Power Electronics Based FACTS Controller for Stability Improvement of a Wind Energy Embedded Distribution System

Transcription

1 Power Electronics Base FACTS Controller for Stability Improvement of a Win Energy Embee Distribution System Sihartha Pana an N.P.Pahy Abstract In recent years generation of electricity using win power has receive consierable attention worlwie. Inuction machines are mostly use as generators in win power base generations. Since inuction machines have a stability problem as they raw very large reactive currents uring fault conition, reactive power compensation can be provie to improve stability. This paper eals with stability improvement of a istribution system embee with win farms by using power electronics base Flexible AC Transmission Systems (FACTS) reactive power compensator controller. The ynamic behavior of the example istribution system, uring an external three-phase fault an uner various types of win spee changes, is investigate. The stuy is carrie out by three-phase, non-linear, ynamic simulation of istribution system component moels. Simulation results are presente for ifferent cases such as with an without FACTS an also for ifferent moes of operation of FACTS controller. The effect of constant win spee an linear change in win spee on stability is also analyze. The simulation analysis of stability of istribute system with win farm is performe using MATLAB/SIMULINK. Keywors Distribute generation, istribution system, FACTS, reactive power compensation, power system stability, win turbine inuction generator. NOMENCLATURE Win Turbine: Mechanical output power of the turbine (W). P m C P Performance coefficient of the turbine. ρ Air ensity (kg/m 3 ). A Turbine swept area (m 2 ). V win λ β P mpu Win spee (m/s). Tip spee ratio of the rotor blae tip spee to win spee. Blae pitch angle (eg). Power in pu of nominal power for particular values of ρ an A. Sihartha Pana is a research scholar in the Department of Electrical Engineering, Inian Institute of Technology, Roorkee, Uttaranchal, , Inia. ( panasihartha@reiffmail.com). N.P.Pahy is Associate professor in the Department of Electrical Engineering, IIT, Roorkee Inia.( , nppeefee@iitr.ernet.in) k p Power gain. C Ppu Performance coefficient in pu of the maximum value of C P. Inuction Machine: R s, L ls Stator resistance an leakage inuctance. R' r, L' lr Rotor resistance an leakage inuctance. Magnetizing inuctance. L m L s, L' r V qs, i qs V' qr, i' qr V s, i s V' r, i' r ϕ qs, ϕ s Total stator an rotor inuctances. q-axis stator voltage an current. q-axis rotor voltage an current. -axis stator voltage an current. -axis rotor voltage an current. Stator q an -axis fluxes. ϕ qr, ϕ r Rotor q an -axis fluxes. ω m θ m P ω r θ r T e J H F T Angular velocity of the rotor. Rotor angular position. Number of pole pairs. Electrical angular velocity. Electrical rotor angular position. Electromagnetic torque. Combine rotor an loa inertia coefficient. Combine rotor an loa inertia constant. Combine rotor an loa viscous friction coefficient. I. INTRODUCTION HE rapi evelopment of istribute generation (DG) technology is graually reshaping the conventional power systems in a number of countries. Win power is among the most actively eveloping istribute generation. Gri-connecte win capacity is unergoing the fastest rate of growth of any form of electricity generation, achieving global annual growth rates on the orer of 20-30% []. The presence of win power generation is likely to influence the operation of the existing power system networks, especially the power system stability [2]-[3]. After the clearance of a short-circuit fault in the external 600

2 network, the gri connecte win turbine shoul restore its normal operation without isconnection cause by inrush current an ippe voltage [4]. The protective isconnection of a large amount of win power may cause an important loss of generation that may threaten the power system stability. Further, ynamic changes of win spee make amount of power injecte to a network highly variable. Depening on intensity an rate of changes, ifficulties with frequency, voltage regulation an stability, coul make a irect impact to quality level of elivere electrical energy [5]. In this context, from stability viewpoint, connection of win turbine generator with isperse generation of electricity, calls for a etaile technical analysis. Majority of the win power base DG technologies employ inuction generators instea of synchronous generators, for the technical avantages of inuction machines like: reuce size, increase robustness, lower cost, an increase electromechanical amping. Win