Sensorless speed control of nonsalient permanent magnet synchronous motor using rotor position tracking PI controller

This paper presents a new velocity estimation strategy of a nonsalient permanent magnet synchronous motor (PMSM) drive without high frequency signal injection or special PWM pattern. This approach is based on the d-axis current regulator output voltage of the drive system that has the information of rotor position error. The rotor velocity can be estimated through a rotor position tracking PI controller that controls the position error to zero. For zero and low speed operation, PI gain of rotor position tracking controller has a variable structure according to the estimated rotor velocity. Then, in zero speed, the rotor position and velocity has a sluggish dynamics because the varying gains are very low in this region. In order to boost the bandwidth of PI controller in zero speed, a loop recovery technique is applied to the control system. The experimental results show the satisfactory operation of the proposed sensorless algorithm under load conditions.