Switching Loss Measurement of Wide-Bandgap Reverse-Blocking Semiconductor Switches in Current-Source Converters

The high achievable switching speeds of wide-bandgap (WBG) semiconductor devices based on silicon carbide (SiC) and gallium nitride (GaN) are a key characteristic to reduce the volume of passive components of electric drive converters and thus increase their power density. In contrast to voltage source converters (VSC), current source converters (CSC) do not come at the risk of high EMI, overvoltages, and thus insulation stress, as it is the case with VSCs, due to the resulting fast rise and fall times of the output voltage. Several approaches for determining the switching losses of the semiconductor devices for the CSC topology have already been described in literature, but all of them linearize the losses between a certain commutation voltage and zero. This paper, in contrast, describes how the occurring switching losses in the CSC can be measured with an appropriate commutation cell at different commutation voltages and how these are distributed over the semiconductor components used, since the CSC's main switching elements consist usually of two semiconductor devices to achieve reverse blocking capability. It also presents an alternative method of calculating switching losses when the component loss energies as a function of commutation voltage are known from additional measurements.