. This SPV based CHB-MLI is called Solar Photovoltaic Shunt Active Power Filter (SPV-SAPF). Further, the modular structure of this CHB-MLI facilitates the integration of large energy using low rated converter components. FFT analysis done for different voltage levels of CHB-MLI shows that Total Harmonic Distortion (THD) is within a permissible limit. Besides, simulation, experimental results are also provided to validate the performance of the proposed scheme.
Keywords: Active and reactive power; cascaded H-bridge multilevel inverter (CHB-MLI); harmonics compensation; instantaneous power balance theory.
Versatile Current Controller Suitable for Two-Level As Well As Three-Level Converters of Shunt Active Power Filters: Part-I
by Siddharthsingh K. Chauhan, Dr. P. N. Tekwani
Abstract: Current control strategy adopted, dominantly governs performance of shunt active power filter (SAPF). A versatile current error space phasor based hysteresis controller for SAPF is presented. The controller keeps the current error space phasor within prescribed hexagon shaped boundary by selecting appropriate voltage vector of SAPF. Switching of optimal voltage vector is ensured unlike non-optomum selection in conventional hysteresis controllers used for SAPFs. Proposed SAPF generates compensating currents effectively by cocordinaing sector change overs and supply frequency. Two different schemes for sector change detection are presented. The concept is simulated, and digital signal processor (DSP) TMS320LF2407A is used to implement the proposed controller. Experimental results depicting steady state as well as transient performance of the controller are presented. Effect of variation in hysteresis band on performance of SAPF is also reported. Adequate compensation provided by the SAPF for harmonic mitigation is evident from simulation and experimental results. However, complex voltage space phasor structure of multi-level converter puts limitation on proposed controller to detect sector changes. Application of proposed controller to multi-level converter based SAPF requires development of a versatile controller. Such a controller having capability to identify sector change in multi-level converters using outer hysteresis band is described in Part-II of this paper.
Keywords: Current Error Space Phasor; Hexagonal Boundary; Multi-Level Converter; Sector Change Detection; Shunt Active Power Filters; Versatile Hysteresis Current Controller.
Model Reference Adaptive System Based Precise Online Inertia Identification of Induction Motor with Error Utilization Technique
by Jay D. Mistry, Dr. P. N. Tekwani, Chirag Raval, Vinod Patel
Abstract: Time varying parameters can be estimated using either adaptive control or robust control. Robust control can be used only when the control law is fixed and varying parameters are bounded. Adaptive control is concerned with control law changing itself. Model Reference Adaptive System (MRAS) is an adaptive control method that can be used to identify initially unknown parameters. Variation in load and machine vibrations affect the control system performance of any motor drive system when it is in operating condition. Estimation of moment of inertia becomes essential to improve the dynamic response characteristics of any high-performance Asynchronous Machine (ASM) drive system. A novel method using Model Reference Adaptive System (MRAS) with Error Utilization Technique (EUT) for precise identification of online varying inertia is presented in this article. The proposed method uses an interesting relation between the estimation error and actual inertia, to compensate for the error and provide high precision online inertia identification.
Keywords: Asynchronous Machine (ASM); Model Reference Adaptive System (MRAS); Error Utilization Technique (EUT); Inertia Identification.
Versatile Current Controller Suitable for Two-Level As Well As Three-Level Converters of Shunt Active Power Filters: Part-II
by Siddharthsingh K. Chauhan, Dr. P. N. Tekwani
Abstract: Current controller presented in Part-I of this paper suffers from limitation in sector change detection for multi-level converter based power filters because of inherent complex voltage space phasor structure. A self-adaptive current error space phasor based hysteresis controller is presented that does not require calculation of voltage vector at point of common coupling for identifying sector changes. It requires one more hysteresis band placed little outside the main hysteresis band used for selection of voltage vectors. Sector change detection is executed only from the movement of current error space phasor and state of comparators on outer band. This versatile technique of sector change detection is equally applicable for two-level as well as three-level converter based power filter. Feature of adjacent voltage vectors switching is retained in the presented controller. Inherent problem of capacitor voltage imbalance is eliminated by effective use of switching state redundancy of three-level flying capacitor converter employed for power filter. Performance of controller is verified for two-level and three-level filter through thorough simulation studies. The controller is then implemented using DSP TMS320LF2407A for two-level filter. Adequate compensation provided by the controller in steady state, during transients and for variation in hysteresis band is evident through presented results.
