International Journal of Power and Energy Conversion (31 papers in press)
Supervisory Control Using Fuzzy Logic for Fault Ride-Through Capability of a Hybrid System in Grid Supporting Mode
by Chayan Bhattacharjee, Binoy Krishna Roy
Abstract: This paper demonstrates a novel supervisory control algorithm for power extraction and its management in a grid-tied low concentration photovoltaic system (LCPV) with battery energy storage system (BESS). The proposed controller functions in grid support mode where it provides different power share between the local load and the grid. Two broad cases are studied based on different irradiance periods. These are healthy and faulty grid conditions. The supervisory controller directs all the power converters and maintains power balance at the common dc link. Reactive power support of the grid inverter during a grid fault is controlled by using the magnitude of grid voltage sag. This control scheme prevents islanding of the dc microgrid in accordance with the Indian grid code. Under normal grid condition, the considered hybrid system will dispatch full power generated, at the point of common coupling. Transient variation in dc link voltage is stabilised via battery charge control. The selection of control parameters for optimum power extraction from low concentration photovoltaic generator during grid faults is done by using fuzzy logic. Both inverter and battery control power references are selected based on different operational modes during normal and faulty conditions of the grid. Use of dump load is avoided at the dc link for dc link voltage transient stabilisation during sudden load changes and grid faults; such a method adopted has increased the system efficiency.
Keywords: Battery Energy Storage System; Low concentration photo-voltaic; Maximum power point tracking; Supervisory controller and Voltage Oriented control.
Optimization of planers tilts angles reflectors for solar hybrid photovoltaic thermal air collector
by Tabet Ismail, Khaled Touafek, Bellel Nadir, Nouredine Bouarroudj, Khalifa Abdelkarim
Abstract: Using concentrators to the output of hybrid photovoltaic thermal solar collectors (PV/T) has been proven cost effective. Flat reflectors offer a simpler, reliable, and cheap solution to increase the amount of solar radiations that fall on the solar collector. They provide a uniform concentration of solar radiation over the PV/T collector and prevent a hot-spot phenomenon. The objective of this study is to find the optimum tilt angle of the reflector with respect to the hybrid PV/T air collector by implementing a particle swarm optimization method (PSO). The PV/T air collector is south oriented and tilted at site latitude angle. The total incident solar radiation on the PV/T air collector surface is estimated. An experimental test was conducted in the southern region of Algeria on a prototype of the hybrid PV/T air collector, with two reflectors mounted on the lower and upper parts of the PV/T air collector. A 9%-19% increase in quantity of solar radiation incidents on the PV/T air collector was observed with the addition of planer reflectors.
Keywords: hybrid PV/T collector; planer reflectors; optimization; PSO.
Improvement of the line losses, weaker buses and saddle-node-bifurcation points using reconfigurations of the identified suitable lines
by Parimal Acharjee
Abstract: For the voltage stability analysis and the security assessment of the power systems, the identification of the weaker lines or buses are very important. For the planning, operation, and design of the modern power systems, the effect of the network reconfiguration of the identified weaker lines are now-a-days investigated. The Saddle-Node Bifurcation (SNB) is one of the most popular voltage stability indexes by which weaker buses or lines can be determined. Gradually increasing the load, the SNB point is determined using modified continuation power flow (MCPF) algorithm considering the practical security constraints. The three different sets of the security limits (i.e. three cases) are judged for the voltage stability analysis. The weakest and the weaker buses are detected from the power flow solution at the SNB point for all cases. The three different reconfigurations are implemented on the identified weaker lines for the standard IEEE-14, 30, and 57-bus test systems separately. For all cases and for all test systems, the loading margin or the SNB point is enhanced and the voltage stability is improved as the voltage magnitudes of the weaker buses are increased. The line loss of each reconfigured line is significantly reduced. The overall network line losses are also minimized for all cases. The optimal location and the suitable lines for the reconfiguration are demonstrated with the results. Using the network reconfiguration, the significant improvement of the SNB points, weaker buses, line losses for the different cases are proved showing results.
Keywords: Network reconfiguration; modified continuation power flow; weaker lines; Saddle-Node Bifurcation; line losses.
Transmission Line Capacity Improvement Using Thyristor Controlled Series Compensation Device Considering Voltage Stability Analysis
by AMRANE Youssouf
Abstract: reactive power planning (ORPP) problem using the thyristor controlled series compensator (TCSC) device with consideration of voltage stability with handling the improvement of transmission line capacity in electrical network. To improve this case of study, two other objective functions are associated. The first is the angle deviation minimisation problem; it minimises the difference between the sending and receiving bus angles. And the second one is voltage deviation problem which aims to improve the system voltage profiles. The choice for these associate objective functions is defined by the most influence of bus angles and voltages to improve the system transmission line capacity. Also, the proposed algorithms satisfy various constraints, which are: power flow equations, generator voltage limits, switchable capacitor banks, transformer tap changer limits and transmission line limits. The fast voltage stability index (FVSI) is used to identify the critical lines to install the TCSC controllers. The methodology has been tested in the equivalent Algerian
electrical power systems 114 bus. The simulation results show the effectiveness
of the proposed approach for improving the reactive power planning problem.
