A New Framework for Reactive Power Market Considering Power System Security

Transcription

1 A New Framewor for Reactve Power Maret Consderng Power System Securty A. Rabee*, H. A. Shayanfar* and N. Amady** Downloaded from eee.ust.ac.r at 2:26 IRDT on Sunday August 19th 2018 Abstract: Ths paper presents a new framewor for the dayahead reactve power maret based on the unform aucton prce. Voltage stablty and securty have been consdered n the proposed framewor. Total Payment Functon (TPF) s suggested as the obectve functon of the Optmal Power Flow (OPF) used to clear the reactve power maret. Overload, voltage drop and voltage stablty margn (VSM) are ncluded n the constrants of the OPF. Another advantage of the proposed method s the excluson of Lost Opportunty Cost (LOC) concerns from the reactve power maret. The effectveness of the proposed reactve power maret s studed based on the CIGRÉ32 bus test system. Keywords: Reactve power maret, Expected Payment Functon (EPF), Total Payment Functon (TPF), Lost Opportunty Cost (LOC). 1 Introducton 1 One of the man reasons for some of the recently maor blacouts n the power systems around the world such as those occurred n September 23, 2003 n Sweden and Denmar, September 28, 2003 and etc. was reported as nsuffcent reactve power of system resultng n the voltage collapse. So, reactve power s essental for the ntegrty of the power system and mantanng the system wth acceptable margn of the securty and relablty [1][3]. In recent years, some papers are publshed n the area of optmal prcng of the reactve power [4][9]. All of them assume that the consumer of the reactve power should pay for the reactve power support servce and the producers of the reactve power are remunerated. The other wors consder techncal ssues of the power system n addton to economcal aspects [10][13]. In [14], the authors determne the mnmum reactve power (Q mn ) that each generator needs to transfer ts own actve power through the power system. The Q mn s determned only for the heavly loaded condton. Kanar Bhattacharya et al have desgned a compettve reactve power maret [15][18]. The Iranan Journal of Electrcal & Electronc Engneerng, Paper frst receved 5 Jul and n revsed form 4 May * The Authors are wth the Center of Excellence for Power Systems Automaton and Operaton, Department of Electrcal Engneerng, Iran Unversty of Scence and Technology (IUST) Emals: rabee@ust.ac.r, hashayanfar@yahoo.com ** The Author s wth the Department of Electrcal Engneerng, Semnan Unversty, Semnan, Iran. Emal: amady@tavanr.org.r generator Expected Payment Functon (EPF) s defned so that the ISO can easly call for reactve bds from all partes [15]. In [16], a compettve reactve power maret s desgned for the reactve power ancllary servce. Mtgatng maret power, a localzed reactve power maret s proposed n [17]. J. Zhong proposed a prcng mechansm for the other components of the reactve power compensator n a compettve maret [18]. A few wors ncluded voltage securty n the reactve power prcng [19][20]. In [19], a costbased reactve power prcng s proposed, whch ntegrates the producton cost of reactve power and voltage stablty margn requrement of pre and postcontngences nto the OPF problem. In [20], a twolevel framewor s proposed for the operaton of a compettve reactve power maret tang nto account system securty aspects. The frst level,.e. procurement, s on a seasonal bass whle the second level,.e. dspatch, s close to the realtme operaton. In that wor, the reactve power procurement s consdered as an essentally longterm ssue,.e. a problem n whch the Independent System Operator or ISO sees optmal reactve power allocaton from possble supplers that would be best suted to ts needs and constrants n a gven season [20]. Ths optmal set should deally be determned based on the demand forecast and system condtons expected over the season [20]. However, seasonal maret for the reactve power encounters problems. Frst, the reactve power consumpton of system s so volatle that ts forecastng over a season 196 Iranan Journal of Electrcal & Electronc Engneerng, Vol. 5, No. 3, Sep. 2009

