Time Domain Analysis of Series-Resonant Converter in Auxiliary Power Supply for Medium-Voltage Converter

The auxiliary power supply with high voltage isolation and low common-mode capacitance is one of the critical components inside medium-voltage power electronic converters. The isolation transformer design often ends up having a high leakage inductance as a consequence of the low isolation capacitance requirement imposed by the high switching voltage slew rate (dv/dt). In the case of series resonant converter this leakage inductance can be compensated by series resonant capacitor. However, the winding resistance in the transformer still leads to increased voltage drop resulting power limitation. The objective of this paper is to deduce the time domain modelling of series-resonant converter considering isolation transformer winding resistor to analyze the trade-off between transformer winding resistance and voltage-drop.