Keywords: Current Error Space Phasor; Flying Capacitor Type Three-Level Converter; Self-Adaptive Sector Change Detection Technique; Shunt Active Power Filters; Two Hexagonal Boundaries; Versatile Hysteresis Current Controller.
An MRAS based Smoothed Kalman Observer for Speed Sensorless Indirect Vector Controlled Induction Motor Drives
by Uma Syamkumar, Jayanand B.
Abstract: This paper proposes a modified Kalman filter algorithm based on fixed-lag smoothing which can be used to estimate the rotor speed and flux of three phase induction motor. The behavior of a typical extended Kalman filter(EKF) algorithm is influenced by the process and measurement error covariance matrices. In EKF, these matrices are chosen by trial and error method and have to be varied according to the varying operating conditions of the motor. In this paper a smoothing based extended Kalman filter(SKF) algorithm which uses additional data points for estimation is proposed. Since additional data is used, the algorithm is able to give a better estimate, for same values of covariance matrices. The performance of the proposed algorithm is explored for sensorless indirect vector control application of three-phase induction motor. Finally, in order to validate the superiority of this algorithm, it is compared with the performance of EKF algorithm for various reference speeds in real-time. rnrnrn
Keywords: Sensorless Control; Smoothing; Observer; Extended Kalman filter; Three-phase induction motor.
Exploration of Bifurcation and Inherent Oscillation in a Current
Mode Controlled Cuk Converter - Effects of Turn-On and
Turn-Off Switching Delays
by Sukanya Parui, B. Basak
Abstract: The nonlinear phenomena in a dc-dc current mode controlled C'uk converter circuit has been explored. In reality, as any switching process is associated with turn-on and turn- off delays, the simulation has been extended considering these delays. The circuit exhibits a LC oscillation which may make the switch current oscillatory and in some cases the conclusion obtained from the bifurcation diagram regarding the dynamics of the system becomes incorrect. A mathematical expression for the oscillation frequency has been presented. A prototype ofrnthe converter has been developed. The simulated results have been verified experimentally.
Keywords: Bifurcation; Chaos; C'uk Converter; Oscillation.
SVM based Current Ripple Reduction with Two Parallel Interleaved Inverters for Induction Motor Drive
by RANVIR KAUR, Gursewak Singh Brar
Abstract: Extensive research has been ongoing in the field of inverter fed induction motor drives. The main challenge in designing Pulse Width Modulation (PWM) fed induction motor drives is to reduce Total Harmonic Distortion (THD) and ripple content in ac output of inverter. The PWM method ensures the voltage balancing between two Parallel Interleaved Inverter (PII) inverters for each switching cycle. The PII includes two parallel units of two level three-phase PWM full bridge having multiple carrier waves with phase rotation analysed as single unit of three level inverter. PII improves the performance of drive while employing Space Vector Modulation (SVM) by reducing THD content by 14% for low modulation indices and improves up to 40% at high modulation indices. Ripple content is significantly reduced in line current for PII. Simulation and experimental results for PII for 5 hp induction motor are presented in this paper to validate low ripple current at output.
Keywords: PWM; three phase full bridge; SVM; parallel inverters; ripple content; induction motor.
New Approach of SOC Estimation Method for lithium-ion battery/Ultra-capacity Hybrid system Based on Multi-Model Strategy
by Qiuting Wang, We Qi
Abstract: The model precision of the lithium-ion battery and the computational complexity of state estimation procedure will not be satisfied at the same time. A new State of Charge(SOC) estimation method based on multi-model strategy (MMS) is proposed to ensure both the estimation accuracy and the real-time performance. Meanwhile, new modelling method and SOC estimation method for the battery energy storage system are presented. The main efforts of our work are, firstly, the hybrid system model is established based on multi-model strategy. Secondly, the model parameters are updated using extended Kalman filter(EKF) algorithm. Thirdly, the electric quantity of lithium-ion battery is estimated using Unscented Kalman filter(UKF) algorithm. The experiments were conducted under dynamic working condition and the NEDC working condition. The results indicate that the SOC estimation accuracy based on MMS is better than that without the strategy.
Keywords: lithium-ion battery; SOC estimation; multi-model strategy; Joint Kalman filtering algorithm; NEDC.
