Influence of the Filter Design on Wide-Bandgap Voltage Source Inverters with Sine Wave Filter for Electrical Drives

State-of-the-art electric drives are mainly equipped with two level three phase voltage source inverters offering an compact setup with good efficiency but electromagnetic interference is an issue especially in sensitive environments. Also bearing currents, excited by common-mode noise, can influence the reliability of the connected machine. To reduce these bearing currents and the inverter's electromagnetic compatibility an output filter can be used. Especially with wide band-gap semiconductors the reduced switching losses offer output filters with low volume. Furthermore, this filter offers several degrees of freedom to optimize the losses of the whole inverter system. Possible filter designs are investigated and compared with each other. A design methodology to find loss optimized filter configurations is presented. By modeling the whole inverter and filter system the losses of the system are calculated for every filter configuration iteratively at a desired operating point. These loss models consider soft switching behavior as well as high frequency losses of the passives to take also configurations with high filter choke current ripple into account.