Angle compensation based rotor position estimation for sensorless vector control of the permanent magnet synchronous motor

Abstract

This paper proposes a new sensorless method for estimating the mechanical speed and rotor position of the Permanent Magnet Synchronous Motor (PMSM). A voltage sensor is employed to measure the terminal voltage of the inverter. The phasor of the measured terminal voltage (phase-A) of the inverter has the same angular frequency as that of the back electro-motive force (emf) of the PMSM. Therefore, the angular frequency of the measured terminal voltage is used for computing the rotational speed of the PMSM. A simplified dynamic angle compensation term is derived that calculates the phase/angle shift between the terminal voltage phasor and the back emf phasor. The calculated phase/angle shift (angle compensation) in terms of time is then used to time-shift the terminal voltage phasor to obtain the exact rotor position of the PMSM. This proposed method does not require any complex estimation/observer based algorithm. The estimated rotor position and mechanical speed are employed for the vector control of the PMSM. A 1 kW laboratory prototype is developed and tested to assess the effectiveness of the proposed method. The proposed rotor position estimation approach is capable of estimating the rotor position with less than 1% error and consequently, tracks the reference speed with less than 0.1% steady-state error.