Modeling, Analysis, and Suppression of Demagnetization for MTPA-Driven Permanent Magnet Motors With Distributed Windings

This paper presents novel modeling, analysis, and suppression methods for the demagnetization fault in maximum torque per ampere (MTPA)-driven permanent magnet motors (PMMs) with distributed windings. Firstly, a novel structural-mathematical technique is employed to formulate the analytical model (AM) for PMMs under a demagnetization fault. Unlike traditional AM methods, the proposed approach considers the motor structure specifically designed for the motors with distributed windings. Additionally, the new model takes the MTPA control method into account, which is well-suited for analyzing the impacts of demagnetization fault on the motor control performance. Secondly, a quantitative analysis of the demagnetization impacts on back-electromotive force (EMF) and MTPA current, based on the proposed AM, is presented. Thirdly, to suppress demagnetization fault in MTPA-driven PMMs, a novel loss optimization-based control strategy is proposed. It utilizes predictive control principles and optimization theory to optimize losses, thus reducing the risk of demagnetization caused by temperature rise. Finally, the proposed AM and suppression strategy are validated by both finite element simulation and experiment conducted on a PMM prototype with 24 slots and 4 poles.