G.J. E.D.T.,Vol.(6:93 (NovemberDecember, 03 ISSN: 39 793 LOAD FREQUENCY CONTROL OF MULTI AREA INTERCONNECTED SYSTEM WITH TCPS AND DIVERSE SOURCES OF POWER GENERATION C.Srinivaa Rao Dept. of EEE, G.Pullaiah College of Engineering and Technology, Kurnool, India. Abtract Thi paper preent the analyi of Load Frequency Control (LFC of multi area ytem coniting of divere ource of power generation. A two area power ytem model coniting of thermal and ga ource ha been employed in thi work. The peed governor are fitted to all the power generating unit. FACTS device like Thyritor Controlled Phae Shifter (TCPS have alo been employed to further increae the dynamic performance of the ytem in term of peak time, overhoot and ettling time. The effect of thee parameter on the ytem i demontrated with the help of computer imulation. A ytematic method ha alo been demontrated for the modeling of thee component in the ytem. Computer imulation reveal that due to the preence of TCPS the dynamic performance of the ytem in term of ettling time, overhoot and peak time i greatly improved. Keyword: Load frequency Control, TCPS, Multi area ytem, dynamic performance, divere ource. I. Introduction Large cale power ytem are normally compoed of control area or region repreenting coherent group of generator. In a practically interconnected power ytem, the generation normally comprie of a mix of thermal, hydro, nuclear and ga power generation. However, owing to their high efficiency, nuclear plant are uually kept at bae load cloe to their maximum output with no participation in the ytem AGC. Ga power generation i ideal for meeting the varying load demand. Ga plant are ued to meet peak demand only. Thu the natural choice for AGC fall on either thermal or hydro unit. Literature urvey how that mot of earlier work in the area of AGC pertain to interconnected thermal ytem and relatively leer attention ha been devoted to the AGC of interconnected hydrothermal ytem involving thermal and hydro ubytem of widely different characteritic. Concordia and Kirchmayer [] have tudied the AGC of a hydrothermal ytem conidering nonreheat type thermal ytem neglecting generation rate contraint. Kothari, Kaul, Nanda [] have invetigated the AGC problem of a hydrothermal ytem provided with integral type upplementary controller. The model ue continuou mode trategy, where both ytem and controller are aumed to work in the continuou mode. Perhap Nanda, Kothari and Satangi [3] are the firt to preent comprehenive analyi of AGC of an interconnected hydrothermal ytem in continuoudicrete mode with claical controller. On the other hand, the concept of utilizing power electronic device for power ytem control ha been widely accepted in the form of Flexible AC Tranmiion Sytem (FACTS which provide more flexibility in power ytem operation and control [4]. A Thyritor Controlled Phae Shifter (TCPS i expected to be an effective apparatu for the tieline power flow control of an interconnected power ytem In the analyi of an interconnected power ytem. Literature urvey how ample application of TCPS for the improvement of dynamic and tranient tabilitie of power ytem. In view of thi the main objective of the preent work are:. To develop the two area imulink model of thermal and ga ytem. To develop the model of TCPS 3. To tudy the improvement of dynamic performance of the ytem through TCPS II. Dynamic Mathematical Model Electric power ytem are complex, nonlinear dynamic ytem. The load frequency controller control the control valve aociated with High Preure (HP turbine at very mall load variation [6]. The ytem under invetigation ha tandemcompound ingle reheat type thermal ytem. Each element (Governor, turbine and power ytem of the ytem i repreented by firt order tranfer function at mall load variation in according to the IEEE committee report [6]. Two ytem nonlinearitie likely Governor Deadband and Generation Rate Contraint (GRC are conidered here for getting the realitic repone. Governor Deadband i defined a the total magnitude of the utained peed change within which there i no change in the valve poition [6]. It i required to avoid exceive operation of the governor. GRC i conidered in real power ytem becaue there exit a maximum limit on the rate of change in the generating power. Figure how the tranfer function block diagram of a two area interconnected ytem coniting of thermal and ga power plant. The parameter of all the model are given in the Appendix. 9
G.J. E.D.T.,Vol.(6:93 (NovemberDecember, 03 ISSN: 39 793 B K K R P C( T g Reheat ytem turbine P D( X E( P R( P G( T t Ga Power Plant KrTr Tr P G( K p T p T KP TP F ( F ( B R P D( The block diagram of Ga power plant i hown in Fig Fig. Two Area Interconnected ThermalGa ytem Fig. Block diagram of Ga Power plant A performance index conidered in thi work to compare the performance of propoed method i given by t J f f Ptie. The ISE criterion i ued becaue it weigh large error heavily and mall error 0 lightly. Even though f and f have very cloe reemblance, eparate weighing factor i.e., and are conidered for each of them repectively o a to obtain better performance. The parameter and are weighing factor which determine the relative penalty attached to the tieline power error and frequency error. A value of 0.65 ha been conidered in thi work a the value for both and. III. Control Employing TCPS The recent advance in power electronic have led to the development of the Flexible Alternating Current Tranmiion Sytem (FACTS. FACTS device are deigned to overcome the limitation of the preent mechanically controlled power ytem and enhance power ytem tability by uing reliable and highpeed electronic device. One of the promiing FACTS device i the Thyritor Controlled Phae Shifter (TCPS. A TCPS i a device that change the relative phae angle between the ytem voltage. Therefore, the real power flow can be regulated to mitigate the frequency ocillation and enhance power ytem tability. a Fig. 3 TCPS in erie with tie line Without TCPS, the incremental tieline power flow from Area to Area in a traditional ytem can be expreed P tie ( X ( Y Area Reheat Unit V T ( ( F F ( a ( TCR ( b c ( TF : TCPS V ( i jx Tieline V Area Where T i the ynchroniing contant without TCPS. When a TCPS i placed in erie with the tie line a in Fig, current flowing from Area to Area i V ( V i ( jx ( T CD Ga Unit ( 0
