A NEW METHOD FOR OPTIMAL LOCATION OF FACTS CONTROLLERS USING GENETIC ALGORITHM

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1 Journa of heoretica and Appied Inforation echnoogy JAI. A rights reserved. A NEW MEHOD FOR OPIMAL LOCAION OF FACS CONROLLERS USING GENEIC ALGORIHM 1 K. Vayakuar, 2 Dr. R. P. Kuudinidevi 1 Research Schoar,Coege of Engineering,Anna university 2 Assistant Professor,Coege of Engineering,Anna university. Eai: kvay_sr@rediffai.co ABSRAC his paper presents a nove ethod for optia ocation of FACS controers in a uti achine power syste using Genetic Agorith(GA). Using the proposed ethod, the ocation of FACS controer, their type and rated vaues are optiized siutaneousy. Aong the various FACS controers, hyristor Controed Series Copensator (CSC) and Unified power Fow Controer (UPFC) are considered. he proposed agorith is an effective ethod for finding the optia choice and ocation of FACS controer and aso in iniizing the overa syste cost, which coprises of generation cost and investent cost of FACS controer using GA and conventiona Newton Raphson s power fow ethod. A VC++ coding is deveoped for Genetic Agorith. In order to verify the effectiveness of the proposed ethod, IEEE 9 bus syste is used. Different operating conditions of the power syste are considered for finding the optia choice and ocation of FACS controers. he proposed agorith is an effective and practica ethod for the optia aocation of FACS controers. Keywords: Optia Power Fow(OPF), Fexibe AC ransission Syste(FACS), Genetic Agorith(GA), Newton Raphson s (NR)power fow. 1. INRODUCION In present days with the dereguation of eectricity arket, the traditiona practices of power syste have been copetey changed. Better utiization of the existing power syste resources to increase capabiities by instaing FACS controers [1] with econoic cost becoes essentia. he paraeters such as transission ine ipedances, terina votages and votage ange can be controed by FACS controers in an efficient way. he benefits brought about FACS incude iproveent of syste dynaic behavior and enhanceent of syste reiabiity. However their ain function is to contro of power as ordered [2,4]. A few research works [,6] were done on the ipact of FACS controers on iproving static perforance of the power syste. here is aso a great need for studying the ipact of FACS controers on optia power fow. he investent costs of FACS controers and their ipact on the power generation cost are aso reported [8].Many researches were ade on the optia choice and the ocation of FACS controers[1-3]. he obective of this paper is to deveop an agorith to siutaneousy find the rea power aocation of generators and to choose the type and find the best ocation of FACS controers such that overa syste cost which incudes the generation cost of power pants and investent cost of FACS are iniized using Genetic Agorith and conventiona Newton Raphson s power fow anaysis. 2. SAIC MODEL OF FACS CONROLLERS Aong the various FACS controers, hyristor Controed Series Copensator (CSC) and Unified Power Fow Controer (UPFC) are considered in this paper. he detaied odes are discussed beow CSC he CSC can serve as the capacitive or inductive copensation respectivey by odifying the reactance of the transission ine. In this paper, the reactance of the transission ine is 1

2 Journa of heoretica and Appied Inforation echnoogy JAI. A rights reserved. adusted by CSC directy. he rated vaue of CSC is a function of the reactance of the transission ine where the CSC is ocated. X = X Line + X CSC, X CSC = rtcsc. X Line (1) where X Line is the reactance of the transission ine and rtcsc is the coefficient which represents the copensation degree of CSC. o avoid over copensation, the working range of the CSC is between 0.7 X Line and 0.2 X Line r tcsc in = -0.7, r tcsc ax = 0.2 (2) 2.2.UPFC he UPFC is a cobination of shunt and series controer. It has three controabe paraeters naey, the agnitude of the boosting inected votage (U ), phase of this votage( Ø ) and the exciting transforer reactive current(i q ) When an UPFC is instaed in the power syste as depicted in figure 1 i.e the exciting transforer of UPFC is directy connected to bus. In figure 1, Z and Y denote the paraeters of transission