Forthcoming articles


International Journal of Power Electronics


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International Journal of Power Electronics (72 papers in press)


Regular Issues


  • Analysis and Modeling of the Role of Temperature in the Static Forward Characteristics of an IGBT   Order a copy of this article
    by Boussouar Layachi, Morel Herve, Bruno Allard, Buttay Cyril 
    Abstract: To effectively simulate the electrical characteristics of an IGBT, it is necessary to have a good model for applications operating in a wide range of temperatures. A new model of the on-state forward characteristics of an IGBT was developed and validated in MAST language in static mode using the SABER simulator. A particular attention was given to temperature dependence, based on the physical analysis of semiconductor device regions and the use of local and physic-based relations. The model was compared to experimental results and to the standard Hefner model. The validation of the model shows a good agreement between measurements and simulation. A clear improvement in the accuracy of the onstate characteristic temperature dependence with the was obtained.
    Keywords: IGBT; MOSFET; Modeling; Power semiconductor devises; Power transistors and Simulation.

  • Control strategy for single phase cascaded nine level inverter with sinusoidal pulse width modulation using LPC 1769 ARM Cortex-M3 microcontroller   Order a copy of this article
    by Biju Kunjuraman Nair, Rijil Ramchand 
    Abstract: The output voltage waveform of a conventional two level inverter is poor due to the presence of harmonics and hence produces power loss which reduces the efficiency of the system. The multilevel inverter is used to improve the voltage waveform by reducing the harmonics, as it synthesizes the output voltage waveform from several levels of input voltage. Thus as the number of voltage levels of multilevel inverter is increased, the harmonics are reduced and hence losses are minimized significantly. The paper describes the implementation of a single phase cascaded nine level inverter with multi carrier based sinusoidal pulse width modulation technique using a low power advanced microcontroller. The simulation of single phase cascaded nine level inverter is done with multicarrier sine PWM technique using MATLAB SIMULINK. Hardware implementation is done for the multicarrier sine PWM single phase nine level inverter using LPC 1769 ARM Cortex-M3 microcontroller. The results of both simulation and hardware implementation are analysed.
    Keywords: multilevel inverter; sinusoidal PWM; level shifted sine PWM; cascaded H-bridge inverter; harmonics.

  • Grid connected wind Energy Conversion System Based on Finite-Set Model Predictive Control   Order a copy of this article
    by Ahmed Rashwan, Tomonobu Senjyu, Mahmoud A.Sayed, Youssef Mobarak1, Gaber Shabib 
    Abstract: Predictive control (PC) theory has been successfully used in a numerous industrial application. In this paper, controlling the torque of a squirrel cage induction generator (SCIG) based on maximum power point tracing (MPPT) in a grid connected wind turbine is presented. Improve the quality of the wind energy conversion system by reducing torque ripples in the SCIG is verified. A decoupled and rapid tracking performance of the reactive power injected to the grid is observed. Online optimization and the included system nonlinearities and restrictions of the proposed algorithm lead to high degree of reliability using only one PI controller. The proposed technique leads to high robustness of the system against the nature of the wind energy fluctuations. DC link voltage was kept constant during the dynamics of the systems. The overall simulation models have been implemented using MATLAB/SIMULINK software.
    Keywords: Predictive control; squirrel cage induction generator; torque-power control; wind energy.

  • A Comparative Analysis of Artificial Neural Network and Synchronous detection Controller to improve power quality in Single Phase System   Order a copy of this article
    by PRATAP PUHAN, Pravat Ray, Gayadhar Panda 
    Abstract: This paper explores the effectiveness of neural network control technique to extract the source current references from the distorted waveform of load current. Artificial Neural Network control technique working under balanced Single phase voltage source conditions is implemented on the shunt active power filter along with unipolar pulse width modulation (U-PWM) , Proportional integral (PI) controller is used for generation of gate signal and regulation of direct current (DC) voltage of the voltage source inverter. The U-PWM technique is based on simultaneously comparing a triangular high frequency carrier signal with a slow-varying regulation signal. A comparative analysis is made between the results obtained in this technique and Synchronous detection technique, It is found that developed neural network controller is very much effective to enhance the power quality in a single phase system by minimizing the Toatal Harmonic Distortion to a level below IEEE-519. To validate the effectiveness of neural network controller , Experimental results are provided using d-space1104 which gives very encouraging results.
    Keywords: Active power filter; Synchronous detection technique; Neural network Technique; U-PWM; d-SPACE1104.

  • Protecting Micro-Grids by A SVM Based Pattern Recognised Islanding Detection Approach and Optimal Placement of PID-FC Controller Using Hybrid ABC-APSO Algorithm   Order a copy of this article
    by Gundala Srinivasa Rao, Gattu Keseva Rao 
    Abstract: The penetration of Distributed Generations (DG) ensures the increase of demand for consistent, reasonable and spotless electricity facing with some design and operational challenges such as islanding and fault current. Several active and passive methods have been suggested in the past to detect islanding with the placement of fault current limiter (FCL) to reduce fault current. As they suffer from the large non-detection zone and a high cost due to the impedance of FCL. In order to overcome such issues we propose a novel Proportional-Integral-Derivative Fault Current Controller (PID-FCC) which is placed optimally by using a Hybrid Artificial Bee Colony with Accelerated Particle Swarm Optimization algorithm (ABC-APSO) to limit the fault current and a SVM based pattern recognising approach for islanding detection in micro-grids. The PID selects the optimal size of the FCC by means of its tuned parameters. The Experimental results shows that our proposed method optimally place the PID-FCC with reduced size and detects islanding with high accuracy.
    Keywords: Islanding; Support Vector Machine (SVM); Fault current controller (FCC); Hybrid Artificial Bee Colony with Accelerated Particle Swarm Optimization (ABC-APSO) Algorithm.

  • Analysis, Design and Simulation of Three-Phase Active Power Filter with Series Capacitor Topology for Current Harmonic Compensation   Order a copy of this article
    by Nirav Pandya, Dr P. N. Tekwani, Vinod Patel 
    Abstract: This paper presents an active power filter with series capacitor topology for the application of harmonic current compensation in case of any three-phase nonlinear load. The proposed system consists of an LC passive filter connected in series with three-phase active power filter. The LC passive filter is tuned to 13th order harmonic frequency. The major portion of harmonic current generated by the nonlinear load is absorbs by the passive filter and active filter is used to improve the filtering performance of the system by providing compensation for the host of other higher order harmonics. The requirement of dc-link voltage of the active filter is very less in the presented scheme as compared to that of the standard voltage source type active power filter without any other passive filtering component. This resulted in significant reduction of cost and the power rating of the active power filter. Systematic analysis and design of various components of the proposed active filter are presented in this paper. The simulation analysis is carried out by using instantaneous active and reactive power (P-Q) theory. The simulation results verify the circuit configuration and filtering performance of the proposed active power filter with series capacitor topology. The proposed system can be an attractive solution for effective harmonic filtering.
    Keywords: Active Power Filter; Active and Reactive Power; Analysis and Design; Passive Filter; Series Capacitor Topology; Total Harmonic Distortion.

  • Analysis, Design and Experimentation with a Four-Element Resonant Immittance Converter Topology as a Constant-Current Power Supply   Order a copy of this article
    by Saylee Koli, Mangesh Borage, Sunil Tiwari 
    Abstract: Resonant immitance converters (RICs) belong to a newly identified family of the resonant converters exhibiting unique characteristics with the help of which a voltage source can be converted to a current source and vice versa. Therefore, RICs are suitable for applications that demand a constant-current (CC) power supply. A fourth-order T-type RIC topology, T5, is analyzed in this paper. Detailed steady-state analysis using fundamental frequency ac analysis is presented providing a detailed insight into the converter characteristics. Analytical results have been used to derive closed-form expressions for calculating the component values and ratings following a converter optimization. The correctness of analysis is validated by developing and testing a 500 W, 109 kHz laboratory prototype converter.
    Keywords: Resonant power conversion; dc-dc converters; resonant immittance converters; constant-current.

  • Analysis and Modelling of wireless battery charger   Order a copy of this article
    Abstract: Wireless battery charger system is considered as a multi parameter and multi constrained nonlinear system. The main objective of this work is to analyse the several blocks of the contactless charger and to refer to metaheuristic methods in performance optimization regarding to the impact of parameter selection during designing in order to find the best global solution. An improved PSO algorithm with a selection strategy based on the use of Euclidean distance method between two individuals chosen randomly to form the population is proposed. The convergence characteristic of the adopted algorithm has been introduced. Simulation results show that the improved method may instead the limit of the local optimum solution and get the global optimum solution faster. A robust optimizer algorithm called GODLIKE is involved to solve optimization problems and to take into account the interactions between design parameters on charger system performance. A perturbation-and-observation-based tracking method is developed through an efficient sensing system to act on the misalignment issue and the car position.
    Keywords: Wireless battery charger; Coreless transformer; PSO; GODLIKE; perturb & observ.

