Sensorless vector control of PMSM using sliding mode observer and fractional-order phase-locked loop

A sliding mode observer and fractional-order phase-locked loop (FO-PLL) method is proposed for the sensorless speed control of a permanent magnet synchronous motor (PMSM). The saturation function is adopted in order to reduce the chattering phenomenon caused by the sliding mode observer. In this proposed FO-PLL method, a regulable fractional order r is involved, which means that the FO-PLL provides an extra degree of freedom, and by selecting a proper fractional order r a better performance may be achieved. In fact, the conventional phase-locked loop (PLL) applied in sensorless PMSM control can be seen as a special case of the proposed FO-PLL. The computer simulation results demonstrate the effectiveness of the proposed method.