717 publications from this institution
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.
This paper proposes a control method for eliminating dc magnetic flux from the series transformer of a DVR. The method is characterized by intentionally injecting no compensating voltage during a one-sixth line cycle (=3.3 ms at 50 Hz). The control sequence is independent of an initial phase angle of a voltage sag, thus requiring no flux detection. The period, during which no compensating voltage is injected, is one-third as short as that of an existing method. This paper verifies the effectiveness and viability of the proposed method, using a 200-V, 5-kW laboratory system. The proposed method brings no dc magnetic flux to the series transformer.
