Three level auxiliary resonant commutated pole inverter for high power applications

A zero voltage switching (ZVS) three level auxiliary resonant commutated pole inverter (ARCPI) is presented for high power GTO inverters. The concept of ARCP for a two level inverter is extended to the three level inverter. The proposed auxiliary commutation circuit consists of one resonant inductor and two bi-directional switches, which provides ZVS condition to the main devices without increasing device voltage or current stresses. The auxiliary device operates with zero current switching (ZCS) which enables use of the low cost thyristors. The proposed ARCPI can handle higher voltage and higher power (1-10 MVA) compared to the two level one. Operation and analysis of the ARCPI are illustrated and the features are compared to those of the snubber circuit incorporated three level inverter. Experimental results with 10 kW, 4 kHz prototype are presented to verify the principle of operation.