An Overmodulation Method Based on Variable-Weight Superposition Theory for Voltage Jump Elimination in PMSM Drives

Overmodulation method is an effective way to improve the voltage utilization for the PMSM drives, thus achieving higher efficiency and power capacity. However, the voltage jump between the output voltage vectors (OVVs) causes the deterioration of both phase voltage and current performance in the high overmodulation region. In order to eliminate the voltage jump, a novel variable-weight superposition theory (VWST) is proposed. Different from other methods, the phase angle of the reference voltage vectors (RVVs) is introduced to construct the variable-weight factor. This elaborate weight factor is assigned to the jump component with the variation of the phase angle. Eventually, the voltage jump is eliminated, and the total harmonic distortion (THD) of both phase voltage and current is decreased, which means smaller current ripple and torque jitter. In addition, the linearity of the modulation index is guaranteed by a convert block based on the Fourier analysis. With the help of the proposed method, the voltage jump can be eliminated, and better performance of phase voltage and current can be achieved. The effectiveness of the proposed method is verified by PMSM bench experiments.