Unbalanced Current Control in Electric Drives for Thermal Management of Inverter Power Devices

The main aim of this paper is to present an effective control strategy enabling the electric motor drive to contain junction temperature increase in power devices composing the inverter, which may arise due to abnormal operations related to cooling, aging issues or widespread in device parameters. The method allows the generation of the same rotating magnetomotive force in the electrical machine even when supplied with unbalanced phase currents. This enables the drive to maintain the same torque capability as during normal operation while simultaneously balancing the thermal status among power switches. The proposed control solution requires a zero-sequence current flow. This can, for instance, be easily generated in motor drive configurations that also feature fault tolerance capabilities. Effectiveness of the solution is verified through simulations and experimental tests performed on a 2.2kW induction motor drive.