22-06-2011, 04:09 PM
Abstract
In this paper steady-state modeling of Static VAR Compensator (SVC) and Thyristor Controlled Series Compensator (TCSC) for power flow studies has been represented and discussed in details. Firing angle model for SVC was proposed to control the voltage at which it is connected. In same manner firing angle model for TCSC is used to control active power flow of the line to which TCSC is installed. The proposed models take firing angle as state variable in power flow formulation. To validate the effectiveness of the proposed models Newton-Raphson method algorithm was developed to solve power flow equations in presence of SVC and TCSC. Case studies are carried out on 9-bus test system to demonstrate the performance of the proposed models.
Index Terms— Newton-Raphson, Power Flow, Static VAR Compensator, Steady-state modeling, Thyristor Controlled Series Compensator.
I. INTRODUCTION
With the rapid development of power system, especially the increased use of transmission facilities due to higher industrial output and deregulation, it becomes necessary to explore new ways of maximizing power transfer in existing transmission facilities, while at the same time maintaining the acceptable levels of the network reliability and stability. On the other hand, the fast development of power electronic technology has made FACTS (flexible AC Transmission system) promising solution of future power system. FACTS controllers such as Static Synchronous Compensator (STATCOM), Static VAR Compensator (SVC), Thyristor Controlled Series Compensator (TCSC), Static Synchronous Series Compensator (SSSC) and Unified Power Flow controller (UPFC) are able to change the network parameters in a fast and effective way in order to achieve better system performance [1], [2], [3], [4]. These controllers are used for enhancing dynamic performance of power systems in terms of voltage/angle stability while improving the power transfer capability and voltage profile in steady-state conditions [5], Static VAR Compensator (SVC) and Thyristor Controlled Series Compensator (TCSC) are FACTS controllers based on thyristor controlled reactor (TCRs), the first is a shunt compensator used for voltage regulation which is achieved by controlling the production, absorption and flow of reactive power through the network. The later is a series compensator, which allows rapid and continuous changes of transmission impedance, controlling power flow in the line and improving system stability. Now, for maximum utilization of any FACTS device in power system planning, operation and control, power flow solution of the network that contains any of these devices is a fundamental requirement, As a result, many excellent research works have been carried out in the literature for developing efficient load flow algorithm for FACTS devices [10], [11], [12], [13], [14]. This paper focuses on the development of SVC and TCSC models and their implementation in Newton-Raphson load flow algorithm, to control voltage of the bus and active power across the line. Incorporation of FACTS devices in an existing power flow algorithm results in increased complexity of programming due to the following reasons: • New terms owing to the contributions from the FACTS devices need to be included in the existing power flow equations of the concerned buses. These terms necessitate modification of existing power flow codes. • New power flow equations related to the FACTS devices come into the picture, which dictate formulation of separate subroutine(s) for computing them. • The system Jacobian matrix contains entirely new Jacobian sub-blocks exclusively related to the FACTS devices. Therefore, new codes have to be written for computation of these Jacobian sub-blocks. In section (II) of this paper derivation of power flow equation for two-port network under steady state conditions is represented, while section (III) demonstrates the modeling of SVC. The rest of the sections are organized as follows: in section (IV) modeling of TCSC is presented. The simulation and results are presented in section (V).Finally; conclusion is discussed in section (VI).
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