ine 1-. Y 1 and Y denote the respective shunt adittance for bus and bus. Figure 1. UPFC is connected between node and, with exciting transforer at node When the UPFC is paced in the transission ine connected between node and, the oad fow equations can be expressed as foows [7]. P P = U U ( G cosδ + B sinδ ) Gi Li i (3) Q Q = U U ( G sinδ B cosδ ) Gi Li i = 1,2....n; but i, i (4) P P = U U ( G cosδ + B sinδ ) + ΔP G L () i Q Q = U U ( G sinδ + B cosδ ) + ΔQ G L (6) P P = U U ( G cosδ + B sinδ ) + ΔP G L (7) Q Q = U U ( G sinδ B cosδ ) + ΔQ G L (8) where n is the tota nuber of nodes of the power syste: P Gi, Q Gi, P Li and Q Li ( i) are the respective rea and reactive power of generator and oad of node i. U i δi ( i, ) are respective agnitude and phase ange of the votage of node i. εi signifies that bus is connected to bus i;. δ = δ i -δ ( i, ) G and B ( i,) are the respective rea part and iaginary part of Y which represents the eeents of the network adittance atrix. Here Y is exacty the sae as that of the network without UPFC. ΔP, ΔQ, ΔP and ΔQ are the odified ites due to the added UPFC. he foruae of odification can then be written as 2 ΔP = U U [ G cos( δ φ ) B sin( δ φ )] + G FU + 2 (9) F F F U U G cos( δ φ ) Δ Q = U U [ G sin( δ φ ) B cos( δ φ )] U I ΔP ΔQ (10) = U U [ G cos( δ φ ) + Bsin( δ φ )] (11) = U U G sin( δ φ ) B cos( δ φ )] [ (12) where G + B = 1/Z 1 ; G F = g 1 + G; B F = b 1 + B; Y = g + b ; he inected votage of UPFC has a axiu votage agnitude of 0.1V,where V is the rated votage of the transission ine where UPFC is instaed. he ange of the UPFC can be varied fro -180 to +180 degrees. 3. COS FUNCION he obective of this paper is to find siutaneousy the optia generation and optia choice and ocation of FACS controers so as to iniize the overa cost function, which q 2

3 Journa of heoretica and Appied Inforation echnoogy JAI. A rights reserved. coprises of generation cost and investent costs of FACS controers. 3.1.Generation Cost Function he generation cost function is represented by a quadratic poynoia as foows: 2 C 2 (P G ) = α 0 +α 1 P G +α 2 P G (13) where P G is the output of the generator (MW), and α 0, α 1 and α 2 are cost coefficients. 3.2.Investent Costs Function of FACS Controers Based on the Sieens AG Database, the cost functions for CSC and UPFC are deveoped he cost functions for UPFC and CSC are : C 1UPFC = S S (US$ / MVar) (14) C 1CSC = 0.001S S+13.7 (US$ / MVar) (1) where C 1UPFC and C 1CSC are in US$/kVar and S is the operating range of the FACS controers in kvar. he cost function for CSC and UPFC are shown in figure 2 subected to E(f,g) = 0 (17) B 1 (f) < b 1, B 2 (g) < b 2 (18) where C ota : the overa cost obective function which incudes the average investent costs of FACS devices C 1 (f) and the generation cost C 2 (P G ). E (f.g) : the conventiona power fow equations. B 1 (f) and B 2 (g) are the inequaity constraints for FACS controers and the conventiona power fow respectivey. f and P G are vectors that represent the variabes of FACS controers and the active power outputs of the generators. g represents the operating state of the power syste. he unit for generation cost is US$/Hour and for the investent cost of FACS controers are US$. hey ust be unified into US$/Hour. Noray the FACS controers wi be in service for any years. However ony a part of its ife tie is epoyed to reguate the power fow. In this paper three years is epoyed to evauate the cost function. herefore the average vaue of the investent costs are cacuated as foows C 1 (f ) = C(f)/{8760 x 3 } (19) Figure 2. Cost functions of the FACS Controers :CSC and UPFC. 4. OPIMAL POWER FLOW WIH FACS CONROLLERS he foruation of the optia aocation of FACS controers can be expressed as foows Miniise C ota = C 1 (f) + C 2 (P G ) (16) As entioned above, power syste paraeters can be changed using FACS controers. hese different paraeters derive different resuts on the obective function. Aso, the variation of FACS ocations and FACS types has aso infuences on the obective function. herefore, using the conventiona optiization ethods are not easy to find the optia ocation of FACS devices, types and contro paraeters siutaneousy. o sove this probe, genetic agorith is epoyed in conunction with conventiona NR power fow ethod.. GENEIC ALGORIHM FOR OPIMAL POWER FLOW INCORPORAING FACS CONROLLERS GAs are goba search techniques based on the echanis of natura seection and genetics. Without any prior knowedge of the obective function they can search severa possibe soution 3

