Sensorless PMSM Harmonic Suppression Strategy Based on PLL with Embedded Double Quasi-Proportional-Resonant Controllers

The model-based position estimation method is well-suited for sensorless permanent magnet synchronous motor (PMSM) drives in medium- and high-speed range. However, the current sampling error and the inverter nonlinearity cause 1st and 6th harmonics in the estimated position respectively, degrading the estimation accuracy. To address the problem, an improved phase locked loop (PLL) is proposed by embedding the double quasi-proportional-resonant (QPR) controllers. Owing to the AC-signal extraction capability of the QPR controllers, the position harmonics can be separated and eliminated by the investigated PLL without additional filters. The simulation results show that the proposed PLL can improve the position estimation accuracy effectively.