WSEAS Transactions on
Power Systems

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Print ISSN: 1790-5060
E-ISSN: 2224-350X

Volume 7, 2012

Issue 1, Volume 7, January 2012

Title of the Paper: Application of Ant Colony Algorithm to the Analysis of High Frequency Equivalent Circuit of DC Motor

Authors: Jinfeng Liu, Xudong Wang, Nan Jiang

Abstract: The Electromagnetic Compatibility (EMC) of direct current (DC) motor windings is a system model which is able to reflect the functional characters of the system in the whole EMC specified frequency(150KHz~30MHz). For most motor designing process, it always evaluated the inductance of windings in lower or working frequency; however, when analyzing the conducted interference, it is necessary to take some parameters in high frequency into account in building up the EMC model, such as the noticeable distributed capacitance among the windings or between windings and shells. Past research neglected the common-mode current generated by the high frequency interference through motor bearings coupled with shells, since the parasitic capacitance of rotor core comes from armature windings supplied sufficient paths. In EMC modelling for DC motor problem, first test the impedance of windings by experiments, then generate the equivalent circuit with total parameters. At present, it is a difficulty that how to choose the parameters. Most researchers preferred to adopt analytical calculation, however, it could not reflect the essence of the model since it requires many simplification. As a result, this paper adopted ant colony algorithm (ACA) with positive feedback to intelligent search and global optimize parameters of equivalent circuit. Simulation result showed that impedance of equivalent circuit calculated by this algorithm was the same as experimental result in the whole EMC frequency. In order to further confirm the validity of ACA, PSPICE circuit simulation was adopted to simulate the spectrum of common mode Electromagnetic Interference (EMI) of equivalent circuit. The simulation result accorded well with the experiment result received by EMI receiver. So it sufficiently demonstrated correctness of ACA in the analysis of high frequency equivalent circuit.

Keywords: Ant colony algorithm, Motor windings, EMC, Conducted interference, Common mode EMI, PSPICE simulation, EMI receiver

Title of the Paper: Optimal Capacitor Placement to Reduce Losses in Distribution System

Authors: Anwar S. Siddiqui, Farrukh Rahman

Abstract: Distribution system provides a final link between the high voltage transmission system and the consumers.To improve the overall efficiency of power system, the performance of distribution system must be improved. An important method of controlling bus voltage is by shunt capacitor banks at the buses at both transmission and distribution levels along lines or substation and loads. The problem of capacitor allocation in electric distribution systems involves maximizing “energy and peak power (demand) loss reductions” by means of capacitor installations. As a result power factor of distribution system improves. A 10 bus radial distribution system is taken as model. The load flow program is executed using Fuzzy Logic toolbox of MATLAB. Fuzzy logic based technique is used for determination of suitable location of capacitor placement. Shunt capacitors to be placed at the nodes of the system will be represented as reactive power injections. Fuzzy techniques have advantages of simplicity, less computations & fast results.

Keywords: Power System, shunt capacitor banks, bus voltage control, Capacitor Placement

Title of the Paper: System Frequency Regulation Investigation in Doubly Fed Induction Generator (DFIG)

Authors: Xue Yingcheng, Tai Nengling

Abstract: The conventional decoupling control in the variable-speed doubly fed wind turbines has little support to the system frequency. The characteristics of doubly fed induction generator (DFIG) wind turbines and conventional plant are compared. The contributions of DFIG to system inertial response and frequency regulation are investigated. The influence of auxiliary loop parameters on the inertial response is illustrated. The paper also introduces a novel algorithm to enhance the participation of DFIG in existing frequency regulation mechanisms. The proposed approach takes advantage of the fast response capability associated with DFIG. The control system consists of four functional modules, i.e. frequency control, rotational speed delay recovery, speed protection and coordination control with conventional generators. Simulation results show that the control strategy has a fast response speed to the transient frequency error. It proves that wind farms can participate in the system frequency regulation to a certain extent.

