An Improved Modulation Scheme with Better Performance for Open-Winding Permanent Magnet Synchronous Motors Drives

In order to improve the performance of voltage synthesis of the open-winding permanent magnet synchronous motors (OW-PMSMs) with isolated DC bus when the voltages of two power supplies are not equal, an innovative voltage modulation method is proposed. The novel method is based on the conventional alternate sub-hexagonal center PWM method, but the low-voltage powered inverter is kept at low-potential clamped state throughout a period instead of having the two inverters clamped alternately. In this way, the high-voltage powered inverter expands the range of voltage synthesis, making up for the deviation between the synthesized voltage and the voltage reference when the high-voltage powered inverter is clamped and the low-voltage powered inverter modulates individually. Therefore, compared with the traditional method, a larger total voltage synthesis range is covered so that the capability of voltage synthesis is enhanced, thereby improving the quality of the corresponding torque and the output current. The simulation and experimental validations are presented to certify the effectiveness of the proposed method under different conditions, and the results prove that the new method indeed improves the current performance and reduces torque ripples.