A SIMPLE CONTROL TECHNIQUE FOR UNIFIED POWER FLOW CONTROLLER (UPFC)

Transcription

1 Volume 116 No , ISSN: (printed version); ISSN: (on-line version) url: ijpam.eu A SIMPLE CONTROL TECHNIQUE FOR UNIFIED POWER FLOW CONTROLLER (UPFC) MR.S.NATARAJAN Reasearch Scholar, Department of EEE Vel TechDr.RR&Dr.SR University, Avadi, Chennai, Tamil Nadu, India. DR.S.BASKAR Professor, Department of Electical and Electronics Engineering, Vel Tech Dr.RR&Dr.SR University, Avadi, Chennai, Tamil Nadu, India. The paper suggested the better application of UPFC over STATCOM and SSSC in terms of reactive power compensation, voltage stability and control in a power system. The main advantage of the UPFC in three phase line compensation is integrated in to a Unified or Generalised power flow controller. This paper describes the simple technique of controlling real and reactive power flow & a comparative study between the conventional power flow controllers like STATCOM & SSSC with UPFC. This paper suggests a simulation study of all the controllers individually through MATLAB simulation tool. 1. Introduction Now-a-days, different power electronics based technologies are used to facilitate the flow of large amount of power. These electronic devices are called Flexible AC Transmission [FACT] devices. These devices generally based on power electronics converters & they will provide the facility of quick and flexible control of power flow in power system.many devices are there to contribute reactive power compensation and in maintaining voltage profile. Under light load condition, the transmission line delivers reactive power where as the transmission line absorbs or consumes the reactive power under heavy load condition. Therefore, the power flow can be controlled by controlling the reactive power flow in the transmission line of power system. So a decrease of reactive power margin may cause voltage fall where as an increase of reactive power margin causes a rise of system voltage.[1]- [2].Generally, voltage stability problem occurs due to change of reactive power availability in the power system. Therefore, FACT devices are used to maintain the voltage profile and control the availability of reactive power in a power system.the Unified power flow controller (UPFC) is used for dynamic control & compensation of power flow in ac transmission system. It consists of two different switching converters basically voltage source inverters regulated with GTO valves as illustrated in figure-1 given below. 469

2 The inverters named as Inverter-1 and Inverter-2 in above figure is linked with each other by a dc link with respect through dc capacitor. This type of network works as a power converter to covert ac to ac and real power can flow in both direction, where both inverter can independently produce or receive reactive power across its terminal.the Inverter-2 supplies an ac voltage Vpq such that 0<Vpq<Vpqmax and conduction angle δ such that 0< δ <3600 at the considered power frequency. the line current starts flowing through the voltage source by creating control of real and reactive power in power system.[1]the principle objective to use Inverter-1 is to govern the real power demanded by means of Inverter-2 at the not common dc link. This power at DC link is then converted to AC again after which fed to the system through shunt linked transformer. The Inverter-1 gives shunt repayment of reactive power for the transmission line. This set up may not guide the continuous flow of reactive power through UPFC.[3].The UPFC facilitates in series and shunt compensation along side phase shifting during power transmission by including or injecting voltage Vpq with terminal voltage Vo. The phasor representation of basic UPFC function may be illustrated as follows. Figure-2- Basic UPFC control functions: (a) voltage regulation (b) series compensation (c) angle regulation (d) multi-function power flow control (e) block diagram of UPFC Series capacitive compensation as shown in above figure-2(b) where V pq =V c is injected in quadraturewith line current I. In figure-2(c), where V pq =V δ is injected with an angle δ as phase shift with respect to V δ. Figure-2(d) represents multi-function power flow control, which is executed by simultaneous terminal voltage regulation along with series capacitive line compensation and phase shifting.[1] V pq = V c +V δ +ΔV 470

3 Overall, we can assume that the UPFC has a greater control over the angular position and magnitude of voltage injected in real time so as to control the real and reactive power flow as demanded by the load in power system. In the following section, this paper illustrates a comparative study of real and reactive power flow through UPFC, SSSC and STATCOM through MATLab simulation on a 500KV, MVA system operated with a frequency of 60Hz system.the proposed model is a 48-Pulse GTO based UPFC (500KV, 100MVA). The UPFC is used between two Buses B 1 and B 2 which control the power flow through Bus B 2 by controlling the voltage of Bus B 1. The converter pair operates in different modes. The shunt converter works as a STATCOM by controlling voltage and VAR compensation. Whereas the series converter operates as SSSC by controlling the voltage injected in quadrature with current.[1] II. UPFC CONTROL When two converters are used in UPFC mode, the series converter operates as SSSC where as the shunt converter operates as STATCOM which controls the voltage at Bus B1 by controlling the reactive power by either generating or absorbing to it. It allows the active power to flow in series converter through DC bus. The overall control of reactive power is obtained by changing the DC bus voltage.at normal power flow, when UPFC is absent, then zero voltage is injected through bus B2 by the series converter, where as in the presence of UPFC, both magnitude & phase of the voltage injected in series can be varied as a result, the real and reactive power can be controlled. When the injected voltage attends its maximum value (0.1PU) and the phase angle is varied from