Keywords: DFIG, inertial response, wind turbine generators, Frequency regulation, power control

Title of the Paper: Aggregate Static Power Load Modeling in Coalmine

Authors: A. O. Pei, M. U. Long-Çua

Abstract: In order to overcome the defects of the traditional static load modeling in coalmine, a new modeling method is proposed in this paper. First, a new clustering method based on improved PSO algorithm is presented to classify the load data in order to reduce the number of load model before modeling. Second, RBF neural network based on improved PSO algorithm is put forward to establish aggregate load model. Finally, verified by an example, the method in this paper can greatly improve the accuracy of the model compared with traditional static load model.

Keywords: aggregate static load model, particle swarm clustering algorithm, subtractive clustering algorithm, K-means clustering algorithm, radial basis neural network, power grid in coalmine

Title of the Paper: Comparing Efficiency of PSO with GA in Transmission Expansion Planning Considering Network Adequacy

Authors: Meisam Mahdavi, Amir Bagheri, Elham Mahdavi

Abstract: The lines adequacy of the network is necessary to provide load demands when the network is expanding, because its lack caused by load interruption. In this paper, in order to take the transmission lines condition after expansion into account from the line loading view points, the adequacy of the transmission network is considered for the solution of the STNEP problem. To obtain the optimal network arrangement, a discrete particle swarm optimization (DPSO) algorithm is being used for minimizing the network construction and operational cost and compared with genetic algorithm (GA). The particle swarm optimization is a recently developed evolutionary algorithm based on the swarm behavior in the nature and has a strong ability to find the most optimistic results. The motivation for using the DPSO technique is to reduce design effort and find an optimum planning network. The effectiveness of the proposed idea is tested on the Garver's six-bus network and an actual transmission network of the Azerbaijan regional electric company in Iran. The evaluation results evaluation reveals that the annual worth of the network adequacy has a considerable effect on the network arrangement. In addition, the obtained network, based on the DPSO algorithm, has lower investment cost and higher adequacy rate. To verify the results, expansion cost index on adequacy rate for IEEE Garvers network has been compared with GA results.

Keywords: DPSO, GA, STNEP, Network adequacy, Optimization problem, Transmission lines

Issue 2, Volume 7, April 2012

Title of the Paper: Synchronised Linear Ramp-Pulse Based Triggering Pulse Generation ON/OFF Control for Solid-State Switches: Capacitor Switching Applications

Authors: K. Subramanian, K. K. Ray

Abstract: This paper describes a newly developed triggering circuit, has been use to turn on and off the solid-state switches, such as TRIAC switched capacitors applications. A linear ramp signal based synchronization technique has been propose and implemented successfully, for the capacitor switching operation of a simple power system. This scheme enables the firing circuit to adjust itself against any phase and/or sequence alterations. This feature leads to elimination of the phase locked-loop (PLL) control, are commonly used to synchronize the pulse generations with respect to the system the supply frequency. Those pulses are, to control the converter / inverter operation of an industrial drives and the FACTS controllers also. The proposed circuit has been constructing and tested experimentally in the laboratory. The simulation work completed using Or CARD software. The result shows a good agreement with the theoretical waveforms.

Keywords: linear ramp signal, synchronization, capacitor switching

Title of the Paper: Application of Fuzzy Principles in Evaluating Quality of Manufacturing Process

Authors: Hrehova Stella, Vagaska Alena

Abstract: The article deals with the possibility of using artificial intelligence elements in order to evaluate the quality of a manufacturing process. There are described selected indexes of a production process quality evaluation based on statistical process control (SPC), their interpretation and evaluation by means of fuzzy sets, which enable us to work with inaccurate, incomplete or vague information about a monitored and reviewed phenomenon. There are described possibilities of using program system Matlab and its toolboxes Simulink and Fuzzy Logic to evaluate quality of the manufacturing process based on fuzzy principles.