Keywords: optimal reactive power planning; ORPP; interior point method; IPM; thyristor controlled series compensator; TCSC; transmission line capacity improvement; Algerian electric power system.
A Modernistic PLL Based on Feed Forward Frequency Estimator with Selective Harmonic Pre filter for Grid Imperfection
by Seema Agrawal, Dheeraj Kumar Palwalia
Abstract: This paper describes a synchronization technique to track phase and frequency of input signal under abnormal grid condition like frequency variation. Proposed control topology consist of a conventional synchronous reference frame phase locked loop (SRF PLL) type -2 along with a feed forward frequency estimator loop with selective harmonic filtering technique. It eliminates phase and frequency error under wide frequency deviation. Phase error is fed into proportional integral regulator which reduces it to zero. It is observed that faster and better dynamic performance is achieved by frequency estimator with higher stability margin. The stability is evaluated by bode plot. An estimated frequency is smooth and close to fundamental frequency as it uses the information from all three phase to estimate a single value for frequency. The feed forward action is implemented with pre filtering stage to improve dynamic performance of system. Simulation results are presented to validate effectiveness of proposed technique.
Keywords: Phase lock loop (PLL); Synchronous reference frame; Dynamic performance; Grid synchronization; Frequency estimation; Selective harmonic filtering.
Impact of Battery Electric Vehicles on Low Voltage Distribution Networks
by Bhuvaneswari Ramachandran, Gnansigamani Bellarmine
Abstract: Due to their high energy capacity and potential mass deployment, Battery Electric Vehicles (BEVs) will have a significant impact on power distribution networks. There are issues for the Distribution Network Operator if BEV charging is allowed to take place without any control on the time of day, duration or charging rate. Specifically, the network voltage may fall below prescribed limits at times of peak demand and power flows may cause a thermal overload of assets. The existing literature on scheduling charging/discharging of BEVs makes use of decentralized/centralized control architectures to study the effect of charging/discharging of BEVs on distribution network. This paper presents a teaching-learning algorithm method to optimally charge and discharge the BEVs and hence mitigate the adverse impacts on the distribution network by considering the driving behavior of car owners. This approach has resulted in reduced transformer loading even when using V2G and G2V modes of operation of the BEVs and hence has prevented transformer aging in low voltage distribution networks.
Keywords: BEV battery; electric vehicles; smart charging and discharging; distribution network; aging of the distribution transformer.
Direct power control of three-phase PWM AC/DC converter based on intelligent approach with dc-bus voltage regulation using sliding mode controller
by Mohamed Akherraz, Mohamed Barara, Mustapha Jamma, Abderrahim Bennassar
Abstract: This research aims to present a novel direct power control (DPC) strategy of three-phase PWM AC/DC converters. In this strategy, the regulation of the dc-bus voltage is based on non-linear sliding mode controller (SMC), therncontrol of the instantaneous active and reactive power is performed by fuzzy logic controllers (FLC) and also the artificial neural networks (ANN) approach is used to select the switching states of PWM AC/DC converter. The sliding mode control is an effective tool to minimize disturbances. Nevertheless, the chattering phenomenon depicts a major problem for variable structure systems (VSS). To overcome this drawback, a saturation function is employed to decrease chattering effects. The proposed method allows, on the one hand, to steer the dc-bus voltage, the instantaneous active and reactive power to their reference values. On the other hand, it enables to reduce the harmonic disturbances, the power ripples and to realize a unity power factor (UPF) operation. Simulation results are provided to confirm the efficiency, the robustness and the performances of the proposed DPC scheme in different conditions of simulation.
Keywords: direct power control; sliding mode controller; artificial neural networks approach; fuzzy logic controller; PWM AC/DC converter.
Performance Evaluation of Backstepping Approach for Wind Power Generation System Based Permanent Magnet Synchronous Generator and Operating Under Non-ideal Grid Voltages
by Youssef Errami, Abdellatif Obbadi, Smail Sahnoun, Mohammed Ouassaid, Mohamed Maaroufi
Abstract: Under the increasing integration of wind energy into power systems, an effective control strategy of a Wind Farm System (WFS) plays a fundamental role in wind power exploitation. This paper presents a nonlinear control strategy to track the maximum power point for 4 MW-WFS based on Permanent Magnet Synchronous Generator (PMSG) and interconnected to the electrical network. The proposed configuration consists of a 2 PMSGs connected to a common dc-bus system through a rectifiers. The dc-bus is connected to the power grid through only one inverter system. The control schemes are based on nonlinear Backstepping theory to control both PMSG and grid-side converters of a WFS. The main objective of this control is to regulate the velocities of the PMSGs with Maximum Power Point Tracking (MPPT) for the complete functioning regions of a wind turbine system. Besides, the grid-side converter is used to control the dc link voltage and to regulate the power factor at varying wind velocity. The stability of the regulators is obtained using Lyapunov analysis. The simulation results through MATLAB/Simulink are presented and discussed to demonstrate the validity and efficiency of the proposed methodology. Finally, a comparison of results based on the proposed Backstepping approach and conventional Proportional Integral (PI) regulator is provided for different grid voltage conditions and under parameter deviations.
