Novel control strategy to improve power capability for high power converters

Power capability is one of the most important criteria for converters in high-power applications. The normal approach for converters increasing the power capability is to use devices with larger Safety Operating Area (SOA). In this paper, a novel control method is proposed to realize power capability improvement at low carrier ratios without hardware changes. It uses the carrier modulation at integer carrier ratios and optimized carrier angles to achieve the best performance in terms of the lowest peak current stress and/or thermal stress of hotspot devices. Meanwhile, for high-power semiconductor devices such as IGCT, the maximum turn-off current is related to the minimum on-state time. This paper dynamically changes the minimum on-state time according to the current requirement to adjust max turn-off current, while keeping the output power quality by injecting minimum active common mode voltage. With these controls, the power capability of high-power converters is pushed to higher level without hardware changes.