A Novel Harmonic Current Control Method for Torque Ripple Reduction of SPMSM Considering DC-Link Voltage Limit

Torque ripple reduction based on harmonic current injection has been widely applied to surface-mounted permanent-magnet synchronous machine (SPMSM) drive systems. However, additional voltages are typically required for harmonic injection, and the dc-link voltage limit should be considered in practical drive systems. This article proposes a novel harmonic control for SPMSMs in which the torque ripple reduction and high dc-link voltage utilization can be achieved simultaneously. The influence of harmonic injection on voltage utilization is investigated in detail. In addition to injecting the appropriate
q
-axis harmonic currents to suppress torque ripple, the
d
-axis harmonics are also optimized and injected. The geometric principle is applied to obtain the analytical expression for the optimal
d
-axis harmonic voltage, which can minimize the maximum magnitude of the stator voltage vector. Since the reference harmonic voltage is directly calculated in accordance with the analytical solution, the implementation complexity of harmonic voltage regulation is relatively low. Moreover, a virtual dual three-phase system with auxiliary currents is developed to decompose the fundamental and harmonic currents without low-pass filters, thus avoiding additional delay in the control loop. Finally, the experimental results are provided to verify the validity of the proposed method.