Current Control of a Direct Current Motor Fed through LC-filter from Power Converter Based on Wide-Bandgap Semiconducting Devices

Wide-bandgap semiconducting devices, such as GaN and SiC switches, being used in drives affect the insulation of the motors by very high voltage derivative causing currents flowing through parasitic capacitance of the windings. This leads to fast ageing of the motor insulation and can be avoided by use of sine- or LC-filters. However, motor control through LC-filter is a challenging task requiring additional voltage sensors at the output of the filter. This study introduces an observer for motor voltage and current estimation with a help of a single current sensor between power converter and LC-filter. Together with the proposed cascaded control having three nested loops of filter current, motor voltage, and motor current the proposed solution enables conventional motor control strategies operating through LC-filter. Simulation results were obtained for direct current motor drive. Similar approach can be used for AC electrical machines including traction application with SiC inverters and servo drives with GaN switches.