Keywords: Wind Farm System; PMSG; MPPT; Nonlinear Control; backstepping approach; Electric Network Connection.
Detection and Classification of Power Quality Events Using Empirical Wavelet Transform and Error Minimized Extreme Learning Machine.
by MRUTYUNJAYA SAHANI
Abstract: The main purpose of this paper is to detect the Power Quality Events (PQEs) by Empirical Wavelet Transform (EWT) and classify by Error Minimized Extreme Learning Machine (EMELM). Empirical Wavelet Transform (EWT) is used to analyze the non-stationary Power Quality Event signals by Multi Resolution Analysis (MRA). Here, the disturbance energy index feature vector of different electric power supply signals have been acquired by applying the EWT on all the spectral components and to analyze the overall efficiency of the proposed method on both ideal and noisy environments, three types of PQ event data sets are constructed by accumulating the noise of 25, 35 and 45dB. ELM is an advanced and efficient classifier, which is implemented to recognize the single as well as multiple PQ fault classes. Based on very high performance under ideal and noisy environment, the new EWT-EMELM method can be implemented in real electrical power systems. The feasibility of proposed method is tested by simulation to verify its cogency.
Keywords: Disturbance Energy Index; Empirical Wavelet Transform; Error Minimized Extreme Learning Machine (EMELM); Multiresolution Analysis; Non-stationary power quality events.
Sensorless control and diagnosis of synchronous generator used in wind energy conversion system under inter turn short-circuit fault
by Samir Bouslimani, Saïd Drid, Larbi Chrifi-Alaoui
Abstract: This paper deals with control and diagnosis of the synchronous generator (SG) used in a wind energy conversion system under inter turn short-circuit fault. In the first part of this paper, a speed sensorless control of the synchronous generator is presented. In this case speed estimation is carried out using model reference adaptive system (MRAS). In the second part, the MRAS observer is associated with the Luenberger observer in order to estimate the stator resistances according d and q axis. The stability of the system is proved by using Lyapunov theory. Finally, the proposed new hybrid observer MRAS-Luenberger is used to detect the turn-to-turn short circuit faults. The Parks vector approach (PVA) is adopted to take decision if there are faults. The proposed technique is tested on dSPACE DS1103 and the results confirm
the efficacy to detect the fault by observing the shape. This method gives us the right information for the fault isolation.
Keywords: synchronous generator; condition monitoring; inter-turn short-circuit; park vector approach; PVA; fault diagnosis; wind power.
A priority list based fuzzy logic controller for short term unit commitment problem
by JITENDRA KUMAR, ASHU VERMA, T.S. Bhatti
Abstract: This paper presents a fuzzy logic based priority list method to solve the unit commitment problem. The priority list order is selected according to the maximum output power rating of the generating units while satisfying all the constraints over a period of time. The turn on (commitment) and turn off (de-commitment) decision of thermal generating units is handled by priority list order with fuzzy logic algorithm. A fuzzy optimization based approach is developed to find the optimal solution by using fuzzy operations and if-then rules. The objective of the optimization is to achieve minimum operating cost by scheduling of generator units. In solving the unit commitment problem reliability and feasibility constraints are checked for the planning interval. This method is implemented on standard IEEE 69-bus, 11-thermal generator system. Use of the fuzzy logic controller with priority list method enables the handling of uncertainties in load forecast in an efficient manner.
Keywords: unit commitment; priority list order; fuzzy logic controller.
Empirical Wavelet Transform and dual feedforward neural network for classification of power quality disturbances
by Karthik Thirumala, Aditi Kanjolia, Trapti Jain, Amod C. Umarikar
Abstract: This paper proposes a novel approach for classification of single and combined power quality (PQ) disturbances. The EWT based adaptive filtering technique is employed first to decompose the signal into its individual frequency components by estimation of frequencies. The frequency estimation in this paper is done using a divide-to-conquer principle based FFT technique and followed by an adaptive filter design. Then, some unique potential features reflecting the characteristics of disturbances are extracted from the mono-frequency components as well as the signal. A single classifier used for the classification of combined disturbances, whose characteristics are alike, gives less classification accuracy. Therefore, the use of a dual FFNN is proposed for the classification of single and combined PQ disturbances to effectively reduce the misclassification and improve the accuracy. The effectiveness of the proposed approach is evaluated on a broad range of time-varying power signals with varying degree of irregularities, noise, and fundamental frequency deviation. The results obtained for both the simulated as well as the real disturbance signals elucidate the efficiency and robustness of the proposed approach for classification of the most frequent disturbances.
Keywords: Power quality (PQ); Fast Fourier transform (FFT); Empirical wavelet transform (EWT); Adaptive filtering; Dual feedforward neural network.
