A STATCOM Based Voltage Stabilization And Reactive .
International Journal of Electrical Engineering.ISSN 0974-2158 Volume 4, Number 1 (2011), pp.103-114 International Research Publication Househttp://www.irphouse.comA STATCOM based Voltage Stabilization andReactive Compensation for 220 KV TransmissionSystem: A Case Study.Swapnil R. Borakhade* and Archana G. ThosarDepartment of Electrical Engineering,Government College of Engineering, Aurangabad. (M.S.), India*Corresponding Author E-mail: swapnil634@ gmail.comAbstractTo study and analyze the dynamic performance of the Flexible ACTransmission System (FACTS) devices, modelling of the FACTS devices isneeded. Reactive power compensation is an important issue in the control ofelectrical power system. Reactive power increases the transmission systemlosses and reduces the power transmission capability of the transmission lines.Moreover, reactive power transmitted through the transmission lines can causelarge amplitude variations in the receiving-end voltage. This paper illustratesthe effect of Static Compensator (STATCOM) in power system on reactivepower control and voltage stabilization by proper modelling of simple powersystem and voltage source converter based STATCOM (Static compensator)using Simulink and Simpower system toolboxes in MATLAB.This paperpresents the use of a new full 48 pulse GTO model of voltage source converterFACTS-STATCOM (Static Synchronous Compensator) for reactive powercompensation and voltage stabilization of 220 KV Karad-Wathar-Mudshingitransmission line located in Karad zone of Maharashtra State ElectricityTransmission Company Ltd. India. (M.S.E.T.C.L).The STATCOM is capable of providing reactive power compensation forfundamental and harmonics; power factor correction under balanced andunbalanced loading conditions. The Power System Block set (PSB) inMATLAB/Simulink is a graphic tool that allows building schematics andsimulation of power systems in the Simulink environment. The analysis andcomplete digital simulation of the STATCOM is performed in theMATLAB/Simulink environment using the Power System Block set (PSB),considering the actual data of the proposed system. The system is simulatedconsidering various locations for STATCOM and the performance of systemis evaluated.
104Swapnil R. Borakhade and Archana G. ThosarKeywords: FACTS, STATCOM, 220 KV System, Voltage stabilization,Reactive power compensation.IntroductionThe Electric supply industry is undergoing a profound transformation worldwide.Market forces, scare natural resources and an ever increasing demand for electricityare some of the drivers responsible for such an unprecedented change. Particularly inthe case of transmission systems, it requires non-discriminatory open access totransmission resources. Therefore sufficient transmission capacity for supportingtransmission services is a great demand to transmission network’s requirement.Further to meet the demand for a substantial increase in power transfers amongutilities, as a major consequence of electricity market, a much more intensiveutilization of existing transmission resource is needed[1]-[3].Voltage stability is increasingly becoming a limiting factor in the planning andoperation of many power systems. With increasing system loading and opentransmission access, power systems are more vulnerable to voltage instability.Together with ever-present disturbances, this may result in a serious consequence of avoltage collapse as shown by number of major incidences throughout the world.Voltage collapse tends to occur from lack of reactive power support in heavilystressed conditions, which are usually triggered by system faults. Voltage collapse canbe initiated due to small changes of system condition (e.g. Load increasing) as well aslarge disturbances (e.g. line outage or generation unit outage). Under these conditions,shunt FACTS devices such as SVC and STATCOM can improve the system securitywith fast and controlled injection of reactive power to the system. However, when thevoltage collapse is due to excessive load increasing, FACTS devices cannot preventthe voltage collapse and only postpone it until they reach to their maximum limits.Under this situations, the only way to preventing the voltage collapse is loadcurtailment or load shedding. So, reactive power control using FACTS devices ismore effective in large disturbances, and contingencies should be considered involtage stability analysis.The advent of Flexible AC transmission systems (FACTS) technology hascoincided with the major restructuring of the electrical power industry. FACTS canprovide benefits in increasing system transmission capacity and power flow controlflexibility and rapidity. As deregulation picks up speed, making the demand forsufficient services is becoming more critical, it is imperative to investigate thecapabilities and potential applications of FACTS on power networks.FACTS devices are solid state converters that have the capability to controlvarious electrical parameters in transmission circuits. FACTS devices includeThyristor controlled series compensator (TCSC), Static VAR Compensator (SVC),Thyristor controlled phase angle regulator (TCPST), Static compensator(STATCOM), Unified power flow controller (UPFC) etc.The STATCOM was proposed by several researchers to compensate the reactivecurrent from or to the power system. This function is identical to the synchronous