  • Design and Implementation of an Improved Tri-state Boost Converter with Optimal Type-III Controller   Order a copy of this article
    by Niraj Rana, ARNAB GHOSH, Subrata Banerjee 
    Abstract: Over the years, DC-DC switched mode power converters (SMPC) are playing important role for technological advancement. Good dynamic performance is the one of the important criterion for designing the closed-loop converters. But some DC-DC switching converters (such as Buck-Boost, Boost, Flyback etc.) have non-minimum phase problem due to a right-half plane (RHP) zero in their small-signal control-to-output transfer function. So, the converters experience poor dynamic performance due to presence of non-minimum phase problem. Tri-state Boost converter with PID controller can solve the non-minimum phase problem easily, but the dynamic response will not be satisfactory. In this work, an improved Tri-state Boost converter with gravitational search algorithm (GSA) based optimized Type-III controller is designed & fabricated in the laboratory. The comparison between closed-loop performances of conventional Boost converter and Tri-state Boost converter with classical (k-factor method) and optimal Type-III controllers have been presented in this work. The experimental results prove the efficacy of optimized controller for the proposed converters. The proposed control scheme based on optimized Type-III controller for Tri-state Boost converter is not found in any literature and is newly introduced in this paper.
    Keywords: Switched-Mode Power Converter; Tri-state Boost Converter; Non-Minimum Phase System; Gravitational Search Algorithm (GSA); Optimal Type-III Controller.

  • Loss Minimization of Trapezoidal BLDCM Drive by UPFC based Optimal Switched Inverter   Order a copy of this article
    by Subhendu Bikash Santra 
    Abstract: This paper presents harmonics behaviour of phase current waveform of trapezoidal BLDC Motor Drive in 120
    Keywords: Brushless DC (BLDC) motor;UPFC (Unified Power Flow Controller);Position sensor less control;loss minimization;Selective Harmonics Elimination (SHE).

  • Active Power Filter using a Novel Adaptive Fuzzy Hysteresis Current Controller   Order a copy of this article
    by Karuppanan PitchaiVijaya 
    Abstract: This paper presents a shunt Active Power Filter (APF) for mitigating harmonics and reactive-power compensation in the distribution system. The compensation process is based on Modified-Synchronous Reference Frame (Modified-SRF) control strategy that is different from conventional-SRF method. A simple and efficient unit vector calculation is used in the proposed Modified-SRF in lieu of phase locked loop for vector orientation that cancels the presence of harmonics and notches in the distribution system. The shunt active power filter is implemented with Voltage Source Inverter (VSI) and its switching pulses are generated through a novel Adaptive-Fuzzy-Hysteresis Current Controller (HCC). The adaptive-fuzzy-HCC calculates the hysteresis bandwidth effectively with the help of Fuzzy Logic Controller (FLC). This method reduces the switching power losses and improves the VSI performances for active filter substantially compared to fixed-HCC and adaptive-HCC. The shunt active filter system is validated through extensive simulation under both steady-state and transient conditions with different non-linear loads. Comparative assessments of conventional-SRF and modified-SRF reference current generator methods are carried out.
    Keywords: Modified-Synchronous Reference Frame; Active Power Filters; Adaptive-Fuzzy-Hysteresis Current Controller; Harmonics.

  • Line Frequency Sine Modulation - A Novel Modulation Scheme for Multilevel Inverters and Its Application Towards Enhanced Illumination of Incandescent Bulb   Order a copy of this article
    by Rakesh Kumar, Deepa Thangavelusamy 
    Abstract: Several modulation schemes are proposed and implemented in multilevel inverters (MLIs) to reduce the total harmonic distortion (THD) content at its output. These schemes may be broadly classified in terms of switching frequencies into fundamental switching frequency (FSF) modulation schemes and high switching frequency (HSF) modulation schemes. This paper proposes a new approach towards employing an FSF modulation scheme to reduce the THD at the output of an MLI. It involves designing two matrices coined as inverter switching characteristics (ISC) matrix and inverter operating modes (IOM) matrix. The switching frequency depends on the line frequency of the MLI output. The presented modulation scheme is implemented in an asymmetrical topology MLI. An experimental setup is also carried for a maximum power rating of 200W. The experimental results show the proposed modulation scheme has improved the parameters of the inverters in terms of the output voltage, output current, THD content of voltage and current waveforms, output power and power factor. Thus the presented modulation control scheme is found to improve the performance of the inverter.
    Keywords: Multilevel Inverter; Topologies; Modulation Techniques; Total Harmonic Distortion.

  • A Simplified and Generalised SVPWM Method Including Over Modulation Zone for Seven Level Diode Clamped Inverter - FPGA Implementation   Order a copy of this article
    by Bogimi Sirisha 
    Abstract: This paper presents simplified and generalized SVPWM technique for a neutral point clamped multilevel inverter of any level. This modulation technique provides a simplistic strategy for transition between various modulation indexes with linear transfer characteristic which provides a general solution for over modulation zone. The proposed technique is based on 60ᵒ co-ordinate system with all the computational work is carried out on-line, generating the desired switching states and their sequences through simplified expressions without any additional storage requirement. This modulation technique combines the concept of reference vector modification and on duration modification during over modulation zones. The performance of the proposed technique is tested through FPGA spartan3A processor experimentally for seven level diode clamped inverter. The simulation and experimental results are validated at various modulation indexes and are in well agreement with each other.
    Keywords: FPGA; SVPWM; Neutral Point Clamped Inverter; modulation index .

  • Design and Implementation of a Speed Adaptive Flux Observer For The Induction Motor Using Sylvester Criterion   Order a copy of this article
    by Mihai Comanescu 
    Abstract: The paper presents the design and implementation of a flux and speed observer for the induction motor drive. The method employs an observer with linear feedback that yields the motor fluxes and also estimates the speed using an adaptive law. The convergence conditions are formulated based on Lyapunovs nonlinear stability theory. The gains of the observer are designed using Sylvester criterion. The method proposed is reasonably simple and yields a series of inequalities that provide insight into the design choices and stability margins of the observer. The paper shows that the observer is not globally stable however, with proper design of the adaptation gains, it can be made locally stable. The observer with the corresponding adaptive speed estimate does not perform during low speed regeneration - the speed estimate diverges; to solve this issue, the paper shows a modified adaptation law that yields a stable speed estimate.
    Keywords: induction motor control; flux estimation; speed estimation; rotor position estimation; Lyapunov stability theory; adaptive control; sensorless control.

  • Neural Network Based Three-Phase NPC Rectifier for DC Bus Capacitor Voltage Balancing Under Perturbed Mains Supply Conditions   Order a copy of this article
    by Deepak Sharma, Abdul Hamid Bhat, Aijaz Ahmad 
    Abstract: This paper presents an artificial neural network based modified space vector pulse width modulation control approach for better performance of three-phase Neutral-Point Clamped rectifier using optimised switching sequences.Use of optimised switching sequences even under ideal supply conditions, it is depicted that source side and load side parameters deviate from acceptable limits and a DC-bus capacitor voltage unbalance occurs. Under the influence of disturbed supply, source side and load side parameters deviate more beyond acceptable limits which causes a very large unbalance in DC bus capacitor voltages. This non-ideal performance of the converter is responsible for the deterioration of quality of source currents and a large stress on power semiconductor devices.The proposed control scheme employs a three-layer feed-forward neural networks at different stages for capacitor voltage balancing of a three-phase three-level neutral-point clamped converter with improved power quality. According to the supply conditions, the neural network varies the speed of the reference vector and forms a required trajectory while passing through the most effective regions of SVPWM hexagon. Proposed controller scheme is modeled in MATLAB/Simulink software. Simulation results show that the proposed implementation of neural-networks controller in three-Phase NPC converter displays better performance under ideal and disturbed mains conditions
    Keywords: Power Quality; Improved Power Quality Converters (IPQCs); Multilevel Converters; Harmonics Compensation; Unbalanced AC Mains; Disturbed AC mains.

  • Selective Harmonics Elimination for Three-Phase Seven-Level CHB Inverter Using Backtracking Search Algorithm (BSA)   Order a copy of this article
    by Sourabh Kundu, Arka Deb Burman, Santu Kumar Giri, Sarbani Mukherjee, Subrata Banerjee 
    Abstract: This paper introduces backtracking search algorithm (BSA) to solve the nonlinear transcendental equations to obtain triggering angles of a three phase seven-level cascaded H-bridge (CHB) inverter and also eliminates 5th and 7th order harmonics while satisfying the requested fundamental component. A comparative study has been made in terms of execution time, the statistical probability of achieving global minima, and a rank of convergence rate to establish the supremacy of the BSA optimization technique over other recognized methods such as genetic algorithm, bee algorithm, and particle swarm optimization techniques. Simulation and experimental results confirm the effectiveness and accuracy for obtaining precise switching instants that fruitfully satisfy the required output voltage quality.
    Keywords: backtracking search algorithm (BSA); bee algorithm (BA); cascaded H-bridge (CHB); genetic algorithm (GA); particle swarm algorithm (PSO); selective harmonic elimination pulse width modulation (SHE-PWM).

  • Analysis of 4HSiC Schottky Barrier Diode with a Comb-Shaped Field Plate   Order a copy of this article
    by Dongwoo Bae, Chungbu Jeong, Taewan Kim, Kwangsoo Kim 
    Abstract: In this study, we have proposed a comb-shaped field plate for use in a 4HSiC Schottky barrier diode; this field plate was expected to improve the electric field distribution in the device and provide a higher breakdown voltage than conventional field plate structures. The main principle of the proposed structure is to distribute the inner electric field in the blocking mode through a stepped oxide structure formed by several trenches. The proposed structure was optimized using a simulation, and we fabricated and measured a number of devices to evaluate the performance of the proposed structure. The proposed devices breakdown voltage was 39% better than that of a SiC Schottky barrier diode containing conventional field plates.
    Keywords: 4H-SiC; wide band gap; power device; trench oxide; edge termination; field plate; electric field crowding; electric field distribution; breakdown voltage; impact ionization.

