Harmonic current suppression method with adaptive filter for permanent magnet synchronous motor

Due to the distortion of air gap magnetic field and the inherent non-linear characteristics of the inverter, the stator current of permanent magnet synchronous motor (PMSM) contains a large number of high order harmonic components, which distorts the current waveform and generates torque ripple, limiting the application of the PMSM in high speed and precision situations. To solve this problem, a harmonic current suppression method is proposed based on synchronous rotating coordinate transformation theory and adaptive filtering algorithm. The PMSM harmonic mathematical model is established and the coordinate transformation method is used to extract the 5th and 7th harmonic currents. On the basis of the original double closed-loop control system, the harmonic current loop is added, and the harmonic components are suppressed by injecting harmonic voltages. In order to improve the filtering effect and reduce the harmonic content, an adaptive filter is designed to replace the conventional low pass filter in the process of harmonic current extraction. According to the results of coordinate transformation, the adaptive filter continuously adjusts the parameters online through the least mean square (LMS) algorithm to extract the harmonic current. The simulation and experimental results proved the correctness and effectiveness of the proposed method.