Zero-voltage-switching 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 ARCPI for a two-level inverter is extended to the three-level inverter. The proposed auxiliary commutation circuit consists of one resonant inductor and two bidirectional switches, which provides the ZVS condition to the main devices without increasing device voltage or current stresses. The auxiliary device operates with zero-current switching (ZCS) which allows the use of low-cost thyristors. The proposed ARCPI can handle higher voltage and higher power (1-10 MVA) with fewer harmonics compared to the two level one. Operation and analysis of the proposed ARCPI are illustrated and the features are compared with 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