FACTS device allocation for Transmission Congestion Management in Deregulated Power Market

Transcription

1 FACTS devie alloation for Transmission Congestion Management in Deregulated Power Market Dipak S.Yeole 1, Dr.P.K.Katti 1 Department of Eletrial Engineering, Dr.Basaheb Ambedkar Tehnologial University, Lonere, Maharashtra (India) Professor Department of Eletrial Engineering, Dr.Basaheb Ambedkar Tehnologial University, Lonere, Maharashtra (India) ABSTRACT:The eletri power industry has over the years been dominated by large utilities had over all ativities in generation, transmission and distribution of power within its domain of operation. Suh utilities have been referred to as vertially integrated utility (VIU).The main part of engineers to reshape three omponents of today s VIU. In the present day senario, the restruturing of the eletriity industries has gained muh attention around the world. The main fous of the restruturing is to enhane the power system performane, inrease the ustomer fous and redue the ost revenue. This gives rise to a deregulated system. Congestion is one of the tehnial hallenge in power system deregulation. In deregulated eletriity market transmission ongestion ours when there is insuffiient transmission apaity to simultaneously aommodate all onstraints for transmission of a line. This paper proposes to relieve ongestion using FACTS devies without disturbing eonomi matter. Further a methods to determine the optimal loation of FACTS has been suggested based on real power flow performane index sensitivity indies. Keywords: - Deregulated Power Market, Flexible AC Transmission Systems (FACTS), Optimal Loation,Thyristor Controlled Series Capaitor (TCSC),Transmission Congestion Management. I. INTRODUCTION For a hundred of year s eletriity and its delivery were thought to be inseparle. But due to inrease in demand from late-1980s and early 1990s things began to fore restruturing with neessary expetation that inrease in ompetition. This ould lead to redution of ost eletriity while enhaning supply quality and reliility also ould enourage new tehnologies. The suess of reforms in airlines and ommuniation setor shows importane of deregulation proess. United Kingdom was the first to restruture its owned power system. Deregulation followed in Norway, Australia and New Zealand and then United States in 199.In India, traditionally power setor owned by Government (>95% distribution and ~98% generation) in various states. In mid-1990 s,orissa starts of fundamental restruturing of power setor and soon same followed by Andhra Pradesh, Haryana,Uttar Pradesh and Rajasthan, Maharashtra [1]. But there are several omplexities in deregulation power market as due to the tremendous demand of eletrial energy,transmission lines are often driven lose to or even beyond their thermal limits. When produers and onsumers of eletri energy desire to produe and onsume in amounts that would ause transmission system to operate at or beyond one or more transfer limits, the system is said to ongested. The ation taken to redue ongestion is alled ongestion management. If ongestion is not relief then it may lead to tripping of overloaded lines, onsequential tripping of other lines and in some ases to voltage stility problems. Hene to avoid suh problem ongestion need to be solve. In this deregulated power market independent system operator (ISO) has to relieve the ongestion, so that the system is maintained in seure state. To relieve the ongestion ISO an use mainly two Types of methods whih are as follows:[] 1) Cost free methods: Out-ageing of ongested lines Operation of transformer taps/phase shifters Operation of FACTS devies partiularly seriesdevies ) Cost based methods: Re-dispathing the generation amounts. By using this method, some generators bak down while others inrease their output. The effet of re-dispathing is that generators no longer operate at equal inremental osts. Curtailment of loads and the exerise of load interruption options. The National Conferene on, Eletrial Engineering Researh & Advanement (EERA-014) 7 Page