  • A New Reduced Switch Count Three Phase Multilevel Inverter   Order a copy of this article
    by GEETHA Ramanujam, Ramaswamy M 
    Abstract: The paper develops a new multilevel inverter (MLI) topology with a view to reduce the number of power switches in the passage of current to reach each level of the output voltage. The philosophy involves the use of bidirectional switches to avert the flow of circulating current between the two sections of the power circuit. The formulation brings in the use of a new pulse width modulation strategy to eliminate the higher frequency components of the output voltage. It incorporates the phase disposition type of modulating scheme to shape both the voltage and current to a nearly sinusoidal waveform. The total harmonic distortion indexed by smaller values for the output voltage over the traditional firing scheme serves to be the highlight for the MLI in acclaiming its place in the inverter world. The experimental results obtained using a prototype validate the simulated performance and establish the viability of the proposed MLI to serve the diverse needs of the utility world.
    Keywords: Multilevel inverter; Total harmonic distortion; Phase disposition; Pulse width modulation.

  • Optimum Pulse-width modulation strategy for a symmetric cascaded Multilevel Inverter   Order a copy of this article
    by Ashraf Yahya, Syed M. Usman Ali 
    Abstract: This paper investigates for the most suitable PWM strategy for a symmetric cascaded Multilevel inverter. The objective is to determine a PWM switching strategy which optimizes inverter performance by ensuring higher DC link utilization and minimum Total Harmonic Distortion (THD) at low switching frequency to minimize switching power losses also. Simulations carried out in Matlab-Simulink environment has given an insight of inverter performance when carrier based PWM techniques are applied. In this parametric evaluation both odd and even multiples of 50 Hz modulating signal were applied for obtaining switching frequency for various Multicarrier based PWM strategies.
    Keywords: Multilevel; inverter; carrier based PWM; modulation index; phase disposition; Inverted sine.

  • A Modular DC-DC Converter with Zero Voltage Switching Capability   Order a copy of this article
    by Farzad Sedaghati, Reza Haghmaram 
    Abstract: A bidirectional DC-DC converter with high power density is proposed in this paper. The presented converter provides power transfer in both directions only with adjusting phase shift angle. Zero voltage switching (ZVS) in both turn on and turn off moments of all switches is the major capability of the converter that makes it suitable for high power applications. ZVS of the converter is provided without any auxiliary devices. High frequency transformers are employed in the converter configuration to match the converter two sides voltage. Moreover, the transformer leakage inductance along with external auxiliary inductance acts as energy storage in power transfer from one side of the converter to the other side. Steady state operation of the converter is analyzed. ZVS criteria of the proposed converter are studied and finally, experimental measurement results of laboratory scale prototype are presented.
    Keywords: DC-DC converter; modular converter; ZVS operation; high-frequency isolation.

  • A Comparative Closed-Loop Performances of a DC-DC Switched-Mode Boost Converter with Classical and PSO based optimized Type-II/III Controllers   Order a copy of this article
    Abstract: The DC-DC switched-mode Boost converter is well-known for its extensive applications ranging from few watts to several megawatts in different engineering fields. In this paper, a closed-loop Boost converter has been designed and implemented by using classical and particle swarm optimization (PSO) based optimized Type-II/Type-III controllers. The closed-loop control for Boost converter is difficult due to presence of a right-half-plane zero, and it is problematic for the conventional PID controller to exhibit good closed-loop performance with line, load changes and parametric uncertainty. The comparative studies between the closed-loop performances of the proposed Boost converter with classical and optimized Type-II/Type-III controllers have been produced. Simulations & experimental results are provided to demonstrate the effectiveness of proposed optimized controllers for the Boost converter. It is found that the PSO optimized Type-III controller exhibits better stability & closed-loop performance than the others reported controllers in this paper.
    Keywords: DC-DC Switched-Mode Power Converter; Boost Converter; Non-Minimum Phase System; Classical Type II/III Controller; Particle Swarm Optimization; Optimized Type-II/III; Simulation and Experimental Results.

  • Fuzzy-PI Controller Applied to PMSM Speed Controller - Design and Experimental Evaluation   Order a copy of this article
    by Hicham Fadil, Mohamed Larbi Elhafyani 
    Abstract: Several advantageous are offered by synchronous motors with permanent magnet (PMSM) which are required in numerous fields for high performance adjustable speed operation. However, PMSMs speed control is related to directly to controllers and it needs to be adjusted using an appropriate regulator. In this paper, a proportional integral (PI) regulator applied for PMSM speed adjusting is considered and enhanced using a Fuzzy logic process by making that PI regulator gains self-adapting and ensures a good performances of the controller in transient states. A PMSM motor controlled using an eZdsp F28335 board is exploited to validate MATLAB/SIMULINK software results, and to show Fuzzy-PI improvement and performance under many constraints.
    Keywords: Fuzzy-PI regulator; Permanent magnet synchronous motor; PI controller; speed control.

  • Power Sharing Control Strategy of Parallel Inverters in AC Microgrid Using Improved Reverse Droop Control   Order a copy of this article
    by Chethan Raj D, Dattatraya N. Gaonkar, Josep M. Guerrero 
    Abstract: Microgrid structure is developed on the basis of distributed generation units. Microgrid distributed generation units and energy storage devices are connected through inverters interface to the point of common coupling. Micro-grid system with multiple inverters, the use of conventional direct and reverse droop control method will cause uneven distribution of power, which is due to the difference between the output impedance and the line impedance of the inverter. In this paper, the traditional reverse droop control method is introduced and the power distribution of inverter output impedance is analyzed, and the defects of traditional reverse droop control are pointed out. Adding virtual resistor in the control loop of reverse droop control improves the power sharing and stability of operation, but also leads to the voltage drop in microgrid. To compensate the output voltage deviation, secondary control is proposed. Simulation results show the correctness and effectiveness of the proposed control strategy.
    Keywords: Droop control; reverse droop control; distributed generation; inverters; microgrid; output impedance; secondary control; virtual resistors.

  • Cascaded H-Bridge Inverter with Reduced Device Count Control Considering Harmonic Distortion Minimization   Order a copy of this article
    by Faouzi Armi, Lazhar Manai, Mongi Besbes 
    Abstract: In this paper, a serial/parallel cascaded H-bridge (CHB) multilevel inverter is presented. The topology has the advantage of reduced number of switching devices, DC-sources and gate driver circuits. Consequently cost and complexity are greatly minimized, providing the same number of output voltage levels even more compared to conventional structures and other topologies given in some recent literatures in which authors have proposed new topologies with reduced circuit devices count (RDC). The main contribution of this work is the ability to choose a set of harmonic order to be eliminated; in other similar works PWM technique is only capable to minimize total harmonic distortion (THD) without eliminating selected harmonic which require a complex output filter. The feasibility and effectiveness of the proposed topology is evaluated with intensive simulation study and experimentally tested on a prototype using a field-programmable gate array (FPGA) to implement N-R algorithm for inverter selective harmonic elimination (SHE) control.
    Keywords: Serial/Parallel CHB multilevel inverter; Reduced Device Count; Newton Raphson algorithm; Switching angles; SHE; THD; FPGA.

  • Study of Complex Dynamics in DC-DC Boost Converter with dSPACE based Real Time Controller   Order a copy of this article
    Abstract: Switching converter circuits are nonlinear and time-varying in nature. In this paper, the complex dynamics in voltage mode controlled (VMC) DC-DC Boost converter has been investigated through simulation and experimentation. The converter is controlled by naturally sampled constant frequency pulse width modulation (PWM) signals in continuous conduction mode (CCM) and converter exhibits fundamental, quasi-periodic & chaotic oscillations for the variation of circuit parameters. In simulation study, the model of Boost converter is computed by non autonomous differential equations and finally the computational waveforms have been verified with experimental results. In order to verify simulation study, a laboratory scale prototype of closed-loop Boost converter has been fabricated. The closed-loop converter is controlled by dSPACE in real-time platform. The results obtained from simulation and experimental study have been presented and compared. It has been observed that the route to chaos is achieved by the slow-scale instability in this proposed study.
    Keywords: Boost converter; voltage mode control; phase-portraits; dSPACE controller; chaos.

    by Ramchandra Nittala, Alivelu M. Parimi 
    Abstract: Voltage deviations which occur frequently in the form of voltage sag/swell cause severe disturbances and damage sensitive loads present on the distribution side of power system. One of the feasible solutions to mitigate these voltage sags/swells is by utilizing FACTS devices. The FACTS device proposed in this paper is Interline Dynamic Voltage Restorer (IDVR) which contains two or more Dynamic Voltage Restorers (DVR) with a common DC link. In this paper, IDVR is designed for a specific application to mitigate power quality problems in an existing real time load. A case study of the load network data of BITS Pilani Hyderabad Campus in Telangana, India which is spread over 200 acres is considered as the real time load. Various multiple voltage sag/swell scenarios are analysed in the real time load. The results have proven that the IDVR can effectively mitigate multiple voltage sags/swells in the considered real time load.
    Keywords: Interline Dynamic Voltage Restorer (IDVR); Power Quality; Voltage Source Inverter (VSI);Voltage Sag/Swell.

  • Three Level Inverter Based Unified Power Flow Controller   Order a copy of this article
    by Khoukha BERRAHAL, Abd El Malek BOUHENTALA, Ahmed BENSALEM 
    Abstract: Unified Power Flow Controller is a power electronics based device utilized to improve transmission line capacity and control power flow transmitted by power transmission systems. This paper presents the application of the decoupled control strategy to control independently active and reactive power in the event of changes in the step points of the powers. Two types of controllers are used to handle the control strategy proposed: conventional PI regulator and fuzzy logic PI regulator. The fuzzy logic controller must have high performance to handle the problem of adjustment of power decoupling. Also, a three level Neutral Point Controller inverter is used in both series and shunt parts of the UPFC to get multistep voltage wave and improve the power quality.
    Keywords: GTO;power flow control;UPFC;FACTS.