turbine inuction generator (WTIG) can be viewe as a consumer of reactive power. Its reactive power consumption epens on active power prouction. Further, inuction generators raw very large reactive currents uring fault occurrence [6]. Following the fault conitions, the voltage recovery may become impossible, an consequently the win farm may experiences voltage collapse at its terminals. One way to prevent this from happening is by proviing reactive power compensation which woul help in preventing the voltage collapse at the terminals of win farms, which woul lea to improving the stability of the win farm. Conventionally, shunt capacitor banks are connecte at the generator terminals to compensate its reactive power consumption. To minimize reactive power exchange between win power plant an istribution network, ynamic compensation of reactive power can be employe [7]-[8]. Further, the normal operation restoration after the clearance of an external system fault can be improve with ynamic reactive compensation. Without the ynamic compensation, it is possible that at some locations only a small number of win turbines coul be connecte ue to weak voltage conitions. This woul not only leave assesse win potential unuse, but it coul also prohibit installation of larger number of win turbines jeoparizing the economics of the whole project. Recent evelopment of power electronics introuces the use of flexible ac transmission system (FACTS) controllers in power systems [9]. Shunt FACTS evices play an important role in controlling the reactive power flow in the power network, which in turn affects the system voltage fluctuation an transient stability. The STATCOM is one of the important FACTS evices an can be use for ynamic reactive power compensation of power systems to provie voltage support an stability improvement [0]. In this work the effect of a STATCOM in improving the stability performance of the istribute network with WTIG is stuie. In orer to overcome negative ynamic impacts cause by WTIGs, a STATCOM is use at the point of WTIGs an istribution network connection. The stuy is base on the three phase non-linear ynamic simulation, utilizing the SimPowerSystem blockset for use with MATLAB/SIMULINK []. Simulation results are presente to show the improve stability performance of a istribute network embee with WTIGs uner severe 60 isturbances with the use of a STATCOM. Further the effects ifferent types of win spee an ifferent control moe of operation of STATCOM on istribution system are presente. II. DISTRIBUTION SYSTEM COMPONENTS MODELS Distribution systems are inherently unbalance ue to the asymmetrical line spacing an imbalance of customer loa. In view of this, single phase moels can not be use for accurate stuies on the operation of istribute systems. Therefore in this work all network components are represente by the three-phase moels []. A. Win Turbine Inuction Generator (WTIG) The block iagram of win turbine the inuction generator (WTIG) is shown in Fig.. The stator wining is connecte irectly to the 60 HZ gri an the rotor is riven by a variable-pitch win turbine. The power capture by the win turbine is converte into electrical power by the inuction generator an is transmitte to the gri by the stator wining. The pitch angle is controlle in orer to limit the generator output power to its nominal value for high win spees. In orer to generate power the inuction generator spee must be slightly above the synchronous spee. Three-phase Gri Stator Rotor Stator Inuction Generator Drive train Turbine Pitch control Win Fig. Block iagram of win turbine with inuction generator Pelect. Pmech. Pitch angle max. Pitch angle controller (PI) Pitch angle min. Pitch angle Fig. 2 Control system for pitch angle control. The pitch angle controller regulates the win turbine blae pitch angle β, accoring to the win spee variations. Hence, the power output of WTIG epens on the characteristics of the pitch controller in aition to the turbine an generator characteristics. This control guarantees that, irrespective of the voltage, the power output of the WTIG for any win spee will be equal to the esigne value for that spee. This esigne power output of the WTIG with win spee is provie by the manufacturer in the form of a power curve. Hence, for a

