The use of decoupled converters to optimize the power electronics of shunt and series AC system controllers

This paper presents a decoupled converter approach for solid-state compensation of ac power systems. The scheme employs a multi-step inverter for control of fundamental frequency components and PWM inverters for harmonic compensation. The inverters are arranged in such a manner that the high-frequency harmonic compensation module uses inverters of low power rating, while the slowswitching fundamental frequency compensation module supports most of the stresses. This decoupled approach is expected to result in a significant reduction in cost and losses associated with active compensators for high-power applications. The basic principle of operation, circuit structures and control strategy for shunt and series compensation based on the decoupled approach are described. Computer simulation and experimental results are presented to demonstrate the performance of the proposed system.