Analysis of impact of atmospheric overvoltages in Kosovo Power System
by Bahri Prebreza, Isuf Krasniqi, Bujar Krasniqi
Abstract: In this paper are given aspects of modelling and analysis of atmospheric overvoltages for Kosovo power system. Atmospheric overvoltages are one of the leading causes of outages in Kosovo power system. Analysis of the impact of these overvoltages increases the effectiveness of the functioning process of transmission of electric energy in general and also involves the use of effective protective equipment in power systems like surge arresters, mainly for improving the performance of high-voltage transmission lines. Different location models for the establishment for surge arresters are also discussed. Transmission lines with poorest performance are discussed, regarding the atmospheric overvoltages. For the analysis of these overvoltages is used ATP/EMTP software, to solve efficiently and economically reasonable protection. In the simulation is used the metal-oxide surge arrester nonlinear model, dependent on the frequency. This model is proposed by the IEEE 3.4.11
working group and it has nonlinear V-I characteristic.
Keywords: alternative transient program/electromagnetic transient program; ATP/EMTP; lightning; overvoltages; surge arresters; transmission lines; Kosovo.
Variable structure power control under different operating conditions of PM synchronous generator wind farm connected to electrical network
by Youssef Errami, Abdellatif Obbadi, Smail Sahnoun, Mohammed Ouassaid, Mohamed Maaroufi
Abstract: The enlarged penetration of wind power into electrical network brings challenges to control strategies of Variable Speed Wind Energy Conversion Systems (VS-WECS). In this study, a nonlinear control scheme for Wind Farm System (WFS) is proposed. The WFS consists of a 3 PMSG which are connected to a common dc bus system with rectifiers. The dc-bus is connected to the power network through only one inverter system, a grid-side filter as well as the transformer. The control technique is realized using Variable Structure Sliding Mode Control (VSSMC). First, a model is elaborated on the basis of the d-q axes reference frame. Furthermore, a VSSMC scheme is obtained in the sense of theorem of Lyapunov stability for the WFS to satisfy several objectives. The generator side rectifiers control is used to keep the generator rotor velocities at an optimal value obtained from the Maximum Power Point Tracking (MPPT) algorithm to maximize the total extracted power. The grid-side inverter injects the generated power into the AC network, regulates DC-link voltage and it is used to achieve unity power factor. Also, a pitch control scheme is proposed in order to prevent wind turbine destruction from excessive wind velocity. The simulation results demonstrate the effectiveness of the proposed VSSMC strategy in different scenarios, and their advantages are shown in comparison with a conventional Proportional Integral (PI) control approach under grid fault conditions and the possible presence of uncertainties.
Keywords: Variable Speed Wind Farm System; PMSG; MPPT; Nonlinear Control; VSSMC approach; Electric Network Connection.
A Hybrid Hilbert Huang Transform and Improved Fuzzy Decision Tree Classifier for Assessment of Power Quality Disturbances in a Grid Connected Distributed Generation System
by Tatiana Chakravorti, R. Bisoi, N.R. Nayak
Abstract: This paper focuses on Discrete Hilbert Huang transform (HHT) and Improved Fuzzy decision tree (IFDT) based detection and classification of power quality (PQ) disturbances as a new contribution to the literature. A distributed generation (DG) based microgrid has been modeled with wind and solar. Different PQ disturbances have been simulated with various wind speed and PV penetration. The PQ signals are passed through Empirical mode decomposition (EMD) to obtain the intrinsic mode functions (IMFs). These IMFs are enforced to the Hilbert Transform (HT) to extract the instantaneous attributes. These attributes of Hilbert Transform (HT) are used for features extraction. Based on these extracted features Improved Fuzzy rules are formed for classification of the PQ disturbances. Synthetically PQ disturbances are simulated to check the performance of the proposed method. All these signal samples are processed through the proposed algorithm. The proposed method has been found to be capable of accurate detection and classification of PQ disturbances than many other techniques in the literature.
Keywords: Distributed Generations (DG); Hilbert Huang Transform (HHT); Improved Fuzzy Decision Tree (IFDT); Pattern Recognition; Power Quality Disturbances.
Design Strategies for Speed Control of an Inverter fed Permanent Magnet Synchronous Motor Drive
by RAMANA PILLA, Alice Mary Karlapudy, Surya Kalavathi Munagala
Abstract: Permenant Magnet Synchronous Motor (PMSM) drives are becoming more popular and replaces DC and Induction motor drives in industrial applications like rolling mills, home appliances, transport systems, robotics & factory automation, hybrid electic vehicles etc. Various control schemes are suggested in the literature for variable speed AC drives fed from static power sources. Among them field oriented control employing vector control strategies has become quite popular in recent years. A disadvantage of the scheme when applied to PMSM drives is that the motor always operates at a lagging power factor. In this paper, a generalized design strategy for speed control loop of an inverter fed PMSM drive is suggested. In this design for different combinations of currents, same torque can be generated, which leads to more general control scheme. The closed loop control system for PMSM drive is simulated using MATLAB. The performance figures of various cases such as internal p.f angle control, torque angle control and field oriented control can be obtained and verified through simulation for different power factors of the motor ranging from lagging to leading through unity.