3 given win spee, power output can be obtaine from the v power curve of the WTIG. s = Rsis ϕs ωϕqs (6) t A Proportional-Integral (PI) controller is use to control the blae pitch angle in orer to limit the electric output power to the nominal mechanical power. The pitch angle is v' qr = R' r iqr ϕ' qr ( ω ωr ) ϕ' r t kept constant at zero egree when the measure electric output power is uner its nominal value. When it increases above its nominal value the PI controller increases the pitch v' r = R' r ir ϕ' r ( ω ωr ) ϕ' qr angle to bring back the measure power to its nominal t (7) (8) value. The pitch angle control system is illustrate in the Fig. 2. The pitch angle is controlle in orer to limit the generator output power at its nominal value for wins exceeing the nominal spee. In orer to generate power the IG spee must be slightly above the synchronous spee. Spee varies approximately between pu at no loa an.005 pu at full loa. Each win turbine has a protection system monitoring voltage, current an machine spee. ) Win Turbine The win turbine moel is employe in the present stuy is base on the steay-state power characteristics of the Te =.5 p( ϕsiqs ϕqsis ) Where, ϕ qs = L siqs Lmi' qr ϕ s = L sis Lmi' r ϕ ' qr = L' r i' qr Lmiqs (9) turbine. The stiffness of the rive train is infinite an the friction factor an the inertia of the turbine are combine ϕ ' r = L' r i' r Lmis with those of the generator couple to the turbine. The win turbine mechanical power output is a function of rotor spee With L s = Lls Lm an L ' r = L' lr Lm as well as the win spee an is expresse as: ρa P 3 m = CP( λ, β ) V win () 2 Normalizing () in the per unit (pu) system as: P 3 m pu = k pcp pu V win pu (2) Vs Rs is ωϕ qs Lls Lm ( ω ωr ) ϕ ' qr L'lr R'r V'r A generic equation is use to moel C P (λ, β). This equation, base on the moeling turbine characteristics is []: c5 c λ λ β 2 C β i P(, ) = c c3 c4 e c6 λ λ i (3) Vqs Rs iqs ωϕ s Lls Lm -axis (a) ( ω ωr ) ϕ ' r L'lr R'r V'qr With = λi λ 0.08 β β 3 The relevant parameters are given in appenix 2) Inuction Machine In the present stuy, the electrical part of the machine is represente by a fourth-orer state-space moel an the mechanical part by a secon-orer system. All electrical variables an parameters are referre to the stator. All stator an rotor quantities are in the arbitrary two-axis reference frame (-q frame). The -axis an q-axis block iagram of the electrical system is shown in Figs. 3 (a) an 3 (b). The electrical equations are given by: (4) vqs = Rsiqs ϕ qs ωϕs (5) t q-axis (b) Fig. 3 Inuction machine equivalent circuits (a) -axis equivalent circuit (b) q-axis equivalent circuit. The mechanical equations are given by: ω m = (Te Fωm Tm ) (0) t 2H θ m = ωm () t B. Protection System Commercial win turbines incorporate sophisticate system for protection of electrical an mechanical components. These turbine-base protection system respon 602

4 to local conitions, etecting gri or mechanical anomalies that inicate system trouble or potentially amaging conitions for the turbine. The protection system shoul respon almost instantaneously to mechanical spee, vibration, voltages, or currents outsie of efine tolerances. In aition, conventional multi-function relays for electric machine protection shoul also be provie to etect a wie variety of gri isturbances an abnormal conitions within the machine. In the present stuy the WTIG protection system consists of the followings: Instantaneous/positive-sequence AC Overcurrent. AC Current Unbalance. AC Overvoltage/Unervoltage (positive-sequence). AC Voltage Unbalance (Negative-sequence / Zerosequence). DC Overvoltage. C. Static Synchronous Compensator (STATCOM) The STATCOM is base on a soli state synchronous voltage source, which generates a balance set of three sinusoial voltages at the funamental frequency, with rapily controllable amplitue an phase angle. The STATCOM block use in the present stuy, moels an IGBT-base STATCOM. However, as etails of the inverter an harmonics are not represente in stability stuies, a GTO-base moel can also be use. Fig. 4 shows a singleline iagram of the STATCOM an a simplifie block iagram of its control system. The control system consists of: A phase-locke loop (PLL) to synchronize on the positive-sequence component of the three-phase primary voltage V. The irect-axis an quarature-axis components of the AC three-phase voltage an currents (labele as V, V q or I, I q on the iagram) are compute using the output of the PLL. The measurement systems measuring the -axis an q- axis components of AC positive-sequence voltage an currents to be controlle an the DC voltage V c. The regulation loops, namely the AC voltage regulator an a DC voltage regulator. The output of the AC voltage regulator an DC voltage regulator are the reference current I q ref an I ref, for the current regulator. An inner current regulation loop consisting of a current regulator, which controls the magnitue an phase of the voltage