2 Capaitive Indutive Among the ove two main methods ost free means do haveadvantages suh as without disturbing eonomi status, so GENCOand DISCO will not be involved. The objetive of using FACTS devies, [3]espeially series FACTS devies like Thyristor Controlled Series Capaitor (TCSC) are onsidered one of method that redued the transmission ongestion in the transmission system. In thispaper, where the objetive is to provide maximumrelief to the ongested line, the optimal loation offacts devie is found out using sensitivitytehnique so that the power flows through the designated path. II. CONCEPT, CHARACTERISTICS AND STATIC MODELLING OF TCSC.1 Conept and Charateristis It onsists of the series ompensating apaitor shunted by a Thyristor ontrolled reator (TCR), as shown in Fig.1.The ombination of TCR and apaitor allow the apaitive reatane to be smoothly ontrolled over wide range and swithed upon ommand to a ondition where bi-diretional thyristor pairs ondut ontinuously and insert appropriate reatane in line. When TCR firing angle 180 degrees, the reator beomes non-onduting and series apaitor has its normal impedane. As firing angle is advaned from 180 degrees to less than 180 degrees apaitive impedane inreases. On the other end, when the firing angle is 90 degrees, the reator beomes fully onduting and TCR helps in limiting fault urrent. The ontrol over firing angle produes a varile effetive apaitane, whih partly ompensates for the transmission line indutane and ontrols the power flow through the line[3][4].this makes TCSC muh more eonomi thansome other ompeting FACTS tehnologies. C XTCSC=XL XC T αl lim α lim α L XTCSC=XC T1 Fig.1shematidiagram of TCSC Resonane Fig.variationofimpedaneinase oftcsc Fig. shows the impedane harateristis urve of a TCSC devie [3] [5].It is drawn between effetive reatane of TCSC and firing angle α. The effetive reatane of TCSC starts inreasing from X L value to till ourrene of parallel resonane ondition X L (α) =X C, theoretially X TCSC is infinity. This region is indutive region. Further inreasing of X L (α) gives apaitive region. Thus, impedane harateristis of TCSC shows, both apaitive and indutive region are possible though varying firing angle (α). α lim α π Capaitive region 0 α α Llim Indutive region While seleting indutane, X L should be suffiiently smaller than that of the apaitor X C. Suppose if X C is smaller than the X L, then only apaitive region is possible in impedane harateristis. In any shunt network, the effetive value of reatane follows the lesser reatane present in the branh. So only one apaitive reatane region will appears. Also X L should not be equal to X C value; or else a resonane develops that result in infinite impedane an unaeptle ondition.. Stati Modelling The Fig. 3 (a)shows a simple transmission line represented by its lumped πequivalent parameters onneted between bus a-and bus-b. Let omplex voltage at bus-a and bus-b are Va δa and Vb δb respetively. The real and reative power flow from bus-a to bus-b an be written as: [6] [7] [8] P = V a G V a V b [G os δ + B sin δ ](1) Q = V a B + B sh V a V b [G sin δ B os δ ]() Whereδ = δ a δ b. similarly, the real and reative power flow from bus-b to bus-a is: P ba = V b G V a V b [G os δ B sin δ ](3) Q ba = V b B + B sh + V a V b [G sin δ + B os δ ](4) The National Conferene on, Eletrial Engineering Researh & Advanement (EERA-014) 8 Page

3 Bus-a Y=G+jB Bus-b Fig.3 (a) model of transmission line The model of transmission line with a TCSC onneted between bus-a and bus-b is shown in Fig.3 (b). During the steady state the TCSC an be onsidered as a stati reatane -jx. The real and reative power flow from bus-a to bus-b, and from bus-b to bus-a of a line having series impedane and a series reatane are: P Q P ba Q ba = V a G V a V b [G os δ + B sin δ ](5) = V a B + B sh V a V b [G sin δ B os δ ](6) = V b G V a V b [G os δ B sin δ ](7) = V b B + B sh + V a V b [G sin δ + B os δ ](8) Bus-a Z=r+jx Bus-b -jx Fig.3 (b) model of TCSC The ative and reative power loss in line having TCSC an be written as: P L = P + P ba = G V a + V b V a V b G os δ (9) Q L = Q + Q ba = V a + V b B + B sh + V a V b B os δ (10) Where G = r r +(x x ) and B = (x x ) r +(x x ) Bus-a Z=r+jx Bus-b Sa Sb Fig.3 () injetion model of TCSC The National Conferene on, Eletrial Engineering Researh & Advanement (EERA-014) 9 Page

4 The hange in the line flow due to series apaitane an be represented as line without series apaitane with power injeted at the reeiving and sending ends of the line as shown in Fig.3(). The real and reative power injetions at bus-a and bus-b an be expressed as: P a = V a G V a V b [ G os δ + B sin δ ](11) P b = V b G V a V b G os δ B sin δ (1) Q a = V a B V a V b [ G sin δ B os δ ](13) Where, Q b = V b B + V a V b G sin δ + B os δ (14) G = x r (x x ) +x ) + x x ) and B = x x +x x ) +x ) + x x ) Due to high ost of FACTS devies, it is neessary to find out optimal loation FACTS devies. III. OPTIMAL LOCATION OF TCSC 3.1 Real Power Flow Performane Index Sensitivity Indies The severity of the system loading under normal and ontingeny ases an be desribed by a real power line flow performane index [6], as given below, b ij =PI= N L ω m P Lm m =1 n P max Lm n (15) Where,ω m is the weighting oeffiient used to reflet the importane of lines,p Lm is the real power flow,p Lm max is the thermal limit of line m,n is an exponent used to adjust the index value to avoid the masking effet in the ontingeny taken as and ω m =1 The real power flow PI sensitivity fators with respet to the parameters of TCSC an be defined as, b k = PI x x k =0(16) k The sensitivity of PI with respet to TCSC parameter onneted between bus-a and bus-b an be written as, PI x k = N L m=1 ω m P 3 Lm ( 1 P max ) 4 P Lm Lm x k (17) The real power flow in a line-m an be represented in terms of real power injetions using DC power flow equations [9] where s is slak bus, P Lm = N n=1 n s N n=1 n s S mn P n S mn P n + P b for m k (18) for m k Using equation (0), the following relationship an be derived, P a P b S P ma + S Lm x mb = k x k x k S ma P a x k + S mb P b x k + P b x k for m k for m = k (19) The terms P a x k x k =0, P b x k x k =0 an be derived as below P a x k x k =0 = P b x k x k =0 = (V a V a V b os δ ) r x +x ) V av b sin δ (x r ) +x ) (0) The National Conferene on, Eletrial Engineering Researh & Advanement (EERA-014) 10 Page