A STATCOM based Voltage Stabilization105condenser with rotating mass, but its response time is extremely faster than of thesynchronous condenser. This rapidity is very effective to increase transient stability,to enhance voltage support, and to damp low frequency oscillation for thetransmission system.In this paper Karad-Mudshingi 220 KV transmission line looped at Wathar issimulated using MATLAB/Simulink. The performance of the system is studied fornormal and transient condition for both cases that is with and without STATCOM.Transient condition is created by applying a heavy load, suddenly. The purpose of thiswork is to investigate the placement of STATCOM for enhancing the voltage stabilityand improvement of voltage profile of the proposed system.Static Synchronous Compensator (STATCOM)The Static Synchronous Compensator (STATCOM) is shunt connected reactivecompensation equipment, which is capable of generating and/or absorbing reactivepower whose output can be varied so as to maintain control of specific parameters ofthe electric power system. The STATCOM provides operating characteristics similarto a rotating synchronous compensator without the mechanical inertia, due to theSTATCOM employ solid state power switching devices it provides rapidcontrollability of the three phase voltages, both in magnitude and phase angle. TheSTATCOM basically consists of a step-down transformer with a leakage-reactance, athree-phase GTO/IGBT voltage source inverter (VSI), and a DC capacitor. The ACvoltage difference across the leakage reactance produces reactive power exchangebetween the STATCOM and the power system, such that the AC voltage at the busbar can be regulated to improve the voltage profile of the power system, which is theprimary duty of the STATCOM. However, a secondary damping function can beadded into the STATCOM for enhancing power system oscillation stability [4]The principle of STATCOM operation is as follows. The VSI generates acontrollable AC voltage source behind the leakage reactance. This voltage iscompared with the AC bus voltage system; when the AC bus voltage magnitude isabove that of the VSI voltage magnitude, the AC system sees the STATCOM as aninductance connected to its terminals. Otherwise, if the VSI voltage magnitude isabove that of the AC bus voltage magnitude, the AC system sees the STATCOM as acapacitance connected to its terminals. If the voltage magnitudes are equal, thereactive power exchange is zero. If the STATCOM has a DC source or energy storagedevice on its DC side, it can supply real power to the power system. This can beachieved adjusting the phase angle of the STATCOM terminals and the phase angleof the AC power system. When the phase angle of the AC power system leads theVSI phase angle, the STATCOM absorbs real power from the AC system; if the phaseangle of the AC power system lags the VSI phase angle, the STATCOM supplies realpower to AC system [5-7].
Swapnil R. Borakhade and Archana G. Thosar106Figure 1: Single-line diagram of a STATCOM.The voltage source-converter or inverter (VSC or VSI) is the building block of aSTATCOM and other FACTS devices. A very simple inverter produces a squarevoltage waveform as it switches the direct voltage source on and off. The basicobjective of a VSI is to produce a sinusoidal AC voltage with minimal harmonicdistortion from a DC voltage. In the last decade commercial availability of Gate TurnOff Thyristor (GTO) devices with high power handling capability, and theadvancement of other types of power-semiconductor devices such as IGBT’s have ledto the development of controllable reactive power sources utilizing electronicswitching converter technology [8]. These technologies additionally offerconsiderable advantages over the existing ones in terms of space reductions andperformance. The GTO Thyristor enables the design of solid-state shunt reactivecompensation equipment based upon switching converter technology. This conceptwas used to create a flexible shunt reactive compensation device named StaticSynchronous Compensator (STATCOM) due to similar operating characteristics tothat of a synchronous compensator but without the mechanical inertia.Simulated Case StudyThe Simulated case study is 220 KV Transmission line located in Karad zone ofMaharashtra State India. Map of the simulated network is shown in Fig 2. Thisnetwork is double circuit network, in which one line is connected between 400 KVKarad substation and 220 KV Mudshingi substation, while other line feeds anothersubstation at Wathar region. System at Wathar is Loop in Loop out (LILO), whichallows Wathar to take power from both the ends. Wathar substation is the onlysubstation on Karad-Mudshingi 220KV line having a load of nearly 150MW. This
