Development of a Parallel Redundant STATCOM System

Abstract

This paper presents a new concept of parallel redundant STATCOM system. This system consists of a number of medium capacity STATCOM units connected in parallel, which can achieve a high operational reliability and functional flexibility. The proposed STATCOM system has such redundant operation characteristics that the remaining STATCOM units can maintain their operation even though some of the STATCOM units are out of service. And also, it has flexible convertibility so that it can be converted to a BTB or a UPFC system easily, according to the diversified change of needs in power systems. In order to realize this concept, the authors developed several important key technologies for the STATCOM, such as the novel PWM scheme that enables effective cancellation of lower order harmonics, GCT inverter technologies with small loss consumption, and the coordination control scheme with capacitor banks to ensure effective dynamic performance with minimum loss consumption. The proposed STATCOM system was put into practical applications, exhibiting excellent performance characteristics at each site.