4 Journa of heoretica and Appied Inforation echnoogy JAI. A rights reserved. siutaneousy. Gas are best suited for a copex probes. Moreover it produces high quaity soution. GA start with rando generation of initia popuation and then the seection, crossover and utation are proceeded unti best popuation is found. GAs are sipe and practica agorith and easy to be ipeented in power syste..1.encoding he obective is to find siutaneousy the optia generation and optia choice and ocation of FACS controers subected to equaity and inequaity constraints. herefore the configuration of FACS devices is encoded by four paraeters: active power outputs of generator, type, ocation and rating of FACS controers. he first vaue of each string corresponds to the active power outputs of generator, second vaue represents the ocation the third vaue represents the type of FACS controers 1 for CSC, 2 for UPFC and 0 for No device. he ast vaue rf represents the rated vaue of each FACS controers. his vaue ranges between -1 and +1. he rea vaue of each FACS device is then converted according to the different FACS ode using the foowing. CSC: It has working ranges between -0.7 X Line and 0.2 X Line. herefore rf is converted into rea degree of copensation rtcsc using the reation rtcsc= rf x UPFC: It has an inected votage agnitude of 0.1 V and the ange of the inected votages varies between -180 and +180 degrees. herefore rf is converted into the working ange range rupfc, using the reation rupfc = rf x 180 degrees..2. Initia Popuation he initia popuation is generated fro the foowing paraeters N G : Active power output of generators. N type : ypes of FACS controers N Location : Possibe ocation of FACS controers. N rated : Rating of FACS controers. N ind : Nuber of individua of the popuation. For each popuation string the first vaue represents a set of generators rea power output which is randoy seected. he second vaue represents the type of FACS controers which is obtained by randoy drawing nuber aong the seected devices (1, 2, 0). he third vaue of each string represents the ocation of FACS controers in the transission ine which is aso randoy seected aong the existing nuber of transission ines in the syste. he fourth vaue represents the rating of the FACS controers again randoy seected between -1 and +1. o obtain the entire initia popuation the above operation is repeated N ind ties..3. Decoding he paraeters of the initia popuation are then decoded to actua vaues. hen for a given oad deand the Newton Raphson s power fow is perfored [7]. H N Δδ ΔP = J L ΔV / V ΔQ (20) After convergence the votage agnitude and phase anges of the bus votages are known. Using these the rea power oss P L is cacuated using the equation (21) P L = n n i= 1 = 1 α = ( i Piα P+ QiαQ - PiβQ + PβQ ) r cos( δ i-δ ) vi. v (21) (22) r sin( δ i-δ ) β = vi. v (23) where r k are the rea coponents of the eeents of the bus ipedance atrix n is the nuber of buses P i is the rea power at bus i Q i is the reactive power at the bus i V i is the agnitude of the votage at bus i.4. Fitness Function After encoding, the obective function (fitness) is evauated for each individua of the popuation. he fitness is a easure of quaity which is used to copare different soutions. In this paper fitness is defined as foows 1 Fitness = N C + W ( P P P ) ota (24) Since the GA can ony find the axiu vaue of the obective, so inverse function is seected to i Gi Di Li 4

