I-f Starting Rapid and Smooth Transition Method of Full-Speed Sensorless Control for Low Current Harmonic Ultra-high-speed PMSM

Inverter-side output LC filter is intended for current harmonics suppression in ultra-high-speed permanent magnet synchronous motors (UhsPMSMs). However, the control accuracy and reliability are degraded caused by voltage drop of this hardware filter. On that account, this paper proposed a second-order generalized integrator (SOGI)-based compensation strategy. Aiming at improving the full-speed range sensorless control performance of UhsPMSMs, I-f starting method is utilized for fast and stable startup to protect the air bearings of UhsPMSMs, and an extended back electromotive force (BEMF) observer considering voltage compensation is proposed to enhance position estimation accuracy. Furthermore, a new transition strategy based on adaptive gradient descent of reference electromagnetic torque (AGDRET) is proposed to realize rapid and smooth operation between two different control schemes. Finally, simulation results of a 100000 r/min, 10 kW UhsPMSM indicate that the proposed control scheme ensures less position estimation error and enhances the transition performance compared with traditional method.