2 Downloaded from eee.ust.ac.r at 2:26 IRDT on Sunday August 19th 2018 becomes very hard. Second, the reactve power requrement of the system strongly depends on the loadng condton of networ whch further complcates the predcton of the reactve power requrement of the power system over a long horzon. Thrd, the occurrence of dfferent planned/unplanned outages and effects of mantenance schedulng (such as generators and transmsson lnes enterng to crcut after ther mantenance perod) n a season can change the confguraton of the power system, leadng to more complexty of desgnng a seasonal reactve power maret. Fourth, over the long tme of a season, the ISO can handle the reactve power requrements of the system only wth the selected generators of the networ that have contract wth them to become avalable for reactve power compensaton whch s to some extent n contradcton wth the local nature of the reactve power. Accordngly, as one of the paper contrbutons, ths paper presents a dayahead reactve power maret model whch consders power system securty. Another contrbuton of the paper s the elmnaton of LOC from the EPF of synchronous generator n the reactve power maret. The maxmum reactve power output of a synchronous generator s lmted by ts capablty curve and f a generator n the reactve power maret s requred, by the ISO, to generate reactve power more than the respectve lmt, t must decrease ts actve power to adhere the capablty curve. Thereby, the generator wll be compensated for the lost of revenue termed as the LOC. Ths actve power reducton of generator however, s assocated wth the reschedulng of generatng unts to balance the load demand of the system. In ths paper, a new framewor for reactve power maret s proposed n such a way that the generators no longer be requred to reduce ther actve power durng the settlement of reactve power maret. 2 The Proposed Method In ths secton, nsprng wth the generator Expected Payment Functon (EPF) proposed n [16], a new EPF for s proposed. The reactve power capablty curve of a generator s shown n Fg. 1. The explanaton to Q base, Q A, Q B can be found n [16]. The offer structure of the th synchronous generator n the reactve power maret s formulated as the followng equaton [16]: 0 = 0, QMn QA QB m2. dq + m3. Q. dq Q base QA EPF a m dq (1) The coeffcents n Eq. (1) represents the varous components of the reactve power cost ncurred by the th unt where a 0 s avalablty prce offer n dollars, m 1 s cost of loss prce offer for operatng n under excted mode (Q mn < Q 0) n $/MVArh, m 2 s cost of loss prce offer for operatng n regon (Q base Q Q A ) n $/MVArh and m 3 s opportunty prce offer for operatng n regon (Q A Q Q B ) n $/MVArh/MVArh (Fg. 2). a 0,, m 1,, m 2,, and m 3, are the bd values of the th provder for the reactve power maret. The opportunty cost s a quadratc functon of Q (Fg. 2). The reactve power s cleared based on the mnmzaton of the total payment to the partcpants of the reactve power maret as [16]: ρ0. W0, ρ1. W1,. Q1, + ρ2. W2,. Q2, TPF = 1 (2) 2 gen ρ2. W3,. QA, ρ3. W3,. Q + + 3, 2 Accordng to Eqs. (1) and (2), the generator receves the opportunty cost by enterng to regon III where, the generator wll be requred to reduce ts actve power n order to meet the system reactve power requrement. Accordngly, a reschedule of actve power dspatch wll be requred to compensate for the correspondng real power devaton from the dspatched values whch are fxed and determned earler n the energy maret [20], [21]. The lost opportunty s a challengng ssue n the reactve power marets. Our proposed soluton for ths problem s the elmnaton of LOC from the reactve power maret desgn whle consderng the capablty curve lmts of the generators. The actve power of each generator s determned n the energy maret and s used as the nput data n the reactve power maret. Fg. 1. Synchronous generator capablty curve Fg. 2. Reactve power offer structure of provder Rabee et al.: A New Framewor for Reactve Power Maret Consderng Power System Securty 197