Keywords: SPC, quality, manufacturing, process, fuzzy, Matlab

Title of the Paper: Lightning Surge Response Improvement by Combinations of Varistors and Gas Discharge Tubes

Authors: Hitoshi Kijima, Kazuo Murakawa

Abstract: This paper proposes a new methodology for protecting power apparatuses against overvoltage or overcurrent caused by lightning surge. Surge Protective Devices (SPDs) are used for protecting apparatuses against overvoltage or overcurrent caused by lightning surge. SPDs are mainly divided into two categories. One is clamping type and the other is switching type. Typical clamping type SPD is a variable resitor (varistor). Typical switching type SPD is a Gas-filled Discharge Tube (GDT). Both varistors and GDTs have problems when using them alone. Therefore both a GDT and a varistor are normally connected in series or parallel. However these simple connections of them have still problems. This paper proposes a lightning surge response improvement by combinations of both varistors and GDTs in order to solve the problems of them. It is that three or more GDTs are connected in series and two or more varistors are connected in parallel. This new methodology has already beeing filed as patents in many countries. The proposed methodology could solve the problems of conventional combinations of a GDT and a varistor.

Keywords: Surge protective device, Varistor, Gas discharge tube, Lightning surge, Overvoltage, Overcurrent

Title of the Paper: Optimal Power System Stabilizer Based Enhancement of Synchronizing And Damping Torque Coefficients

Authors: Ali M. Yousef, Ahmed M. Kassem

Abstract: Design of power system stabilizer for enhancement power system stability is proposed. The effect of the proposed PSS on the synchronizing and damping torque coefficients is proved. To study the effectiveness of the proposed linear quadratic regulator (LQR) power system stabilizer, a sample power system in a linearized model is simulated and subjected to different operating conditions. The Linear Quadratic Gaussian (LQG) power system stabilizer is proposed. The power system dynamic responses after applying a variety of operating points with the proposed LQG-PSS stabilizer are plotted. The output of such stabilizer is fed directly to the automatic voltage regulator (AVR) of the synchronous machine. The input to such stabilizer are four state variables, two are accessible which are the deviation of the speed (Äù) and rotor angle (Ää). The other two inaccessible states that are the deviation of the Voltage proportional to q-axis flux linkage. (ÄE'_q) and the Generator field voltage (ÄE_fd). An observer has been designed to access the two inaccessible states. Further, the effect of connecting the proposed power system stabilizer on synchronizing and damping torque coefficients is tabulated. A comparison between the effect of the power system stabilizer based on either LQR approach, the proposed LQG stabilizer in terms of either power system responses or its eigenvalues due to different load condition is reported.

Keywords: Power Systems, LQR Control, LQG Power System Stabilizer

Title of the Paper: Optimizing the Inspection Routine for the Detection of Electrical Energy Theft in AES Eletropaulo in São Paulo, Brazil

Authors: L. J. Hernandes Jr., L. C. Duarte, F. O. Morais, E. C. Ferreira, J. A. Siqueira Dias

Abstract: This work describes the development of a non-invasive and low-cost process that allows for the improvement of the energy theft inspection routine, increasing the field inspection team productivity and reducing the customer's embarrassment in cases where no irregularity is found. This new process is based on the development of an electronic Ah meter device that can be installed on the customer's pole input connections to the power lines. Using the recorded Ah value in the device, it is possible to estimate, within a margin of error, the energy consumption of the customer during a small period, typically one week. This energy value is compared to the customer's regular energy meter reading for the same period. A comprehensive statistical study performed with a database of more than 80000 customers in distribution area of the utility company AES Eletropaulo in São Paulo, Brazil concludes that the comparison between these readings can clearly indicate when tampered or defective meters are found.

Keywords: Electrical energy theft, fraud inspection routine, electricity tariffs, sustainable development, emergent countries, energy efficiency, illegal energy consumers

Issue 3, Volume 7, July 2012

Title of the Paper: Determination of Steady State Stability Margin Using Extreme Learning Machine

Authors: Indar Chaerah Gunadin, Muhammad Abdillah, Adi Soeprijanto, Ontoseno Penangsang

Abstract: Power systems have increased in size and complexity due to rapid growth of widespread interconnection. This situation will make power system operated closer to steady-state stability limit (SSSL) resulting in higher probability voltage instability or voltage collapse. This paper presents SSSL assessment in power system using Extreme Learning Machine (ELM) model based on REI-Dimo method. The equivalent REI-Dimo is used to determine SSSL index of the power systems. Then, the result of REI-Dimo will be taught on ELM method via online. The results of ELM will compared with Artificial Neural Network (ANN) method. Studies were carried out on a Java-Bali 500kV system. The simulation showed that the proposed method could accurately predict the proximity to SSSL in power system. The proposed method was computationally efficient and suitable for online monitoring of steady-state stability condition in the power systems.