Phase locked loop Parameterization in AC/DC Interconnected System for a multi-source AGC system under Open market Environment
by Debdeep Saha, Lalit Chandra Saikia
Abstract: This article emphasizes on deregulated AGC of a realistic multi-machine gas thermal plant with dish-Stirling solar-thermal (DSTS) as additional power generation sources in each control Area by taking into accounts of AC/DC with phase locked loop dynamics (PLL). Eigenvalue analysis confirms the steadiness of the reasonable power system with various interconnections such as AC, AC/DC link and AC/DC with PLL dynamics. A series form of proportional-integral-derivative (PID) namely proportional gain cascaded with integral and double-derivative (PI+DD+) controller is employed as secondary controller in each control areas for robust AGC to carry out market transactions under deregulated environment. Exploring the system with different type of interconnections infer that proper tuning of PLL function parameters may synchronize the grid better than without employing PLL. The performance of PI+DD+ controller along with optimum PLL gains commensurate with wide variations in governor, turbine, fuel and compressor discharge time constant of gas turbine plant.
Keywords: Automatic generation control ; dish-Stirling solar thermal ; deregulated ; Eigen value; phase locked loop; series controller.
Development and Implementation of a Voltage Harmonic Elimination Method for the Single-Phase Inverter Operating with Nonlinear Load
by Bogdan Proca, Mihai Comanescu
Abstract: Single-phase inverters are widely used in power conversion systems. When operating with linear loads, these inverters produce regulated output voltages that are quasi-sinusoidal. However, when feeding nonlinear loads, these absorb currents that are non-sinusoidal (distorted) and the inverters output voltage deteriorates it contains high levels of harmonics. This paper presents a control method that reduces the harmonic content of the output voltage and improves the total harmonic distortion (THD). The control strategy is based on selective harmonic elimination the method eliminates some of the low order harmonics of the output voltage using feedback. The proposed method reduces the distortion in the output voltage and improves the voltage THD. The method uses a voltage controller followed by a current controller both are implemented in the stationary reference frame. The voltage controller regulates the fundamental and eliminates certain harmonics using a modulation-demodulation technique. In the paper, the 3rd, 5th and 7th harmonics are eliminated. However, the scheme can be expanded to eliminate more higher-order harmonics. It is shown that the control proposed significantly reduces the Total Harmonic Distortion (THD) of the inverters output voltage, from 5.8% (at full load, uncompensated) to 1.64% (at full load, with compensation). The method proposed is directly applicable for industrial single-phase inverters and is validated by simulations and experimental tests.
Keywords: single-phase inverter; total harmonic distortion; harmonic elimination; sliding mode current control.
Performance Investigation of a Transistor Clamped H-Bridge Inverter Based Dynamic Voltage Restorer for Mitigating Various Power Quality Problems.
by Humeera Altaf, Abdul Hamid Bhat
Abstract: This paper presents design and analysis of dynamic voltage restorer (DVR) employing five-level Transistor Clamped H-Bridge (TCHB) inverter that increases the applicability of DVR to medium voltage networks. TCHB inverter is a newly developed topology of multilevel inverters (MLIs) which uses lesser number of components as compared to other topologies. Synchronous Reference Frame Theory (SRFT) based control algorithm is used for implementation of proposed DVR. The compensation capability of proposed DVR is tested for various voltage related power quality problems like sag, swell, harmonics, imbalance and their combinations through MATLAB/Simulink software and the simulation results are verified experimentally by using Digital Real Time Simulator.
Keywords: Dynamic Voltage Restorer (DVR); Multilevel inverter (MLI);Transistor Clamped H-Bridge inverter (TCHB); Medium voltage application; Power quality problems.
A Novel Hybrid Discontinuous PWM Algorithm for 3L-NPC Inverter
by Li-ping ZHONG
Abstract: Wider linear modulation range, less switching loss and simplicity are the goals pursued by various modulation methods of multilevel inverters. This paper proposes a new hybrid discontinuous pulsewidth modulation (HDPWM) strategy for 3L-NPC inverter that can achieve the above goals to a certain extent. According to the position of the reference voltage vector and the actual situation of the neutral point voltage, different control modes and clamping types are selected. The neutral point voltage is controlled by DPWM strategy, which can not only greatly reduce the switch loss, but also maintain the balance of the neutral point voltage and expand the linear modulation range. The implementation of the algorithm combines the advantages of carrier-based PWM (CBPWM) and space vector PWM (SVPWM). There is no need to select the nearest three vectors (NTV) and calculate their dwell time. Only the reference voltage needs to be modified according to the control requirements, and then by comparing the modified reference voltage with the carrier, the driver pulse required by the switching devices can be generated. Compared with the existing PWM methods, it is more simple and easy to implement. Experimental results results verify the validity of the method.