5 P b x k x k =0 = P b x k x k =0== (V b V a V b os δ ) r x +x ) + V av b sin δ (x r ) +x ) (1) 3. Criteria for Optimal Loation The FACTS devie should be plaed on the most sensitive line. Following riteria an be used for its optimal plaement: In Real Power Flow Performane Indexmethod TCSC should be plaed in a line having most negative sensitivity index. IV. SIMULATION RESULTS To find out optimal loation of TCSC, the analysis has been implemented on 5-bus system as shown in Fig.4 below. MATLAB has been used for simulation Fig.4 5-bus system Power flow of ove 5-Bus system is alulated. From the load flow, it was found that real power flow in -3 was 0.13 whih is more than its line loading limit. Tle I: alulated sensitivity indies Line i-j b ij e e e e+08 The sensitive of real power flow performane index sensitivity indies with respet to TCSC ontrol parameter has been omputed and are shown in Tle I. The sensitive lines are highlighted in Tle I. It an be observed from Tle I that line 1 is more sensitive as per real power flow performane index method. Power flow result after plaing TCSC in line 1 is as shown in Tle II.The value of ontrol parameter of TCSC for omputing power flow is taken as 0.04.It an be observed from Tle IIongestion is relieved in line3after plaing TCSC presented in bold type. Tle II: power flow result after plaing TCSC Line Power flow without TCSC Power flow with TCSC in Line The National Conferene on, Eletrial Engineering Researh & Advanement (EERA-014) 11 Page

6 V. CONCLUSION From ove disussion, it is observed that ongestion is major issues in deregulated power system and need to be solve. FACTS devies are found to be useful to redue power flow in heavily loaded lines. Beause of the onsiderle osts of FACTS devies, it is important to obtain optimal loation for plaement of these devies. This paper summarizes,real Power Flow Performane Index Sensitivity Indies for optimal plaement of the TCSC devies. Using this method optimal loation of FACTS devies an be aurately determined in order to redue line ongestion. This methods an be applied to n (n=1,, 3 ) bus transmission system to relieve ongestion. REFERENCES [1]. A.R.Abhyankar, Prof.S.A.Khaparde, Introdution to deregulation in power industry L.Rajalakshmi, M.V.Suganyadevi, S.Parameswari Congestion Management in Deregulated Power System by Loating Series FACTS Devies []. International Journal of Computer Appliations ( ) Volume 13 No.8, January 011 Text Book by N.G.Higorani& Laszlo Gyugyi,Understanding FACTS Conept and tehnology of Flexible AC Transmission Systems [3]. Christian Shaffner,Goran Anderson, Performane of a TCSC for ongestion relief Anwar S. Siddiqui, Rashmi Jain, Majid Jamil and Gupta C. P. Congestion management in high voltage transmission line usingthyristor ontrolled series apaitors Journal of Eletrial and Eletronis Engineering Researh Vol. 3(8), pp ,otober011, [4]. Seyed Abbas Taher, Hadi Besharat, Transmission Congestion Management by Determining Optimal Loation of FACTS Deviesin Deregulated Power [5]. Systems Amerian Journal of Applied Sienes 5 (3): 4-47, 008 [6]. Verma K.S., Singh S.N., Gupta H.O., 001. FACTS devies loation for enhanement of total transfer apility, Power [7]. Engineering Soiety Winter Meeting, IEEE, Vol. : [8]. Singh S.N., David A.K., 000. Plaement of FACTS devies in open power market, Advanes in Power System Control, Operation and Management, Vol. 1: [9]. Wood A.J., Wollenberg B.F., Power Generation, Operation and Control (John Wiley, New York, 1996) The National Conferene on, Eletrial Engineering Researh & Advanement (EERA-014) 1 Page