generate by the PWM converter. V AC Voltage Measurement III. SYSTEM UNDER STUDY V ac V ref AC Voltage Regulator V q The one line iagram of the test system employe in this stuy is shown in Fig. 5. The network consists of a 20-kv, 60-Hz, sub-transmission system with short circuit level of 2500 MVA, fees a 25 kv istribution system through 20/25 kv step own transformers. A win farm consisting of six.5-mw win turbines is connecte to the 25-kV istribution system, exports power to the 20-kV gri through a 25-km 25-kV feeer. Very large reactive currents are rawn by IGs uring fault conitions an hence reactive power compensation is provie. Part of the reactive power consume by the inuction generators is locally supplie by fixe capacitors of 400 kvar each, installe at the terminals of the machines. Dynamic reactive power compensation is provie by a 3 MVA STATCOM locate at the point of WTIGs connection to the istribution network (bus 3). Both WTIG an STATCOM use in the present stuy are phasor moels which are vali for transient stability solution. 20 kv/2500 MVA Sub transmission system /25kV 5 MW 2 MVAr 3x25 kv/575v 3 MW MVAr 3 MVA STATCOM 3x3MW WTIG 3x400kVAR Fig. 5 Single-line iagram of the istribution system embee with win turbine inuction generators an a STATCOM. Win turbines use squirrel-cage inuction generators. The stator wining is connecte irectly to the 60 Hz gri an the rotor is riven by a variable-pitch win turbine. In orer to limit the generator output power at its nominal value, the pitch angle is controlle for wins exceeing the nominal spee of 9 m/s. To inject active power to the istribution network, the IG spee must be slightly above the synchronous spee. Spee varies approximately between pu at no loa an.005 pu at full loa. Each win turbine has a protection system monitoring voltage, current an machine spee. All the relevant ata are given in appenix. Therefore, the amount of active power injecte by WTIGs to the istribution system is limite by transient stability issues. Alternatively, as long as the WTIGs inject active power to the istribution network, transient stability is maintaine [4]. I V V 2 Voltage Source Convt. (VSC) Pulse I V DC θ PWM Moulator PLL DC Voltage Measurement V 2 V 2q θ = ωt V c V c ref Current Regulator V q DC Voltage Regulator Current Measurement I q I q ref I ref I Fig. 4 Single-line iagram of control system of STATCOM I I q IV. SIMULATION RESULTS The ynamic behavior of the WTIGs uring an external three-phase fault is analyze an presente in this section. The active power generate by the WTIGs epens upon the win spee. Two type of win spee namely; constant win spee an linear change of win spee, are consiere in the present stuy as shown in Fig. 6. Further, the reference voltage an the reference reactive power are set to pu for both voltage controlle moe an VAr controlle moe. 603

5 Three cases are consiere for all the types of win spee changes: Case-: System without STATCOM. : System with STATCOM, operating in the voltage control moe of operation. : System with STATCOM, operating in the VAr/power factor control moe of operation. Win spee (m/s) Constant w in spee Linear change of w in spee Fig. 6 Types of win spee A. Constant Win Spee A constant win spee of 9 m/s is applie to the win turbine. A three phase fault is applie at the bus no. 3, at t=2 sec. an cleare after 9 cycles. The original system is restore upon the fault clearance. Three cases as mentione above are analyze. Fig. 7 shows the response of WTIG terminal voltage for the above contingency. WTIG terminal voltage (pu) Case Fig. 7 WTIG terminal voltage response for a 9 cycle 3-phase fault It can be seen from Fig. 7 that, as the fault is applie near to the WTIGs (bus-3), the WTIG terminal voltage rops rastically on the occurrence of the fault. The low voltage conition starts at t=2 sec, at which the fault is applie an lasts for 9 cycles i.e. the uration of the fault. For case of system without STATCOM (shown in Fig. 7, with legen Case-), the WTIG terminal voltage rops to 0.69 pu immeiately after the fault clearance. The AC Unervoltage limit set by the protection system being equal to 0.75 pu, this low voltage conition results in tripping of WTIGs at t= 5 s, the tripping being been initiate by the AC Unervoltage protection. For the system with STATCOM 604 (shown in Fig. 7, with legens & 3), because of reactive power support, the WTIG terminal voltage is slightly more than 0.75 pu immeiately after the fault clearance, an is within the limit set by the protection system. So the system maintains stability an finally the WTIG terminal voltage recovers close to pu for both