  • Hexagon Hysteresis Current Control Based STATCOM for Grid Connected Wind Turbine System   Order a copy of this article
    by Munireddy Gundala, Gowri Manohar T 
    Abstract: The use of renewable power sources, like wind power, has been increased recently due to climatic changes caused by fossil fuels and fast depletion of fossil fuels. This has lead to the tremendous increase in the interconnection of wind turbines to power system grid. This interconnection of wind turbines on a large number in to grid causes problems such as power quality, maintaining system voltage, reactive power compensation, control of grid frequency and aspects of power system grid stability. In this paper, STATCOM utilizes Hexagon Hysteresis Current Controller (HHCC) to improve the power quality. The proposed control scheme supplies the required reactive power to the system and thus relieves the source, leading to unity power factor (UPF) at the source and also it injects currents to reduce THD to satisfy IEC standard. In the proposed HHCC, the current control has been achieved by transforming the three phase (a, b, c) system in to stationary (α, β) reference frame and the complex space vector concept is employed. Further, the proposed systems dynamic response has been studied and the results have been presented.
    Keywords: Wind Turbine System; Static Synchronous Compensator; Hexagon Hysteresis Current Control; Battery Energy Storage System; Total Harmonic Distortion.

  • An Efficient Crowbar to Improve the Low Voltage Ride-Through Capability of Wind Turbines Based on DFIG Excited by an Indirect Matrix Converter   Order a copy of this article
    by Ahmad Khajeh, Reza Ghazi, Mohamad Hosseini Abardeh, Mahmoud Oukati Sadegh 
    Abstract: Due to numerous advantages, in this work the traditional Back-to-Back converter is substituted with an Indirect Matrix Converter (IMC) to control the doubly-fed induction generator (DFIG). The recent grid codes require that the wind turbines must have the low voltage ride-through (LVRT) capability. One of the main challenges of the IMC that slows down the industrial applications is the fault currents handling. In this paper a new low cost, simple and reliable method is proposed to protect the IMC from large fault currents. This method is based on a novel crowbar structure. The PSIM simulation results confirm the efficiency of the proposed method in satisfying the new LVRT standards. Also, experimental results of a laboratory prototype verify the effectiveness of the proposed method.
    Keywords: Wind turbine; DFIG; Indirect matrix converter; Low voltage ride-through; Crowbar.

  • Artificial Neural Network (ANN) based Power Quality Compensator   Order a copy of this article
    by Dr P. N. Tekwani, Ashwin Chandwani, Sagar Sankar, Neel Gandhi, Siddharthsingh Chauhan 
    Abstract: A reliable and efficient adaptive neural network based active power filter to estimate and compensate harmonic distortion from supply mains is presented in this paper. Now-a-days, there is drastic rise of current and voltage harmonics in power systems, caused by nonlinear loads. Active Power Filters (APF) are used to mitigate harmonics and thereby improve power quality. This paper deals with application of artificial neural network in shunt active power filter which provides ease in implementation and fast dynamic response compared to conventional active power filters. In depth analysis of neural network applications in the intelligent control and estimation for power quality compensation is presented in this paper. Here, both, reference compensating current generation scheme as well as current controller for the active power filter are developed using artificial neural network technique. Effective compensation provided by the proposed artificial neural network based shunt active power filter is proved through simulation results. Experimental analysis carried out using dSPACE DS1104 also validates power quality improvement by the proposed APF scheme.
    Keywords: Artificial Neural Network; Hysteresis Current Controller; Power Quality; Shunt Active Power Filter.

    by Shenbagalakshmi Rengamani, Vijayalakshmi Subramanian, Geetha Krishnan 
    Abstract: A thorough and effective analysis of the positive output super lift Luo converter along with the discrete PID controller has been carried out. The converter is designed to operate under continuous conduction mode and modeled using state space averaging method. The closed loop control is based on time domain approach and current mode discrete PID controller thus designed tunes the system in such a way that the converter specifications are satisfied. The Luo converter along with the controller thus designed is robust, shows stiff output voltage regulation without any overshoots or undershoots and highly efficient. The steady state error is almost zero. Extensive simulation is carried out and the results are illustrated. The controller platform is verified using LabVIEW.
    Keywords: closed loop control; current mode control; dc-dc converter; discrete PID controller; Positive Output Super Lift Luo converter (POSLL).

  • Stability Improvement of Power System with Connected Wind Turbine Using Three Levels STATCOM   Order a copy of this article
    by Ahcene Bouzida, Radia ABDELLI, Abderrazak AIBECHE, Aimad BOUDOUDA 
    Abstract: The penetration of Doubly Fed Induction Generator (DFIG) into the power grid has become an important concern for power system engineers today. Voltage stability is an important factor to maintain the wind farm in service during some abnormal operating conditions. This paper deals with the integration of Synchronous Static Compensator STATCOM to overcome the voltage stability issue for the power systems with connected wind turbine. A dynamic model for the wind turbine equipped with DFIG and connected to the power system has been presented and the integration of a STATCOM as a dynamic reactive power compensator to maintain stable voltage and protecting the DFIG has been studied during a severe low voltage condition. The developed system is simulated and the results demonstrate that the good control of STATCOM enhances voltage regulation as well as transient stability of the variable-speed wind generators system during three phase faults. Many verifications based on time-domain simulations for powers, voltages and currents have been presented in order to show the STATCOM capability in improving transient stability of the studied power system.
    Keywords: STATCOM; Wind turbine; Transient stability; DFIG; Power compensation; Voltage Regulation.
    DOI: 10.1504/IJPELEC.2019.10010629
    by Ravindranath Tagore Yadlapalli, Anuradha KOTAPATI 
    Abstract: This paper discusses the modeling, design and implementation of Quadratic Buck Converter (QBC) for low voltage CPU voltage regulator applications. The small-signal modeling of QBC is characterized by state-space averaging technique. The QBC has been applied with Average Current-Mode (ACM) control strategy in order to evaluate steady sate as well as dynamic performance. The hardware development of QBC is exploited using FPGA controller. The PSIM simulation results are validated with the experimental results in terms of line and load regulations. It can be verified from results that the system stability is guaranteed for a wide range of operating conditions.
    Keywords: Switched-Mode power supply (SMPS); Right-half-plane zeros (RHPZ); Average current-mode (ACM) controller; Transient settling time (TST); Transient voltage deviation (TVD).

  • Digital Variable Switching Frequency Controlled Integrated Power Converter for Class C & Class D Appliances   Order a copy of this article
    by Mopidevi Subbarao, Ch SaiBabu, S. Satyanarayana 
    Abstract: Existing methods for integrated switched mode power converters are mainly based on voltage controller technique, but they fail to comply with international regulatory standards (IEC 6100-3-2 and IEEE 519-1992) for class C and class D electrical appliances. Variable switching frequency current controller has been proposed in this work, owing to its features, viz- fast dynamic response, no compensation circuit and less complexity in design. Integrated converter for 100W load operating in universal range of voltage (90V-230V), 50Hz has been designed and implemented using MATLAB/Simulink, verified in hardware using TMS320F2812 digital processor board and thus results found to be complying with international regulatory standards.
    Keywords: Switched mode power converter; Variable switching frequency; IBFC; Integrated Converter; power Factor correction; DSP.

  • Modular Switched Mode Power Supply, Tested With DC Motor Load   Order a copy of this article
    by Kandadai Nagaratnam Srinivas 
    Abstract: A modular switched power supply fit to be used as a standby supply in the electrical laboratories or in the industrial work floors is proposed in this paper. Conventional switched power supply involves bulk transformers. Various disadvantages arise due to this bulkiness. This work makes an attempt to address this issue and proposes a solid state switched power supply. The description of the proposed circuit, simulation of its operation and the working model are presented.
    Keywords: Modular switched power supply; DC supply; solid state devices.

  • Non-isolated High Gain Bidirectional DC-DC Converter: Design and implementation   Order a copy of this article
    by Adel Karami, Ali Nahavandi, Bahman Eskandari 
    Abstract: This paper proposed a non-isolated bidirectional dc-dc converter with high step-up/down voltage gain. This converter has the ability to transfer the energy in both directions. The proposed converter uses three inductors that are coupled together pairwise with same winding turns. In step-up mode; the inductors operate in parallel in charging mode and series in discharging mode. In step-down mode; the inductors operate in series to be charged and parallel to be discharged. The proposed converter has higher step-up and step-down voltage gains than the conventional bidirectional dc-dc boost/buck converter. Simulations are obtained by using PSCAD/EMTDC software and the results are presented. Finally a laboratory prototype is implemented to validate theoretical analysis.
    Keywords: Non-isolated; bidirectional dc–dc converter; coupled inductors.

  • Development and experimental validation of fault detection and diagnosis method in SPWM modulated symmetric cascaded H-bridge multilevel inverter   Order a copy of this article
    by Nithin Raj, Anjali Anand, Jagadanand G, Saly George 
    Abstract: This paper discusses gate open-circuit fault detection and diagnosis method in SPWM modulated symmetric cascaded H-bridge multilevel inverter. First, an output voltage modelling under fault condition in cascaded H-bridge multilevel inverter is presented. Further, simulations of fault conditions have been carried out for the development of the fault detection and diagnosis method. Based fault modelling and simulations, a fault detection and diagnosis method have been proposed based on the mean values of the bridge voltages as the diagnostic feature. Further, the proposed method has been validated experimentally on a 5-level symmetric sine pulse width modulated cascaded H-bridge multilevel inverter.
    Keywords: cascaded H-bridge (CHB); fault detection and diagnosis (FDD); fault modelling; gate open-circuit fault; sine pulse width modulation (SPWM); multilevel inverter (MLI).