Keywords: Extreme Learning Machine, ANN, REI-Dimo Equivalent, SSSL, Voltage Collapse

Title of the Paper: Intelligent Load Management Scheme for a Residential Community in Smart Grids Network Using FEDRP

Authors: Muhammad Ali, Z. A. Zaidi, Qamar Zia, M. Zakaria, S. M. Ahsan, M. Rameez

Abstract: In the framework of liberalized deregulated electricity market, dynamic competitive environment exists between wholesale and retail dealers for energy supplying and management. Smart Grids topology in form of energy management has forced power supplying agencies to become globally competitive. Demand Response (DR) Programs in context with smart energy network has influenced prosumers and consumers towards it. In this paper Fair Emergency Demand Response Program (FEDRP) is integrated for managing the loads intelligently by using the platform of Smart Grids for Residential Setup. The paper also provides detailed modelling and analysis of respective demands of residential consumers in relation with economic load model for FEDRP. Due to increased customer’s partaking in this program the load on the utility is reduced and managed intelligently during emergency hours by providing fair and attractive incentives to residential clients, thus shifting peak load to off peak hours. The numerical and graphical results are matched for intelligent load management scenario.

Keywords: Demand Response (DR); Fair Emergency demand response program (FEDRP); Intelligent Load Management (ILM); Residential Area Networks (RAN); Smart Grids

Title of the Paper: Diagnosis of Power Transformer Faults based on Five Fuzzy Ratio Method

Authors: N. K. Dhote, J. B. Helonde

Abstract: Dissolved Gas Analysis is one of the most useful method to detect incipient faults in transformer. Amongst the conventional DGA methods, IEC three ratio method is widely used. One of the disadvantages in its present form is that a significant number of DGA results in- service fall outside the existing IEC codes and cannot be diagnosed. To overcome this limitation, additional eighteen new combinations to the existing nine are proposed in this paper. Further, Ratio codes are quantized to define the crisp boundaries of 0,1 and 2. In practice these boundaries are non crisp (Fuzzy) especially under multiple faults condition. These codes could lead to errors in diagnosis moving across the crisp boundaries from one fault to another. To overcome these limitations, Five Fuzzy ratio method for diagnosis of multiple faults is developed. The paper used 100 different cases to test the accuracy of these methods in interpreting the transformer condition.

Keywords: Expert System (ES),Dissolved Gas Analysis(DGA),International Electro Commission Method (IEC), Incipient Faults, Power Transformer, Fault Diagnosis, Fuzzy Diagnostic System, Ratio Methods

Title of the Paper: Wavelet Entropy: Application in Islanding Detection

Authors: Smita Shrivastava, Shailendra Jain, R. K. Nema

Abstract: With the increased demand of electrical power, penetration of distributed generation in the grid is also increased. Connecting distributed generators with grid created many interconnection problems. Islanding detection is an important and challenging issue of them. Several methods are available in literature based on passive and active detection schemes. Both schemes have their own problems like non detection zone, nuisance tripping, and power quality degradation. This paper proposes wavelet entropy based passive detection scheme. This method can detect islanding with zero non detection zone (NDZ) and without affecting the output power quality. The implementation of the method is done on Matlab- Simulink and its effectiveness is test for standard IEEE test circuit.