A STTATCCOMM baasedd VolV tagge StaS abiilizaatiion1007worrk is a laargge indi dusstriaal zonz ne in Mahaaraashhtraa statee inn Inndiia. In thiis regr gionn thherre areaenetwgestt suugaar facctoriees, irriigaatioon schhemmee, teexttilee millm ls. Heencce pop weer netn twoorkk off thhisslaargreegiionn iss veeryy immpporttannt. It isi verv ry esssenntiaal tot mamainttainn verv ry goog od quualiityy off powp werrsuuppplyy. ItI canc n beb undu derrstooodd byb thee factf t thhatt, a sllight drrop inn suuppplied vooltaagee canc ncaausse a quaq alityy redr ducttion ini indi dustriees, whhicch cann ultimu maatelly cauc usee a miilliionn off ruupeeessloosss too innduustrriall coonssummerrs ofo thiis regr ionn. SoS takkinng alla thiis facf cts intto conc nsidderratiionn ittiss veryv y esse sential to mamainttainn thet e voltv tagge levl vel att WatW thaar subs bstaatioon whicw ch caan beeacchiievvedd byy placp cing thet FAACCT devvicce that at iss STAS ATCOOMM att desiiredd loocaatioon.F gurre 2:Fig2 MaMap of Kaaraad-MMuudsshinngii TranT nsmmisssioon Neetwworrk.Thee deetaiils off the systTs temm prop opoosedd inn thhiss paapeer area e prreseenttedd ass:A thee conAllc nstrructtioonall detad ailss annd sppacingg area as peer TheT e IndI diann ElecE ctriicitty Ruuless anda dsttanndaardss off MaMahaaraashttra stas ate EleE ctrriciity TraT ansmiissiionn Coommpanny LimL mittedd(MM.SS.EE.TT.CC.L). ForF r propp possedd 220KVV trant nsmmisssioon systeemss thhe lenngtth ofo thet e liine is assfoolloowws; KarK radd s//s tot MuMudshinngii s//s - 933 KMKM KarK radd s//s tot WaWathaar s/ss -667 KMKM WaWathaar s/ss to MudM dshhinggi s/ss - 26 KMKM
Swapnil R. Borakhade and Archana G. Thosar108Simulation ToolsThe modeling of STATCOM with proposed 220 KV transmission system is done byusing the SimPower systems toolboxes in MATLAB /Simulink. The modeling is doneby connecting a three phase source of 1200 MVA and RL loads through atransmission line. The source is representing a bus feeding Karad s/s and the RL loadsare representing the different s/s. The power flow in the system without STATCOM isfirst studied. The AC voltage at source is maintained at 220 KV (1.p.u) and thefrequency is 50Hz. The load is varied and the real and reactive power flows in the busare observed. Using the active and the reactive power blocks available in SimPowerSystem, the reactive power flow through the line is plotted against time. In each casethe simulation results for both the system with and without STATCOM are compared.Fig.3 (a) shows the simulink diagram of proposed 220 KV System withoutSTATCOM having AC source, load, transmission line and measurement blocks. Thesource is a 3 phase synchronous generator having a capacity of 1200MVA at13.8 KVand 50Hz.The required voltage level of 220 KV is achieved with the help of a powertransformer. The synchronous generator is also assisted by Power System Stabilizer,Exciter and Hydraulic Turbine and Governor System. The load at different buses isRL load, having real and reactive power ratings according to the original s/s load. TheTransmission lines are of mentioned length and having 0.4 ACSR ZEBRAconductors.Figure 3 (a): Proposed System without STATCOM.Fig.3 (b) shows the simulink diagram of proposed 220 KV System withSTATCOM located at Wathar Bus (bus B1) and has a rating of /- 100MVA. ThisSTATCOM is a phasor model of a typical three-level PWM STATCOM. All the otherelements are same as that of system without STATCOM. A remote fault will besimulated on both systems using a fault breaker in series with a fault impedanceconnected at Karad bus. The value of the fault impedance has been programmed toproduce 25 percent voltage sag at Wathar bus B1for approximate10 cycles. The otherbuses are bus B2- Mudshingi and bus B3- Karad.
A STATCOM based Voltage Stabilization109Figure 3(b): Proposed System with STATCOM.Results and DiscussionsThe solutions for optimal possible location of STATCOM in the proposed system toget the optimal voltage stabilization and reactive power compensation for theproposed systems were obtained and discussed below. The simulation studies werecarried out in MATLAB/Simulink environment for following possible conditions.Dynamic Response of STATCOMFor observing the dynamic response of the STATCOM its reference voltage iscontrolled externally. Fig.3 displays the Vref signal (magenta trace) along with themeasured positive-sequence voltage Vm at the STATCOM bus (blue trace). Thesecond graph displays the reactive power Qm absorbed (positive value) or generatedby the STATCOM. The signal Qref (magenta trace) shows the ref reactive power inthe system.Figure 4: Dynamic response of STATCOM.
