Improved square-wave voltage injection method for sensorless control of PMSM and its adaptability to motor parameter variations

The high-frequency square-wave voltage injection method is proposed recently for sensorless control of permanent magnet synchronous motor. In the method, the frequency of the injection signal is increased to the switching frequency of the inverter, and filters are removed by utilizing a special signal processing method, as a result, the dynamic performance is improved significantly. However, it is shown that further improvements are still needed in the method, especially in the case with mismatched motor parameters and at high operation speed. Several improvement measures are proposed in this paper. Simulation results show that the improved schemes can estimate the rotor position and speed accurately in a wide speed range even at the situation that motor parameters are mismatched, and they have little effect on the dynamic response.