Reactive power compensation using switching cell structured direct PWM AC-AC converter

Abstract

In this study, a new topology, using switching cell structured direct pulse width modulation (PWM) ac-ac converter, is proposed for reactive power compensation. A reactive power compensator using conventional ac-ac converters has been recently introduced. It realizes the concept of the chopper-controlled impedance (CCI) to get variable reactive power compensation. When compared with conventional solutions such as static synchronous compensators (STATCOMs) and static Var compensators (SVCs), this approach is a low-power-loss solution and requires a low volume of reactive elements, a fact that makes this solution very attractive in high-power systems. However, this approach suffers from the commutation problem due to the ac switches of the converter. Unlike compensators using conventional ac-ac converters, the ac-ac converters of the proposed scheme adopt a basic switching cell (SC) structure and use coupled inductors to implement the phase legs of the converters. As a result, the ac-ac converters can be short- and open-circuited without damaging the switching devices. Neither the lossy RC snubber nor dedicated soft commutation strategy is required in the proposed scheme. This fact makes this compensator a more reliable system. To verify its performances, simulation and experiment results are shown for single-phase system.