Keywords: Field Oriented Control; Internal Power Factor Angle Control; Permanent Magnet Synchronous Motor; PI controller; Speed Controller; Torque Angle Control.
Reliability Analysis of the PMU Microwave Communication Networks Using Generalized Stochastic Petri Nets
by D.K. Mohanta, Bhargav Appasani
Abstract: The phasor measurement units (PMUs) have evolved as powerful extrapolations of the supervisory control and data acquisition (SCADA) systems due to their profound applications. The PMU combines the measured voltage and current phasors with the time signals received from the global positioning system (GPS), to provide an effective solution for real time monitoring of the smart grid (SG). In the SG several such PMUs continuously generate the time tagged quantitative data which are communicated to a central monitoring station known as the phasor data concentrator (PDC). This quantitative data carries the information pertaining to the grid dynamics. At the PDC the data collected from several PMUs is synchronized and is subsequently analyzed by a decision making expert. The communication system plays a pivotal role in the transfer of the phasor measurements and thus should be highly reliable. This article presents a detailed approach for the construction of the generalized stochastic petri nets (GSPNs) for the reliability analysis of the PMU microwave communication networks (MCNs). These communication networks are optimally planned to achieve maximum reliability without compromising the system observability. Case study results for the North Eastern power grid of India are presented to demonstrate the efficacy of the proposed approach.
Keywords: Reliability; Smart Grid; Phasor Measurement Unit; Generalized Stochastic Petri Nets.
A Control Scheme for Grid-Tied Hybrid Modular Multilevel Converter under Grid Voltage Unbalance
by RASHMI RANJAN BEHERA
Abstract: This paper presents a Finite-Control-Set Predictive Current Control
(FCS-PCC) scheme for the recently proposed Hybrid Modular Multilevel
(HMMC) based grid connected system. The HMMC has several advantages over
the conventional Modular Multilevel Converter (MMC) as well as other multilevel
topologies. This topology has reduced number of switch counts compared to the
conventional MMC, eliminates the problem of circulating current and having
higher efficiency. The required number of Sub-Modules (SM) is half of the
conventional MMC, along with an H bridge circuit per phase. This paper analyses
the real and reactive power control through FCS-PCC and addresses the AC side
grid unbalance by third harmonics injection method. During grid side voltage
unbalance, there is a problem of the unequal amount of power exchange between
per-phase converter and grid, which needs to be taken care of with an appropriate
control method. This study proposed a method to add or subtract an amount of
third harmonic component with the reference current signal given to the predictive controller to maintain the grid current at the desired level. The whole concept has been presented along with a simulation study in Matlab/Simulink environment and the results are presented in support of the described concept.
Keywords: Hybrid modular multilevel converter; grid-connected; predictive current control; grid voltage unbalance control.
Fresh particle crowd optimization of efficiency-oriented control in interior permanent magnet synchronous motor during operation
by Hakchol Jong
Abstract: High-efficiency electric drive systems claim not only optimally designed electric machines but also efficiency-oriented control strategies. Taking machines and drives into synergetic consideration, this paper proposes a fresh particle crowd optimization (FPCO) of efficiency-oriented control algorithm named maximum outer torque per ampere (MOPA) control and maximum efficiency per ampere (MEPA) control, aiming to maximize the efficiency of interior permanent magnet synchronous machines during operation. Difference from conventional id = 0 or maximum torque per ampere control, MOPA and MEPA fully consider the cross effect Core loss, iron loss, supplementary loss and mechanical loss, from which the full-order loss model of interior permanent magnet synchronous motor (IPMSM) is built. In order to identify the accuracy of the efficiency-oriented control algorithm, the efficiency-oriented controlled system on based FPCO using nonsingular terminal sliding (NTS) controller is built, on the base of this, the stabilization of the the current trajectory and the voltage vector from simulation and testing are inspected. After that, the higher effectiveness of MOPA and MEPA is proved through the operation experiment of IPMSM.
Keywords: Fresh particle crowd optimization; interior permanent magnet synchronous motor; maximum outer torque per ampere; maximum efficiency per ampere; nonsingular terminal sliding; space vector pulse width modulated.
Fuel Cell Integration with Grid using Voltage Source Converter and its Control
by Sabha Raj Arya, N. Sharath Kumar, Ashutosh Giri, Amin Qureshi
Abstract: Due to increased burden on the grid, voltage and frequency control becomes very difficult. Moreover nonlinear domestic appliances are also contributing towards power quality problems related with voltage and current. To share the burden of grid and for increasing the power quality at the end users authors have proposed new topology comprising fuel cell along with voltage source converter (VSC) used as DSTATCOM connected in shunt at point of common coupling of load and source. To control the VSC, forward backward least mean square algorithm (FBLMS) is used. In this algorithm, error between desired and estimated signal is calculated in both forward and backward directions. The average error is calculated based on forward path error. Further the active weight components and the reactive weight components are used to calculate reference source current for gate pulse generation. The complete system is simulated and validated in the laboratory environment with one prototype, the results are satisfactory.
