International Journal of Power and Energy Conversion (33 papers in press)
Comparative Analysis of Several Linear Controllers with Developed Feedback Controllers for DSTATCOM
by Amr Elnady
Abstract: This paper analyses the performance of the distribution static
compensator (DSTATCOM) for two linear controllers and two developed state
feedback controllers. The paper clarifies how the DSTATCOM controls the
reactive power using the quadrature current, Iq, and the active power for
adjusting its DC voltage across its capacitor, Vdc. The PI and PID controllers
are employed as an example for a linear controller. The linear quadratic
regulator (LQR) and a novel structure and formulation of the decoupled
state feedback controller, SFC, are adopted as tools for the pole placement so as
to control the operation of the DSTATCOM. A comprehensive analysis for
these four controllers is given to justify the merits and demerits of each
controller. In addition, the proposed state feedback is also compared to an
integral sliding mode controller, SMC, to prove its superior performance.
Finally, three different applications for the developed state feedback controller
are demonstrated to prove the meritorious performance of this developed
control scheme for the operation of the DSTATCOM to control the reactive
power and mitigate voltage quality problems within distribution systems.
Keywords: distribution static compensator; DSTATCOM; PI; PID; linear
quadratic regulator; LQR; SMC; decoupled state feedback controller.
Perturbation and Observation as MPPT for Highly Penetrated Grid-Integrated PV Generator Considering Symmetrical Three-Phase Fault
by Tha'er Sweidan, Mohammad Widyan, Mohammed Rifai
Abstract: This paper presents Perturbation & Observation (P&O) as Maximum Power Point Tracking (MPPT) technique applied on grid-integrated PV generator. The interfacing is carried out via DCDC 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 when the PV generator is intensified with different solar irradiance levels. The dynamic stability analysis is executed based on the nonlinear dynamical mathematical model of the complete power system elements in d-q stationary reference frame. 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 and power system running conditions. The results show that the highly penetrated grid-integrated PV generator can keep the stability of its operating point despite the large-disturbance considered at wide range of solar irradiance levels. 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 & Observation; MPPT; Photovoltaic Generator; Power System Dynamics; Large-Signal Stability; Symmetrical Three-Phase Fault.
A New Model of Self-Excited Induction Generator (SEIG) to Feed a Single Phase Load with an Application in Lighting Animal Farm
by Nassim Iqteit, Abdelkarim Daud
Abstract: This paper presents a new model of self-excited single-phase induction generator, used by a three-phase machine for lighting animal farm through biogas energy. The designs and applications of the previous generator models have been found to be very complex, for this reason simple and effective model of SEIG is proposed. The transient equations of the proposed model were represented by SIMULINK blocks, while the steady state equations by electrical equivalent circuit. The model is derived from Steinmetz connection circuit, stationary reference frame qd-axes theory and symmetrical component theorem. Experimental and simulation using MATLAB are the two methods used to prove the validity of the present model. Results obtained from the two methods were closed to each other. Also, the perfect balance point was achieved at unity power factor. This application proved that the output voltage and current have sinusoidal waves which implying that the generator was operating efficiently.
Keywords: self-excited induction generator; SEIG; biogas engine; lighting animal farm; dynamic model; steady state model.
Improving the dynamic frequency regulation of a Multisource Power System considering GRC and Deadband with TCSC and SMES
by Rajesh Joseph Abraham, Deepak M
Abstract: Coordinated operation of Superconducting Magnetic Energy Storage (SMES) and Thyristor Controlled Series Compensator (TCSC) for dynamic frequency regulation on a multisource power system consisting hydro, thermal and gas generating units is presented in this paper. The optimal integral gains of the control areas are obtained by tuning a quadratic performance index comprising frequency deviations and tie-line power error using Integral Squared Error technique. The effects of Generation Rate Constraint and Governor Dead Band nonlinearities are also considered. Time domain simulations carried out in MATLAB on a sample two area multi-unit power system comprising hydro, thermal and gas power plants reveal that the SMES-TCSC combination can effectively damp out deviations in area frequencies and tie-line power flow following a sudden load perturbation with better transient performance and reduced settling time.
Keywords: Dead Band; Generation Rate Constraint; Integral Squared Error ; Superconducting Magnetic Energy Storage; Thyristor Controlled Series Compensatorrn(.
