Publication

Abstract : Electric power transmission systems can be effectively controlled with FACTS devices. Unified Power Flow Controller (UPFC) is a multi-functional FACTS device that can control different parameters of the power system under dynamic conditions. UPFC consists of two Voltage Source Converters (VSCs), which are connected back to back to a common DC link. In this paper, a non linear state-space model of UPFC is developed by including VSC output voltage functions, the effect of source impedance and energy variation in the passive elements. The non linear model of the UPFC is controlled with a non linear controller. The paper also proposes a non linear controller Partial Feedback Linearization (PFBLC) for UPFC. PFBLC modifies the control input such that UPFC is able to behave linearly under all non linear dynamics occurs in the system. The proposed system is designed, analyzed and tested in an interconnected power system network. The hardware implementation is also carried out in a five bus test bench. It was observed that the UPFC shows satisfactory performance in all operating conditions.