A Sensorless Drive Strategy for Open-End Winding PMSM With Common DC Voltage Based on Lower Switching Frequency

A novel sensorless drive strategy with lower switching frequency for open-end winding permanent magnet synchronous machine (OW-PMSM) with common dc voltage is proposed. The reference voltage of two inverters is distributed into two reference voltages with same amplitude and 120° electrical angle shift so that the disturbance of the two converters on zero-sequence current (ZSC) can be avoided. Based on that, the position information is extracted by the proposed method of angle extraction. Meanwhile, a torque controller is introduced to suppress the ripple component of torque, which is generated mainly by ZSC. In addition, a novel simplified modulation strategy with smaller computation burden is proposed to implement the modulation with lower switching frequency, in which only zero basic voltage vector (000) and three active basic vectors (100), (010), (001) are utilized as the basic voltage vectors for both inverters. The duty ratio of each phase can be determined by the reference voltage directly and only three-phase duty ratios of one inverter are necessary due to the symmetry. Finally, the proposed strategy is tested experimentally on the OW-PMSM platform.