A Fractional-Order Repetitive Control Method for Low-Order Current Harmonic Mitigation in LC-Filtered High-Speed Permanent Magnet Synchronous Motors

To address the heating, vibration, and torque ripple issues in high-speed permanent magnet synchronous motor (HSPMSM) caused by stator current harmonics, an LC filter is commonly implemented between the inverter and the motor to effectively suppress high-order harmonics. However, low-order harmonics may persist due to inverter nonlinearity, nonsinusoidal flux linkage, and three-phase asymmetry. Selecting suitable locations for current sensors can also pose challenges. To harness the advantages of both inverter current and stator current feedback in mitigating low-order harmonics for the LCfiltered HSPMSM system, this paper proposes a novel approach that integrates an adaptive extended state observer (AESO) with fractional-order repetitive control (FORC). This method only samples the inverter currents, utilizing AESO to accurately estimate the stator current and employing FORC for harmonic suppression, resulting in superior performance compared to traditional integer-order repetitive control (IORC). Experimental results on an HSPMSM platform validate the effectiveness of this approach, demonstrating significant reductions in low-order current harmonics.