3 Downloaded from eee.ust.ac.r at 2:26 IRDT on Sunday August 19th 2018 Suppose that the actve power of a unt be P g0 as shown n Fg. 3. If ths unt produces reactve power more than Q g0 then t enters nto regon III. The value of Q g0 s determned by the feld current lmt f P g0 s lower than P GR, and by the armature current lmt f P g0 s greater than P GR. P GR s the ntersecton of feld current and armature current lmt curves (MVA ratng of the generator [16]). In the reactve power maret, f the maxmum reactve power producton of the unt s lmted to Q g0, then the unt never enters nto regon III. Hence, devaton from the actve power dspatch of the energy maret and consequent reschedulng of the generatng unts no longer s requred. As another result, the LOC payment wll be elmnated form the TPF of the reactve power maret. In ths wor, avodng from enterng to regon III and dealng wth ts assocated problem, the maxmum reactve power producton of each unt s lmted to ts Q g0,.e. Q Q g0 where, Q s the reactve power output of the generator. The man advantage of the proposed soluton s the elmnaton of actve power redspatch n addton to the elmnaton of the lost opportunty cost from the reactve power maret. Another advantage of the proposed method s that the EPF of the generator ust ncludes the avalablty and cost of losses component and the quadratc part of EPF related to the LOC s removed, changng the EPF from nonlnear to lnear whch s easer to solve. So, the EPF of generator n the new framewor can be wrtten as follows. 0 EPF = a0,. m2. dq (3) + m1 dq + Q Q Qbase, Fg. 4 shows the EPF of the proposed framewor for reactve power maret. Form ths fgure t can be observed that the EPF s a lnear functon. Furthermore, t can be seen that the generator can produce reactve power ultmately up to ts Q g0. The modfed TPF can be mathematcally formulated as follows: ρ0,. W0, ρ1. W1,. Q+ TPF = (4) gen ρ2. W2,.( Q Qbase, ) Fg. 3. Synchronous generator capablty curve Fg. 4. EFP of new reactve power maret framewor The bnary varables W 0, W 1,, W 2,, n Eq. (4) have smlar descrpton to Eq. (2). If the th provder s selected n the reactve maret and operated n one of the regons I, II then W 1, +W 2, =1, otherwse W 1, +W 2, =0. ρ 0, ρ 1, ρ 2 n Eq. (4) are also smlar to Eq. (2). The new TPF shown n Eq. (4) s the obectve functon of the OPF problem, whch should be solved for clearng of the reactve power maret. 3 Maret Settlement Clearng of the reactve maret n the form of the OPF s formulated as follows: Mn ( ρ0, W0, ρ1w1, Q+ ρ2w2, ( Q Qbase) ) (5) gen Subect to the followng constrants: 1) Load flow constrans: Pg Pd = VV Y ( δ δ θ ) Q g Q d = V V Y cos (6) ( δ δ θ ) sn (7) ( ˆ ˆ ) ( ˆ δ ˆ δ θ ) Pˆ ˆ ˆ ˆ g Pd = VV Y cos δ δ θ (8) Qˆ Qˆ = Vˆ Vˆ Y sn (9) g d where, The buses ndces P g Actve power generaton at bus n per unt at current operatng pont P d Actve power demand at bus n per unt at current operatng pont Q g Reactve power generaton at bus n per unt at current operatng pont Q d Reactve power demand at bus n per unt at current operatng pont V Voltage magntude at current operatng pont δ The angle of voltage at current operatng pont ^ A symbol ndcatng securty loadng pont Y Magntude of element and of admttance matrx θ The angle of element and of networ admttance matrx 198 Iranan Journal of Electrcal & Electronc Engneerng, Vol. 5, No. 3, Sep. 2009

4 Downloaded from eee.ust.ac.r at 2:26 IRDT on Sunday August 19th ) The operaton constrants of generators: W0,,W1,,W2, {0,1} : The unt ndex (10) Q W.Q 0 (11) W mn, 1, 2,.Qbase, W2,.Q Qg0, W 1, W2, W0, (12) + (13) Q Q Q (14) mn, g0, ( V,, ) 2 2 tia Pg0, f Pg0, > PGR, 2 2 Q t, af, 2 t, g0, = V E V Pg0, (15) X s, Xs, f Pg0, < PGR, where P g 0, s the th unt actve power generaton determned earler n the actve power maret and P GR, s the ntersecton of the feld current and armature current lmt curves (MVA ratng of the generator). 