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Optimal placement of custom power Optimal placement of custom power Document Transcript

  • INTERNATIONALIssue Engineering– and Technology (IJEET), ISSN ENGINEERINGInternational Journal of Electrical0976 – 6553(Online) Volume 3, JOURNALDecember (2012), © IAEME 0976 – 6545(Print), ISSN 3, October OF ELECTRICAL & TECHNOLOGY (IJEET)ISSN 0976 – 6545(Print)ISSN 0976 – 6553(Online)Volume 3, Issue 3, October - December (2012), pp. 187-199 IJEET© IAEME: www.iaeme.com/ijeet.aspJournal Impact Factor (2012): 3.2031 (Calculated by GISI) ©IAEMEwww.jifactor.com OPTIMAL PLACEMENT OF CUSTOM POWER DEVICES IN POWER SYSTEM NETWORK FOR LOAD AND VOLTAGE BALANCING D.K. Tanti1, M.K. Verma2, Brijesh Singh3, O.N. Mehrotra4 1,4 Department of Electrical Engineering, Bihar Institute of Technology, Sindri (INDIA) E-mail: 1dktanti@yahoo.com , 4 onmehrotra@gmail.com 2,3 Department of Electrical Engineering, Indian Institute of Technology (BHU), Varanasi (INDIA) E-mail: 2mkverma.eee@iitbhu.ac.in , 3brijeshsingh81@indiatimes.com ABSTRACT In this paper, a criterion based on Artificial Neural Network (ANN) has been developed for optimal placement of Distribution Static Compensator (DSTATCOM), Dynamic Voltage Restorer (DVR) and Unified Power Quality Conditioner (UPQC) in a power system network for balancing of load voltage and current against switching of unbalanced load across it, and to balance voltage at all other buses which get affected due to connection of unbalanced load in the system. A feed forward neural network with back propagation algorithm has been trained with unbalanced bus voltages with targets defined as balanced bus voltages prior to connection of unbalanced load in the system. The optimal bus has been taken as the bus having maximum squared deviation of three phase unbalanced bus voltage from its target value. The DSTATCOM, DVR and UPQC have been placed at the optimal bus or in the line connecting optimal bus. Case studies have been performed on IEEE 14-bus system. Simulations have been carried out in standard MATLAB environment using SIMULINK and power system block-set toolboxes. The effectiveness of proposed approach of placement of custom power devices in load and voltage balancing has been established on the test system considered. KEYWORDS: Load balancing, Voltage balancing, DSTATCOM, DVR, UPQC, ANN 187
  • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME1. INTRODUCTION The present distribution systems are facing severe power quality problems such as poorvoltage regulation, high reactive power demand, harmonics in supply voltage and current, andload unbalancing [1]. Therefore, maintenance of power quality is becoming of increasingimportance in worldwide distribution systems. Industrial consumers with more automatedprocesses require high quality power supply else equipments such as microcontrollers, computersand motor drives may get damaged. High quality power delivery includes balanced voltagesupply to consumers. Connection of unbalanced load at a bus may cause unbalanced voltage andcurrent drawn by other loads connected at that bus. Switching of unbalanced load at a bus mayalso result in unbalanced voltage at some other buses. Unbalanced voltages contain negative andzero sequence components which may cause additional losses in motors and generators,oscillating torques in Alternating Current (AC) machines, increased ripples in rectifiers,saturation of transformers, excessive neutral currents and malfunctioning of several type ofequipments. With the advancement in power electronics, new controllers known as Flexible ACTransmission System (FACTS) have been developed [2]. These controllers have been proved tobe quite effective in power flow control, reactive power compensation and enhancement ofstability margin in AC networks [3]. Power electronics based controllers used in distributionsystems are called custom power devices. Custom power devices have been proved to be quiteeffective in power quality enhancement [1]. The custom power devices may be series, shunt, andseries-shunt or series-series type depending upon their connection in the circuit. Most prominentcustom power devices include Distribution Static Compensator (DSTATCOM), DynamicVoltage Restorer (DVR) and Unified Power Quality Conditioner (UPQC) [1]. There are severalpapers reported in literature on placement of custom power devices in balancing of unbalancedload in radial distribution systems. Load voltage balancing using DVR against unbalancedsupply voltage in radial distribution system has been considered [4], [5]. Placement ofDSTATCOM in weak AC radial distribution system for load voltage and current balancing hasbeen considered in [6]. Balancing of source currents using DSTATCOM in radial distributionsystem has been considered in [7]. In [7], unbalancing has been caused by connection ofunbalanced and non-linear load. Load compensation using DSTATCOM against unbalancingcaused by opening of one of the phase of the load in radial distribution system has beenconsidered in [8]. Balancing of supply across an unbalanced 4-phase load along with powerfactor improvement using DSTATCOM has been suggested in [9]. A Voltage Source Converter(VSC) based controller has been proposed in [10] to balance terminal voltage of an isolatedstandalone asynchronous generator driven by constant speed prime mover. A non-linear andunbalanced load has been connected at the generator terminals in [10] to create unbalance insupply voltages. A DVR/APF (Active Power Filter) based on Proportional Resonant (PR)controller has been proposed in [11] to protect sensitive industrial loads at the point of commoncoupling, against voltage harmonics, imbalances and sags. The Artificial Neural Network (ANN)based methodologies have been successfully applied in several areas of the ElectricalEngineering, including detection of voltage disturbances, voltage and reactive power control,fault detections [12]-[14]. An AI based UPQC has been modeled using MATLAB toolbox toimprove power quality [15 ].To generate switching signals for the series compensator of theUPQC system NNC algorithm such as MRC and NARMA-12 has been used. The paper [16 ] has 188
  • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEMEproposed a model for UPQC to compensate input voltage harmonics and current harmonicscaused by non-linear load. The control strategies are based on PI and ANN controller. Again, inpaper [17 ] the ANN based controller has been designed and trained off-line using data from theconventional proportional, integral controller. The performance of ANN and PI controller hasbeen studied and compared for UPQC using MATLAB simulation. An ANN based approach foroptimal placement of Custom Power Devices to mitigate voltage sag in a meshed interconnectedpower system, has been suggested in [18]. Unbalanced load connected at a particular bus may cause voltage unbalances at severalother buses in an interconnected power system network. No effort seems to be made in optimalplacement of custom power devices in an interconnected power system network in balancing busvoltages at all the buses caused by unbalanced load connected at a particular bus. In this paper,an Artificial Neural Network (ANN) based approach has been proposed for optimal placement ofcustom power devices to balance unbalanced voltages in the whole power system network. TheANN has been trained with Levenberg Marquardth back-propagation algorithm (trainlm ). Casestudies have been performed on IEEE 14-bus system. [19].2 CUSTOM POWER DEVICES MODEL2.1 DSTATCOM model In the present work, the DSTATCOM has been represented as three independentlycontrollable single phase current sources injecting reactive current in the three phases at the pointof coupling. The proposed DSTATCOM model has been shown in Figure-1. The control schemeconsists of three control switches which can be set on/off as per compensation requirement. Themaximum and minimum reactive power injection limit of DSTATCOM has been taken as +50MVAR and -50 MVAR, respectively. Figure-1. Proposed DSTATCOM model 189
  • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME2.2 DVR model In the present work, the DVR has been represented as three independently controllablesingle phase voltage sources injecting complex voltages in series with the line in the threephases. The magnitude and angle of injected voltages may be controlled to balance load voltageat different buses. The proposed DVR model has been shown in Figure-2 . The control schemeconsists of six control switches which can be set on/off as per compensation requirement. Duringoff condition, the three control switches connected in series with the controllable single phasevoltage sources are open and the other three control switches in parallel with controllable voltagesources, are closed. When compensation is required , the three switches connected in series withindependently controllable voltage sources are closed, and the remaining three switches are madeopen. This permits injection of controllable complex voltages in the three phases of the linewhich causes load balancing and voltage balancing of different buses. Figure-2. Proposed DVR model2.3 UPQC model In the present work, UPQC has been considered as combination of DSTATCOM andDVR models suggested in sections 2.1 and 2.2, respectively.3. METHODOLOGY In this work, feed forward Artificial Neural Network with back propagation algorithmhas been used to find optimal location for DSTATCOM placement. The architecture of thisnetwork has been shown in figure-3. In figure-3, the input data p(1), p(2), ……….p(R) flow through the synapses weights wi,j.These weights amplify or attenuate the input signals before being added at the node representedby a circle. The summed data flows to the output through an activation function f. The neuronsare interconnected creating different layers. An elementary neuron with R inputs has been shownin figure-3. Each input is weighted with an appropriate weight w. The sum of the weighted inputsand the bias, b forms the input to the transfer function f. 190
  • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME Once the network weights and biases are initialized, the network is ready for training.The training process requires a set of examples of proper network behavior network inputs, p behavior—networkand target outputs, t. During training the weights and biases of the network are iterativelyadjusted to minimize the network performance function. The default performance function forfeed forward networks is Mean Square Error (MSE) — the average squared error between the henetwork outputs and the target outputs. The gradient is determined using a technique called back back-propagation, which involves performing computations backward through the network. In the proposed neural network archite architecture there are 20 hidden layers and 14 outputlayers. This network can be trained to give a desired pattern at the output, when thecorresponding input data set is applied. The training process is carried out with a large number ofinput and output target data. The system has been made unbalanced by connection of highlyunbalanced load at different load buses. The three phase balanced per unit (p.u.) voltages ofbuses prior to connection of unbalanced load, have been taken as output target data. The threephase p.u. voltages of buses under unbalanced loading conditions have been considered as inputdata to train the neural network. Once the network is trained some data are used to test thenetwork. The testing results provide information about the optimal location for the placement of locationDSTATCOM controller. Mean Square Error has been computed for all the buses. The load buscorresponding to highest mean Mean Square Error value has been selected as the optimal bus forthe placement of DSTATCOM controller. The placement of DVR is considered in each of the lacementlines connected to the optimal bus. The line where placement of DVR results in the maximumbalancing of voltage and load is considered as the optimal line for the placement of DVR. TheUPFC placement is considered in optimal line towards optimal bus. red (a) (b) Figure- Artificial Neural Network architecture -3. 191
  • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME4. CASE STUDY Case studies were performed on IEEE 14-bus system [15] having 14 buses and 20 lines.The system consists of 5 synchronous machines three of which are synchronous condensers.There are 11 loads in the system having a net real and reactive power demand of 259 MW and81.3 MVAR, respectively. The single-line-diagram of the system has been shown in figure-4.Simulation model of IEEE 14-bus system was developed using software packageMATLAB/SIMULINK [16]. The simulation block diagram of the system has been shown infigure-5. The developed plant model shown in figure-5 was used to find three phase balanced busvoltages prior to switching of unbalanced load, unbalanced three phase voltage and current at thebus where unbalanced load is switched on, and unbalanced three phase voltages at other buses inthe system. In order to create unbalance loading condition, an additional Y- connected highlyunbalanced load ; Phase A [P=1MW, Q=100MVAR] , Phase B [ P=25KW,Q=200KVAR] , Phase C [ P=1KW, Q=0.1KVAR] was connected at each bus considered at atime, with all other buses having balanced base case loadings. A feed forward neural networkwas trained with three phase unbalanced bus voltages. The balanced three phase voltages ofdifferent buses prior to connection of unbalanced load at a bus were considered as target data forthe neural network. The Mean Square Errors (MSE) were calculated for all the buses usingtraining data and target data. The MSE of all the buses have been shown in figure-6. It isobserved from figure-6 that bus-5 has maximum MSE value. Therefore, bus-5 was selected asthe optimal location for the placement of DSTATCOM controller. Placement of DVR wasconsidered in each of the lines connected to bus-5 viz. line 5-1, line 5-2, line 5-4 and line 5-6,respectively, and the three phase voltages of different buses were observed. It was found thatplacement of DVR in line 5-4 was more effective in voltage load and voltage balancingcompared to DVR placement in line 5-1, line 5-2 and line 5-6, respectively. Therefore, line 5-4was selected as the optimal line for the placement of DVR controller. UPFC placement wasconsidered in optimal line 5-4 towards optimal bus-5. Three phase voltage at all the buses and three phase current at the bus with unbalancedload were plotted versus time for the four cases – (i) without any controller (ii) with placementof DSTATCOM at the optimal bus (iii) with the placement of DVR in the optimal line and (iv)with the placement of UPQC in optimal line towards optimal bus. The relative performance ofDVR, DSTATCOM and UPQC in load and voltage balancing is studied to decide most suitablecontroller out of the three controllers considered. The variation of three phase voltage withrespect to time for all the buses and variation of three phase current with respect to time at thebus with unbalanced load were plotted using MATLAB software [16]. Three phase voltage andcurrent at bus-2 with unbalanced load connected at bus-2 have been shown in figure-7. Threephase voltage at bus-5 and at bus-10 with unbalanced load connected at bus-2 have been shownin figure-8. Three phase voltage and current at bus-10 with unbalanced load connected at bus-10have been shown in figure-9. Three phase voltage at bus-4 and at bus-5 with unbalanced loadconnected at bus-10 have been shown in figure-10. Three phase voltage and current at bus-12with unbalanced load connected at bus-12 have been shown in figure-11. Three phase voltage atbus-4 and at bus-7 with unbalanced load connected at bus-12 have been shown in figure-12. It isobserved from figures 7, 9 and 11 that placement of custom power devices in the network resultsin considerable balancing of load voltage and current at the bus with unbalanced load. It isobserved from figures 8, 10 and 12 that placement of custom power devices in the network isalso able to produce considerable voltage balancing at other buses. 192
  • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME Figure-4. Single-line-diagram of IEEE 14-bus system Figure-5. IEEE-14 Bus system (MATLAB/SIMULINK) model 193
  • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME Figure-6. Mean Square Error for different buses (IEEE 14-bus system) Unbalance load connected at Bus 2Bus No. 2 (Voltage waveform) 2 (Current waveform)WithoutControllerWith DVRin Line 5-4WithDSTATCOM at Bus 5WithUPQC atLine 5-4TowardBus 5 Figure-7. Three phase voltage and current at bus-2 with unbalanced load connected at bus-2 194
  • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME Unbalance load connected at Bus 2Bus No. 5 (Voltage waveform) 10 (Voltage waveform)WithoutControllerWith DVR inLine 5-4WithDSTATCOMat Bus 5With UPQCat Line 5-4Toward Bus 5 Figure-8. Three phase voltage at bus-5 and at bus-10 with unbalanced load connected at bus-2 Unbalance load connected at Bus 10Bus No. 10 (Voltage waveform) 10 (Current waveform)WithoutControllerWith DVR inLine 5-4WithDSTATCOMat Bus 5With UPQCat Line 5-4Toward Bus 5 Figure-9. Three phase voltage and current at bus-10 with unbalanced load connected at bus-10 195
  • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME Unbalance load connected at Bus 10Bus No. 4 (Voltage waveform) 5 (Voltage waveform)WithoutControllerWith DVRin Line 5-4WithDSTATCOM at Bus 5With UPQCat Line 5-4Toward Bus5 Figure-10. Three phase voltage at bus-4 and at bus-5 with unbalanced load connected at bus-10 Unbalance load connected at Bus 12Bus No. 12 (Voltage waveform) 12 (Current waveform)WithoutControllerWith DVRin Line 5-4WithDSTATCOM at Bus 5With UPQCat Line 5-4Toward Bus5 Figure-11. Three phase voltage and current at bus-12 with unbalanced load connected at bus-12 196
  • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME Unbalance load connected at Bus 12Bus No. 4 (Voltage waveform) 7 (Voltage waveform)WithoutControllerWith DVRin Line 5-4WithDSTATCOM at Bus 5With UPQCat Line 5-4Toward Bus5 Figure-12. Three phase voltage at bus-4 and at bus-7 with unbalanced load at connected at bus-125. CONCLUSION In this work, an Artificial Neural Network based approach has been suggested for theplacement of Custom Power Devices in power system to balance three phase voltage andcurrent at a bus where a highly unbalanced load is switched on, and to balance three phasevoltage at all other buses which become unbalanced due to connection of an highly unbalancedload at a particular bus. Case studies were performed on IEEE 14-bus system usingMATLAB/SIMULINK. Simulation results on the test system validate the effectiveness of theproposed approach of placement of custom power devices in load and voltage balancing. Theplacement of UPQC seems to be more effective in load and voltage balancing compared toplacement of DSTATCOM and DVR controllers. The proposed approach of optimal placementof custom power devices is quite simple and easy to adopt.REFERENCES[1] A. Ghosh and G. Ledwich, “Power quality enhancement using custom power devices”,KluwerAcademic Publishers (London) 2002.[2] N. G. Hingorani and L. Gyugyi, “Understanding FACTS: Concepts and technology of Flexible ACTransmission System”, IEEE publication, 2000.[3] J. Dixon, Luis Moran, Jose Rodriguez, “Reactive power compensation technologies: State of artreview”, Proceedings of the IEEE, Vol.93, No. 12, pp. 2144-2164, December 2005. 197
  • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEME[4] ArindamGhosh and Gerald Ledwich, “Compensation of distribution system voltage using DVR”,IEEE Transactions on Power Delivery, Vol. 17, No. 4, pp. 1030-1036, October 2002.[5] PendroRoncero-Sanchez, Enrique Acha, Jose Enrique Ortega-Calderon, Vicente Feliu, and AurelioGareia-Cerrada, “A versatile control scheme for a Dynamic Voltage Restorerfor power quality improvement”, IEEE Transactions on Power Delivery, Vol. 24, No. 1, pp. 277-284,January 2009.[6] ArindamGhosh and Gerald Ledwich, “Load compensating DSTATCOM in weak AC systems”, IEEETransactions on Power Delivery, Vol. 18, No. 1, pp. 1302-1309, October 2003.[7] C. N. Bhende, Dr. M. K. Mishra, and Dr. H. M. Suryawanshi, “ A D-STATCOM modeling, analysisand performance for unbalanced and non-linear loads”, Institutions of Engineers(India) Journal – EL ,Vol. 86, pp. 297-304, March 2006.[8] Wei-Neng Chang and Kuan-DihYeh, “Design and implementation of D-STATCOM for fast loadcompensation of unbalanced loads, “Journal of Marine Science and Technology” , Vol. 17, No. 4, pp.257-263, 2009.[9] Zakir Husain, Ravinder Kumar Singh and ShriNiwasTiwari, “ Balancing of unbalanced load andpower factor correction in multiphase ( 4 phase ) load circuits using D-STATCOM”, Proceedings of theWorld Congress on Engineering 2010, Vol. II WCE-2010, June 30-July 2, 2010, London (U.K).[10] Gaurav Kumar Kansal and Bhim Singh, “Harmonic elimination, voltage control and load balancingin an isolated power generation”, European Transactions on Electrical Power, Vol. 20, Issue 6, pp.771-784, September 2010.