Power Flow Control Analysis of Transmission Line Using Static VAr Compensator (SVC)

Transcription

1 Amercan Journal of Engneerng Research (AJER) 015 Amercan Journal of Engneerng Research (AJER) e-ssn: p-ssn : olume-4, ssue-10, pp Research Paper Open Access Power Flow ontrol Analyss of Transmsson ne Usng Statc Ar ompensator () J. U. Agber 1,. O. Onah 1,. G. Onate 1 Department of Electrcal and Electroncs Engneerng, Unversty of Agrculture, Maurd, Ngera. Wors Department,Kog State Unversty,Anygba, Ngera. Abstract:ontrol of reactve power and voltage consttute part of the major challenge n the power system ndustry. Adequate absorpton or njecton of reactve power nto electrc power transmsson systems solves power qualty problems le voltage profle mantenance at all power transmsson levels, transmsson effcency and system stablty. Globally, there s ncreasng demand for electrcty to feed the technology-drven economy, whle the commensurate expanson of power generaton and transmsson to meet up wth such demand has been severely lmted due to nadequate resources and envronmental factors. Flexble A Transmsson System (FATS) controllers, such as the Statc Ar ompensator (), employ latest technology n the desgn of power electronc swtchng devces for electrc power transmsson systems to control voltage and power flow, and mprove voltage regulaton wthout the need to expand the power generaton and transmsson facltes. n ths wor, the capablty of n stablzng power system s voltage through reactve power compensaton was nvestgated. Power flow equatons nvolvng voltage drop wth/wthout were developed. Modelng equatons for were also developed and used to determne ts parameters. The Ngera 330 networ, 8-bus power system used for the study was modeled usng MATAB/SMUNK software. From the smulatons, the compensated and uncompensated voltages at each of the 8 buses were evaluated. t was observed from the analyss that some buses n the networ had very wea voltage profle consequent to ether excessve generaton or absorpton of the reactve power at such buses. t s therefore pertnent to note that not all the buses wthn the networ need voltage compensaton and as such, only buses wth very wea voltage profle requre the ncorporaton of. Hence t can be concluded that n order to enhance the transmsson system performance of the Ngeran 330 power system, the control of the voltages at certan buses through the applcaton of s requred. Keywords: Facts, Svc, Transmsson ne Analyss, Reactve Power ontrol, 8-bus. ntroducton Globally, there s ncreasng demand for electrcty to feed the technology-drven economy, whle the commensurate expanson of power generaton facltes and transmsson lnes to meet up wth such demand has been severely lmted due to nadequate resources and envronmental factors. n power system networ voltage control, reactve power s both the challenge and the soluton. t s, therefore, mportant that a balance of reactve power be obtaned n the operaton of electrc power transmsson systems because the control of voltage can be lost f ths s not acheved. Adequate reactve power regulaton of electrc transmsson networs can solve power qualty problems by mprovng the power system voltage profle, transent stablty mprovement, ncrease n power transfer capacty and mnmzaton of transmsson lne loss. FATS controllers, such as the Statc Ar ompensator (), employ latest technology n the desgn of power electronc swtchng devces. These devces are used to control the voltage and power flow n a transmsson system to mprove voltage regulaton wthout the need to expand the power generaton and transmsson facltes. By dynamcally provdng reactve power, can be used for voltage regulaton and compensaton, transent stablty mprovement, power system oscllaton dampng mprovement, ncrease n power transfer capacty and mnmzaton of transmsson lne loss. w w w. a j e r. o r g Page 1

2 Amercan Journal of Engneerng Research (AJER) 015. Bacground To The Study The ablty to control power flow n an electrc power transmsson system wthout generaton reschedulng or topology changes can mprove the power system performance. Usng controllable components, the lne flows can be changed n such a way that thermal lmts are not exceeded, stablty margn ncreased, n addton to ncrease n power transfer capacty and mnmzaton of transmsson lne loss wthout volatng the economc generaton dspatch. FATS technology s the ultmate tool for gettng the most out of exstng power system nfrastructures through rapd regulaton of the system s reactve power. Al [1] nvestgated the performance of Statc Synchronous ompensators (STATOM) and on voltage stablty n power system. n the study, MATAB/SMUNK software smulatons showed that STATOM s more effectve n mdpont voltage regulaton on transmsson lne. omparson between STATOM and under fault condton was also smulated and the result showed that STATOM has the capacty to provde more reactve power for the perod of a fault than. The response tme of STATOM was faster than that of. n the wor by Mural [], smulaton and comparson of varous FATS devces usng PSPE software have been done. How to mprove steady state stablty by placng at dfferent places has been dscussed n the study by Bhavn [3]. n the study by Ater [4], MATAB/SMUNK software smulaton was used to demonstrate the performance of the system for each of the FATS devces for example, Statc Ar compensator (), STATOM, Thyrstor controlled seres capactor (TS), Statc synchronous seres compensator (SSS) and Unfed power flow controller (UPF) n mprovng the power profle and thereby voltage stablty of same. Usng MATAB/SMUNK software, performance of Fxed capactor, shunt Thyrstor ontrolled Reactor (F-TR) and STATOM has been dscussed n the wor by Das [5]. Modelng and Smulaton of varous FATS devces (F-TR, STATOM, TS and UPF) have been done usng MATAB/SMUNK software n the wor by Dpt [6]. The research by Pardeep [7], dscussed how has successfully been appled to control the dynamc performance of transmsson system and regulate the system voltage effectvely.. Methodology applcaton studes requre approprate power system models and study methods coverng the partcular problem to be solved by the applcaton. The followng studes are normally requred for an applcaton from the early plannng stage tll operaton [8]. oad flow studes. Small and large dsturbance studes. Harmonc studes. Electromagnetc transent studes and Fault studes. 3.1 Modelng of Statc Ar ompensator for Power System Studes The functonal dagram of the n fg.1 shows that one branch of the s purely nductve whle the other branch s purely capactve. Therefore, the consumes no actve power. t ether njects (capactve) reactve power to ncrease the system s voltage or consumes (nductve) reactve power to reduce the system s voltage. Snce the reactor consumes reactve power, the (nductve) reactor current s postve whle the capactor whch njects reactve power nto the system, has negatve current. Fgure1: Functonal dagram of a TR-TS From crcut theory, t s shown that: 0 (1) Therefore the current at maxmum Ar absorpton, could be expressed as follows: oong at pont A and usng Krchoff current law (K), we have: w w w. a j e r. o r g Page

