A smooth transition method between position sensorless control algorithms of PM machines

This paper presents a method of smoothly transitioning between low-speed and high-speed position sensorless control algorithms of permanent magnet synchronous machines (PMSMs). The transition method estimates the load torque, synchronizes the estimated outputs of both algorithms, and then smoothly transitions from one algorithm to the other. This is achieved by commanding a calculated open-loop torque reference while the estimator that is taking over reaches steady-state. The effectiveness of the proposed method has been experimentally verified by transitioning between various low-speed and high-speed control algorithms using an 11-kW interior permanent magnet (IPM) motor.