3) Constrants related to maret prce determnaton: W0,. a0, ρ0 (16) W1,. m1, ρ1 (17) W2,. m2, ρ2 (18) 4) Securty constrans: max Sb, Sb, (Overload constrant, S b, s the apparent power of branch at current operatng pont) (19) mn max V V V (Voltage drop constrant at current operatng pont) (20) spec VSM VSM (VSM constrant) (21) ( λ λmn ) (Voltage securty margn constrant) (22) Pˆ g = (1+ λ + G ) Pg (23) where, the varable K G represents the unnown losses for the securty power flow Eqs. (8) and (9) [22]. Pˆ = (1+ λ ) (24) d P d Qˆ = (1+ λ ) (25) d Q d max b, Sb, S ˆ b, Ŝ ( ndcates apparent power of the th branch at securty loadng pont) (26) mn max V Vˆ V (Voltage drop constrant at securty loadng pont) (27) When the th reactve power provder s not selected or s selected and operated n one of regons I, II then the constrant (13) wll be satsfed n the equalty form (0=0 and 1=1, respectvely). However, when the th provder s selected for the reactve reserve then ths constrant wll be satsfed n the nequalty form (0 < 1). Equaton (14) ndcates that the reactve power generaton of each unt should not be more than Q g0, whch s determned by (15), reflectng the capablty curve lmt of each unt and avodng from enterng to regon III. Under certan loadng condton, some generators may be ased to supply reactve power n regon III, n whch case, the generators wll be requred to reduce ther actve power n order to meet the system requrement. Consequently, a reschedulng of ther actve power dspatch wll be requred to compensate for ths real power devaton from the already dspatched values. Equaton (14) however, solves ths problem wth another method. In ths method the generators are allowed to produce reactve power no more than the Q g0 of unts determned by Eq. (15). The lac of the reactve power of the system s compensated by the ncrease of reactve power output of other nearby unts not reachng the capablty curve lmt. In other words, nstead of enterng a unt nto the nonlnear regon III, reactve output of a number of unts s ncreased n the lnear regon II to meet the reactve power requrement of the system. Therefore, by the proposed method, reactve power settlement no longer requres actve power redspatch. Equatons (19) to (27) nclude securty constrants at the current operatng pont,.e. Eq. (19) and Eq. (20), VSM constrant,.e. Eq. (21), voltage securty constrants,.e. Eq. (22) to Eq. (25), and constrants of the securty loadng pont,.e. Eq. (26) and Eq. (27). From Eq. (22) t can be observed that voltage securty margn should be greater than the specfed value [22]. For ths purpose, there should be enough dstance between the current operatng pont and the voltage collapse pont. In the steady state voltage stablty studes, the PV curve, as shown n Fg. 5, has been generally used and ts nose pont consdered as the system voltage collapse pont. However, n the lterature t has been shown that n the systems wth nconstantpower loads, the real voltage collapse pont s the SNB of the bfurcaton curve (or pont B'' on PV curve n Fg. 5) nstead of the nose pont (NP) of PV curve (pont B') [23]. Nevertheless, when all the loads are constantpower type, nose pont ust concdes wth the saddle pont node [24]. It should be mentoned that n ths wor the loads are assumed to be constantpower type. Referrng to Fg. 5 as a typcal PV curve of a power system, the Voltage Stablty Margn (VSM) value s the horzontal dstance between the current operatng pont (B) and the voltage collapse pont (B'). The VSM n the load doman (λ) ndcates the power system maxmum loadablty n terms of voltage stablty. In other words, the constrant of the voltage stablty restrcts the ncrement of loadng level of the power system and the VSM demonstrates ts related upper lmt n the load doman [25]. Accordngly, the VSM ndex whch s used n ths wor wll be as the followng equaton: MVA MVA VSM = N MVA L N MVA( B ) MVA = MVA ( B) ( B) (28) Rabee et al.: A New Framewor for Reactve Power Maret Consderng Power System Securty 199