Keywords: Hybrid discontinuous pulsewidth modulation; space vector pulsewidth modulation; clamping type; neutral point voltage balancing; output level sequency type.
Optimum Regulation of THD Profile in Multilevel Inverter Using Parameter-less AI Technique for Electrical Vehicle Application
by KAUSHAL BHATT, Sandeep Chakravorty
Abstract: This article proposes investigation on harmonic profile improvement using a novel fitness function in the multi phase multilevel inverter. For the proposed study in this paper, three-phase, seven-level cascaded H-bridge (CHB) multilevel inverter (MLI) is considered. Modulation of the stepped waveform output of the MLI is done using selective harmonic elimination (SHE) method. Many algorithms are proposed for solving the set of nonlinear transcendental trigonometric equations for SHE methods. Teaching learning based optimization (TLBO) algorithm is a parameter less optimization technique. Due to the lack of controlling parameters, the proposed algorithm is most robust among the family of artificial intelligence (AI) techniques. In this paper, an investigation is carried out on a novel fitness function proposed for controlling total harmonic distortion (THD) for the proposed inverter. It is observed that the proposed fitness function improves THD profile below IEEE standards. It is also observed that THD profile obtained through this method is far better than THD profile obtained through various proposed methods so far. The results of THD profile from the MATLAB Simulink simulations are verified experimentally using 7-level 3-phase hardware controlled by Arduino MEGA 2560 low cost controller.
Keywords: Multilevel inverter; artificial intelligent algorithm; teaching learning based optimization technique; selective harmonic elimination; total harmonic distortion.
BSA Based Analysis of Three-Phase Standalone Asynchronous Generator Using Two-Port Network
by Sambaran Ray, Himadri S. Chatterjee, Dipanjan Samajpati, Sankar N. Mahato, Nirmal K. Roy
Abstract: This paper presents the analysis of steady-state behavior of a three-phase standalone asynchronous generator (SAG) supplying three-phase load based on binary search algorithm (BSA). The concept of two-port network is used to model the generator system along with the load. Two model equations developed from the modeling of SAG are solved by BSA to get the frequency (a) and magnetizing reactance (Xm). The performance equations are formed with the help of frequency, magnetizing reactance and magnetizing characteristics of the machine to understand the steady-state behavior of SAG. The waveforms of generated voltages and currents in the generator are also investigated and their corresponding harmonic contents are recorded. The simulated results are verified through the experimentation and it shows that the experimental results closely agree with the simulated results. The BSA based analysis of three-phase SAG is easier, more efficient and accurate.
Keywords: Binary search algorithm; self-excited induction generator; standalone asynchronous generator; steady-state performance; two-port network; waveform.
Advanced Predictive Flux Control For B6 Inverter Fed Induction Motor Drives
by Wiem ZOUARI, Imen NOUIRA, Bassem EL BADSI
Abstract: Predictive torque control (PTC) strategy has already been introduced to cope with the problem of the torque and flux ripples of AC machines. However, the simultaneous control of the electromagnetic torque and the stator flux magnitude in conventional PTC scheme is not very trivial. Alternatively, the predictive flux control (PFC) strategy has been suggested based on removing the weighting factor from the implementation scheme. This paper proposes the development of two new phase-clamping (PC) PFC schemes, founded on the basis of modulating two legs of the two-level inverter fed induction motor (IM). Both PC-PFC strategies allow the clamping of one stator phase to the positive or negative terminals of the dc-bus voltage during each 60
Keywords: Predictive Flux Control; Induction Motor; Phase-Clamping; Duty-Cycle Optimization; Switching Frequency; Harmonic Distortion; flux and Torque ripple.
