Independent Phase Current Control of a Permanent Magnet Motor

Open-winding permanent magnet (PM) motors are gaining popularity in transportation applications due to several advantages over traditional PM motors, such as a wider speed range, and better fault tolerance. This paper presents a current control technique wherein the individual harmonics of the winding current, resulting due to the harmonics in the machine back-EMF waveform, are controlled. Multiple harmonic controllers are used on different harmonic reference frames to ensure control of the corresponding harmonic currents. Real-time simulations are first presented to show the dynamic performance of the machine with the proposed current control technique for a wide variety of transient conditions such as machine start-up and fault operation with only two phases energized. To further validate the utility of the proposed current control technique, a torque-ripple minimization algorithm available in the literature, is used to generate current references for the proposed current controller. Real-time simulations are also presented for the torque-ripple minimization algorithm implementation along with the proposed current controller. This is followed by experimental implementation of the proposed controller. In the experimental implementation high bandwidth linear amplifiers are used to control the winding currents of a physical open-winding PM machine.