  • Analysis and Design of Novel Non-Isolated Quadratic Boost DC-DC Converter.   Order a copy of this article
    by Subhendu Bikash Santra, Tanmoy Roy Choudhury 
    Abstract: This column elucidates analysis and design of novel single switch non-isolated quadratic boost converter. The operating principle is discussed both in CCM and DCM mode. Analysis includes closed loop average current mode control. The proposed converter exhibits stable operation under input voltage and load change. Linear control theory is applied for the loop compensator design. The suitability of the proposed scheme is well visualized and validated through simulation results procured using PSIM 9.1.1 and experimental results obtained from a practical 75 watt converter. The converter is designed for 75 Watts with 89-90% measured efficiency, where voltage and current ripple is 2 % of output voltage and 1 % of rated inductor current, respectively.
    Keywords: Quadratic Boost converter; CCM and DCM mode; Voltage stress; Voltage step-up ratio; Current mode Control; Efficiency.

  • Adaptive RBF Neural Network Based on Sliding Mode Controller for Active Power Filter   Order a copy of this article
    by Huiyue Zhang, Yunbo Liu 
    Abstract: In this paper, an adaptive radical basis function neural network (RBFNN) is proposed to deal with dynamic tracking error problems which is the mathematic model uncertain or complex for the three-phase active power filter (APF). The adaptive RBFNN systems are employed to approximate the system function term in the sliding mode controller. Different from back propagation neural network (BPNN), RBFNN is local uniformly convergence so that it enhance the convergence speed of weights. According to Lyapunov stability analysis guarantee the control algorithm stable implementing that is working out the adaptive law and dragging the states onto the sliding surface and sliding along it. This approach is almost model-free requiring a minimal amount of a priori knowledge and is robust in the face of parameter changes. The simulation results of APF demonstrate the outstanding compensation performance and strong robustness.
    Keywords: APF; RBF neural network; Sliding Mode Controller; Active Power Filter.

  • Design and Implementation of a Novel Single Phase Universal Power Converter   Order a copy of this article
    by Mudadla Dhananjaya, Swapnajit Pattnaik 
    Abstract: Universal power converter have drawn the attention of researchers in the recent past, as they can be used for dc-dc, dc-ac, ac-dc, ac-ac and variable frequency conversion. In this paper a novel universal power converter has been proposed with a simple switching structure which is formed by the reduction of device count as compared to individual conventional converters. Further, it will give the most economic operation with less complexity and compact in size. This converter can be configured as dc-dc, dc-ac, ac-dc, ac-ac and cycloconverter. The operation of the proposed converter in all configurations have been discussed. The proposed converter is simulated in MATLAB environment to evaluate its performance and experimental results are verify with simulation results.
    Keywords: dc-dc converter; dc-ac converter; ac-dc converter; ac-ac converter and cycloconverter.

  • A New EABC for DC-link Capacitor Voltage Equalization of MPC based 5-L HPFC   Order a copy of this article
    by Naveen Yalla, Pramod Agarwal 
    Abstract: In this paper, a new multi-device unidirectional buck boost topology is proposed to equalize the DC link capacitor voltages of multi-point clamped (MPC) based five-level high power factor (HPF) converter. Two independent controlled chopper topologies (consisted with two parallel connected control devices and one single uni-directional diode) makes the proposed topology effectively and efficiently to mitigate the deviation of DC link capacitor voltages, which is caused due to voltage drift phenomena. The desired pwm signals are generated by a phase shift control strategy. Proposed configuration provides two times ripple frequency current through the inductor, which can contribute less inductor size, all most 50% of traditional one, and therefore the lesser weight of the core and its corresponding losses. The contribution of proposed topology is analyzed mathematically and results are verified by simulation as well as prototype experimental setup.
    Keywords: AC/DC power conversion; External auxiliary balancing circuit; Multi point clamped; Multi level converter; High power factor converter.

  • An Improved Topology of Cascaded Multilevel Inverter with Low Switch Count   Order a copy of this article
    by Bikram Das, Manas Patra, Debashis Chatterjee, Aniruddha Bhattacharaya 
    Abstract: An improved topology of a multilevel inverter is described in this paper. Proposed topology is comprised of the basic module to get positive levels at the output. An H-bridge can be formed to obtain ac output. Developed topology significantly reduces the number of IGBTs, DC voltage sources, gate drivers for the same number of levels. Different algorithms are presented to determine the number of levels, switches and total blocking voltage. Comparison of the proposed topology with the conventional cascaded multilevel inverters and other existing topologies in the literature has been carried out to show the advantages of the newly proposed topology. The operation and performance of the proposed multilevel inverter are verified by suitable experimental results with a single phase 15-level multilevel inverter considering resistive and inductive loads.
    Keywords: Cascaded Multi level inverter; reduced switch; Loss comparison; total standing voltage,H-Bridge;.

  • Increasing quality of SMPS through proper design of a high-frequency transformer   Order a copy of this article
    by Michal Frivaldsky, Pavol Spanik, Viliam Jaros, Andrej Kanovsky 
    Abstract: High frequency transformer significantly influences power losses, power density and efficiency of isolated power converter. With optimal design of high frequency transformer high efficiency and power density can be obtained, what is necessary for achievement of the upcoming regulations and standards for dc-dc converters. This paper deals with verification of the design procedure of high frequency transformer, which id oriented for high efficiency achievement of switched mode power system. Simulation model of dc-dc converter with precise model of high frequency transformer is developed for the verification purposes. The proposed procedure servers for optimal selection of best solution for high-frequency transformer in terms of ferrite material as well as shape of magnetic core.
    Keywords: efficiency; transformer core; core shape; ferrite material; high frequency,.

  • Synchronous Reference Frame Sliding Mode Observers for the Inverse of the Rotor Time Constant of the Induction Motor   Order a copy of this article
    by Mihai Comanescu 
    Abstract: The paper discusses the problem of inverse rotor time constant estimation for the induction motor (IM) and presents two sensorless sliding-mode observers (SMOs) that are constructed using synchronous reference frame models. Estimation is done assuming that the magnitude of the flux is available. A voltage model observer is used to estimate the αβ fluxes: these are used to compute the field-orientation angle and the flux magnitude. The paper develops an observer based on the first-order model; however, this does not perform well under parameter variations. A second observer is developed using an augmented model (which now involves the speed of the motor) this is transformed into a sensorless design by feeding it with a speed estimate (assumed inaccurate). It is shown how to design the feedback gains in order to reduce the sensitivity of the estimate to the input speed error. The theoretical developments are supported with simulations and experiments.
    Keywords: induction motor control; voltage model observer; sliding mode observer; rotor time constant estimation.

  • Design and Performance Evaluation of Self-Supported Dynamic Voltage Restorer for Mitigating Various Power Quality Problems   Order a copy of this article
    by Shubhendra Pratap Singh, Abdul Hamid Bhat 
    Abstract: Dynamic voltage restorer (DVR) is used to shield voltage sensitive loads from harmonic distortion and sag/swell in supply voltage consistently. In this paper, a self-supported dynamic voltage restorer (DVR) is discussed. The control methodology based on calculation of unit templates is used for dynamic voltage restorer (DVR). Fundamental of terminal voltage is extracted by using the synchronous reference frame (SRF) theory and the reference load voltage is obtained. The comparison is done between the reference load voltage and the sensed load voltage to generate the error signal and this error signal is processed by the pulse width modulation (PWM) controller to generate the control pulses for voltage source converter (VSC) of dynamic voltage restorer. In this paper, designing of main system parameters such as VSC-DC link capacitance, ripple filter, AC side inductance and Insulated gate bipolar transistor (IGBT) based VSC rating is given in detail. In the capacitor supported dynamic voltage restorer, injected voltage is in quadrature with line current so there is no need of active power injection during steady state. At the time of any disturbance in supply side, dynamic voltage restorer only supplies or absorbs the reactive power to maintain the load voltage constant. By using MATLAB/Simulink simulation studies, the above control strategy is tested. The simulation results for voltage harmonic distortion, voltage sag/swell and voltage unbalancing demonstrate the viability of DVR controller.
    Keywords: Dynamic voltage restorer (DVR); Voltage sag/swell; Total harmonic distortion (THD); Power quality; Custom power devices; Fuzzy logic controller (FLC).

  • Performance Analysis of SPRS based Induction Motor Drive using Multi-level Inverter and Buck-Boost Chopper   Order a copy of this article
    by Sita Ram Bhardwaj 
    Abstract: This paper presents the performance analysis of induction motor drive (IMD) utilizing slip power recovery scheme (SPRS) with two and three level voltage source inverter (VSI) and buck-boost chopper employing gate turned off thyristor, metal-oxide semiconductor field effect transistor, insulated gate bipolar transistor as switching devices. A mathematical model of 2 hp, 400V, 50Hz, 1440 rpm IMD has been developed and Simulated in MATLAB. The performance parameters taken for induction motor drive are reactive power, power factor, efficiency, and total harmonic distortion (THD) of the supply. The novelty of proposed scheme lies in the implementation of simulation model of SPRS using three level inverter and buck-boost chopper from the dynamic model library of MATLAB/Simulink. The simulation results have shown that two-level VSI with chopper controller has enhanced the power factor and efficiency of IMD compared to the SPRS without chopper. The three-level inverter has reduced the reactive power consumption and THD, consequently, enhanced the quality of power supply.
    Keywords: Buck-boost chopper; efficiency; induction motor drive; inverter; power factor; slip power recovery scheme.