the cases. Further, it can be seen from Fig. 7 that, for the case of STATCOM operating in VAr control moe (), the terminal voltage is slightly more than pu as the controller tries to supply the rate reactive power. But, when the STATCOM is operating in voltage control moe (), the controller tries to maintain the terminal voltage constant at the set value of pu an the STATCOM supplies that much reactive power as is require to maintain the terminal voltage constant. The response of the active power injecte into the network is shown in Fig. 8. The active power injecte to the istribution network reuces rastically uring the uration of fault for all the cases. For the case of system without STATCOM (Case-), because of the tripping of the WTIGs, the active power injecte becomes zero after the fault clearance. But, for the cases of system with STATCOM (shown in Fig. 8, with legens Cases- 2 & 3), because of the reactive power support, the stability of the system is maintaine an the WTIGs continue to supply the rate power to the istribution network after the fault clearance. Active power injecte (MW) Case Fig. 8 Response of active power injecte to the network for a 9 cycle 3-phase fault Q STATCOM (MVAR) Case Fig. 9 Reactive power supplie by the STATCOM Fig. 9 shows the variation of the reactive power supplie by the STATCOM for the above contingency, for all the cases. When the STATCOM is inactive (shown in Fig. 9,

6 with legen, Case-), the reactive power supplie by it is obviously zero. It is also clear from Fig. 9 that, for the case of STATCOM operating in voltage control moe (shown in Fig. 9, with legens ), the controller tries to maintain the terminal voltage constant at the set value of pu an consequently the STATCOM supplies that much reactive power as is require to maintain the terminal voltage constant. In case of STATCOM operating in VAr control moe (shown in Fig. 9, with legens ), as the reference reactive power is set to pu, the controller tries to supply the rate reactive power. Hence the reactive power supplie for is more than that of. The response of WTIG spee is shown in Fig. 0. The spee of the WTIGs increases at the occurrence of the fault at t=0.2 sec, for all the cases. For the case of system without STATCOM (Case-), as explaine earlier, the system looses stability an the spee of the WTIGs continues to increase. For the system with STATCOM (shown in Fig. 0, with legens & 3), the stability of the system is maintaine after the fault clearance. Further, it can be seen from Fig. 0 that the WTIG spee for is slightly more than that for. This is ue to the fact that, the reactive power supplie by the STATCOM is more in Case- 3, compare to the. In, the WTIGs raw the ifference reactive power from the istribution network an hence the WTIGs are slightly overloae compare to Case- 3. WTIG spee (pu) Case Fig. 0 Response of WTIG spee simulate. The response of WTIG spee is shown in Fig.. It can be seen from Fig. that, when the STATCOM is operating in voltage control moe (shown in Fig. with legen ), the system looses stability ue to the tripping of the WTIGs by the protection system. In case of STATCOM operating in VAr control moe (shown in Fig. with legen ), stability of the system is maintaine. The ifference between the reactive power requirement of the WTIGs an the reactive power supplie by the STATCOM is rawn from the istribution network. As explaine earlier, the reactive power supplie by the STATCOM is more in, compare to the. In orer to meet the reactive power requirement, the WTIGs are slightly overloae in compare to the. Hence, VAr control moe of operation of STATCOM improves the stability compare to the voltage control moe of operation. B. Linear Change of Win Spee A linear change of win spee as shown in Fig. 6 is applie to the win turbine. This type of win spee change enables the win turbine to inject active power into a network from minimum to maximum value in a manner slow enough not to inuce unwante oscillations. As the maximum win spee reaches m/s, the active power injecte to the network increases to 9.0 MW compare to constant win spee (9 m/s) generation of 8.7 MW. The reactive power requirement of WTIG increases with the increase in the active power generation. WTIG terminal voltage (pu) Case WTIG spee (pu) Fig. Response of WTIG spee for ifferent control moes of operation of STATCOM To compare the performance of two moes of operation on transient stability improvement, the fault clearing time is increase by half a cycle an the same contingency is Fig. 2 Response of WTIG terminal voltage for linear change of win spee Fig. 2 shows the response of