G.J. E.D.T.,Vol.(6:93 (NovemberDecember, 03 ISSN: 39 793 V ( V P tie jqtie V ( jx (3 Separating the real part of Eqn. (3 V V P tie in( (4 X But in Eqn. (4 perturbing, and from their nominal value, and repectively V V Ptie co( in( X (5 But for a mall change in real power load, the variation of bu voltage angle and alo the variation of TCPS phae angle are very mall. A a reult ( i very mall and hence, in( (. So Eqn. (5 can be written a V V Ptie co( ( X (6 P tie T( (7 V V Where T co( (8 X P tie T( T (9 But f dt and f dt (0 Eqn. (9 can be modified a P tie T ( fdt f dt T ( The Laplace tranform of Eqn. ( i T P ( tie F F T( ( A per Eqn. (, it can be oberved that the tieline power flow can be controlled by controlling the phae hifter angle. Auming that the control input ignal to the TCPS damping controller i Error and that the tranfer function of the ignaling conditioning circuit i K C (, where K i the gain of the TCPS controller KC( Error (3 And C (4 T p The phae hifter angle ( can be written a K Error (5 T p Where K and Tp are the gain and time contant of the TCPS and Error i the control ignal which control the phae angle of the phae hifter. Thu, Eqn. ( can be rewritten a T K Ptie F F T Error Tp A. Logic of TCPS Control Strategy Error can be any ignal uch a the thermal area frequency deviation f or Ga area frequency deviation f or ACE of the thermal or ga area to the TCPS unit to control the TCPS phae hifter angle which in turn control the tieline power flow. Thu, with Error f, Eqn (3 can be written a K F (7 Tp The above logic can be demontrated a follow F ( K T Tp Fig 4 Logic of TCPS in erie with tie line (6
G.J. E.D.T.,Vol.(6:93 (NovemberDecember, 03 ISSN: 39 793 V. Reult and Dicuion The propoed ytem in modeled in MATLAB/SIMULINK environment and the reult have been preented. A load change of 0.04 p.u M.W in each area ha been conidered to tudy the comparion between the performance of the ytem. A value of 0.5 ha been conidered a the gain of integral controller. Table how the comparion of both type of ytem in thermal and ga area. Table repreent the performance index of both the ytem. It can be oberved that the ytem with TCPS give better performance than the ytem without TCPS. Figure 5 repreent the comparion between the frequency deviation and tie line error deviation for both the area. The comparion between the ytem in term of performance index i repreented in Figure 6. It can be oberved that the ytem with TCPS ha le performance index a compared to the ytem without TCPS. With TCPS Table: Comparion of ytem performance with and without TCPS. Thermal area Ga area Peak time Settling Peak time Overhoot (ec Time (ec (ec Overhoot Settling Time (ec 0.735 0.007936 3.995 0.765 0.007 5.065 Without TCPS 0.375 0.00339 0.65 0.3 0.0069.85 % Improvement 48.97 70.5 84.60 45.5 43.7 64.6 Table : Comparion of Performance Index Value. Performance Index Value With TCPS 5.435 0 Without TCPS 5 3.74 0
G.J. E.D.T.,Vol.(6:93 (NovemberDecember, 03 ISSN: 39 793 Figure 5: Comparion of Frequency and tie line power deviation with and without TCPS. Figure 6: Comparion of Performance Index of both the ytem. VI. Concluion A ytematic method ha been uggeted for the deign of a Thyritor Controlled Phae hifter for a twoequalarea ga thermal ytem. Thi paper ha alo invetigated the performance of the ytem with and without TCPS with repect to reduction of frequency deviation and tie line power deviation during a load change on a two area ga thermal ytem. The imulation reult indeed how that the propoed method indeed uccefully mitigate the frequency and tie line power deviation during a load change and alo it can be een that the performance index of the ytem with TCPS i le than the ytem without TCPS which indicate the uperiority of the propoed method. Reference [] C. Concordia and L.K.Kirchmayer (954 TieLine Power and Frequency Control of Electric Power Sytem Part II, AIEE Tranaction, vol. 73, Part A, pp. 3346. [] M.L.Kothari, B.L.Kaul and J.Nanda (980, Automatic Generation Control of HydroThermal ytem, journal of Intitute of Engineer(India, vo.6, pt EL, pp859. [3] J.Nanda, M.L.Kothari, P.S.Satangi,(983 Automatic Generation Control of an Interconnected hydrothermal ytem in Continuou and Dicrete mode conidering Generation Rate Contraint, IEE Proc., vol. 30, pt D, No., pp 455 460. [4] Dynamic Model for team and Hydro Turbine in Power ytem tudie (973, IEEE committee report. Tranaction in Power Apparatu & Sytem, Vol.9, No.6,pp.90495. [5] ChunFeng Lu, ChunChang Liu and ChiJui Wu. (995, Effect of battery energy torage ytem on load frequency control conidering governor dead band and generation rate contraint IEEE tranaction on energy converion Vol. 0, pp.555 56. [6] S. C. Tripathy, R. Balaubramanian & P. S. Chandramohanan Nair, (99, Small rating Capacitive Energy Storage for dynamic performance improvement of Automatic Generation Control, Proc. IEE, vol. 38, no., pp. 03. 3