5 Downloaded from eee.ust.ac.r at 2:26 IRDT on Sunday August 19th 2018 Fg. 5. Bfurcaton and PV curves of an nconstantpower load. In Eq. (21), VSM spec ndcates specfed value of the VSM. Consderng a broader vewpont, n Fg. 6 both voltage securty margn and VSM are shown. The securty loadng pont refers to the maxmum allowable load ncrement at whch overload and voltage drop constrants, ndcated n Eq. (26) and Eq. (27), are satsfed. The voltage securty margn s the dstance between the current operatng pont and securty loadng pont (Fg. 6). The conventonal voltage stablty ndces, le Eq. (28), ndcate the stablty border at whch the power system has stable soluton wthout consderng the qualty of the operatng pont. Besdes, the operator usually determnes a proper voltage range, as shown n Fg. 6, n order to eep hgh qualty voltages and to prevent the electrc power devces from damages n addton to actve power losses reducton [26]. In other words, the securty constrant should be satsfed not only at the current operatng pont but also at the system securty loadng pont (Fg. 6). The nequalty constrants Eqs. (21) and (22) show the VSM constrant and voltage securty constrant, respectvely. Both VSM and λ have been mplemented by usng the contnuaton curve. The contnuaton curve n ths paper s obtaned by the wellnown predctor/corrector mechansm. Detals of ths mechansm can be found n [27]. Accordng to Fg. 6 of the paper, securty loadng pont (λ) s the ntersecton of horzontal lne V mn wth the contnuaton curve. It s noted that the load ncrease scenaro of loads and generaton ncrease scenaro of the generatng unts n contnuaton curve, s based on the equatons Eq. (23) to Eq. (25) of the paper. The above formulaton from Eq. (5) up to Eq. (27) shows a mxed nteger nonlnear programmng (MINLP) optmzaton problem. It should be noted that n ths wor, the varaton of actve power losses of transmsson lnes due to the reactve power adustments s gnored and so the outputs of the actve power dspatch (obtaned from the energy maret) can be assumed constant durng the clearng of reactve power maret. Fg. 6. Representaton of current and securty loadng ponts 4 Results The proposed reactve power maret framewor s examned on the wellnown CIGRÉ32 bus test system [28], shown n Fg. 7, and compared wth the framewor presented n [16]. The test system s separated to three voltagecontrol areas usng the concept of electrcal dstance [17], resultng n the localzed reactve power maret. In the prevous method, the partcpants of reactve power maret are supposed to submt ther four components of offer prces (a 0, m 1, m 2, m 3 ). Fg. 7. CIGRÉ32 bus test system networ confguraton. Synchronous condensers are partcpated n the reactve power maret wth ther opportunty cost (m 3 ) equal to zero as well. In the new framewor however, the partcpants should submt (a 0, m 1, m 2 ) and the 200 Iranan Journal of Electrcal & Electronc Engneerng, Vol. 5, No. 3, Sep. 2009

6 Downloaded from eee.ust.ac.r at 2:26 IRDT on Sunday August 19th 2018 component of LOC offer prce,.e. m 3 s not needed. In ths examnaton, a unform random number generator s used to smulate the offer prces of generators shown n Table 1 [16]. It should be noted that the prce components for the cost of losses (m 1, m 2 ) are assumed to be equal (m 1 = m 2 ). Accordng to the pervous method, the partcpants are also requred to send ther Q base, Q A and Q B (Fg. 1). Le [16], t s assumed that Q B = Q max, Q base = 0.10*Q max and Q B =1.5*Q g0 (Q B =1.5*Q A ). The lower and upper bounds of voltage are taen 0.95 pu and 1.05 pu, respectvely. The power flow lmts of all transmsson lnes are smply based on ther voltage ratng (2000 MVA for 400 V lnes, 350 MVA for 220 V, and 250 MVA for 130 V [21]). Table 1. Reactve power offer Prces of partcpants and MCPs for the 3 rd case of the new framewor Zone a b c Bus No Unt No a 0 m 1, m 2 m 1 =m 2 m MCPs of the 3 rd Case ρ 0 = 0.96 ρ 1 = 0.59 ρ 2 = 0.86 ρ0 = 0.92 ρ1 = 0.00 ρ2 = 0.99 ρ0 = 0.92 ρ1 = 0.00 ρ2 = Clearng of the Prevous Method and the Proposed Method The clearng of the proposed reactve power maret framewor s a MINLP problem. The model s solved n generalzed algebrac modelng systems (GAMS), whch s a hgh level programmng platform, usng the DIscrete COntnous OPTmzaton (DICOPT) solver on a Pentum IV, 512 MB RAM computer. The obtaned results of the framewor of [16] are shown n Table 2. The generator of bus 4021 n zone (b) enters to regon III and s pad ($) for LOC whch s equal to 19.68% of TPF. In addton to the LOC payment, a redspatch of energy maret s also needed to compensate the decrease n the output of unt 4021 and balance the load of the system, whch n turn mposes an addtonal payment to the system operator. In the proposed framewor, both the voltage