Application of zero-voltage-switching to a DC voltage-controlled static VAr compensator using quad-series voltage-source inverters

This paper discusses the potential of applying the zero-voltage-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 zero-voltage-switching. Experimental results obtained From a small-rated laboratory model of 10 kVA verify the operating principle and effectiveness of the zero-voltage-switched SVC proposed in this paper. The zero-voltage-switching enables reduction of dv/dt across each switching device, thus resulting in reduced EMI and switching losses.