Keywords: Voltage source converter; Power Quality; Proton Exchange Membrane (PEM),Fuel Cell,FBLMS.
OPTIMAL REACTIVE POWER ALLOCATION AND SETTLEMENT IN DEREGULATED POWER MARKET
by Sarmila Har Beagam, Jayashree R, Abdullah Khan
Abstract: DC Power Flow Model is a constant matrix, non-iterative model which is built into DC Optimal Power Flow Model for market clearing and settlement of real power market. DC Optimal Power Flow Method is fast when compared to Non linear Optimal Power Flow and the accuracy level is acceptable for security analysis. It is widely used for active power flow analysis in deregulated power system. As of now, there are few papers available in DC Optimal Power Flow Model for reactive power flow analysis. This paper proposes a new Optimal Q Flow (OQF) method for market clearing and settlement of pure reactive power market to overcome the variability of loss price due to change in marginal bus. A lumped linear model is proposed for fast convergence. The power balance equality constraint and voltage inequality constraints are incorporated in the OQF method. In this method a unique reference for delivery / withdrawal point for reactive power called Market Center is proposed to share the total transmission loss equitably between the GENCO and DISCO participants in a transparent manner for pure Q Market using incremental loss factor method. The objective function is to minimize the cost of the reactive power payable to GENCOs with respect to market center. The compensation received by GENCO participants and Locational Marginal Price to be paid by DISCO participants are derived for a single sided auction market. The OQF method is tested on a Radial Five Bus System, Ward and Hale 6 Bus System and Indian Utility 119 Bus System .The bus voltage magnitude computed using the Iterative Q Flow method is accurate and obtained for a mismatch tolerance of 0.1 MVAr. The objective function is to minimize the cost payable to GENCOS and reactive power balance constraint includes the reactive power losses. The proposed algorithm when applied to test system indicates that the losses are reduced.
Keywords: Iterative Q Flow; Market Center; Incremental loss factor; Loss Allocation; Market clearing and settlement; Locational Marginal Compensation and Locational Marginal Price.
Frequency and Tie-line Power Awareness in Eco-AGC of multi-area Power system with SSO based Fractional Order Controller
by Prakash Chandra Sahu, Ramesh Chandra Prusty
Abstract: The article focuses on how a conventional AGC (Automatic Generation Control) will be economically efficient. A very less research has been carried out owing to this economical aspect of AGC. The main function of AGC is to control mechanical power in accordance with unexpected load variation. AGC aims to keep system frequency and net scheduled interchanges between different control areas (tie-line power) within predetermined values. This conventional AGC tries to keep Area Control Error (ACE) zero to maintain system stable. Though frequency and tie-line power are maintained within predetermined values but generation may not be economically dispatched. So ACE based AGC are economically inefficient to absorb its own load deviation and are economically weak. To generate power economically with scheduled frequency value and to make economically efficient to conventional AGC, it is required to combine Conventional AGC with Economic Load Dispatch (ELD) which combined known as Economic AGC (Eco-AGC). In Eco-AGC concern unlike conventional AGC, deviation in frequency is brought back to zero but scheduled interchanges never comes to zero rather settled to a new value as power always flows from lower incremental fuel cost generating station to higher incremental cost generating station in response to load demand. To perform Eco-AGC, this research article proposes a novel Salp Swarm Optimization (SSO) based Fractional order fuzzy controller for reducing errors and to maintain system stable with economic efficient. To justify robustness of proposed controller different sensitive analysis has been done with wide variation of system parameters. In regard to optimization process Integral of Time Multiplied Absolute Error (ITAE) has been used as objective function due to its improved dynamic response producing capability.
Keywords: Automatic Generation Control (AGC); Area Control Error (ACE); Economic Load Dispatch (ELD); Salp Swarm Optimization (SSO); Step Load Perturbation (SLP); Fractional Order Fuzzy PID (FO-FPID).
Design of Fractional Order Proportional Integral (FOPI) Controller for Load Frequency Control of Multi Area Power System under Deregulated Environment
by KURAKULA VIMAL, V. GANESH
Abstract: The main objective of the present article is introduced to focus how efficiently to minimize the deviations in frequency and Area Control Error caused by load fluctuations and uncertainties in load under the deregulated environment of power system. This work is carried out to eliminate the frequency errors by using Fractional Order Proportional Integral (FOPI) Controller under deregulated environment by considering the effect of one possible bilateral contract scenario. In Electrical industry under deregulated environment, the Load Frequency Control and Automatic Generation Control system have been considered by taking the effect of bilateral contracts. So a DISCO has liberty to have agreements with GENCOs in other areas also. The proposed work is to enhance the system parameters such as line transmitted power, frequency deviation error, and area control error (ACE) using Fractional Order PI Controller for hydro-thermal, thermal-thermal power system under deregulated power system. Because of system nonlinearities, uncertainties and continuously fluctuant load demand the design of these controllers is quite complicated in deregulated environment. hence it is proposed an integer Fractional order PI (FOPI) Controller is to solve LFC problem of interconnected multi area Hydro-Thermal, Thermal-thermal systems in deregulated environment by considering one bilateral contract scenario. The results have been analyzed with classical integer order PI controller and FOPI controller. It is observed that the efficacy of the results is satisfied and improved when compared with previous work.