Design, Implementation and Performance Evaluation of Different Digital Control Techniques for Current Controlled DC-DC Buck Converter
by Dipen M. Vachhani, Rajesh Arya, Uma Rathore Bhatt
Abstract: The paper presents modelling, control architecture, analysis and design of digital compensators for single feedback-loop voltage mode control as well as two feedback-loop average current mode control and peak current mode control of current controlled DC-DC Buck converter operating in continuous conduction mode with output current as control variable. The compensators are derived using digital redesign approach, simulated on MATLAB, implemented as control algorithms on Texas Instruments 32-bit TMS320F28069M microcontroller platform, and experimentally validated by testing with a laboratory prototype of current controlled Buck converter. Simulation and experimental results are discussed, compared and evaluated for converter output current performance in tracking reference current signal as well as in regulation against input voltage and load disturbances. Salient features of each control technique are identified and described to determine its suitability in applications of DC-DC converters requiring controlled output current.
Keywords: Digital control techniques; digital voltage mode control; digital average current mode control; digital peak current mode control; current controlled DC-DC Buck converter; continuous conduction mode; digital redesign; digital compensators; type-2 compensator; 2p2z compensator.
Power quality improvement using multilevel inverter-based active filter for medium-voltage high-power distribution system: a comprehensive review
by Soumyadeep Ray, Nitin Gupta, R.A. Gupta
Abstract: Medium-voltage distribution system faces great challenges as the number of high-power loads is increasing which inject nonlinearity into the grid. On the other side, sinusoidal and uninterrupted voltage and current waveform at rated frequency is highly desirable at the consumer end. Two-level inverter-based active filter is facing great challenges in medium-voltage distribution network due to the use of high rating switching devices and use of a line-frequency transformer. Multilevel inverter (MLI) posses a great solution in such scenario as it generates higher voltage output with lower rating switching devices. MLI technology is widely accepted in medium to high-voltage industrial applications. Therefore, this paper presents a widespread review on MLI-based active filter (AF) by assessing its potential to replace two-level inverter-based AF in medium-voltage distribution sector. Different possible configurations, control techniques and their different applications are reviewed comprehensively. A list of 78 research papers is decisively examined and is appended for quick reference.
Keywords: active filter; multilevel inverter; power quality; control technique.
Decoupled control of quasi-Z source inverter for decentralised renewable energy application
by Arvind Yadav, Vinay Kumar Deolia, Sanjay Agrawal
Abstract: Decentralised renewable energy (DRE) systems are acclaimed worldwide as it serves as an alternate to the grid extension to remote areas having no access to electricity. The impedance source inverter (ZSI) has overcome the limitations of conventional voltage source inverter (VSI), have buck/boost capabilities. This paper presents an alternative approach of obtaining shoot-through pulses in a quasi-Z source inverter (qZSI) along with decoupled control by keeping dc link voltage constant instead of capacitor voltage. Dynamics of the system are investigated by deriving small signal model, the proposed control methodology uses separate controllers to handle dc and ac side dynamics to get desired shoot-through pulse and modulation index without any overlap, performance of the control methodology is verified under normal condition and under disturbances. Results are obtained using PSIM which verifies the control methodology and depicts the ability of disturbance rejection and effective reference tracking without compromising stability issues.
Keywords: DRE system; photovoltaic; PV module; quasi-Z source inverter; qZSI; shoot-through; ST; decoupled control.
An improved low switching frequency modulation scheme for a symmetric CCS-multilevel inverter
by A. Rakesh Kumar, T. Deepa
Abstract: In this paper, a low switching frequency modulation scheme is proposed for the symmetrical configuration of cross-connected sources-based multilevel inverter (CCS-MLI). The proposed scheme, named modified nearest level modulation (mNLM), is an improvement over the conventional nearest level modulation (NLM) scheme for MLI. The implementation of mNLM, compared to the NLM, has shown a considerable reduction in total harmonic distortion (THD) at the ac output of MLI. The mNLM works through variations in the switching angles of the MLI. By suitably varying the switching angles, the THD content is brought to the minimum. An algorithm for the same is also proposed which enables the mNLM to be implemented on other MLI topologies. Simulation is carried out in MATLAB/Simulink environment and it is also extended to a hardware prototype. The effectiveness of the proposed modulation scheme is also seen in terms of improved inverter parameters such as rms voltage, rms current and generated power.
