Quasi resonant 3-phase IGBT inverter

This paper presents a novel soft switching quasi resonant 3-phase IGBT inverter capable of operating at high switching frequency for high power applications (up to 100 kW). The circuit enables zero voltage switching with reduced device stresses for all switches. It provides reduced voltage rate of change du/dt and hence low conducted and radiated emission. The proposed circuit utilizes an auxiliary zero voltage switching circuit (ZVS) which can be triggered on demand, to create a zero-voltage switching interval for the inverter switches, thereby ensuring nearly lossless switching. A new space vector delta modulation is introduced to overcome the problem of the minimum dwell time of switching state required for soft switching. Experimental results from a 50 kVA, 400 V inverter for 3-phase induction motor verified the expected advantages of the novel inverter and of the proposed space vector delta modulation concerning the switching frequency and the output spectrum characteristics. The paper concludes with comparison to the popular space vector modulation for a 3-phase motor drive