Keywords: LFC; AGC;PI Controller; FOPI Controller and Integer Order PI Controller.
Finite Element Validation of the Analytical Model of Variable Reluctance Motor
by Souhir TOUNSI
Abstract: In this paper, we present a methodology for the parameterized modeling of a synchronous motor with variable reluctance. This methodology is based on the analytical method offering the possibility of the coupling of the analytical program to optimization algorithms of large dimensions since this method is fast in term simulation time. The analytical model is validated by the finite element method in two dimensions in linear regime and in saturated regime.
Keywords: Variable Reluctance Motor; Analytic Method; Finite Element Method; Validation.
Solar power forecasting using Robust Kernel Extreme Learning Machine and Decomposition Methods
by Irani Majumder, Ranjeeta Bisoi, Niranjan Nayak, Naeem Hannoon
Abstract: This paper proposes both wavelet and Empirical Mode Decomposition (EMD) based robust Kernel Extreme Learning Machine (RKELM) variants to achieve a precisely predicted value of solar power generation in a smart grid environment with a high penetration of solar power. The non-stationary historical solar power data is initially decomposed into various intrinsic mode functions (IMFs) using EMD technique or several approximate and detailed coefficients using wavelets, which are subsequently passed through the proposed robust Morlet wavelet kernel extreme learning machine (RWKELM) in order to predict 15 minutes, 1 hour and 1 day ahead solar power, respectively. Further a reduced kernel matrix version of RWKELM is used to decrease the training time significantly without appreciable loss of forecasting accuracy. For validation of the proposed solar power forecasting technique, the real time data from a 1 MW Photovoltaic (PV) station in the state of Odisha, India is used. By implementing the real time data for validation of the proposed method for short term solar power prediction it can be observed that the proposed EMD based RWKELM outperforms other kernel functions and other prevalent methods, in terms of different performance matrices and execution time, under various prediction horizons. Further the computational overhead of the proposed EMD-wavelet kernel can be reduced by selecting a subset of randomly chosen support vectors from training samples which drastically reduces the computational time with a slight loss in the forecasting accuracy in solar power prediction. The solar power prediction results on experimental data show the lowest errors which proves the highest prediction accuracy as compared to some of the well known forecasting techniques like ELM, EMD based ELM, WD based ELM, SVM, RBFLNN and other variants of kernel functions.
Keywords: Solar power forecasting; Empirical Mode Decomposition (EMD); Wavelet transform decomposition (WD); extreme learning machine (ELM); Robust Kernel based Extreme Learning Machine (RKELM); Reduced kernel matrix.
A comprehensive simulator of AC autotransformer electrified traction system
by Mohammad Hossein Bigharaz, Seyed Hossein Hosseinian, Ahmad Afshar, Amir Abolfazl Suratgar, Mehdi Amiri Dehcheshmeh
Abstract: In this paper a comprehensive simulator for a 2 × 25 kV AC autotransformer electrified traction system with MTL arrangement is developed. The main goal of this simulator is to complete performance analysis of a traction system consisting of some moving trains controlled by a virtual driver or ATO system under natural constraints and traction power limits. In order to evaluate the electrical performance, an advanced load flow analyser is proposed, which calculates all electrical parameters of the system by generating the equivalent admittance matrix of the entire system. The electrical effects of trains on each other are well extracted, when they are moving with various operational modes and speeds on a track. This simulator is well adapted to the real system Tehran-Golshahr suburban railway as a case study. A genetic algorithm-based optimisation core with some predefined objectives is developed and analysed for current balancing as a sample capability.
Keywords: high speed transportation; autotransformer traction system; multi-conductor transmission line; MTL; load-flow; simulation; electric railway.
Decomposition method for solution of a multi-area power dispatch problem
by Senthil Krishnamurthy, Raynitchka Tzoneva
Abstract: Large interconnected power systems are decomposed into areas or zones based on the size of the electric power system, network topology and geographical location. Multi-area economic emission dispatch (MAEED) problem is an optimisation task in power system operation for allocating amount of generation to the committed units within these areas. Its objective is to minimise the fuel cost subject to the power balance, generators limits, transmission lines, and tie-line constraints. The solution of the MAEED problem in the conditions of deregulation is difficult, due to the model size, nonlinearity, and interconnections. It determines the amount of power that can be economically generated in the areas and transferred to other areas if it is needed without violating tie-line capacity constraints. High-performance computing (HPC) gives possibilities for reduction of the problem complexity and the time for calculation by the use of parallel processing for running advanced application programs efficiently, reliably and quickly.
Keywords: multi-area dispatch problem; Lagrange’s decomposition method; electricity market; high performance computing; parallel computing.
