Robust Current Observer Design for PMSM Drives Using a Single DC-Link Current Sensor

In permanent magnet synchronous motor (PMSM) drives, compared to the traditional approach of using at least two current sensors, single dc-link current sensor control (SDCSC) offers cost reduction and a more compact drive system. The switching-state phase shift (SSPS) method can suppress the current reconstruction dead zone (CRDZ) in the low modulation region and sector boundary regions for SDCSC. Still, due to the asymmetry of the SSPS method, reconstruction errors and current harmonics are introduced, which affect the bandwidth of the PMSM current loop. This article analyzes the errors introduced by the SSPS method and proposes a robust dq-axis current observer to resolve this problem. Based on the theory of Lipschitz nonlinear systems, the tuning principle of the correction gain for the proposed observer is derived. A speed decoupling term is proposed to maintain the desired observer performance, and the computation of the optimal correction gain combining the speed decoupling term and the gradient method is given. A disturbance compensation component is further proposed to enhance the robustness of the proposed current observer. The proposed method suppresses the reconstruction errors of the SSPS method and improves the current-loop bandwidth under SDCSC. Experiments are performed on a PMSM platform to verify the effectiveness and feasibility of the proposed method.