110Swapnil R. Borakhade and Archana G. ThosarCase AIn this case the sudden change in load is applied at the generator bus 3- at Karad andthe position of the STATCOM is varied, for all the 3 possible locations. Thesimulation is carried out for each case and results are obtained and plotted againsttime. These are shown in Fig.4, the numbers 1-3 are used to indicate the STATCOMpositions at respective buses. Vm (pu) 1shows the voltage profile for the systemhaving STATCOM at Wathar bus B1 similarly Vm (pu) 2 and Vm(pu) 3 are thevoltage profiles for the systems having STATCOM at Mudshingi bus B2 and at Karadbus B3. It can be easily observed from the graph that there are large variations involtage profile in System without STATCOM than the system with STATCOM andalso change in STATCOM position does not produce a large variation in the voltageprofiles. The other graph in each case is for reactive power compensation done bySTATCOM. It is also clear from the graph that the STATCOM regulates voltage at itsterminal by controlling the amount of reactive power injected into or absorbed fromthe power system. When system voltage is low, the STATCOM generates reactivepower (STATCOM capacitive). When system voltage is high, it absorbs reactivepower (STATCOM inductive).Figure 5: Voltage profiles and reactive power flow for the system with and withoutSTATCOM.Table 1 show the values of voltage in per unit for different STATCOM positions,when the sudden load is applied and removed from the generator bus. When thesudden load is applied at Wathar bus B1 the voltage drops to value 0.48 pu withoutSTATCOM and it drops to value 0.9 pu with STATCOM. When it is removed the
A STATCOM based Voltage Stabilization111voltage rises to 1.95 pu without STATCOM and it is observed that after installation ofthe STATCOM the value raises only up to 1.08 puTable 1STATCOMLocation.Bus 1 - WatharBus 2 – MudshingiBus 3 – KaradVm (pu) .950.481.96Vm (pu) With 09Case BIn this case the sudden change in load is applied at different buses and the position ofthe STATCOM is also varied, for all the 3 possible locations. The simulation iscarried out for each case and results were obtained and plotted against time. These areshown in Fig.5 (a) and Fig 5 (b). The case A is repeated by changing the location ofthe application of load and all the results are tabulated so as to get a clear view.Figure 6 (a): Load at Wathar bus and STATCOM at various locations.
Swapnil R. Borakhade and Archana G. Thosar112Figure 6(b): Load at Mudshingi bus and STATCOM at various locations.Table 2 shows the values of voltage in per unit for different STATCOM positionsand different load positions, when the sudden load is applied and removed from thesystem. This values results in better understanding of the system and helps in findingthe optimal location for installation of the STATCOM.Table 2STATCOMLocation.Bus 1 WatharBus 2 –MudshingiBus 3 –KaradLoad at Bus 1- WatharVm (pu)Vm (pu)WithW/OSTATCOM STATCOM0.481.6 0.76 1.07Load at Bus 2- MudshingiVm (pu)Vm (pu)WithW/OSTATCOM STATCOM0.52 1.55 0.81 1.07Load at bus 3 - KaradVm (pu)Vm (pu)WithW/OSTATCOM STATCOM0.48 9From the table it is clear that the system with STATCOM faces lesser voltagefluctuations on transients as compared to the system without STATCOM. This isachieved with the help of reactive power compensation of the STATCOM.
