Closed-loop control strategy for PM machines with non-sinusoidal back-EMFs using dual-inverter open-end winding

This paper presents a closed-loop control strategy for dual inverter-fed, permanent magnet synchronous motors with non-sinusoidal back-EMFs. The inverters are connected to both ends of the machine winding but use only one power source, thus providing a path for zero sequence currents to circulate in the motor windings. If neglected, the zero sequence current can cause higher maximum peak and rms phase currents. Moreover, for the PMSM machine, the zero sequence current is heavily influenced by the back-EMF. Therefore, a closed-loop control strategy to suppress the circulation of zero sequence currents and amplitude of the dominant harmonics caused by non-sinusoidal back-EMF is developed and demonstrated by experiment. It is shown to reduce the zero sequence current. The efficiency of the system before and after the suppression of the zero sequence current is also considered. Analysis of experimentally measured efficiency shows that the losses are higher without harmonic suppression which reduces the efficiency.