Novel Carrier Signal Injection Method Using Zero-Sequence Voltage for Sensorless Control of PMSM Drives

In this paper, a novel pulsating carrier signal injection strategy utilizing zero-sequence voltage is proposed for sensorless control of permanent-magnet synchronous machine (PMSM) drives. Different from the conventional zero-sequence carrier voltage sensing method using rotating signal injection in the stationary reference frame, the proposed pulsating injection is based on the estimated reference frame, which rotates anticlockwise at twice estimated rotor electrical angular speed. Then, the rotor position estimation is fulfilled via enabling the zero-sequence carrier voltage to zero. Compared with conventional rotating injection using zero-sequence voltage, the proposed strategy is simpler for signal demodulation and more robust to signal processing delays due to the fact that it is amplitude modulated by machine saliency and phase shifts of saliency position due to signal processing delays are intrinsically cancelled, which is the same as the classical pulsating injection in the estimated synchronous reference frame with carrier current sensing. Therefore, the proposed method can combine the synergies of zero-sequence method (i.e., high bandwidth and stability) and pulsating injection (i.e., increased accuracy and fast dynamic response). Furthermore, the cross-coupling magnetic saturation effects on zero-sequence voltage sensing-based sensorless control are discussed in detail. All the theoretical analyses are validated by experiments on a laboratory surface-mounted PM (SPM) machine.