5 Journa of heoretica and Appied Inforation echnoogy JAI. A rights reserved. convert the obective function into a axiu one. hen reproduction, crossover and utation are appied successivey to generate the offspring... Reproduction Reproduction is a process where the individua is seected to ove to a new generation according to their fitness. he biased rouette whee seection is epoyed. he probabiity of an individua s reproduction is proportiona to its part on the biased rouette whee..6. Crossover he ain obective of crossover is to reorganize the inforation of two different individuas and produce a new one. A singe point crossover is appied and probabiity of crossover is seected as Mutation Mutation is used to introduce soe sort of artificia diversification in the popuation to avoid preature convergence to oca optiu. he above-entioned operations of seection, crossover and utation are repeated unti the best individua is found. 6. RESULS A VC++ coding is deveoped for Genetic Agorith. In order to verify the effectiveness of the proposed ethod IEEE 9 bus syste is used. Different operating conditions are considered for finding the optia choice and ocation of FACS controers. he tota popuation size is seected as 10, the utation probabiity as 0.01 and crossover probabiity as 1.0. Case 1 For the nora oading of IEEE 9 bus syste it has been found that No FACS controers are required. he generators outputs are 202MW, 31.6MW, 86.4MW, 204MW, 19 MW and 7MW respectivey. Case 2 When the oading at bus is increased twice it is found that CSC is seected at transission ine 3. he VAR copensation required is MVAR. he generators outputs are 116.4MW, MW, 170MW, 113MW, 101MW and 17MW respectivey Case 3 When the oading at bus is increased by three ties and reoving the generation at bus 3 it has been found that UPFC is seected in the transission ine 4 and VAR copensation required is MVAR. he generators outputs are 24.3MW, 263.6MW, 0MW, 20MW, 223MW and 183MW respectivey. Apart fro that different oading conditions are considered and the resuts are given in abe 1 7. CONCLUSIONS In this paper a genetic agorith based optia power fow is proposed to deterine the type of FACS controers, its optia ocation and rating of the devices in power systes and aso to siutaneousy deterine the active power generation for different oading condition. he overa syste cost function which incudes generation cost of power pants and the investent costs of FACS controers are epoyed to evauate the power syste perforance. he proposed agorith is an effective and practica ethod for the aocation of FACS controers.

6 Journa of heoretica and Appied Inforation echnoogy JAI. A rights reserved. abe 1. Optia Choice, Location and Rating of FACS controers BUS LOADING DEVICE RAING (MVAR) LOCAION Nora oading wice nora oading 3 ies nora oading 3 ies nora oading & without generation at bus 3 wice nora oading 3 ies nora oading wice nora oading & without generation at bus 2 DEVICE YPE NO DEVICES LINE 3 CSC LINE 4 CSC LINE 4 UPFC LINE 2 CSC LINE 2 UPFC LINE 6 UPFC REMARKS - Line 3 connects th & 6 th bus Line 4 connects 3 rd and 6 th bus 6 th bus is connected directy to th bus Line 4 connects 3 rd and 6 th bus.6 th bus is connected directy to th bus Line 2 connects 4 th & th bus. 4 & 9 th bus are directy connected Line 2 connects 4 th & th bus. 4 th & 9 th bus directy connected 6 th ine connects buses 7 & 8. 8 th bus is connected to 9 th bus REFERENCES [1]. S.Gerbex, R. Cherkaoui and A. J. Gerond, Optia Location of Mutipe ype FACS Devices in a Power Syste by eans of Genetic Agorith, IEEE rans. Power Systes, Vo. 16, pp , August [2]... Lie, And W. Deng, Optia Fexibe AC ransission Systes (FACS) Devices Aocation, Eectrica Power & Energy Systes, Vo. 19, No. 2 pp , [3]. P. Patei, S. Vitet, M. Bena, And A. Yokoyaa, Optia Location of Phase Shifters in French Network by Genetic Agorith, IEEE rans. Power Systes, Vo. 14, pp , August [4].. S. Chung, And Y. Z. Li, A Hybrid GA for OPF with consideration of FACS Devices, IEEE Power Engineering Review, pp. 47-7, February []. X. Duan, J. Chen F. Peng, Y. Luo, Y. Huang, Power Fow Contro with FACS Devices, IEEE rans. Power Systes, pp , [6]. L. Gyugyi, C.D Schauder, S. L. Wiias, Et A., he Unified Power Fow Controer : A New Approach to Power ransission Contro, IEEE rans. Power Deivery, Vo. 10, No. 2, pp , 199. [7]. F. Waniang, H. W. Ngan, Extension of Newton Raphson Load Fow techniques to cover Muti Unified Power Fow Controers, Proceedings of the 4 th Internationa Conferences on Advances in Power Syste Contro Operation and Manageent, Honkong, [8]. L. Gyugyi, C.D Schauder, S. L. Wiias, Et A., Optia Paceent of FACS Controer in Power Syste by a Genetic Based Agorith, IEEE Internationa Conference on Power Eectronics and Drive and Systes, Honkong,