A Novel Third-Order PLL-Based Sensorless Control Method for TSSM in Zero and Low-Speed Operation

In this paper, a rotor position estimation method based on secondary harmonic self-injection is proposed for sensorless control of the three-stage synchronous machine (TSSM) in the zero and low-speed range. The second-order generalized integrator (SOGI) is employed as a filter for the accurate response signal extraction, and an advanced third-order phase-locked loop (third-order PLL) is proposed to replace the conventional phase-locked loop with a PI regulator cascaded with an integrator (PI-PLL). Then, the steady-state error of the estimated rotor position during the acceleration procedure can be eliminated, and the anti-disturbance performance of the system is enhanced. Finally, the effectiveness of the proposed method is verified by simulation.