Impact of optimal location and sizing of distributed generation and automatic reclosers in distribution systems
by Luis F. Grisales, Alejandro Grajales, Oscar D. Montoya, Ricardo A. Hincapie, Mauricio Granada
Abstract: In this paper, a cascade methodology of two stages to solve the problem of the optimal location and sizing of distributed generators (DG), and determining an adequate protection scheme to improve reliability indices and reduce the nonsupplied energy level (NSEL) is proposed. In stage I, the optimal location of DG is determined by using a mathematical model, in which the objective function is composed by a linear combination between reduction of power losses and investment cost. To solve this problem, three sensitivity indices to determine a candidate set of nodes to install DG and three types of technologies are considered. A hybrid methodology based on Chu-Beasley genetic algorithm and particle swarm optimization is used as a solution technique. In stage II, normally closed and normally open reclosers are located; the concept of operational areas is analyzed and a multi-objective problem is formulated, where the investment costs minimization is the first objective function and NSEL minimization is the second objective function. To solve this stage, the NSGA II algorithm is employed. A 102-node test feeder was used in order to prove the efficiency of the methodology proposed.
Keywords: Automatic reclosers; Chu & Beasley genetic algorithm; distributed generation; multi-objective optimization; non-supplied energy level; NSGA-II; operational areas; particle swarm optimization.
Optimal placement of DSTATCOM, DG and their performance analysis in deregulated power system
by Surajit Sannigrahi, Sriparna Roy Ghatak, Debarghya Basu, Parimal Acharjee
Abstract: Recently, incorporation of Distributed Generation (DG) and Distributed Static Compensator (DSTATCOM) is increased in Radial Distribution System (RDS) due to the enormous electrical energy demand, power system deregulation, and different restriction over existing network expansion. However, the proper allocation of these devices is essential to ensure maximum potential benefit from the device. In this article, the optimal placement of DG and DSTATCOM is determined on IEEE 33-bus and 69-bus RDS with an aim to enhance voltage profile, reduce line losses, and maximize financial benefit. To reduce the search space and computational burden, the performance assessments of these devices are carried out only at weak bus locations that are identified using Voltage Stability Index (VSI). To quantify the financial benefit after a certain period of time, authors developed a logical formula namely Economic Benefit (EB). In addition, an innovative formula namely Relative Pollution Index (RPI) is developed to assess the environmental impact of these devices. First time, on the basis of the technical, economical, and environmental aspects, performance comparison between DG and DSTATCOM is thoroughly analyzed in this study, which will facilitate the planning engineers to identify the most beneficial device for the RDS.
Keywords: Optimal Placement; Distributed STATCOM; Distributed Generation; Deregulated Power System; Recovery Time; Economic Benefit; Relative Pollution Index.
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.
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
Keywords: High speed transportation; Autotransformer Traction System; MTL; Load-flow.
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 Sergio Rivera, Camilo Arevalo, Fabian Santos
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 behavior 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 Modeling.
Optimal Placement and Sizing of Distributed Generation in an Unbalance Distribution System using Gray Wolf Optimization 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.
Simulation of Different Power Methods for Induction Generator Faults Detection and Diagnosis
by Abdeslem Leksir, Bachir Bensaker
Abstract: This paper deals with a simulation of different power methods to detect and diagnose induction generator faults. Instantaneous partial and total power, active and reactive power, complex apparent power and transformed power from mechanic to electric nature are revisited, simulated and discussed in this paper for induction generator rotor broken bars and stator short cuts faults detection and diagnosis. Fast Fourier transform (FFT) and PQ transform algorithms are used as comparison tools. Simulation results show that, on one hand, active, reactive and complex apparent power can only be used to detect evolution of rotor faults. On the other hand, partial, total and power transferred from mechanical to electrical nature are able to detect induction generator faults evolution with the advantage of eliminating electrical distortions and influence of low quality of supplying voltage. Furthermore, the implementation of the PQ transformation offers the possibility to isolate load influence from rotor faults and stator ones.
Keywords: induction generator faults diagnosis; power modelling; partial; total power; complex; transformed power; active-reactive power; rotor-stator fault
Optimal AGC Scheme Design Using Hybrid Particle Swarm Optimisation and Gravitational Search Algorithm
by Nour E.L. 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, standard two-area system is used. 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.