securty margn and VSM (Fg. 6) are consdered n the reactve power maret. The lower lmt of VSM (VSM spec ) s consdered 10%. To represent the effect of VSM and voltage securty margn on the TPF of reactve power maret, three cases are consdered. In the frst case, the securty constrants are exclusvely consdered at the current operatng pont. Nether voltage securty margn nor VSM constrants are ncluded n ths case. In other words, only (19) and (20) from the securty constrants are ncluded n ths case. In the second case, only the VSM constrant,.e. (21), s added to the constrants of the frst case. Fnally, n the thrd case the securty constrants at securty loadng pont,.e. (25) and (26) are also taen nto account. The results of the three cases are shown n Table 3 and compared wth the results of the framewor gven n [16]. Table 2. Results of the framewor n [16] Zone ρ 0 ρ 1 ρ 2 ρ 3 LOC Payment TPF (a) (b) ($) (c) Total payment ($) Table 3. Results of the proposed framewor n three cases and framewor of [16] Prevous Method [16] Proposed Method 1 st Case 2 nd VSM s pec Case 10% 3 rd Case 10% Securty Loadng Pont 6% Total Payment VSM (%) Executon Tme (Sec) Rabee et al.: A New Framewor for Reactve Power Maret Consderng Power System Securty 201

7 Downloaded from eee.ust.ac.r at 2:26 IRDT on Sunday August 19th 2018 Accordng to ths Table, the second case has more cost than the frst one snce n the second one, the VSM constrant should be also satsfed. The thrd case has more cost than the two prevous cases due to addtonally satsfyng the constrants of the securty loadng pont,.e. the securty margn constrant (Fg. 6). Therefore, t s concluded that, the ISO should charge more n the reactve power maret for the purpose of havng enough reactve support n the system and correspondngly mantanng the system securty constrants at the specfed levels. Table 4 shows the optmal soluton of the new framewor for the 3 rd case, ndcatng status of each unt n the reactve power maret, the amount of the reactve power output of each unt and also the payment of each unt. Table 4. Optmal soluton of the new framewor for the 3 rd Case Zone a b c Bus No Unt No W 0 Qg (MVAr) Payment ($) Total From ths Table t can be observed that some unts (unt#1 of bus#1012 for example) are partcpated by the ISO n the reactve power maret to have enough reactve reserve. These unts are ust pad for the avalablty payment and ther reactve power output wll be ultmately up to ther Q base. Also n the last column of Table 1, MCP of each component of the bd (ρ 0, ρ 1, ρ 2 ) for each zone of the networ s taen Comparson of the Prevous Method wth the Proposed Method In the proposed method, n addton to smply clearng of the reactve power maret wthout any LOC payment, the ISO can clear the reactve power maret based on the desred voltage stablty and securty margns by the proposed method. Comparng the results of the prevous method wth the proposed one, even n the case three, the ISO payment to the partcpants of the reactve power maret s lower than the pervous method (as shown n Table 3). Accordng to Table 3, the value of the TPF n the 3 rd case of the proposed method s dollars whch s $ lower than the TPF of prevous method ($3534.7). Ths s due to the fact that, the LOC payment, whch s a quadratc functon of Q and thereby ncludes hgh cost, s omtted from the TPF; leadng to the lower payments n the reactve power maret. These are the man advantages of the proposed method that can clear the reactve power maret n a smpler and more transparent manner wth lower total payment whle consderng the securty of the power system. The LOC elmnaton from TPF maes the TPF to a smple lnear obectve functon whch totally could decrease the nonlnearty of the OPF problem (maret clearng procedure). Besdes that, the actve power dspatches of generatng unts are not changed durng the settlement of the reactve power maret, whch s another advantage of the proposed framewor. It s observed that the voltages of all buses n both current and securty loadng ponts are n the gven boundares and the voltage drop and overvoltage concerns are releved. Moreover, the lnes flows of the networ are less than ther contnuous MVA ratng n the current and securty loadng ponts. 