PMSM Sensorless Control Based on Position Estimation Correction Using All-Pass Filters

Abstract

This paper proposes a novel flux estimation method for the position sensorless control of permanent magnet synchronous motors (PMSMs). In general, the stator flux linkage for position estimation in PMSMs is obtained using the pure integration of voltages. The infinite DC gain of the pure-integrator, however, causes numerical drifts in the obtained stator flux linkage due to the DC offset in the input of this integrator. To address this problem, a quasi-integrator is often substituted instead of the pure integrator to restrict the DC gain, leading to another problem in which the phase characteristics vary according to the operating frequency. As a result, the ideal phase characteristics (-90° constant) cannot be held, and the position estimation performance deteriorates.  Therefore, this paper proposes a phase characteristic correction method for quasi-integrators using all-pass filters (APFs), which achieves extremely precise estimation under transient conditions as well as in steady state.