A STATCOM based Voltage Stabilization113ConclusionIn this paper, brief information about STATCOM and its effect at different places onproposed power system have been considered. This study is very useful especially ininvestigating the effectiveness of the different methods in optimizing the optimumSTATCOM location in the proposed system, by analysis the effects of power systemcontingency on static voltage stability, we specified optimal location for installingSTATCOM in proposed power system to improve stability in network voltages.In this research, the placement is determined conventionally based on the resultobtained using MATLAB/simulink software. General idea of this work is todemonstrate the importance of STATCOM allocation for describing the effect ofSTATCOM and its placement on the proposed 220 KV Karad-Wathar-Mudshingielectrical power system. The simulated results indicated that, improper selection ofSTATCOM and its capacity, as well as its placement may result in not achieving theobjectives accordingly. Considering the high cost of these elements, it is veryimportant to have a better judgment and analysis, prior to purchasing and installationprocess.References[1] N.G. Hingorani and L. Gyugyi, Understanding FACTS Concepts andTechnology of Flexible AC Transmission Systems, IEEE Press, 2000, ISBN 07803-3455-8.[2] R.M. Mathur and R.K. Varma, Thyristor based FACTS controllers forElectrical transmission systems, John Wiley & Sons Inc., 2002.[3] Y.H. Song and X.F. Wang, Operation of market oriented power system,Springer-Verlag Ltd, 2003, ISBN: 1-85233-670-6.[4] Y. Liang and C.O. Nwankpa, “A new type of STATCOM based on cascadingvoltage-source inverter with phase-shifted unipolar SPWM,” IEEE Trans. Ind.Appl., vol. 35, no. 5, pp. 1118–1123, Sep./Oct. 1999.[5] P. Giroux, G. Sybille, and H. Le-Huy, “Modeling and simulation of adistribution STATCOM using simulink’s power system blockset,” in Proc.Annu. Conf. IEEE Industrial Electronics Society, pp. 990–994.[6] Q. Yu, P. Li, and Wenhua, “Overview of STATCOM technologies,” in Proc.IEEE Int. Conf. Electric Utility Deregulation, Restructing, PowerTechnologies, Hong Kong, Apr. 2004, pp. 647–652.[7] lam,”Applications of static phase shifters in power systems,” IEEETrans on Power Delivery, Vol 9, No. 3, July 1994, pp. 1600-1608.[8] “Static Synchronous Compensator,” CIGRE, Working group 14.19,1998.P.Giroux, G. Sybille, and H. Le-Huy, “Modeling and simulation of a distributionSTATCOM using simulink’s power system blockset,” in Proc. Annu. Conf.IEEE Industrial Electronics Society, pp. 990–994.
114Swapnil R. Borakhade and Archana G. Thosar[9] Q. Yu, P. Li, and Wenhua, “Overview of STATCOM technologies,” in Proc.IEEE Int. Conf. Electric Utility Deregulation, Restructing, PowerTechnologies, Hong Kong, Apr. 2004, pp. 647–652.[10] A. Krämer, J. Ruff, ”Transformers for phase angle regulation considering theselection of On-load tap-changers,” IEEE Trans on Power Delivery, Vol. 13,No.2, April 1998, pp. 518-523.[11] Yong Hua Song, Allan T. Johns, Flexible AC transmition systems FACTS, IEEPower and Energy Series 30, 1999.
106 Swapnil R. Borakhade and Archana G. Thosar Figure 1: Single-line diagram of a STATCOM. The voltage source-converter or inverter (VSC or VSI) is the building block of a STATCOM and other FACTS devices. A very simple inverter produces a square voltage waveform as it
Power Quality Enhancement in STATCOM connected Distribution 909. 3. Overview of D-STATCOM with proposed control algorithm In the paper, the GSA method is proposed for enhancing the performance of D-STATCOM. Figure 1 portrays a schematic diagram of a three-phase VSC based DSTATCOM linked to a
A Robust STATCOM Controller for Power System Dynamic Performance Enhancement A, H. M.A.Rahim S,A,A1-Baiyat F.M.Kandlawala Department of Electrical Engineering K.F.University of Petroleum and Minerals Dhahrrm,Saudi Arabia. Abstract: A robust controller for providing damping to power system transients through STATCOM devices is presented. Method
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Temporary Corporate Credit Union Stabilization Fund (Stabilization Fund) and credit union money. Credit unions have paid 4.8 billion in stabilization assessments and 5.6 billion in depleted capital into the Stabilization Fund to cover resolution costs for the failure of five corporate credit unions during the Great Recession.
The low voltage converters that make up INGEGRIDTM LV STATCOM solutions are three-phase conververters which feature LV IGBT semiconductors in 2-level topology. The medium voltage converters that make up the INGEGRIDTM MV STATCOM solutions are three-phase converters that feature HV-IGBT semiconductors in 3L-NPC topology.
1 Enhancement of Power Quality Utilizing Photovoltaic fed D-STATCOM Based on Zig-Zag Transformer and Fuzzy Controller Hamid Karimi1, Mohsen Simab2*, Mehdi Nafar3 1 Department of Electrical Engineering, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran.Mobile: 98
(Proportional-Integral-Derivative) controllers was reported in [19, 20]. In this paper, the new PID controller design and synthesis approach for STATCOM control is introduced based on the root counting and signature theory [21, 22]. This approach can find the complete set of stabilizing PID controllers
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