the WTIG terminal voltage (without fault), for all the cases. For the case of system without STATCOM (shown in Fig. 2, with legens Case- ), the WTIG terminal voltage rops below 0.75 pu, ue to the insufficient reactive power compensation. This low voltage value is less than the AC Unervoltage limit of 0.75 pu, set by the protection system. This low voltage conition results in tripping of WTIGs at t= 5 s, the tripping being been initiate by the AC Unervoltage protection. Hence the stability of the system is lost for Case-. For the system with STATCOM (shown in Fig. 2, with legens & 3), the WTIG terminal voltage improves to 0.92 pu because of reactive power support. This is well within the limit set by the protection system. So the system stability is maintaine an finally the WTIG terminal voltage recovers close to 0.95 pu for both the cases. Further, it can also be 605

7 seen from Fig. 2 that, for the case of STATCOM operating in VAr control moe (), the terminal voltage is slightly more than that of STATCOM operating in voltage control moe (). As explaine earlier, this is ue to the fact that the reactive power supplie by the STATCOM is more in than the. In, the WTIGs raw more reactive power from the istribution network an hence the WTIGs are slightly overloae compare to Case- 3. To compare the performance of two moes of operation on improving the stability, a three phase fault of 5 an half cycle uration is applie at the bus no. 3, at t=2 sec. The original system is restore upon the fault clearance. The response of the WTIG spee is shown in Fig. 3. In the prefault perio, the WTIG spee settles to aroun.005 pu after the initial transients. The WTIG spee increases rastically at the occurrence of the fault at t=2 sec, for both the cases. It can be seen from Fig. 3 that, when the STATCOM is operating in voltage control moe (shown in Fig. 3 with legen ), the system stability is lost ue to the tripping of the WTIGs by the protection system. As explaine earlier an shown in Fig. 2, the WTIG terminal voltage in is slightly less than that of. Hence the WTIG terminal voltage rops to a lower value in compare to, upon the occurrence of the fault. This low voltage conition results in tripping of the WTIGs for. The tripping is initiate by the AC Unervoltage protection. In case of STATCOM operating in VAr control moe (shown in Fig. 3 with legen ), stability of the system is maintaine. This is ue to the fact that, in the pre-fault WTIG terminal voltage was comparatively higher, an upon the occurrence of the fault, rops to a value within the limit set by the protection system. Hence stability of the system is maintaine in. WTIG spee (pu) Fig. 3 Response of WTIG spee for ifferent control moes of STATCOM rastically uring the fault uration for both the cases. As explaine earlier, the low voltage conition in results in tripping of the WTIGs, upon the clearance of the fault. Hence, the active power injecte to the istribution network becomes zero (shown in Fig. 4, with legens ). In case of STATCOM operating in VAr control moe, ue to the higher pre-fault WTIG terminal voltage, stability of the system is maintaine upon the clearance of the fault (shown in Fig. 4 with legen ). Active power injecte (MW) Fig. 4 Response of active power injecte to the network for ifferent control moes of STATCOM V. CONCLUSION This paper presente a stuy about the stability improvement of a istribution system embee with win farms. For ynamic reactive power compensation, a FACTS-base controller is employe. The ynamic behavior of the example istribution system, uring an external three-phase fault an uner various types of win spee changes, is investigate. Simulation results show that the FACTS-base reactive power compensation prevents large eviations of bus voltage magnitue inuce by reactive power rawn from istribution network by WTIGs. It is observe that, for the case of FACTS controller operating in voltage control moe, the controller tries to maintain the terminal voltage constant, at its preset reference value of pu. Consequently the FACTS controller supplies that much reactive power as is require to maintain the voltage constant. For the case of FACTS controller operating in VAr control moe the controller tries to supply the preset reference reactive power of pu an hence tries to supply the rate reactive power. As the reactive power supplie for VAr control moe is more than that of voltage control moe, the VAr control moe of operation of FACTS controller is more effective in improving the stability of the system compare to the voltage control moe of operation. The response of the active power