3 Amercan Journal of Engneerng Research (AJER) 015 (3) and (4) where nductve reactance of the apactve reactance of the apactance of the fxed capactor nductance of the nductor Magntude of the bus voltage On the assumpton that no real power s consumed by the (.e. P 0 ) then: (5) omparng equatons (1) and (5): (6) ombnng equatons (), (3) and (6), yeld equatons (7) to (9): 1 1 (7) (8) (9) controllers are desgned n such a way that the TR s swtched on when the bus voltage becomes hgher than the reference voltage and vce-versa. As a result, when the Ar absorpton s at maxmum, the TR become operatonal and. Hence: When the Ar absorpton s at mnmum, 0. Hence: max 1 mn 1 c 0 (11) Thus, the bus voltage would be regulated at or near the base voltage. 3. Equatons for the Bus oltage and oltage Drop onsder an electrc power transmsson lne connectng two buses and n any gven power system networ as represented n Fg.. () (10) Fgure : Transmsson lne model of a power system networ w w w. a j e r. o r g Page 3

4 Amercan Journal of Engneerng Research (AJER) 015 Defnton of the symbols used n the confguraton of the transmsson lne model n fg. are as follows: R omplex voltage at bus complex voltage at bus omplex current flow from bus to The transmsson lne resstance between buses and The transmsson lne mpedance between buses and The transmsson lne reactance between buses and From Fg., the voltage drop between buses and can be expressed as: d d (1) By applyng Ohm s law, the complex current flowng from bus to s expressed as: (13) where R Equaton (13) s expressed n the admttance form as: Y (14) where 1 Y and s defned as the admttance of the transmsson lne. The complex power S flowng from bus to s gven by: S (15) Expressng the complex power of equaton (15) n real power (P) and reactve () power form yelds; S P (16) Tang the conjugate of the equaton (16) yelds: P (17) hence P (18) omparson of equatons (1), (13) and (18) gves equaton (19) as: P dy onsequently: d = P - Y Analyss of equaton (0) shows that by adjustng the system s reactve power at bus whle eepng the voltage at bus constant, the voltage between buses and can be controlled and the system s total voltage drop mnmzed. Assumng that the s nstalled at bus, then equaton (1) becomes: (1) d omparng equatons (9) and (1) yelds: d () From equaton (1), t can be seen that f the voltage at bus s ept constant, then by regulatng the voltage at bus at or near the base voltage, the power system s voltage s stablzed and the voltage drop mnmzed. (19) (0) w w w. a j e r. o r g Page 4

5 Amercan Journal of Engneerng Research (AJER) 015. Results And Dscusson The test system confguraton s based on the Ngeran 330, 8-bus power system. The Ngeran Electrcty Networ comprses 11,000 m transmsson lnes (330 and 13 ), 4000 m of sub-transmsson lne (33 ), 19,000 m of dstrbuton lne (11 ) and,500 substatons (Natonal ontrol entre, Power Holdng ompany of Ngera, 01). t has only one major loop system nvolvng Benn-eja West-Ayede- Oshogbo and Benn. The absence of loops accounts manly for the wea and unrelable power system n the country. The sngle lne dagram of the exstng 8-bus 330 Ngeran transmsson networ used as the test system s shown n fgure 3. t comprses 9 generatng statons, 8 buses and 5 transmsson lnes. Based on the MATAB/SMUNK confguraton for ths wor, smulatons were carred out at all the load buses wthn the 330, 8-bus Ngera power system. Smulatons of each load bus n the system wthout the were done and the system voltage magntude at each of the load bus were obtaned. onversely, smulatons of each load bus n the system wth the ncorporaton of were carred out and the system voltage magntude at each of the load bus were also obtaned. To show the performance of the, the system voltage dfferental at each of the load bus wth/wthout, were computed. Fgure 3:The 330, 8-bus Ngeran power system (Natonal ontrol entre, Power Holdng ompany of Ngera, 01) Table 1: The th and th bus voltages of the Ngeran 8-bus power system wth/wthout. Bus No connected connected Performance of pu pu pu pu w w w. a j e r. o r g Page 5

