Flux-Weakening Control for Permanent Magnet Synchronous Motors: A Systematic Review of Challenges, Fundamentals, and Strategies

A permanent magnet synchronous motor (PMSM) is widely used in different scenarios such as electric vehicles, rail transit systems and so forth, due to its distinct advantages including high power density, high efficiency and high reliability, especially its wide speed range. However, as its rotational speed increases until it reaches the base speed, it will be constrained by the increasing back electromotive force (EMF) and the inverter’s voltage limit. To address this bottleneck, the flux-weakening control (FWC, i.e. weak magnetic control) technology is developed to weaken the air-gap magnetic field by regulation of the d-axis current. This article provides a systematic review of FWC issues, including the main challenges faced by FWC, the basic principle of FWC, the classic FWC strategies and the innovative FWC strategies. Finally, this article summarizes and compares characteristics and the applications of different FWC strategies mentioned in the references, in order to provide the reference for the further research and the development of FWC technology.