Keywords: Distributed generators, Islanding detection, Wavelet, Energy Entropy, Non detection zone, Inverter

Title of the Paper: Bidding Strategies for Generation Companies in a Day-ahead Market using Fuzzy Adaptive Particle Swarm Optimization

Authors: J. Vijaya Kumar, D. M. Vinod Kumar, K. Edukondalu

Abstract: This paper presents a methodology based on Fuzzy Adaptive Particle Swarm Optimization (FAPSO) for the preparation of optimal bidding strategies corresponding unit commitment by Generation companies (Gencos) in order to gain maximum profits in a day-ahead electricity market. In a competitive electricity market with limited number of suppliers, Gencos are facing an oligopoly market rather than a perfect competition. Under oligopoly market environment, each Genco may increase its own profit through a favorable  bidding strategy. In FAPSO the inertia weight is tuned using fuzzy IF/THEN rules. The fuzzy rule-basedsystems are natural candidates to design inertia weight, because they provide a way to develop decision mechanism based on specific nature of search regions, transitions between their boundaries and completely dependent on the problem. The proposed method is tested with a numerical example and results are compared with Genetic Algorithm (GA) and different versions of PSO. The results show that fuzzying the inertia weight improve the search behavior, solution quality and reduced computational time compared to GA and different versions of PSO.

Keywords: Bidding Strategy, Electricity Market, Fuzzy Inference, Market Clearing Price (MCP), Particle Swarm Optimization (PSO)

Title of the Paper: Optimization Assisted Load Tracing via Hybrid Ant Colony Algorithm for Deregulated Power System

Authors: Z. Hamid, I. Musirin, M. N. A. Rahim, N. A. M. Kamari

Abstract: The development of electricity tracing theory is to solve the problem concerning fair and non-discriminatory transmission service pricing of a deregulated power system. As the traditional methods such as postage stamp allocation and megawatts-mile methodology neglect the consideration of physical power system constraints, the allocation of service charge is said to be unreliable and rather biasing. At the same time, proportional sharing principle (PSP) based power tracing techniques necessitate for matrix inversion process; in which sometimes cannot be performed due to singularity property of the matrix. As a result, the tracing results are unable to be obtained due to error in mathematical operation. To try a new approach, this paper demonstrates the technique to implement Artificial Intelligence (AI) based optimization for performing load tracing, that is, by means of a new hybrid algorithm; Blended Crossover Continuous Ant Colony Optimization (BX-CACO) with simple and easy formulation steps. Experiment on IEEE 30-bus system together with comparative studies justifies the capability of the proposed technique for real system application.

Keywords: BIM, BX-CACO, Load Tracing, Matrix Singularity Property, PSP, TLDF

Issue 4, Volume 7, October 2012

Title of the Paper: Unit Commitment and Economic Load Dispatch using Self Adaptive Differential Evolution

Authors: Surekha P., N. Archana, S. Sumathi

Abstract: Unit Commitment (UC) and Economic load dispatch (ELD) are significant research applications in power systems that optimize the total production cost of the predicted load demand. The UC problem determines a turn-on and turn-off schedule for a given combination of generating units, thus satisfying a set of dynamic operational constraints. ELD optimizes the operation cost for all scheduled generating units with respect to the load demands of customers. The first phase in this project is to economically schedule the distribution of generating units using Genetic Algorithm (GA) and the second phase is to determine optimal load distribution for the scheduled units using Self Adaptive Differential Evolution (SADE) algorithm. GA is applied to select and choose the combination of generating units that commit and de-commit during each hour. These pre-committed schedules are optimized by SADE thus producing a global optimum solution with feasible and effective solution quality, minimal cost and time and higher precision. The effectiveness of the proposed techniques is investigated on two test systems consisting of six and ten generating units and the experiments are carried out using MATLAB R2008b software. Experimental results prove that the proposed method is capable of yielding higher quality solution including mathematical simplicity, fast convergence, diversity maintenance, robustness and scalability for the complex UC-ELD problem.