  • Comparative Analysis of Non-Inverting Buck Boost Converter Topologies for Fuel Cell Low Voltage Applications.   Order a copy of this article
    by M.Venkatesh Naik 
    Abstract: The FC sources are unregulated voltage sources and require power converter devices to get a regulated output voltage. When these devices are used in low voltage low power applications DC-DC buck boost converters (BBC) are required to get the regulated voltage on load side. The multi device multi switch operation of the buck boost converters are usually employed for successful operation of the FC stacks. In this paper, the different non inverting type of buck-boost converters i.e., Buck Boost Converter (BBC), Multi Device Buck Boost Converter (MDBBC), Interleaved Buck Boost Converter (IBBC), and Multi-Device Interleaved Buck Boost Converters (MDIBBC) are analyzed and comparative study among them are presented with respect to the parameters like, ripple current, component size, power losses and efficiency. The comparative study demonstrates that the multi device converter topologies are more efficient than the other converter topologies employed in low voltage low power applications.
    Keywords: buck boost converters; ripple current reduction; fuel cell low voltage applications.

  • Fractional Order PID Controller for DC Link Voltage Regulation in Hybrid System Including Wind Turbine- and Battery Packs- Experimental Validation   Order a copy of this article
    by Boualam Benlahbib, Farid Bouchafaa, Noureddine Bouarroudj, Saad Mekhilef 
    Abstract: This paper presents a Fractional Order PID (FOPID) to control the operation of a stand-alone hybrid energy system with a wind turbine based on Permanent Magnet Synchronous Generator (PMSG) and a battery bank. In order to maintain the DC-link voltage at its reference value, regardless the variation in wind speed and load impedance a FOPID controller using a DC-DC buck-boost converter fed by a lead acid battery bank is used. The line to line AC output voltage regulation based on PID controller to supply RL load with constant amplitude and frequency has been achieved. The proposed FOPID controller is examined through simulation using MATLAB-SIMULINK and experimentally via an experimental test bench under step change variation of wind speed and load impedance. The obtained simulation and experimental results using FOPID controller show better performances than the conventional PID regulator in terms of less settling time and lower overshoot in the transient state as well as a minimum steady state oscillation.
    Keywords: Wind Energy Conversion System(WECS); Fractional Order PID; (Energy Storage System)ESS; PMSG; DC-link control strategy; battery packs.

  • Rotor Vibration Control of Hybrid Pole Bearingless Switched Reluctance Motor with C-Dump Converter   Order a copy of this article
    by V.S.Sobhan Polamraju, G. V. Nagesh KUMAR, P.V. Ramana Rao 
    Abstract: Rotor vibration control during start up, acceleration and deceleration phases is one of the key problems besides stable levitation, in high-speed applications of bearingless switched reluctance motor (BSRM). In this paper, an effective intelligent sliding mode controller is proposed for suppressing the rotor vibration due to residual unbalance and external disturbance during levitation and motoring phases. The parameters of time-varying sliding surface for avoiding high control gains and chattering are adjusted integrating the sliding mode control (SMC) and features of fuzzy logic control. The experimental studies conducted on a prototype BSRM system confirm that the application of fuzzy SMC guarantees the robust performance with less chattering under model uncertainties and unknown external disturbances compared to classical sliding mode controller.
    Keywords: BSRM; C-Dump Converter; Fuzzy Logic; Radial force control; Rotor vibration; SMC.

  • Modified GSA for Minimization of THD of Voltage Source Multilevel Inverter   Order a copy of this article
    Abstract: Optimization techniques have always been a reliable friend while dealing with complex non-linear problems. Among a wide gamut of available optimization techniques, Genetic Algorithm (GA) has always stood out on account of its being flexible and adaptable. This paper is an attempt to find a worthy competitor to GA. In the process, a new heuristic algorithm Gravitational Search Algorithm (GSA) has been chosen for implementation. The new technique, GSA is based on the laws of gravity and mass interaction. In order to obtain an efficient solution and quick convergence to the problem of minimization of THD of the 15 level MLI under study; the algorithm is further modified. In the modified GSA (MGSA) the initial gravitational constant (Go) and the updating constant (α) are suitably modified. In this paper, SHE equations are used to find the optimum switching angles in both GA and GSA to minimize the total harmonic distortion (THD) of the inverter output voltage. The simulation and hardware results rendered by sinusoidal pulse width modulation (SPWM), GA, GSA and MGSA are compared for validity with each other. It is found that hardware results are in concurrence with the simulation results
    Keywords: GSA; MGSA; GA; MLI; SPWM; THD; power quality.

  • DC DC Buck Converter with Second Order Sliding Mode Control: Analysis Design and Implementation   Order a copy of this article
    by Brijesh Naik, Axaykumar Mehta 
    Abstract: This article discusses about the analysis, design and implementation of the DC DC Buck converter with the Second Order Sliding Mode Control (SOSMC) or 2-sliding control. Also, performance of the converter is tested for both classical sliding mode control and the SOSMC. The analysis of DC DC Buck converter with the SOSMC is presented. The output feedback is used. The bounds of controller parameters are obtained to assure stability. The systematic implementation guidelines are provided. Effects of varying controller parameters are explored with simulation and experimental results. Effects of the load disturbance are also studied. It is shown that the use of SOSMC reduces the chattering in the controlled variable i.e. the load voltage of the converter. Finally, the simulation and experimental results are presented.
    Keywords: higher order sliding modes; 2-sliding control; sliding mode control; buck converters; chattering alleviation.

  • Universal Control Algorithm for Automatic Current Regulated LED Driver   Order a copy of this article
    by Vishwanath Gupta, Biswarup Basak, Kamalika Ghosh, Biswanath Roy 
    Abstract: In the present work a universal control algorithm is proposed which automatically regulates the output current of an LED driver as per the connected load requirements. The unique features of the proposed control algorithm is its operability in a wide output power range and remaining unaffected by the unequal current sharing among the LED strings arising due to mismatch among same wattage LED chips. The proposed control algorithm is tested by modelling and simulating an LED driver in MATLAB SIMULINK to operate LED modules having series-parallel combination of 3W LED chips in the range of 18W-72W. The results obtained from simulation show that the proposed control algorithm successfully regulates the output current of the LED driver according to load requirements. The electrical performance of the simulated LED driver on universal AC supply complies with IEC 61000-3-2:2014 Class C regulations and shows significant improvement over previously proposed LED drivers.
    Keywords: Universal control algorithm; automatic current regulation; LED driver; LED modules; modelling and simulation.

  • Gbest-guided artificial bee colony algorithm based simultaneous placement of distributed generation and shunt capacitor in distribution networks
    by Mukul Dixit, Prasanta Kundu, Hitesh R. Jariwala 
    Abstract: This paper presents a combined placement of distributed generation (DG) and shunt capacitor in distribution network for the purpose of power loss reduction. The locations of DG and shunt capacitor are evaluated by using power loss index approach and index vector method, respectively. The population based Gbest-guided artificial bee colony meta-heuristic optimisation technique has been implemented to evaluate the optimum size of DG and shunt capacitor simultaneously. This methodology is being demonstrated on 33-bus and 85-bus distribution network. In addition to that, the two load scenarios are considered in this study. The technical analysis has been carried out for different combinations of DG and shunt capacitor. Comparison between various cases for power loss, minimum system voltage, voltage stability index and total voltage deviation are also mentioned in this paper. The numerical results obtained through proposed approach have been compared to the published research papers for showing its effectiveness.
    Keywords: distributed generation; GABC algorithm; index vector method; load model; optimization; power loss; power loss index; shunt capacitor; voltage deviation; voltage profile; voltage stability index.
    DOI: 10.1504/IJPELEC.2018.10008122
  • An improved nearest-level modulation for modular multi-level converters
    by Keli Li, Yong Liao, Ren Liu, Jimiao Zhang 
    Abstract: Voltage balancing and switching frequency reduction are common problems of modular multi-level converters. In this research article, an improved nearest-level modulation strategy, which applies fuzzy control and minimal switching frequency pulse pattern, is proposed to coordinate voltage balancing and switching frequency reduction. The performances of voltage balancing and switching frequency reduction can be regulated by changing the parameters of the fuzzy control and the weighting coefficients of the two parts. The simulations are implemented through a high-voltage direct current system which connects a wind farm. The simulation results validate the practicability of the proposed strategy.
    Keywords: fuzzy control; high-voltage direct current; modular multi-level converters; nearest-level modulation; switching frequency reduction; voltage balancing.
    DOI: 10.1504/IJPELEC.2018.10008126
  • Design of backstepping controller for PV-wind hybrid system with grid-interfacing and shunt active filtering functionality
    by V.N. Jayasankar, U. Vinatha 
    Abstract: This paper presents the design of a double loop controller for the grid interconnection of PV-wind hybrid system with shunt active filtering and neutral current compensation capabilities. Using Lypunov stability theory-based procedure, a backstepping controller is designed for the outer loop DC link voltage control. The adaptive nature of back stepping controller results in better dynamic performance compared to conventional controllers. Inner loop consists of instantaneous power theory-based controller for harmonic current compensation. Instantaneous power theory is modified by employing positive sinusoidal sequence regulator and self-tuning filter to improve the system performance in unbalanced and distorted grid voltage conditions. A dynamic model of the system is considered for the design. Numerical simulations are done in MATLAB/Simulink platform for different system conditions to verify the effectiveness of controller in grid interfacing of renewable sources, and the shunt active filtering.
    Keywords: backstepping control; DC link voltage control; grid connected renewable system; shunt active filter; wind-solar hybrid system.
    DOI: 10.1504/IJPELEC.2018.10008125
  • An efficient islanding detection method in distributed generation using hybrid SVM-based decision tree
    by Gundala Srinivasa Rao, Gattu Keseva Rao 
    Abstract: Islanding is one of the most important concerns of interconnecting the grid-connected distributed resources to the distribution system. At the point when a bit of the distribution system turns out to be electrically detached from the rest of the power system, yet keeps on being empowered by distributed generator (DG) islanding happens. Islanding is an undesirable circumstance, since it is conceivably a hazardous condition for the upkeep work force and might harm the DG and loads on account of unsynchronised reconnection of the lattice because of stage distinction between the grid and DG. So effective and accurate islanding detection is essential to protect the distributed system while landing occurs in a distributed network. In this paper, a hybrid support vector machine with decision-tree classifier is proposed to provide an accurate detection and classification of islanding based on extracted features within less detection time. The proposed method is actualised in MATLAB, and the test results demonstrate the significance and viability of our proposed system than the current islanding discovery strategies.
    Keywords: DG; distributed generator; forward feature selection algorithm; islanding; support vector machine with decision tree.
    DOI: 10.1504/IJPELEC.2018.10008124
  • An improved control strategy without current sensors for DSTATCOM
    by Sanath Saralaya, K. Manjunatha Sharma 
    Abstract: An improved control strategy based on power balancing algorithm without using current sensors is presented in this paper. The mathematical model of this improved method is discussed. Point of common coupling (PCC) voltage and DC link voltage are taken as voltage commands for reference signal generation. Sinusoidal pulse width modulation is used to generate the pulses for distribution static compensator (DSTATCOM). Proportional integral (PI) controller is used to control the PCC voltage and DC link voltage of the voltage source converter of DSTATCOM. This improved method is tested for different load conditions using PSCAD/EMTDC package. The improved control strategy is validated by simulation results for linear and non-linear load conditions.
    Keywords: distribution static compensator; PI controller; power quality; total harmonic distortion; voltage source converter.
    DOI: 10.1504/IJPELEC.2018.10008159

