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Transfer Mechanism Analysis of Injected Voltage Harmonic and its Effect on Current Harmonic Regulation in FOC PMSM

Harmonic injection method is widely used in the suppression of current harmonic and torque ripple in field-oriented control (FOC) permanent magnet synchronous motor (PMSM) servo system. However, under some working conditions of FOC PMSM, the harmonic injection method fails to suppress the current harmonics and causes oscillation. To analyze the cause of oscillation, the transfer mechanism of injected voltage harmonic is analyzed in this article, and the relation between injected voltage harmonic and current harmonic is derived. The theoretical analysis results show that the relation between harmonics will change with motor speed and parameters of FOC PMSM. When the relation between harmonics is reversed, the existing harmonic injection method will fail and cause harmonic oscillation. To solve this problem, a simple improvement of the harmonic injection method is proposed in this article based on the proposed close-loop model. The correctness of the mathematical derivation and the effectiveness of the proposed method is evaluated by experiment and simulation.