Position Sensorless Direct Torque Control for PMSM Based on Pulse High Frequency Stator Flux Injection at Low Speed
Abstract: In the direct torque control (DTC) system of permanent magnet synchronous motor (PMSM), the stator flux estimator based on current model is usually adopted at low speed. However, the rotor position information is necessary in this observer. Thus, it is difficult to realize position sensorless operation for PMSM DTC system. In order to solve this problem, a position sensorless DTC for PMSM based on pulse high frequency stator flux injection at low speed is proposed in this paper. Firstly, a high frequency signal is added on the constant stator flux amplitude. Then, the high frequency current would be induced in the three phase windings. Secondly, the position signal can be demodulated from the induced high frequency phase currents. Accordingly, the obtained rotor position signal is utilized in the stator flux estimator based on current model. However, the accuracy of the stator flux estimator would be affected if the rotor position is not completely accurate. In this paper, an improved stator flux estimator is proposed to improve the accuracy of traditional stator flux estimator based on current model. Finally, experimental research on the proposed strategy has been done. The experimental results verify the feasibility and effectiveness of the proposed strategy.
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