A novel method for loss reduction in high-voltage inverters

This paper presents a high-voltage inverter configuration employing series connections of 1.2 kV rated standard IGBTs instead of high-voltage rated IGBTs, which allows the losses of switching devices to considerably decrease. Voltage balancing across all of the IGBTs connected in series, which is one of the most critical issues especially during the transient phases, is realized by magnetically coupling of all the gate wires with a two-winding transformer without any snubber components or active gate controls. Moreover, influence of stray capacitance associated with insulators in IGBT modules on the voltage sharing is investigated, and an optimized configuration including these heat sinks is proposed to achieve a more accurate voltage equalization. To validate the performance on the series connection of the standard IGBTs with respect to the voltage sharing and the device losses in practical uses, a prototype 170 kVA rated inverter based on three series connection of 1.2 kV rated IGBTs are implemented and tested. The experimental results are shown.