5 Conclusons Ths paper proposes a new framewor for the reactve power maret. The TPF presented earler n the lterature are modfed n such a way that t no longer ncludes the quadratc term related to the LOC payment, resultng n a lnear obectve functon whch s easer to optmze n comparson wth the prevous framewor. Besdes, the proposed method ncludes both voltage stablty and securty concerns of the power system. In other words, n the new framewor, the ISO can clear the reactve power maret at the specfed levels of the VSM and voltage securty margn. The other mportant 202 Iranan Journal of Electrcal & Electronc Engneerng, Vol. 5, No. 3, Sep. 2009

8 Downloaded from eee.ust.ac.r at 2:26 IRDT on Sunday August 19th 2018 advantages of the proposed method are the lower payment of the ISO to the partcpants of the reactve power maret, and clearng the reactve power maret wthout changng the actve power output of the generatng unts determned n the energy maret. Instead of seasonal procurement model, n ths paper a dayahead reactve power maret model s proposed. The longterms (seasonal) contracts for reactve power procurement would lely reduce the possblty of exercsng maret power by generators, and could mtgate the problem of prce volatlty, whch may arse when reactve power servces are prced on a realtme (dayahead) bass. On the other hand, n the longterm procurement of reactve power, the optmal set of generators should deally be determned based on the reactve power demand forecast and system condtons expected over the season that encounter some serous problems mentoned n secton I (ntroducton) of the paper. Consderng the problems of seasonal procurement model for the reactve power, n a trade off between seasonal and dayahead model, n ths paper a dayahead reactve power maret model s proposed. The proposed reactve power maret framewor deserves to more explanaton n cases that system strongly requres to the reactve power of a specal unt for any reason but t cannot be produced by that unt due to the capablty curve lmt. In ths case, the remnder of the requred reactve power should be produced by the other partcpants of the reactve power maret not reachng to ther capablty curve lmts. If no local partcpant can be found n ths case, the requred reactve power should be produced by remote unts, whch n heavy load condtons mght lead to ncrease the losses of the system and overload lnes. Nevertheless, ths dsadvantage can be allevated by extendng the partcpants of the reactve power maret to the other sources of reactve power le FACTS devces and fast swtchng capactor bans. Ths remedy wll be assessed n the future wor. 6 References [1] Baldc R., Reactve ssues reactve power n restructured marets, IEEE P & E Mag. Vol. 2, No. 6, pp. 1417, [2] Wang J., Wen R.G. and Yang R.S., On the procurement and prcng of reactve power servce n the electrcty maret envronment, IEEE PES General Meetng, Vol. 1, pp , [3] Zhong J. and Bhattacharya K., Reactve power management n deregulated power systemsa Revew, n Proc. IEEE PES Wnter Meetng, Vol. 2, pp , [4] Baughman M. L., Sddq S. N., Real tme prcng of reactve power: theory and study results, IEEE Trans. Power Syst., Vol. 6, No. 1, pp. 2329, [5] ElKeb A. A., Ma X., Calculatng shortrun margnal costs of actve and reactve power producton, IEEE Trans. Power Syst., Vol. 12, No. 2, pp , [6] Cho J. Y., Rm S. H., Par J. K., Optmal real tme prcng of real and reactve powers, IEEE Trans. Power Syst., Vol. 13, No. 4, pp , [7] Gl J. B., Román T. G. S., Rĺo J. J. A. and Martĺn P. S., Reactve power prcng: A conceptual framewor for remuneraton and chargng procedures, IEEE Trans. Power Syst., Vol. 15, No. 2, pp , [8] Ahmed S., Strbac G., A method for smulaton and analyss of reactve power maret, IEEE Trans. Power Syst., Vol. 15, No. 3, pp , [9] Ln X. J., Yu C. W., Chung C. Y., Prcng of reactve support ancllary servces, IEE Proc. Gener. Transm. Dstrb., Vol. 152, No. 5, pp , [10] Hao S., Papalexopoulos A., Reactve power prcng and management, IEEE Trans. Power Syst., Vol. 12, No. 1, pp , [11] Krschen D., Strbac G., Tracng actve and