Keywords: multilevel inverter; MLI; pulse width modulation; inverter modulation scheme; total harmonic distortion; THD; nearest level modulation; NLM; cross-connected sources-based inverter.
A novel modelling and control strategy for a full-wave ZCS quasi-resonant boost converter for a PV-based battery charging system
by Reza Sabzehgar, Rami Ghali
Abstract: In this paper, a novel modelling and control strategy is proposed for a DC-DC quasi-resonant boost converter utilised in a photovoltaic-based (PV-based) battery charging system. The MOSFET switch of the boost converter is operated at zero current using a resonant tank, providing soft-switching functionality, to reduce the switching losses experienced by conventional boost converters. The principles of operation of the utilised converter are analysed in detail and a characteristic function representing the model of quasi-resonant converter circuit is derived. This model is then used to design and implement a frequency control technique, which will maintain a constant DC voltage at the output stage of the converter to charge the battery. Simulation studies are conducted using MATLAB Simscape toolbox to evaluate the performance of the proposed controller. Simulation results validate the soft-switching functionality of the converter and its ability to reach and maintain the desired output voltage for charging a battery load in the presence of varying input voltage generated by a PV system with intermittent nature.
Keywords: zero current switching; ZCS; full-wave quasi-resonant converter; soft-switching; boost converter; photovoltaic system; photovoltaic; PV; battery charger; control; power electronics converter.
Development of generalised and optimum structures of a multilevel inverter using switched capacitor technique for renewable energy conversion systems
by Tapas Roy, Neha Aarzoo, Abhijit Dasgupta
Abstract: A novel multilevel inverter topology is presented in this paper. The presented topology is based on the concept of switched capacitor technique. The important features of proposed topology are that it uses symmetrical DC power sources to generate different output voltage levels, it has self-voltage balancing capability to balance the capacitor voltages and it can boost the input voltages to desire voltage levels. Further, optimal structure of proposed topology is developed from general structure of presented topology. The proposed topology requires less components such as switching devices, DC power supplies, capacitors, diodes to generate specific number of output voltage levels in comparison with other topologies. Phase disposition pulse width modulation (PDPWM) scheme is employed for switching the proposed inverter. Extensive simulation and experimental studies of 17-level proposed inverter structure prove its merits and effectiveness. The proposed topology can be applied in renewable energy conversion systems such as photovoltaic systems to generate boosted multilevel output voltage from low voltage DC renewable sources.
Keywords: boosting factor; multilevel inverter; switched capacitors; voltage level.
Modified whale optimisation-based optimal location of UPQC in distribution system for power quality improvement
by Kaladhar Gaddala, P. Sangameswara Raju
Abstract: A number of researchers has studied the unified power quality conditioner (UPQC) as an eventual solution to enhance the power quality in the electrical distribution system. However, due to the high cost, the location or position of UPQC in distribution system needs to be decided with immense care and must preferably be solved as the optimisation problem. This paper presents a power quality improvement model based on a new modified optimisation algorithm, namely worst solution linked whale optimisation algorithm update (WS-WU). The proposed algorithm finds the optimal location of the UPQC device concerning the power system losses, UPQC cost, and voltage stability index as well. The experimentation is carried out in both IEEE 33 and 69 bus systems. The performance of the proposed model is compared over other conventional methods in terms of performance and convergence analysis, and proves the superiority of the proposed method.
Keywords: optimal location; unified power quality conditioner; UPQC; power quality; power loss; voltage stability index; WOA nomenclature.
Special Issue on: Smart Computational Intelligence-based Intelligent Control of Power Electronics Devices and its Application in Smartgrids
A Modified Type-2 Neuro-fuzzy SVM based inverter fed IM drive
by G. Srinivas, G. Durga Sukumar
Abstract: In indirect vector control, the conventional speed and current controllers operate satisfactorily when the operating point is constant. But the operating point is always dynamic, the reference voltages obtained in a closed-loop system feeding to the inverter contains more harmonics. Due to this, the pulses which are going to produce are uneven. Which intern produces the inverter output voltages which are more harmonics contained. In order to produce a better output voltage from the inverter, this paper presents the neuro-fuzzy type-2 space vector modulation (NFT2) technique. Performance comparison of the inverter is done with conventional space vector modulation(SVM) and neuro-fuzzy type- 1(NFT1) system using MatLab simulation & experimental validation. The performance parameters of the induction motor based on current, torque, and speed with neuro-fuzzy type-2 space vector modulation is compared with conventional and type-1neuro fuzzy SVM. The % THD of inverter output voltages are also compared. The experimental validation of a DSpace-1104 is used to analyze the performance of the induction motor which is obtained by the simulation. The experimental validations are carried out considering 2HP Induction motor in the lab.