4 UPFC controllable region SSSC VOLTAGE INJECTION IV. SIMULATION FINDINGS STATCOM [VAR COMPENSATION] STATCOM [VOLTAGE CONTROL] + SSSC [VOLTAGE INJECTION] UPFC [POWER FLOW CONTROL] STATCOM [VOLTAGE CONTROL] 472

5 V.ANALYSIS The simulation results suggest the following outcomes. Initially, the real and reactive power reference values are P ref = +8.7PU/100MVA (+870MW) and Q ref = -0.6PU/100MVA (-60MVAR) respectively. But at time 0.25sec P ref value is changing to +10PU (+1000MW), which is suggesting the rise of real power flow during UPFC mode control system. Then after time 0.5sec, Q ref value is changing to +0.7PU (+70MVAR), which is suggesting the reactive power compensation during UPFC mode control system. During UPFC mode operation, the series injected voltage magnitude due to which the reactive power is compensating, can be controlled by varying the conduction angle. VI. CONCLUSION In comparisons with conventional FACT devices, UPFC provides dynamic control of line parameters, which results the smooth and effective control of power flow. The Unified Power Flow Controller may also be used primarily as generalised power flow controller which is capable of maintaining the required real and reactive power flow at the respective buses of ac line. A better flexibility in controlling ac power transmission of STATCOM and SSSC can be achieved through UPFC in a power system. VII. REFERENCES [1] Gyugyi L, Schauder CD, Torgerson SL, Edris A. The unified power flow controller: a new approach to power transmission control. IEEE Trans Power Delivery 1995;10(2): [2] Hingorani NG, Gyugyi L. Understanding FACTS concepts and technology of flexible AC transmission systems. IEEE Press; [3] RakhmadSyafutraLubis. "Digital simulationof the FACTS system with 60-pulse GTO based Voltage Source Converter", nd International Conference on Instrumentation Communications Information Technology and Biomedical Engineering, 11/

6 [4] Rajesh, M., and J. M. Gnanasekar. "Consistently neighbor detection for MANET." Communication and Electronics Systems (ICCES), International Conference on. IEEE, [5] Rajesh, M. "Object-Oriented Programming and Parallelism." [6] Rajesh, M., Protected Routing in Wireless Sensor Networks: A study on Aimed at Circulation Computer Engineering and Intelligent Systems, Vol.6, No.8, 2015 [7] Rajesh, M., A SYSTEMATIC REVIEW OF CLOUD SECURITY CHALLENGES IN HIGHER EDUCATION, The Online Journal of Distance Education and e-learning, Volume 5 Issue 4, 2017 [8] Rajesh, M., and J. M. Gnanasekar. "Congestion control in heterogeneous WANET using FRCC." Journal of Chemical and Pharmaceutical Sciences ISSN 974 (2015): [9] Rajesh, M., and J. M. Gnanasekar. "A systematic review of congestion control in ad hoc network." International Journal of Engineering Inventions 3.11 (2014): [10] Rajesh, M., and J. M. Gnanasekar. "Hop-by-hop Channel-Alert Routing to Congestion Control in Wireless Sensor Networks." Control Theory and Informatics 5.4 (2015):

7 UPFC", 2015 International Conference on Electrical and Information Technologies (ICEIT), [5] Edris, A. Mehraban, A.S., Rahman, M., Gyugyi, L.,Arabi, S., Rietman, T.,'Cotnrolling the Flow of Real and Reactive Power', IEEE Computer Application in Power, January 1998, p [6] C.Su and Z.Chen, Damping Inter-Area oscillations using static synchronous series compensator (SSSC), Universities Power Engineering Conference, [7] N.Mithulananthan, C.A.Canizares, J.Reeve and G.J.Rogers, Comparison of PSS, SVC and STATCOM Controllers for damping power system oscillation, IEEETrans., Vol.18, No.2, May Modelling & control design of unified power flow controller for various control strategies, International Journal of Engineering Science & Technology,Vol.2,No.11,pp ,2010. [8] Rajesh, M., and J. M. Gnanasekar. "Consistently neighbor detection for MANET." Communication and Electronics Systems (ICCES), International Conference on. IEEE, [9 Rajesh, M. "Object-Oriented Programming and Parallelism." [10] Rajesh, M., Protected Routing in Wireless Sensor Networks: A study on Aimed at Circulation Computer Engineering and Intelligent Systems, Vol.6, No.8, 2015 [11] Rajesh, M., A SYSTEMATIC REVIEW OF CLOUD SECURITY CHALLENGES IN HIGHER EDUCATION, The Online Journal of Distance Education and e-learning, Volume 5 Issue 4, 2017 [12] Rajesh, M., and J. M. Gnanasekar. "Congestion control in heterogeneous WANET using FRCC." Journal of Chemical and Pharmaceutical Sciences ISSN 974 (2015): [13] Rajesh, M., and J. M. Gnanasekar. "A systematic review of congestion control in ad hoc network." International Journal of Engineering Inventions 3.11 (2014): [14] Rajesh, M., and J. M. Gnanasekar. "Hop-by-hop Channel-Alert Routing to Congestion Control in Wireless Sensor Networks." Control Theory and Informatics 5.4 (2015):

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