Investigating the Use of UPFC Device for Reduction of SPA in a Power System

Abstract

The phase angle associated with the voltage of an AC power system under real and reactive power balanced operating condition is referred to as Standing Phage Angle (SPA) of the bus. During restoration of power system EHV/HV transmission line, it is to be ensured that SPA across the breakers of the two ends of the disconnected line (i.e. the difference of SPA between the two ends of the disconnected line) has to be below the prescribed value for the category of the line. Closing breakers with large SPA across the two ends of a transmission line could damage the system equipments, and could lead to system outage. This paper aims at investigating the possible use of Unified Power Flow Controller (UPFC) device for reduction of SPA in a power system. For this purpose, sensitivity relation between change in SPA across two end buses of a disconnected transmission line and the change in power flow through the line having UPFC device have been formulated. The sensitivity relations are used to reschedule the power flow through the line having UPFC device to reduce SPA across the line to be re-connected. Simulations were carried out on IEEE 118 to examine the applicability of the proposed method. It has been observed during simulation that the voltage magnitude of series controller of UPFC plays vital role in reduction of excessive SPA process.