Keywords: indirect vector control; Neuro-Fuzzy type-2 controller (NFT2); Neuro-Fuzzy type-1 Controller (NFT1); Space vector modulation (SVM); Induction motor (IM); Third harmonic distortion (THD).
Genetic Algorithm and Anti-predatory Swarm Optimization-based Solutions for Selective Harmonic Elimination in Multilevel Inverters
by YATINDRA GOPAL, Kaibalya Panda, Dinesh Birla
Abstract: The elimination of harmonics and need of a large number of switches in multilevel inverters (MLIs) have been the focus of research from the last few decades. In this paper work using genetic algorithm (GA) and anti-predatory particle swarm optimization (APSO) is described to minimize harmonics in MLIs, which is a complex optimization problem involving non-linear transcendental equation. Switching angles are calculated for different modulation indices by proposed algorithms considering minimum THD and best optimum results are taken for controlling the operation of MLIs. MATLAB/SIMULINK software is used for simulation of two topology i.e. 7-level cascaded H- cascaded H-bridge multilevel inverter (CHB MLI) and a 7-level reduced switch multilevel inverter (RS MLI) with an equal number of DC sources. Theoretical results are verified by developing a prototype of both the MLIs and are compared. FFT analysis shows that used structure effectively eliminates specific lower order harmonics and obtained output voltage contains low THD with reduced number of switches thereby reducing the switching loss to a great extent.
Keywords: Anti-predatory PSO; Multilevel inverter; Cascaded H-bridge multilevel inverter; Genetic algorithm; Reduced switch multilevel inverter; Selected harmonic elimination; Total harmonic distortion; Modulation index.
Battery and Super Capacitor Powered Energy Management Scheme for EV/HEV using Fuzzy Logic Controller and PID Controller
by Nitesh Tiwari, Shekhar Yadav, Sabha Raj Arya
Abstract: The main aim of this paper is to propose a scheme for the internal and external energy management of the EV/HEV and try to analyse the performance of the EV/HEV in terms of speed tracking and output power. This paper is focused on to achieve the maximum efficiency with the minimum cost so their proposed different types of the DC-DC converter with their different controlled technique. Due to the analysis purpose, there are using PID and FLC controlled technique for designing the motor driver. Here a parallel connection of supercapacitor (followed by BBBC) and battery bank (followed by UBBC) is proposed for reducing the stress on the battery bank and getting the optimized energy at every point. Now Simulink software named MATLAB and Simulink is used for verifying our results.
Keywords: Electric vehicle (EV); hybrid electric vehicle (HEV); unidirectional buck-boost converter (UBBC); bidirectional buck-boost converter (BBBC); proportional integral derivative (PID); the fuzzy logic controller (FLC); battery; supercapacitor (SC).
Application of Artificial Intelligence techniques in the operation of Neutral-Point Clamped Rectifier under Perturbed Conditions
by Deepak Sharma
Abstract: This paper will demonstrate the viability of Neural Network algorithm for solving power quality rnproblems in three- phase Neutral-Point Clamped Converter. A neural network algorithm is proposed here for the better performance of the Converter under perturbed conditions. The neural network algorithm modifies conventional space vector pulse width modulation algorithm. The proposed algorithm generates ideal switching sequences for the converter by developing best path for the reference vector in the hexagon of the space vector. The data set required to train the neural network was collected from well tuned PI controlled model. In this work, the implementation of neural network is described and simulation results are presented using MATLAB/Simulink software. Simulation results proves fast minimizing the potential difference at the clamped bus of the converter with minimum switching losses and excellent performance of converter in terms of unity power factor, better total harmonic distortion at the source side.
Keywords: Neural Network (NN); Back Propagation Neural Network (BPN); Modified Space Vector Pulse Width Modulation; Neutral-Point Clamped Converter (NPC); Minimizing Potential Difference ; Harmonics eliminations.