Special Issue on: Advanced Power Electronics for Distributed Generation and Microgrids

  • The Optimal Configuration of the multistage model with embedded chance constraints of Mini-type Hydroelectric-Photovoltaic Power Distribution Networks on the Basis of the Improved Genetic Algorithm   Order a copy of this article
    by MengYu Wang, Ziwei Zhu, Hongquan Hu 
    Abstract: The grid-connection of mini-type hydroelectric, photovoltaic and other renewable energy sources has brought remarkable volatility and randomness to the system of power distribution network. But during the planning of that system, the comprehensive model of hydroelectric-photovoltaic planning model is rarely considered. This article brings forward multistage planning model with embedded chance constraints to address the issue of comprehensive planning of mini-type hydroelectric photovoltaic power distribution networks. Firstly, the multistage within different periods of time model which considers the sequence of the hydroelectric generator, the photovoltaic power generator and the capacitors was established. The objective functions of the three stages were respectively set as minimizing annual cost, minimizing transmission losses and abandoned water, and minimizing the times of the switching of transformer taps as well as of the switching of capacitors. Secondly, the objective function, the chance constraint of state variable and control variable and the constraint of the active and reactive power output of the hydroelectric generator, the photovoltaic power generator and the capacitors was comprehensively considered. After that, crossover model was introduced, in order to rectify the prematurity of genetic algorithm. Lastly, the form of IEEE 33-bus system can effectively enhance the utility of resources, reduce transmission losses and gross cost. The comprehensive model was also capable of keeping the voltage of the network stable and lower the times of adjustment of the transformers and the capacitors, improve the durable years of the facility.
    Keywords: multistage model Mini-type Hydroelectric-Photovoltaic Improved Genetic Algorithm Optimal Configuration.

  • TSFLC Based DC Link Voltage Regulation of Grid Connected DC Micro Grid   Order a copy of this article
    by SHIKHA GUPTA, Rachna Garg, Alka Singh 
    Abstract: Abstract: Integration of micro grid with utility power network has major concerns such as active power control and maintaining desired power quality (PQ) standards. Among several power quality issues, voltage dip and harmonics are critical concerns impacting the overall performance and stability of system. In this paper, a grid connected DC micro grid (DCMG) is designed and controlled to ensure requisite power allocation between the micro-grid and utility grid system vis-
    Keywords: Voltage Source Converter (VSC); DC Micro Grid (DCMG); Distributed Generation Source (DGs); Fuel Cell (FC); Photovoltaic cell (PV); Wind Energy System (WES).

  • Implementation and Performance Analysis of Cascaded Multilevel Inverter using Modified SVPWM Techniques   Order a copy of this article
    by Lokeshwar Reddy Chintala, Satish Kumar Peddapelli 
    Abstract: The Space Vector Pulse Width Modulation (SVPWM), which is considered as an efficient PWM technology can also be used for multilevel inverters. This method is originally designed for two-level inverters. This paper introduces a modified SVPWM technique. The cascaded H-bridge multilevel inverter (CMLI) of 7-level, 9-level and 11-level are simulated for three different carrier PWM techniques. Here, Carrier based Sinusoidal Pulse Width Modulation (SPWM), Third Harmonic Injected Pulse Width Modulation (THIPWM), and Modified Carrier-Based Space Vector Pulse Width Modulation (SVPWM) are used as modulation strategies. These modulation strategies include Phase Disposition technique (PD), Phase Opposition Disposition technique (POD), Alternate Phase Opposition Disposition technique (APOD), and Phase Shifted Carrier (PSC). These strategies have been implemented by using simulation and validated by experiment. The detailed examination of the simulation results has been presented and validated with experimental results of 11-level CMLI.

Special Issue on: Power Electronics, Industrial Electronics and Their Applications

  • LMI based Stability analysis of Non-linearly perturbed DC Motor Speed Control System with Constant and Time-varying Delays   Order a copy of this article
    by Venkatachalam V, Prabhakaran D, Thirumarimurugan M, Ramakrishnan K 
    Abstract: In this research work describes the time-delays effect on speed control of DC motor system with nonlinear load disturbance in the states. With this task, the paper presents a linearized model of speed control system based on delay-dependent state equation. Since the non-linearly load disturbance in the DC motor system (with time-delay) ultimately affects the evolution of the system states, the non-linear load disturbance is modeled (mathematical) as a non-bounded non-linear function of current state vector and delayed state vector, subsequently included into the system stability analyses. In the analysis, two cases are employed: constant time-delay and time-varying delay with exogenous load disturbance. In the proposed results, for broad range of PI controller gains, the maximum value of upper bound delay of DC motor speed control system are determined and new stability criterion was identified.
    Keywords: DC motor speed control; Delay-dependent stability; Linear Matrix Inequalities (LMIs); Lyapunov-Krasovskii functional technique; Network Control Systems (NCSs); Nonlinear-load perturbations; Time-delays.

  • A comparative study of Universal Fuzzy Logic and PI speed controllers for Four Switch BLDC Motor Drive   Order a copy of this article
    Abstract: This paper presents a comparison of PI controller and fuzzy controller for speed control of a low cost brushless DC (BLDC) motor drive used in variable speed drive applications. The cost reduction in BLDC drive system is achieved by the reduction of power semiconductor switches. A PI controller and universal fuzzy controller are designed for the speed control and tested by simulation for various conditions. The simulation is performed by using MATLAB Simulink toolbox and the results show the effective response of the fuzzy controller. The rise time and steady state error of fuzzy controller is improved on an average of about 26% and 55% respectively compared to the conventional PI controller.
    Keywords: Four switch drive; BLDC motor; switching sequence; PI controller; Fuzzy controller.

    Abstract: The growing demand for electricity is driving power system nearer to operating limits. The penetration of renewable energy sources, generation diversity and various other technological advancements have added to the variable operating conditions and increasing complexity of present power system. As the configuration of power system is constantly changing due to changing loads, network switching operations or faults, the system may not necessarily be always at its maximum or minimum. The relays settings based on pre-determined static system conditions that are in general maximum or minimum, may not suffice, leading to inaccurate relay operation for a dynamic power system. Malfunction of conventional protection system has been one of the main causes of catastrophes and unwanted cascading trips in power grid . Selection of suitable relay characteristics that will be an appropriate compromise for all loading conditions and contingencies is a matter of concern. The relevance of adaptive relay settings inWide Area Monitoring, Protection, and Control (WAMPAC) using Phasor Measurement Units (PMU) is brought out in this paper using case studies of occurences in Indian grid. The significance of new Wide Area Adaptive Protection System (WAAPS) using synchrophasor measurement in Indian grid is analsyed and an architecture is suggested. The contribution of WAAP in improving the reliability and safety of power transmission through networks with a high level of operational uncertainties, is put forth. Thus, the need for neutralizing the proliferation of disturbances in the grid by acquiring system-wide and chosen restricted information as well as modification of the setting of relays to constitute a class of adaptive or predictive protective devices using Phasor Measurement Units is studied.
    Keywords: Phasor Measurement Units (PMUs); Synchronized Measurement Technology (SMT); Adaptive relay; Protection.

    by Annamalai Thiruvengadam, Udhayakumar K 
    Abstract: In this paper, a new single phase multi-level inverter using modified H-bridges is proposed. The proposed multi-level inverter consists of bi directional switches which are used to create the various voltage levels via capacitor. Hence it requires lesser number of dc voltage sources and power switches, which results in decreased control complexity and total cost of the inverter. The proposed multi-level inverter can be cascaded to generate n number of levels with reduced number of switches. The new modified developed H Bridge with two bi-directional switches capable of thirteen levels of output-voltage levels (
    Keywords: Multi-level inverter; Modified H-bridge.

