An Online Phase Current Derating Method with Asymmetrical Limits of Multiphase Motors

Multiphase motors naturally have a higher fault-tolerant capability and therefore their fault tolerant control(FTC) has attracted a wide range of attention. Unfortunately, existing research on phase current derating fault tolerant control (PCDFTC) is only aimed at motors with multiple sets of identical symmetrical stator windings and can only be derated using the entire set of windings as the smallest unit. The torque operation range(TOR) is therefore limited. To overcome the limitation, this paper proposes an online PCDFTC method employing asymmetrical current RMS constraints that can be implemented online to generate current references and achieve the minimum stator copper losses(SCL) in the full TOR while ensuring a circular fundamental rotating magnetic field. This approach solves the problem that the current references based on the offline optimization method are too large to store in the microcontroller. The effectiveness of the proposed method is verified by experimental results.