A practical approach to switching-loss reduction in a large-capacity static var compensator based on voltage-source inverters

This paper presents a simple method for reduction of switching and snubbing losses in a large-capacity static var compensator (SVC) consisting of mult iple three-phase voltage-source square-wave inverters, The proposed method is characterized by a "commutation capacitor" connected in parallel with ea ch switching device. The commutation capacitor allows the SVC to perform ze ro-voltage switching, and to reduce switching losses. The electric: charge stored in the commutation capacitor is not dissipated, but regenerated to t he de-link capacitor. Moreover, a soft-starting method for the SVC is also presented to avoid forming a short circuit across the commutation capacitor during startup. Experimental results obtained from a 10-kvar laboratory se tup are shown to verify the viability of the operating principle of the com mutation capacitor.