Control and performance of UPFC connected to a transmission line

The unified power flow controller (UPFC) is the most versatile and complex power electronic equipment that has emerged for the control and optimization of power flow in electrical power transmission system. This paper presents control and performance of UPFC intended for installation on a transmission line. A control system which enables the UPFC to follow the changes in reference values like AC voltage, DC voltage and angle order of the series injected voltage is proposed. In this control system, a generalized pulse width modulation technique is used to generate firing pulses for both the converters. When no UPFC is installed, any interruption in the line due to fault reduces the active power flow through the line. Installing the UPFC makes it possible to control an amount of active power flowing through the line. Simulations were carried out using PSCAD software to validate the performance of the UPFC.