Uncertainty cost functions for solar photovoltaic generation, wind energy generation, and plug-in electric vehicles: mathematical expected value and verification by Monte Carlo simulation
by Juan Camilo Arevalo, Fabian Santos, Sergio Rivera
Abstract: Electrical power systems which incorporate solar or wind energy sources, or electric vehicles, must deal with the uncertainty about the availability of injected or demanded power. This creates uncertainty costs to be considered in stochastic economic dispatch models. The estimation of these costs is important for proper management of energy resources and accurate allocation of the amount of energy available for the system. In this paper, analytical formulas of uncertainty penalty costs are calculated, for solar and wind energy and for electric vehicles, through a mathematical expected value formulation. In order to get the proposed uncertainty cost functions, probability distribution functions (PDF) of the energy primary sources are considered, that is to say: log-normal distribution for solar irradiance PDF, Rayleigh distribution for wind speed PDF and normal distribution for loading and unloading behaviour PDF of electric vehicles. The analytical formulation is verified through Monte Carlo simulations.
Keywords: wind and solar energy; electric vehicles; uncertainty cost; economic dispatch models; mathematical modelling.
Optimal placement and sizing of distributed generation in an unbalance distribution system using grey wolf optimisation method
by Arjun Tyagi, Ashu Verma, Lokesh Kumar Panwar
Abstract: The distributed generation sources (DGs) are becoming increasingly attractive due to introduction of small scale renewable energy sources. They can be integrated in to low voltage distribution networks, to reduce the burden on transmission and sub transmission network. However, the number of DGs, their placement, and sizing can influence the advantages from the distribution network operation point of view. Also, most of the time the planning is done considering the peak load demand only. However, the losses obtained at peak load, may not give the realistic picture. This paper demonstrates the application of a grey wolf optimisation method for obtaining the optimal size and location of DGs (solar photovoltaic-based) in an unbalanced distribution network. The method proposed in this paper provides a set of solutions from the point of view of voltage stability enhancement and loss minimisation. The utility can prioritise either voltage stability enhancement or loss minimisation or both to choose the best compromised solution. Moreover, the losses are calculated by considering the seasonal load and PV generation patterns during the year to simulate the real picture of distribution system. Results on 33 bus balanced and 25 bus unbalanced distribution system are taken to demonstrate the potential of the proposed algorithm.
Keywords: distributed generator; energy loss; grey wolf optimiser; GWO; optimal size; optimal location.
Perturbation and observation as MPPT for highly penetrated grid-integrated PV generator considering symmetrical three-phase fault
by Tha'er O. Sweidan, Mohammad S. Widyan, Mohammed B. Rifai
Abstract: This paper presents perturbation and observation (P&O) as maximum power point tracking (MPPT) technique applied on grid-integrated PV generator. The interfacing is carried out via DC-DC buck-boost converter, three-phase sinusoidal DC-AC inverter, LC filter, transformer and two identical transmission lines. Large-signal stability analysis has been carried out considering symmetrical three-phase to ground fault as a case study at the middle of one of the transmission lines. The idea behind introducing the DC-DC converter is to adjust its duty cycle using the P&O algorithm such that to extract the maximum power available in the PV generator at all practical solar irradiance levels. The results show that the highly penetrated grid-integrated PV generator can keep the stability of its operating point despite the large-disturbance considered. It is also concluded that overshoot and settling time of the power system are highly affected by the fault clearing time and solar irradiance level. The higher the solar irradiance level is, the higher the critical clearing time, the larger the overshoot and the lower the settling time tend to be.
Keywords: perturbation and observation; P&O; maximum power point tracking; MPPT; photovoltaic generator; power system dynamics; large-signal stability; symmetrical three-phase fault.
Optimal AGC scheme design using hybrid particle swarm optimisation and gravitational search algorithm
by Nour El Yakine Kouba, Mohamed Menaa, Mourad Hasni, Mohamed Boudour
Abstract: In this paper, a novel hybrid particle swarm optimisation and gravitational search algorithm (HPSO-GSA) is proposed to design an optimal automatic generation control (AGC) scheme in interconnected power system. The proposed algorithm combines the advantages of both particle swarm optimisation (PSO) and gravitational search algorithm (GSA). This new meta-heuristic HPSO-GSA is applied to achieve the optimal proportional-integral-derivative (PID) controller parameters. Hence, the optimal PID controller is used to reduce the system fluctuations with the best dynamic performances. The AGC issue is formulated as an optimal load frequency control problem, where the frequency fluctuations and the tie-line power flow deviations are to be minimised in the same time. In order to test the performance of the proposed HPSO-GSA strategy, the integral time multiplied by absolute error (ITAE) is used as an objective function. To evaluate the efficiency of the proposed approach over disturbances, the standard two-area power system is used for the simulation. The obtained simulation results are compared to those yielded using classical and heuristic optimisation techniques surfaced in the recent state-of-the-art literature. The comparative study demonstrates the potential of the proposed strategy and shows its robustness to solve the optimal AGC problem.
Keywords: automatic generation control; AGC; load frequency control; LFC; optimal control; particle swarm optimisation; PSO; gravitational search algorithm; GSA; hybrid PSO-GSA.