A rotor position detection method for synchronous motors based on high-frequency injection voltage estimation

A rotor position detection method based on high-frequency injection is proposed in this paper to solve the related problems of rotor pulsation during low-speed starting. Considering the characteristics of the electrically excited synchronous motor, high-frequency voltage signal is injected into the excitation to generate a high-frequency excitation current. The high-frequency voltage signal have rotor position information is collected. After filtering and coordinate transformation, effective rotor position information is collected. Finally, a phase-locked loop is employed to lock the rotor position. In a thyristor driven system, during the current commutation, the motor's back electromotive force of the motor is distorted, leading to significant high-order harmonics in the terminal voltage. Accurately collecting effective high-frequency signals becomes challenging. Therefore, a rotor position detection method for synchronous motors based on high-frequency injection voltage estimation is proposed in this paper. The estimated voltage is used as the input signal for the phase-locked loop during commutation to prevent distorted high-frequency harmonic from entering the phase-locked loop. The simulation results show that adding voltage estimation effectively avoids the harmful effects of commutation voltage distortion on rotor position detection and improves the accuracy and reliability of high-frequency injection rotor position detection.