Application of Soft-Switching Technique to a DC Voltage-Controlled Static Var Compensator Using Quad-Series Voltage-Source Inverters.

This paper discusses the potential of applying the soft-switching technique to a dc voltage-controlled static var compensator. The main circuit of the static var compensator (SVC) consists of quad-series voltage-source six-step inverters and four three-phase transformers. The SVC is characterized by a “commutation capacitor” connected in parallel with each switching device, without any additional active or passive element. The commutation capacitor plays an essential role in achieving soft-switching.Experimental results obtained from a small-rated laboratory model of 10kVA verify the operating principle and effectiveness of the soft-switched SVC proposed in this paper. The zero-voltage-switching enables to reduce dv/dt across each switching device, thus resulting in reduced EMI and switching losses.