Self-sensing control of open-end winding PMSMs fed by an asymmetrical hybrid multilevel inverter

This paper deals with a self-sensing control for Open-end Winding Permanent-Magnet Synchronous Motors fed by Asymmetrical Hybrid Multilevel Inverters. In this kind of system, a main multilevel inverter (MLI) supplies the PMSM on one side, while an auxiliary two-level inverter (TLI) acts as active power filter on the other side of the machine. The MLI works at a low-switching frequency and high voltage while the TLI is pulse width modulated at low voltage. A sensorless high frequency injection method is adopted to detect the rotor position at low and zero-speed. The high frequency voltage injection is performed by the TLI in order to keep low and constant the MLI switching frequency, thus minimizing power losses. At high speed, the rotor position is instead detected by estimating the motor back-EMF. The proposed self-sensing approach gives both high efficiency and high control performance in all the operating speed range. Experimental results confirm the effectiveness of the self-sensing implementation.