injecte into the istribution network is shown in Fig. 4, for the same contingency an for both the cases. As the linear change of win spee from 8 to m/s is applie to the win turbines, the active power injecte to the istribution network increases with the increase in win spee. After the initial transients the active power injecte to the istribution network finally settles to its rate value of 9 MW. As the fault is applie at t=2 sec., near the WTIG bus (bus-3), the active power injecte to the istribution network reuces APPENDIXES Example istribution system ata (All ata are in pu unless specifie otherwise; the notations use are efine in []). Transformer parameters: Substation: 47 MVA, 20/25 kv, R 2 =0.0026, L 2 =0.08, R m =500Ω, X m =500 Ω. 606

8 WTIG to istribution network: Each 4 MVA, 25 kv/575 V, R 2 =0.0008, L 2 =0.025, R m =500Ω, X m = inf. Transmission line parameters per km: R =0.53 Ω, R 0 =0.43 Ω, L =.05 mh, L 0 =3.32 mh, C =.33 nf, C 0 =5.0nF. STATCOM parameters: 25 kv, MVA, R=0.07, L=0.22, V c =4KV, C c = 0.00 F, Regulator gains: Vac- K p =5 & K i =000, Vc- K p =0.000 & K i =0.02, I- K p = 0.3, K i =0 & K f =0.22, Droop=0.03. WTIG parameters: Turbine: Each- 3 MW, base win spee =9 m/s, β controller K p =5, K i =25, max β =45 0. Generator: Each- P=3.33 MVA, V=575V, f= 60 Hz, R s = , L s = 0.248, R r = , L r =0.79, L m =6.7, H=5.04, F=0.0, p=3. ynamic stability, FACTS, optimization techniques, istribute generation an win energy. Narayana Prasa Pahy was born in Inia an receive his Degree (Electrical Engineering), Masters Degree (Power Systems Engineering) with Distinction an Ph.D., Degree (Power Systems Engineering) in the year 990, 993 an 997 respectively in Inia. Then he has joine the Department of Electrical Engineering, Inian Institute of Technology (IIT) Inia, as a Lecturer, Assistant Professor an Associate Professor uring 998, 200 an 2006 respectively. Presently he is working as a Associate Professor in the Department of Electrical Engineering, Inian Institute of Technology (IIT) Inia. He has visite the Department of Electronics an Electrical Engineering, University of Bath, UK uner Boyscast Fellowship uring His area of research interest is mainly Power System Privatization, Restructuring an Deregulation, Transmission an Distribution network charging, Artificial Intelligence Applications to Power System an FACTS. REFERENCES [] OECD/IEA, Win Power Integration into Electricity Systems, Case Stuy 5, [Online]. Available: [2] F. Jurao an J. Carpio, Enhancing the istribution networks stability using istribute generation, The International Journal for Computation an Mathematics in Electrical an Electronic Engineering, vol. 24, no., 2005, pp [3] Vijay Vittal, Consequence an impact of electric utility inustry restructuring on transient stability an small-signal stability analysis, IEEE Proceeings, vol. 88, no. 2, 2000, pp [4] O. Samuelsson an S. Linahl, On spee stability, IEEE Trans. Power Systs., vol. 20, no. 2, 2005, pp [5] N. D. Hatziargyriou an A. P. S. Meliopoulos, Distribute energy sources: technical challenges, IEEE Power Engineering Society Winter Meeting, vol. 2, 2002, pp [6] R. Gnativ an J. V. Milanovi, Voltage sag propagation in systems with embee generation an inuction motors, IEEE Power Engineering Society Summer Meeting, vol., 200, pp [7] N. Dizarevic, M. Majstrovic an G. Anersson, Reactive power compensation of win energy conversion system by using Unifie Power Flow Controller, Int. J. Energy Technology an Policy, vol. 3, no. 3, 2005, pp [8] W. Freitas, E. Asaa, A. Morelato an Xu Wilsun, Dynamic improvement of inuction generators connecte to istribution systems using a DSTATCOM, Proceeings, International Conference on Power System Technology, PowerCon, vol., 2002, pp [9] N. G. Hingorani an L. Gyugyi, Unerstaning FACTS: Concepts an Technology of Flexible AC Transmission System. IEEE Press [0] L. Gyugyi, Dynamic Compensation of AC Transmission Lines by Soli-state Synchronous Voltage Sources, IEEE Trans. on Power Delivery, vol. 9, no. 2, 994, pp [] SimPowerSystems User guie. Available Sihartha Pana receive the M.E. egree in Power Systems Engineering from University College of Engineering, Burla, Sambalpur University, Inia in 200. Currently, he is a Research Scholar in Electrical Engineering Department of Inian Institute of Technology Roorkee, Inia. He was an Associate Professor in the Department of Electrical an Electronics Engineering, VITAM College of Engineering, Anhra Praesh, Inia an Lecturer in the Department of Electrical Engineering, SMIT, Orissa, Inia. His areas of research inclue power system transient stability, power system 607