  • Three Phase PWM Converter using PI and Fuzzy with Hysteresis Current Controller   Order a copy of this article
    by ANURAG DWIVEDI, Amar Nath Tiwari 
    Abstract: The research work presents hysteresis current controlled 3-phase PWM converter. The switching control is applied on three-phase bi-directional switches, to attain sinusoidal input current at unity power factor and constant output voltage.The dc-link voltage is controlled by outer loop fuzzy controller and PI controller. The converter can be used for regeneration or bi-directional power flow. The converter is especially suitable for mid to low power application (i.e., 515 kW).The bi-directional switches operate at low frequency, crossover zero voltage (at turn-on) and conduct for 1/12th of line voltage cycle. The THD analysis of the controlled input phase current shows significant reduction in the THD as compared to the uncontrolled input phase current. The dc-link voltage follows the reference value.
    Keywords: Hysteresis current controller; 3-phase pulse width modulation Voltage source rectifier; Fuzzy Controller Park’s transformation; three IGBT based switch.

  • Design and Simulation of Bidirectional DC-DC Converter with Dual Switch Forward Snubber   Order a copy of this article
    by Kunalkumar Bhatt, R.A. Gupta, Nitin Gupta 
    Abstract: A novel isolated bidirectional buck-boost converter is presented for energy storage application. Isolated boost bidirectional DC-DC converters are required to meet the wide voltage variation demand. The conventional isolated boost converters have some auxiliary circuits to provide an auxiliary path for mismatch current between source inductance and leakage inductance of the transformer. The dual switch forward snubber circuit is adopted as auxiliary circuits along with dual active bridge (DAB) converter in the proposed converter. The proposed converter has distinct advantages like zero voltage switching starting (ZVS), no voltage stress on main switches, no additional conduction losses and improved efficiency as compared to RCD snubber based converter system. The wide voltage variation in output side for 45V to 320V bidirectional DC-DC converter has been simulated with PSIM. Charging mode and discharging mode with energy storing mode has been explained in detail. Simulation results show the effective performance of proposed converter system. The loss comparison has been shown between RCD snubber based converter and dual switch forward snubber which proves that dual switch forward snubber has high efficiency compared to RCD snubber circuit.
    Keywords: Bi-directional DC-DC (BDC) converter; Dual switch forward snubber; wide voltage variation; RCD snubber.

  • An Experimental Investigation of Scalar Control based Induction Motor Drive using Digital Signal Processor   Order a copy of this article
    by Nitin Gupta, Jitendra Nama 
    Abstract: This paper presents hardware implementation of anti-windup proportional integral (AWPI) controller based scalar control of three phase induction motor (IM) drive using digital signal processer (DSP). The space vector pulse width modulation (SVPWM) is used generally for motor control application. The proposed control scheme is built on DSP which reduces speed error by using AWPI controller. The response of AWPI controller is used to modify amplitude and speed reference of rotating vector in stationary plane. The controller performance is assessed by MATLAB/ Simulink simulation results and validated by experimental results using TMS320F28335 DelfinoTM kit. A comparative assessment is also presented between conventional PI controller and proposed controller. The proposed AWPI controller gives the better performance in terms of peak overshoot and settling time during transient conditions.
    Keywords: Scalar control; Digital signal processor; Anti-windup PI controller; V/f Control.

  • A Novel Three Phase Multilevel Inverter Structure using Switched Capacitor Basic Unit for Renewable Energy Conversion Systems   Order a copy of this article
    by Tapas Roy, Neha Aarzoo, Pradip Kumar Sadhu, Abhijit Dasgupta 
    Abstract: This paper presents a new three phase multilevel inverter structure based on popular switched capacitor basic units. Each phase of the proposed topology consists of a number of switched capacitor basic units and a leg of two-level voltage source inverter in cascaded arrangement. The proposed topology is supplied by only one DC power supply and it has the ability to boost the input supply to the desired level and can generate desired output waveforms. Further, by employing simple switching strategy, capacitor voltage balancing can be achieved. A multi-carrier phase disposition pulse width modulation has been developed for switching the proposed topology. The generalized expressions for different parameters of the proposed topology have been presented. The proposed topology can generate the three phase output waveforms with less number of power supplies and power semiconductor devices compared to other recently developed three phase multilevel inverter topologies. For proving the effectiveness of the proposed topology, a seven level line to line voltage proposed topology is simulated in MATLAB/Simulink and a laboratory prototype of same is developed and tested successfully for experimental investigation.
    Keywords: Multilevel Inverter; Multicarrier PWM; Pole voltage; Switched Capacitor; Voltage balancing.

  • Harmonic injection technique based grid impedance estimation for an LCL-filtered grid connected inverter An investigation   Order a copy of this article
    by Parthiban Raja, Nivetha Thirugnanasambandan, Umamaheswari Bhaskaran 
    Abstract: Harmonic injection technique for grid impedance estimation involves active perturbation of the system through LCL-filtered Grid Connected Inverter (GCI) and processing the measured voltage and current responses at the point of common coupling (PCC). The relative effect of the perturbation on the power quality is kept low by injecting harmonic signal intermittently. This paper presents an analysis of harmonic injection based grid impedance estimation for an LCL-filtered GCI and investigates the several factors which should be considered for fast and accurate estimation. The estimation includes postprocessing of the signal responses captured at PCC in a digital platform. This paper brings out the effect of the computational time on the choice of the number of harmonic cycles to be injected. Based on the analysis it also suggests how to reduce estimation time. The analysis is aided by necessary simulation results.
    Keywords: grid connected inverter; LCL-filter; grid impedance estimation; harmonic injection.

Special Issue on: DC Microgrids and LVDC Distribution Networks

  • Solar-DC Microgrids for multi-storied Building Complexes in Emerging Nations   Order a copy of this article
    by Prabhjot Kaur 
    Abstract: The emerging nations, like India, are a growing economy and are likely to construct over the next 15 years as many homes and buildings as they exist today. Further the availability of power in these countries is limited and since power is expensive they would want to deploy large-scale decentralized solar PV, especially as the cost of solar PV falls and installation costs of these PV during construction is minimal. For these new homes and building complexes, the DC power-line could provide considerable advantage. It would still need a lot of work to be done before the promised gains would be fully realized, the work such as standardization of voltages, guidelines for wiring practices and making DC-powered appliances available. The potential gains of such deployments, referred to as solar-DC deployments, are enormous.rnIndia therefore took the lead, first focusing on off-grid homes. A 48 V DC micro-grid was driven in homes, by a 125 W solar PV and connecting to a battery which gave effective storage of 0.5 kWh. This could power an LED tube light, two LED bulbs, two BLDC fans and a cell-phone charger in the homes. Such a set-up is now powering 4000 homes located in the deserts of Rajasthan in India and about 1000 homes in other states of India. The advantages in terms of energy-savings and costs to customers are enormous.rnSimilar advantages will apply to offices and multi-storied building complexes. This paper is a study of such pilot implementations as well as development of an eco-system that made these building-owners adopt DC powerlines. The paper starts with a discussion of the architecture used for DC power in such buildings and use of combined 230 V AC and 48 V DC, as well as combined 380 V DC and 48 V DC. It describes the eco-system for DC appliances and then describe test-implementations in three types of buildings as well as some early-results from such deployments.
    Keywords: solar-DC; Inverterless; energy efficiency; economical system;.

  • Overview Paper on: Low Voltage Direct Current (LVDC) Distribution System Standards   Order a copy of this article
    by Kyle Smith, Dong Wang, Abdullah Emhemmed, Stuart Galloway, Graeme Burt 
    Abstract: Low Voltage Direct Current (LVDC) systems have recently been recognised as one of the key enabling technologies that can facilitate the connection of more distributed renewables with improved efficiency and enhanced controllability. This is in addition to the potential provision of increased power flow capacity which is required to meet the anticipated growth in electric transport and heat demand. However, there is still a shortage of mature experience and practical technical solutions that can support the uptake of such systems and increase commercial interest. One of the barriers is the lack of standards necessary to increase industry confidence and for the development of cost effective technical solutions that will accelerate the commercialization of LVDC technologies. Most of the existing international standards focus on alternating current (ac) systems with limited areas covering direct current (dc). Recently, new standard activities at national and international levels have begun to cover specific LVDC applications. However, it is still not clear whether these activities, in addition to existing standards, are sufficient and comprehensive to provide the necessary tools for best practice system design. This paper therefore reviews and evaluates the available LVDC standards within the context of the establish ac system to determine the state of the art of dc standardization and the areas where future work is required.
    Keywords: Low Voltage Direct Current (LVDC); Distribution; Applications; Standards.

    by Marco Carminati, Enrico Ragaini, Enrico Tironi 
    Abstract: Growth of distributed generation, increasing presence of power electronic devices and energy storage systems are arousing an increasing interest towards LVDC microgrids. Fault protection of such systems it thus becoming more and more important. This paper provides an overview of different possible cases of fault behavior of LVDC microgrids connected to the AC utility grid: commonalities and differences between normal operation and fault condition are highlited. After discussion of some existing critical issues, some possible solutions able to guarantee an effective and selective protection of DC microgrids and avoid the damage of the power electronic converters are proposed.
    Keywords: microgrids; short circuits; ground faults; power electronics; converters; protections; solid state circuit breakers.