In order to expand the modulation index of the single DC-link shunt permanent magnet synchronous motor drive and improve the motor's operating frequency and load capacity, an improved overmodulation strategy is proposed in this paper. A phase current reconstruction strategy based on vector phase shifting is applied to both modulation linear and nonlinear region. To improve the stability of the motor at high speed, an improved flux weakening strategy based on the voltage angle control method is applied, which can effectively reduce the current harmonics. In addition, this paper proposes a dual-mode overmodulation strategy considering the influence of vector phase shift, and the analysis shows that this strategy can effectively improve the modulation index. Finally, the experimental results show the effectiveness of the proposed method in different operation conditions.

An accurate inertia identification is particularly important for the controller self-tuning to achieve high-performance permanent magnet synchronous motor (PMSM) drives. In this paper, a variable-period inertia identification strategy based on Landau adaptive method is proposed to improve the identification accuracy under low-acceleration conditions. According to the speed measurement rule of low-resolution encoder, the speed updating period of the Landau adaptive inertia identification method is redesigned and auto-adjusted under low-acceleration conditions. Finally, the proposed method is verified on a 2.2-kW PMSM drive platform.

Permanent magnet linear synchronous motor (PMLSM) has many superior advantages, but the unique structure leads to the large end force. And PMLSM is also affected by other disturbance forces such as the cogging force and friction force. These forces result in the large thrust ripples, which seriously reduce the performance of PMLSM drives. Firstly, the dynamic model and thrust ripple characteristics of PMLSM are analyzed. On this basis, a thrust ripple suppression method based on the Fourier transform compensator cascaded an improved extended state observer (ESO) is proposed. The Fourier transform compensator extracts the amplitude of the 2nd harmonic of the speed ripple, and outputs the feedforward compensation to suppress the detent force in the thrust ripples. The improved ESO observes and compensates other harmonic components. These two parts adopt cascade structure to comprehensively suppress the thrust ripples of PMLSM. Finally, experiments are carried out on a 750W PMLSM drive platform to verify the effectiveness of the proposed suppression method.