LAUSR

The permanent magnet synchronous machines system includes various harmonics caused by asymmetric impedance, current measurement errors, spatial harmonics, and inverter nonlinearity. The asymmetric impedance and the current measurement scaling error cause an asymmetry among three-phase currents, which produces a negative-sequence fundamental current. The controller cannot distinguish between their effects and reduce asymmetric currents. Therefore, a novel modulation-based current harmonic control strategy is proposed in this paper. The complex-vector system model accounting for these harmonics is established to illustrate the modulation effects of motor saliency, the asymmetric impedance, and the current measurement scaling error. According to modulation principles, the actual negative-sequence fundamental current is reconstructed to suppress the harmonic current caused by the asymmetric impedance. Meanwhile, the measured negative-sequence fundamental current is employed to compensate for the scaling error, and the DC component of current measurements is employed to compensate for the offset. The harmonic current controller also suppresses other harmonic currents. The harmonic current controller and the current measurement compensator based on the complex vector control are designed. Experiments verify the correctness and feasibility of the proposed control strategy.