6 + - v Amercan Journal of Engneerng Research (AJER) Table : dentfed wea buses wthn the networ and ther compensated voltage values. Bus dentfcaton Name No Bus voltage wthout nstalled (pu) Bus voltage wth nstalled (pu) Jos Gombe Kano Ajaouta N-Haven B-Kebb Bus voltage compensaton (pu) ontnuous Per unt converter powergu rms sgnal oltmeter oltage dsplay 330 e3 RMS Normnal voltage oltage waveform S S4 T47 T T v - oltmeter 1 Scope 1 T45 Scope 4 S1 T4 T T38 T44 T5 7 T48 T15 T17 16 T0 8 power to load scope port T T 1 T39 T measurement pont power n 1 4 T 8 T10 4 T6 T3 T36 s8 R8 T 9 T T T7 11 T11 T34 8 T1 T33 T35 T 9 vs7 33 T 31 T3 T S3 T 13 T7 S 0 T s T s6 4 T41 T 8 31 Fgure 4: SMUNK model of the Ngera 330, 8-bus power system Table 1 s a detaled analyss of the voltages at each of the load bus wthn the networ wth/wthout compensaton. t has been observed from ths analyss that some buses n the networ have very wea voltage profle consequent to ether excessve generaton or absorpton of the reactve power. t s pertnent to note that not all the buses wthn the networ need compensaton and as such, only buses wth very wea voltage profle requre the ncorporaton of. Ths nformaton could be very valuable to the power engneers n the nstallaton of n the networ. The buses, where compensaton wth s needed, were dentfed and depcted n table. From the analyss, the overall system voltage compensaton wth was 10.18%. w w w. a j e r. o r g Page 6

7 Bus voltage (pu) Amercan Journal of Engneerng Research (AJER) Wthout Wth Bus code Fgure 4: Wea bus voltage compensaton representaton. oncluson n ths research wor, based on the and the power system parameters, SMUNK blocs have been used to mplement the Ngeran 330 power system networ, whch comprses 9 generaton statons, 8- buses and 5 transmsson lnes. The smulatons were carred out n the MATAB/ SMUNK envronment. From the smulatons, the compensated and uncompensated voltages at each of the 8 buses were evaluated. t was observed from the analyss that some crcuts (buses) n the networ have very wea voltage profle consequent to ether excessve generaton or absorpton of the reactve power flow at such buses. t s, therefore, pertnent to note that not all the buses wthn the networ need voltage compensaton and as such, only buses wth very wea voltage profle requre the ncorporaton of. Hence, t can be concluded that n order to enhance the transmsson system performance of the Ngeran 330 power system, the control of the voltages at certan buses through the applcaton of s requred. Ths could be practcally mplemented on the Ngeran power system networ to mprove the huge demand for power n the country, because at the moment, only synchronous reactors, whch are not as effectve as, are beng used to control the flow of reactve power n the networ. REFERENES [1]..W.Al and A.U. Asar, Smart power transmsson system usng FATS devce, nternatonal Journal of Appled Power Engneerng (JAPE) ol., No., August 013, pp. 61~70 SSN: 5-879, []. D. Mural, M. Rajaram, and N. Rea, omparson of FATS devces for power system stablty enhancement. nternatonal Journal of omputer Applcatons, volume 8-No4, 010. [3]. M.P. Bhavn, Enhancement of steady state voltage stablty usng and TS. Natonal onference on Recent Trends n Engneerng and Technology. pp 13-14, 011. [4]. S. Ater, A. Saha and P. Das, Modellng, smulaton and comparson of varous FATS devces n power system. nternatonal journal of Engneerng Research and Technology, 1(8), 01. [5]. A.P. Das and A.K. haraborty, Performance analyss and comparson of varous FATS devces n power system. nternatonal Journal of omputer Applcatons, 46(15), 01 [6]. M. Dpt, A. Azz and M.A. heen, Modelng, smulaton and performance analyss of FATS controller n transmsson ne. nternatonal Journal of Emergng Technology and Advanced Engneerng, 3(5). Pp , 013. [7]. S.. Pardeep and K.G. jay, Power system stablty mprovement of long transmsson lne system by usng statc Ar compensator (). nt. Journal of Engneerng Research and Applcatons. 3(5). pp , 013. [8]. E. Acha,.R.F. Esquvel, H.A. Perez and.a. amacho, FATS modellng and smulaton n power system networs. 41pp. hap. John Wley & Sons td, Brtsh brary, 004. [9]. Natonal ontrol entre, Power Holdng ompany of Ngeran, 01 w w w. a j e r. o r g Page 7