Fuzzy Based Unified Power Flow Controller to Control Reactive Power for a Practical Thermal Power Station

Unified Power Flow Controller (UPFC) is a power electronic based device that has capability of controlling the power flow through the line by controlling appropriate its series and shunt parameter. It has been reported that UPFC can improve transient stability of a simple system. The UPFC consists of two solid-state voltage source inverters (VSIs) connected by a common DC link that includes a storage capacitor. The first one is a static synchronous compensator (STATCOM) the second one is a static synchronous series compensator (SSSC). The proposed fuzzy logic controller is used to arrange the controls of the STATCOM and SSSC, in order to take into account, by approximated reasoning, the system nonlinearity and devices interaction. UPFC is a well-known Flexible AC Transmission System (FACTS) device that can control power-system parameters such as terminal voltage, line impedance and phase angle. The objective in this paper is to maintain a constant voltage profile irrespective of changes in the load. This is achieved either by injecting or absorbing the reactive power. In this paper for implementing fuzzy logic approach two inputs (error voltage and capacitor value) are taken and the "Inverter Pulse" which is used for UPFC power electronic device to control the voltage is taken as an output. Case studies have been performed for National Thermal Power System of a practical system. Three generating stations each of 210 MW have been considered in this work. These three generators (Unit 1, 2, 3) are connected to a common load bus bar of 230 kV system. This practical system is considered as a conventional method without UPFC. Simulation work in MAT lab has been carried our with fuzzy controller and UPFC. It is observed that with Fuzzy and UPFC the reactive power requirement is less and a constant voltage of 230 kV has been achieved. Copyright (C) 2012 Praise Worthy Prize S.r.l. - All rights reserved.