Full Speed Range Sensorless Control of Surface Permanent Magnet Synchronous Motor Based on Novel Nonlinear Flux Observer

The nonlinear flux observer provides feedback compensation by estimating the amplitude error between the rotor flux and the permanent magnet flux. This observer has been successfully applied in medium to high-speed sensorless control of surface permanent magnet synchronous motor (SPMSM). However, this method exhibits poor stability at standstill and low speed. To address this limitation, an adaptive high-frequency signal injection method is proposed to ensure the fulfillment of the persistency of excitation (PE) at standstill and low speeds, while also facilitating smooth switching during full-speed operation. Furthermore, in the medium and high-speed range, the performance is enhanced through adaptive adjustment of the observer gain. In comparison with conventional methods, the proposed control strategy requires only a single observer for position closed-loop control across the full speed range. The effectiveness of the proposed control strategy is demonstrated through simulations and experiments.