Design of snubber circuit for the 4500 V/4000 A GTOs in a 20 MVA STATCOM

This paper analyzes the generation process of the overvoltages V/sub DSP/ V/sub DM/ and V/sub R/ during the turn-off process of GTO and the measures to suppress the overvoltages. Through analyses of the features of conventional RCD snubber circuit and three kinds of low-loss snubber circuit, the snubber circuit for the 4500 V/4000 A GTOs in a 20 MVA STATCOM installation is proposed. The snubber circuit is the low-loss /spl Delta/-type snubber circuit with a clamping capacitor. Experimental results demonstrate that the proposed snubber circuit is very effective for large capacity two-level GTO inverter.