Mitigation of subsynchronous oscillations by 48-pulse VSC STATCOM using remote signal

Abstract

Series compensated power system may lead to a very unusual problem known as Subsynchronous Resonance (SSR). Flexible AC Transmission Systems (FACTS) controllers are widely applied to mitigate subsynchronous oscillations. The Static Synchronous Compensator (STATCOM) is a shunt device of the FACTS family using power electronics to control power flow and improve transient stability on power grids. With the advent of Wide Area Measurement (WAM) technology, it is possible to measure the states of a large interconnected power system with synchronized Phasor Measurement Units (PMU). In this paper the concept of using remote signals acquired through PMU has been proposed to damp SSR. An auxiliary subsynchronous damping controller (SSDC) for a STATCOM using the remote accelerating power of generator signal as the stabilizing signal has been designed to damp subsynchronous oscillations. This paper deals with a cascaded multilevel converter model, which is a 48-pulse (three levels) source converter. The voltage source converter described in this paper is a harmonic neutralized, 48-pulse GTO converter. The IEEE Second Benchmark (SBM) model is considered for the analysis and the complete digital simulation of the STATCOM within the power system is performed in the MATLAB/Simulink environment using the Power System Blockset (PSB).