Performance assessment of PV integrated Model Predictive Controller based hybrid filter for Power Quality Improvement
by Soumya Ranjan Das, Prakash K. Ray, Debani P. Mishra, Himansu Das
Abstract: The role of predictive controller in recent days is found to be vital in controlling the voltage source inverter (VSI) of the active power filters (APF). It is realized that, the improvement of power quality (PQ) in the utility network using non-linear loads, with integration of renewable sources, has become an open challenge to the researchers. This paper proposes an integration of Photovoltaic (PV) system with three phase power distribution system using series hybrid filter (SEHF). The objective of the paper is to reduce the harmonic components and dc link control of VSI for improving the PQ and simultaneously provide uninterrupted supply to the load by compensating the reactive power. In this work, the Fuzzy Logic Controller (FLC) is employed for maximum power point tracking (MPPT) in PV system and a model predictive controller with robust extended complex Kalman filter (MPC-RECKF) technique is applied for calculating the fundamental components from distorted value in SEHF. The results obtained using the proposed MPC-RECKF is compared and analysed with traditional controllers in MATLAB/SIMULINK environment.
Keywords: Model predictive control; Photovoltaic array; robust extended complex Kalman filter; Series hybrid filters.
Virtual Inertia Support in the microgrid, its research challenges and its technology potentials in recent years
by Neethu Elizabeth Michael, Shazia Hasan
Abstract: This paper epitomizes the various aspects of virtual inertia using energy storage systems for satisfactory regulation against uncertain frequency and voltage fluctuations. Since the power system switches from a generator-dominated system to an inverter-dominated system it results in the culmination of lack of inertia due to the massive penetration of renewable energy resources. This eventually leads to problems of frequency stability and power quality. The principle of virtual inertia, which emulates the operation of the synchronous generator by providing the power system with inertia remotely, was a topic of research from 2007 and is now gaining recognition. Software simulations and hardware implementation will open the way for a thorough investigation of the technology in the future. Furthermore, it also addresses the different types of virtual inertia topologies, application with renewable energy sources, evaluation for ancillary services, potential opportunities, risks posed, and future research directions.
Keywords: virtual inertia; renewable energy sources; frequency stability; microgrid; energy storage systems; power quality.
Implementation of Energy Management in Hybrid Renewable Energy Island Systems using Soft Computing Techniques
by Srishti , Prerna Gaur
Abstract: Microgrid based EMS (Energy Management System) is designed and implemented in this paper to manage the energy balance between renewable resources and the load i.e. supply-demand balance of energy. Wind energy generation is done through PMSG using the method of vector control of synchronous generator. Further, the investigation of modelling and control of SOC (State of Charge)-Based BMS (Battery Management System) in microgrid for autonomous/islanding mode is presented in the form of aggregated battery model. Since BMS is critical in maintaining the optimum performance of battery and hence, a battery system has been designed in present work. The results of the comparative study of the proposed MPPT techniques i.e. CSA, ANN, FLC with conventional P&O using MATLAB/SIMULINK in terms of accuracy, electric power efficiency, duty cycle, D.C. link voltages, load power of proposed techniques are presented in the present work. The working of the proposed EMS for hybrid PV-Wind-Battery system is verified through simulation results using various control algorithms.
Keywords: MPPT; PES; WECS; BMS; EMS.
Analysis of Tilt Integral Derivative Controller Based Automatic Load Frequency Control of Multi-Area Multi-Source System
by Manmadha Kumar Boddepalli, Prema Kumar Navuri
Abstract: In this paper, a new tilt integral derivative (TID) controller is implemented for a multi-area multi-source power system. The parameters of the TID controller are optimized using a firefly algorithm (FA) and it is employed with integral time multiplied absolute error (ITAE) as an objective function. Initially, three area nine-unit power system is designed in MATLAB/SIMULINK environment. The superiority of the proposed controller is established by comparing simulation results ZieglerNichols (ZN) based PID and FA based PID controllers for the same designed model. The simulation results reveal that frequency responses and tie-line power deviations are enhanced with FA based TID when compared to ZN and FA based PID controller. Finally, the effectiveness of the proposed controller is examined by doing robust analysis under varied system parameters.
Keywords: Ziegler–Nichols (ZN) method; Firefly Algorithm (FA); Tilt Integral Derivative (TID) controller; Integral Time multiplied Absolute Error (ITAE).