An Improved Rotor Position Estimation Method for PMSM Based on Pulsating Square-Wave-Type Voltage Injection

This paper presents a pulsating high-frequency square-wave-type voltage signal injection based sensorless rotor position estimation method for permanent magnet synchronous motors (PMSM). In order to increase the injection frequency so as to enhance the control system's bandwidth, square-wave-type voltage is injected instead of sinusoidal voltage. To avoid disturbances, the sampling frequency is set as equal to the PWM switching frequency so that the injection frequency can be half of the switching frequency. Due to the characteristics of the square-wave-type voltage, the signal processing is further simplified without the use of filters, which can eliminate the time delay and increase the system's computational efficiency and feasibility. As a result, the rotor position estimation performance is improved and the sensorless control system's dynamics is enhanced. Results of simulation verify the effectiveness of the proposed method and its applicability to PMSM sensorless control systems.