Robust Initial Rotor Position Estimation of Permanent Magnet Brushless AC Machines with Carrier Signal Injection-Based Sensorless Control

In sensorless control of permanent magnet brushless AC machines, it is necessary to identify the initial rotor position prior to start-up the machine. Although saliency tracking based sensorless techniques are proven to be a good candidate to estimate the initial rotor position in sensorless control, magnetic polarity identification is another important issue. Since the machine saliency undergoes two cycles in single electrical period, the estimated position information based on machine saliency has an angle ambiguity of pi. With the aid of magnetic saturation effect, this paper proposes a robust initial rotor position estimation scheme, which utilizes both d- and q-axis carrier current, instead of only q-axis carrier current in conventional pulsating carrier signal injection based sensorless control algorithm. Finally, the experimental results confirm the effectiveness and robustness of the proposed method.