Are paralleled IGBT modules or paralleled IGBT inverters the better choice?

The power range which can be handled by PWM inverter applying available IGBT modules is about 150 kW. For higher power levels more than one device per bridge arm is necessary. In this paper, possibilities to enlarge the output power of IGBT inverters using parallel circuits are discussed. For direct parallel operation of advanced IGBT devices, difficulties are caused by the negative temperature coefficient of the on-state voltage. This includes a risk of thermal runaway or large imbalance of current sharing. The necessary conditions for a good current balance are deduced. Satisfying these conditions, direct paralleling of high current IGBT modules is possible for up to three devices. For higher power levels with a larger number of IGBT modules, it is not possible to achieve close thermal coupling which is essential for good on-state current sharing. For such high power-levels, paralleled inverters with electronic controlled current imbalance are advisable