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: In this paper, the Interior Point Method (IPM) is applied to the Optimal Reactive Power Planning (ORPP) problem using the Thyristor Controlled Series Compensator (TCSC) device with consideration of voltage stability with handling the minimization 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 minimization problem it minimizes 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 chosen of 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; Interior point method; Thyristor controlled series compensator; transmission line capacity; 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 non-linear V-I characteristic.
Keywords: ATP/EMTP; lightning; overvoltages; surge arresters; transmission lines.
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.
Optimisation of blade profiles of cross flow turbine
by Assad Zaffar, Bilal Ibrahim, M. Awais Sarwar, Javed Ahmed Chattha, Muhammad Asif
Abstract: The areas where the supply of grid power is very difficult cross flow turbines (CFT) are used for low head power production. Results are presented for optimum profile of the leading edges of blade. Four different profiles (flat tip blade profile, round tip blade profile, pointed tip blade profile and oval tip blade profile) are modelled and simulated with ANSYS CFX and then compared their performance in terms of their efficiencies. The complete turbine is analysed for the determination of the leading edge of the blade in the first stage and the trailing edge in the second stage. The design and simulation conditions are based on the installed CFT at Chitral City of Pakistan. The results show that efficiency of the round tip blade profile is better than the other three profiles of the blade.
Keywords: blade profiles; cross flow turbine; CFT; turbine efficiency; renewable energy; hydro-power.
Analysis of power efficient compressor with fuzzy logic MPPT-based PV/FC system
by Rupendra Kumar Pachauri, Yogesh K. Chauhan
Abstract: In this paper, a hybrid photovoltaic (PV)/fuel cell (FC) power generation system is considered, where the hydrogen generated by the electrolysis process is used for subsequent FC operation. A novel induction motor-based compressor is proposed to boost up the pressure of hydrogen, and hence to improve the performance of the FC system. A fuzzy logic-based maximum power point tracking (MPPT) system is designed for the considered PV system. Finally, a coordinated control scheme is applied for controlling the power supplied to the load by integrating both the sources. The complete model is realised in the MATLAB/Simulink environment. Extensive simulation studies are conducted to verify the developed model. The performance of the complete system is found satisfactory under different conditions.
Keywords: solar PV system; electrolyzer system; hydrogen generation; fuzzy logic-based MPPT; coordinated control.
Robust loss coefficients: application to power systems with solar and wind energy
by Dario Arango, Ricardo Urrego, Sergio Rivera
Abstract: In a power system analysis, it is useful to find the relation between power losses and generated power on a power system. It can be performed using loss coefficients. The main drawback of traditional loss coefficients is that they must be recalculated in case that change in conditions takes place in the power system. In this paper, a comparison is performed by using different estimation methods of loss coefficients. The first method is the traditional Kron method (KM); the second one is a proposed modification of the traditional incremental method (IM); finally, a heuristic estimation method, robust under different changes in conditions of power systems, is proposed. Additionally, the paper presents an application of power losses estimation in power systems with solar and wind energy. The stochastic behaviour of solar and wind energy is modelled using the probability distribution of solar irradiance and wind speed, respectively.
Keywords: power losses; loss coefficients; solar energy; wind energy; heuristic optimisation.
Modified evolutionary programming for short-term hydrothermal scheduling
by Chitralekha Jena, Mousumi Basu, Chinmoy Kumar Panigrahi
Abstract: This paper presents modified evolutionary programming (MEP) method to determine the optimal hourly schedule of power generation in a hydrothermal system. Evolutionary programming (EP) is a class of evolutionary algorithm based on the basic genetic operation of human chromosomes. EP is capable of determining the global or near global solution. In this paper, MEP has been proposed to enhance speed and quality of solution. The MEP algorithm is tested on two test problems and two hydrothermal multi-reservoir cascaded hydroelectric test systems having prohibited operating zones and thermal units with valve point effect. The ramp-rate limits of thermal generators are taken into consideration. The transmission losses are also accounted for through the use of loss coefficients. The results of the proposed MEP approach have been compared with those obtained by other evolutionary methods. It is found that the proposed MEP approach can provide better solution at lesser computational effort.
Keywords: modified evolutionary programming; MEP; hydrothermal scheduling; ramp-rate limits; valve point effect; prohibited operating zones.