Improved EEMF-Based Position Sensorless Control for Non-sinusoidal Back-EMF PMSMs

초록

A restricted number of the stator and rotor slots in PMSMs distorts the air-gap flux distribution and effective air-gap length. Such distortions result in varying machine parameters with rotor position. In particular, the rotor flux linkage harmonics cause a non-sinusoidal back-EMF, which introduces machine harmonic currents if PI current controllers are employed. As a result, it deteriorates the rotor position estimation performance in extended EMF (EEMF)-based sensorless control. This is because both sinusoidal machine current and back-EMF are assumed for the rotor position estimation. Such degradation of the angle estimation performance can result in controller trips due to overcurrent, especially in the case of step load changes. This paper presents a detailed modeling of the harmonic rotor flux linkage and voltage, and introduces virtual rotor flux linkage terms in the synchronous reference frame to simplify the harmonic voltage terms. From the harmonic voltage model, a harmonic voltage injection method is proposed in addition to conventional EEMF-based sensorless control. The proposed scheme can provide sinusoidal motor current control for entire operating conditions. Additionally, experimental results confirm that the proposed control method can achieve the improved performance of the EEMF-based sensorless control.

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