Abstract: In the zero low speed operation control of sensorless permanent magnet synchronous machines (PMSM), the high frequency signal injection method is often used to track the position information, which will cause torque fluctuation and time delay. In this paper, a filter free rotor position identification method is proposed by combining sliding mode speed control and high frequency square wave signal injection. By increasing the frequency of square wave signal to the switching frequency of inverter and taking advantage of the characteristic that the fundamental wave signal cycle is far less than the high-frequency injection signal cycle, the signal separation in the traditional high-frequency signal injection is avoided through two current samples in the single high-frequency signal injection cycle. Meanwhile the filter is removed to effectively improve the system convergence speed. The simulation results show that compared with the traditional high-frequency signal injection method, the proposed method can achieve high-precision low-speed operation under sensorless control of PMSM, and has good steady-state characteristics and dynamic performance.

Key words: PMSM, high frequency square wave signal injection, sliding mode speed controller, position sensorless control