[11] Pablo Fernandez-Comesana, Francisco D. Freijedo, Jesus Doval-Gandoy, Oscar Lopez, Alejandro G.Yepes, JanoMalvar, “Mitigation of voltage sags, imbalances and harmonics in sensitive industrial loadsby means of a series power line conditioners”, Electric Power Systems Research, Vol. 84, Issue 1, pp. 20-30, March 2012.[12] E.A.Mohamed , N.D. Rao, “Artificial Neural Network based fault diagnostic system for electricpower distribution feeders,” Electric Power Systems Research, Vol. 35, No. 1, pp. 1-10, 35 October 1995.[13] Ernesto Vazquez, Hector J. Altuve, Oscar L. Chacon, “Neural network approach to fault detection inelectric power systems”, IEEE International conference on Neural Networks, Vol. 4, pp. 2090-2095, June3-6, 1996, Washington, DC, USA.[14] F.J. Alcantare, J. R. Vazquez, P. Salmeron, S.P. Litran, M.I. Arteaga Orozco, “On line detection ofvoltage transient disturbances using ANNs,” International Conference on Renewable Energies and PowerQuality (ICREPQ 09) 15th to 17th April 2009, Valencia, Spain.[15] Moleykutty George, “ Artificial Intelligence based three phase Unified Power Quality Conditioner”,Journal of Computer Science (3) 7 : pp. 465-477, 2007.[16] R.V.D. Rama Rao, Dr. SubhransuSekhar Dash, “ Power Quality Enhancement by Unified PowerQuality Conditioner using ANN with Hysteresis control”, InternationalJournal of Computer Applications (0975-8887), Vol. 6-No.-1, pp. 9-15, Sept.2010.[17] N. Ramchandra, M. Kalyanchakravarthi, “ Neural Network Based Unified Power QualityConditioner”, International Journal of Modern Engineering Research. (IJMER), Vol.2, Issue 1, pp. 359-365, Jan.-Feb.2012.[18] D. K. Tanti, M. K. Verma, Brijesh Singh and O. N. Mehrotra, “ Optimal Placement of Custom PowerDevices in Power System Network to Mitigate Voltage Sag under Faults”, International Journal of PowerElectronics and Drive System (IJPEDS), Vol. 2, No. 3, pp. 267-276, September 2012[19] “Power systems test case archieve” available athttp://www.ee.washington.edu/research/pstca/pf14/pg_tca14bus.htm[20] MATLAB 7 User’s Guides for SIMPOWER SYSTEMS and Neural Network Tool-box. 198
  • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN0976 – 6553(Online) Volume 3, Issue 3, October – December (2012), © IAEMEBIOGRAPHIESD. K. Tanti received B.Sc. (Eng.) degree in Electrical Engineering from Muzaffarpur Institute ofTechnology (India) in 1990 and M.Sc. (Eng.) degree in Electrical Engineering from BiharInstitute of Technology, Sindri (India) in 2000. Presently, he is Associate Professor in theDepartment of Electrical Engineering, Bihar Institute of Technology, Sindri (India), and pursuingfor his Ph.D degree at Vinoba Bhave University, Hazaribag (India). His research interestsinclude application of FACTS controllers, power quality and power systems.M. K. Verma received B.Sc. (Eng.) degree in Electrical Engineering from Regional EngineeringCollege, (presently National Institute of Technology), Rourkela (India) in 1989, M.Sc. (Eng.)degree from Bihar Institute of Technology , Sindri (India) in 1994 and Ph.D. degree from IndianInstitute of Technology, Kanpur (India) in 2005. Presently, he is Associate Professor in theDepartment of Electrical Engineering, Indian Institute of Technology (BHU), Varanasi (India).His research interests include voltage stability studies, application of FACTS controllers,operation and control of modern power systems, power quality and smart grid.Brijesh Singh received B.Tech. degree in Electrical Engineering from Faculty of Engineeringand Technology, Purvanchal University, Jaunpur (India) in 2003 and M.Tech. degree fromKamla Nehru Institute of Technology, Sultanpur (India) in 2008. Presently, he is persuing for hisPh.D. degree at Indian Institute of Technology (BHU), Varanasi (India). His research interestsinclude modeling and analysis of power systems, application of FACTS controllers and powerquality.O. N. Mehrotra received B.Sc. (Eng.) degree in Electrical Engineering from MuzaffarpurInstitute of Technology (India) in 1971, M.E. (Hons.) degree in Electrical Engineering fromUniversity of Roorkee, (presently Indian Institute of Technology, Roorkee, India) in 1982 andPh.D. degree from Ranchi University (India) in 2002. Presently, he is Professor (retired),Department of Electrical Engineering, Bihar Institute of Technology, Sindri (India). His researchinterests include control and utilization of renewable energies, power quality and power systems. 199