Keywords: Unit Commitment, Economic load dispatch, Genetic Algorithm, Self Adaptive Differential Evolution, computational time, IEEE 30 bus system

Title of the Paper: Excitation Control of the Synchronous Machines with use an Error Function of the Complex Argument

Authors: Oleg N. Agamalov

Abstract: In paper the new structure of the automatic voltage regulator (AVR) and the power system stabilizer (PSS) of the synchronous machines is considered. It is known, that the primary goal, that solved AVR are maintenance of a terminal voltage of the synchronous machine according to the reference. For PSS the goal is mitigation the electromechanical oscillations of the synchronous machine at various disturbances. For these purposes as inputs of AVR and PSS the set of state variables of the synchronous machine is used: terminal voltage, armature current, frequency, speed, power, etc. The key feature of offered excitation control system is use only the phasor of terminal voltage for the decision of all above-stated problems, that considerably reduces influence of noises and disturbances, simplifies its design and operation.

Keywords: Hilbert transform, error function of the complex argument (EFCA), Wirtinger calculus, differential of EFCA, small-signal stability, transient stability

Title of the Paper: Field Orientation Control of a Wind Driven DFIG Connected to the Grid

Authors: Mahmoud A. Mossa

Abstract: This paper aims to develop a method of field orientation scheme for controlling both active and reactive powers of a DFIG (double fed induction generator) driven by a wind turbine. The controlled system consists of a wind turbine that drives a DFIG connected to the utility grid through AC-DC-AC link. The control method is based on the theory of controlling the ed and eq axes components of voltage and current for both rotor side and line side converters using PI controllers. The main control objective is to regulate the dc link voltage for operating at the maximum available wind power. A mathematical dynamic model of a DFIG driven by a wind turbine system is presented. Digital simulation has been carried out in order to evaluate the effectiveness of the proposed system. The results confirm that good steady state and dynamic performances of the proposed system has been achieved under different types of wind speed variations.

Keywords: Wind turbine, DFIG, reactive power control of induction machines, PI controller, field orientation, WECS, MATLAB simulation

Title of the Paper: A Comprehensive Simulation Platform for Switched Reluctance Generator System

Authors: A. Arifin, I. H. Al-Bahadly, S. C. Mukhopadhyay

Abstract: A Switched Reluctance Generator (SRG) system normally encompasses three main components: SR machine, controller and converter. On-going research on simulation and modelling of SRG system has focused on one component. There is a lack of a more comprehensive approach which integrates all three components into one simulation platform. We have developed a simulation model comprising SR machine, control and converter using MATLAB/Simulink. The main advantage of a simulation model is to reduce time and cost by having to perform changes on the prototype machine. In this paper, the work is focused on developing the optimal control algorithm for the platform. Optimal parameters are identified and characterized in terms of highest percentage of power generated. From simulation, the most influential parameters affecting the power generated are the firing angles and voltage level. So, a function relating the optimized parameter with machine performance was developed. The proposed control technique will provide easy implementation and ensure high machine performance. The effectiveness of the proposed method is demonstrated by simulation results. The work will aid in development of SRG by providing a platform to determine the best generating operation before real implementation, reducing manufacturing time and cost.

Keywords: Current control, Finite Element Method, Optimization, Simulation of SRG drive, Switched reluctance generator (SRG), SRG control

Title of the Paper: Application of DE & PSO Algorithm For The Placement of FACTS Devices For Economic Operation of a Power System

Authors: B. Bhattacharyya, Vikash Kumar Gupta, S. K. Goswami

Abstract: In this paper, use of Differential Evolution (DE) based and Particle swarm optimization (PSO) based algorithm for the allocation & coordinated operation of multiple FACTS (Flexible AC Transmission System) devices for the improved power transfer capacity and economic operation of an interconnected power system is presented. Both the DE and PSO based approach is applied on IEEE 30-bus system. The system is reactively loaded starting from base to 200 % of base load and the system performance is observed with and without FACTS devices. Active and reactive power flow in different lines gives an idea in determining the positions of FACTS devices to be placed in the system for the improved performance. Then the DE & PSO based optimization approach is applied to find the size of the FACTS devices and the comparative analysis between these two techniques are made. This differential evolution (DE) based approach for the installation of FACTS devices found as more beneficial than PSO based method.

Keywords: Line Power Flow, FACTS devices, Optimal location of FACTS devices, Operating cost, Differential Evolution, Particle Swarm Optimization