reactve power between generators and loads usng real and magnary current, IEEE Trans. Power Syst,. Vol. 14, pp , [12] Lo K. L., Altur Y. A., Toward reactve power marets. Part 1: reactve power allocaton, IEE Proc. Gener. Transm. Dstrb., Vol. 153, No. 1, pp. 5970, [13] Xu W., Zhang Y., da Slva L., Kundur P. and Warrac A., Valuaton of dynamc reactve power support servces for transmsson access, IEEE Trans. Power Syst., Vol. 16, pp , [14] Wang Y., Xu W., An nvestgaton on the reactve power support servce need of power producers, IEEE Trans. Power Syst., Vol. 19, No. 1, pp , [15] Bhattacharya K., Zhong J., Reactve power as an ancllary servce, IEEE Trans. Power Syst., Vol. 16, No. 2, pp , [16] Bhattacharya K., Zhong J., Toward a compettve maret for reactve power, IEEE Trans. Power Syst., Vol. 17, No. 4, pp , [17] Zhong J., Noble E., Bose A., Bhattacharya K., Localzed reactve power marets usng the concept of voltage control areas, IEEE Trans. Power Syst., Vol. 19, No. 3, pp , Rabee et al.: A New Framewor for Reactve Power Maret Consderng Power System Securty 203

9 Downloaded from eee.ust.ac.r at 2:26 IRDT on Sunday August 19th 2018 [18] Zhong J., Prcng mechansm for networ reactve power devces n compettve maret, IEEE Power Inda con. pp. 1012, [19] Chung C. Y., Chung T. S., Yu C. W., Ln X. J., Costbased reactve power prcng wth voltage securty consderaton n restructured power systems, Electr. Power Syst. Res., Vol 70, No. 2, pp. 8591, [20] ElSamahy I., Bhattacharya K., Cañzares C. A., Anos M. F., Pan J., A procurement maret model for reactve power servces consderng system securty, IEEE Trans. Power Syst., Vol. 23, No. 1, pp , [21] ElSamahy I., Canzares C. A., Bhattacharya K., Pan J., An optmal reactve power dspatch Model for deregulated electrcty marets, IEEE PES General Meetng, pp. 17, [22] Coneo A. J.,Mlano F.,Bertrand R. G., Congeston management ensurng voltage stablty, IEEE Trans. Power Syst, Vol. 21, No. 1, pp , [23] Overbye T. J., Effects of load modelng on power system voltage stablty, Electr. Power & Ener. Syst., Vol. 16, No. 5, pp , [24] Honge J., Xaodan Y., Yxn Y., An mproved voltage stablty ndex and ts applcaton, Electr. Power & Ener. Syst., Vol. 27, No. 8, pp , [25] Amady N., Esmal M., Voltage securty assessment and vulnerable bus ranng of power systems, Electr. Power Syst. Res., Vol. 64, pp , [26] Kataoa Y., Watanabe M., Iwamoto S., A new voltage stablty ndex consderng voltage lmts, IEEE PSCE, pp , [27] Kundur P. Power system stablty and control, New Yor: McGrawHll, [28] Walve K., Nordc 32A CIGRÉ test system for smulaton of transent stablty and long term dynamcs, Svensa Kraftnat, Sweden, Abdorreza Rabee receved hs B. Sc. and M. Sc. degrees n Electrcal Engneerng n 2002 and 2004 from Shahd Chamran Unversty of Ahwaz and Iran Unversty of Scence and Technology (IUST), respectvely. Currently he s pursung hs PhD degree at IUST n electrcal engneerng. Hs research nterests nclude dstrbuton systems, power system economcs and optmzaton. Hedar Al Shayanfar receved hs B.S. and M.S.E. degrees n Electrcal Engneerng n 1973 and 1979 and the PhD degree n Electrcal Engneerng from Mchgan State Unversty, U.S.A., n Currently, He s a Full Professor n Electrcal Engneerng Department of IUST, Tehran, Iran. Hs research nterests are n the applcaton of Artfcal Intellgence to power system control desgn, dynamc load modelng, power system observablty studes and voltage collapse. He s a member of Iranan Assocaton of Electrcal and Electronc Engneers (IAEEE) and IEEE. Nma Amady (M 97) was born n Tehran, Iran, on February 24, He receved the B.Sc., M.Sc., and Ph.D. degrees n electrcal engneerng from Sharf Unversty of Technology, Tehran, n 1992, 1994, and 1997, respectvely. At present, he s a Professor wth the Electrcal Engneerng Department, Semnan Unversty, Semnan, Iran. He s also a Consultant wth the Natonal Dspatchng Department of Iran. Hs research nterests nclude securty assessment of power systems, relablty of power networs, load forecastng, and artfcal ntellgence and ts applcatons to the problems of power systems. 204 Iranan Journal of Electrcal & Electronc Engneerng, Vol. 5, No. 3, Sep. 2009