Quasi‐discrete modelling of PMSM phase currents in drives with low switching‐to‐fundamental frequency ratio

Abstract

This study proposes a new quasi-discrete approach to modelling the permanent magnet synchronous motor (PMSM). The quasi-discrete modelling reflects the impact of continuous rotor movement, which takes place during a control cycle, on the shape of motor current waveforms. This provides much improvement in current modelling accuracy under inverter low switching-to-fundamental frequency operation. The proposed approach may be used in predictive control to compute current at forthcoming instants or in classical control to improve precision of determining mean current feedback. The superior accuracy of the quasi-discrete model is confirmed by simulation and experiment for an exemplary PMSM drive operating at inverter switching frequency of 5 kHz and fundamental frequency reaching 400 Hz.