strategy of location and control of facts devices

Strategy of Location and Control of FACTS Devices for Enhancing Power Quality Belkacem Mahdad 1 , Tarek Bouktir 2 , Kamel Srairi 1 1 Laboratory of Energy Systems Modeling (LESM), Department of Electrical Engineering University of Biskra, BP 145, Biskra 07000, Algeria. Phone/Fax: + 213 33 74 91 54, Email: electrobe [email protected], ksrairi@yahoo .fr 2 Department of Electrical Engineering, University of Oum El Bouaghi, 04000, Oum El Bouaghi, Algeria. Email: [email protected] Abstrac t —In pract ical installa tion of FACTS in the powe r system, there are three common requirements as follows: What Kinds of FACTS devices should be installed?. Where in the system should be placed?. How much capacity should it have?. This paper focus on the first two of these requirements. Choosing the type of FACTS devices and deciding the installation location and control of FACTS. We presented a simple algorithm based in heuristic and practical rules to seek the optimal location of two types of FACTS, shunt compensation ‘SVC’ and series compensation ‘TCSC’. The system loadability and loss minimization are applied as a measure of power system performance. Results show the impact of optimal operating points of FACTS (SVC and TCSC) devices under various conditions of power system. The proposed methodology to install and operates facts devices properly is verified on the 9-bus system where FACTS devices operated under normal and abnormal condition. Key word s —Power flow, Static Vo ltage Stability, FACTS, SVC, TCSC, Optimal Location, Power Quality , He uristic Methods. I. I NTRODUCTION The capacity of transmission lines is becoming the main bottleneck of electricity transmission in the deregulated power industry. The competition of electricity may aggravate loadability of some transmission lines. To meet the load demands in a power system and to satisfy the stability and reliability criteria, the existing transmission lines must be utilized more efficiently. The purpose of the transmission network is to pool power plants and load centers in order to supply the load at a required reliability and maximum efficiency at a lower cost. A technically attractive solution to above problems is to use some efficient controls with the help of FACTS (Flexible AC Transmission Systems) devices. The conception of FACTS as a total network control philoso phy was first introduc ed by N.G. Hingo rani [1] from the Electric power research institute (EPRI) in the USA in 1988, although the power electronic controlled devices had been used in the transmission network for many years before that. The application of FACTS in electric power System is intended for the Control of power flow, improvement of stability, voltage profile management, power factor correction, and loss minimisation. Thyristor Controlled Series Capacitors (TCSC) and Static Var Compensators (SVC) are the most popula r device s of the FACTS. The main func tionality of the SVC is to regulate the voltage at a chosen bus by controlling the reactive power injection at the location. Maintaining the rated voltage levels is important for proper operation and utilization of loads. Under voltage causes deregulation in the performance of loads such as induction motors, light bulbs, etc.., whereas over voltage causes magnetic saturation and resultant harmonic generation, as well as equipment failures due to insulation breakdown. These devices are characterised by rapid response, wide operational range and high reliability. Series capacitor compensation is another approach to improve stability limits and increase transfer capabilities. The transmitted powe r through a line is inverse ly proportion al to the transfer impedance. For example, considering other parameters consta nts, 50% series compe nsation approximately doubles the steady-state transmitted power, whereas 75% series compensation would increase the transfered power to about four times the original value. In this paper we propose a simple approach based in heuristic and practical rules for the optimal location of two different FACTS devices, SVC and TCSC, with specific characteristics. The system loadability and loss minimization are applied as an objective function and a measure of power system performance. They are modeled for steady-state analysis [10] and located in order to maximize the security margin of the system in terms of branc h loading and voltage levels. The propose d approach is verified on the 9 bus system with FACTS devices under normal and abnormal condition. II. MODELLING OF FACTS CONTROLLERS The FACTS devices can be categorized into three types, namely series controllers, shunt controllers and combined series-shunt controllers. Fig. 1 shows a schematic diagram outlying the basic model of FACTS devices [3]. In principle, series controllers inject voltage in series with the line and the shunt controllers inject current into the system at the point of connection. The combined series-shunt controllers inject current into the system with the shunt part of the controllers and voltage in series in the line with the series part of the controllers. IEEE MELECON 2006, May 16-19, Benalmádena (Málaga), Spain 1-4244-0088-0/06/$20.00 ©2006 IEEE 1068

strategy of location and control of facts devices

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