Flux-weakening strategy for high speed PMSM for vehicle application

Abstract

High speed Permanent Magnet Synchronous Motors (PMSM) are used in electrical vehicles because of their strong power density. The high speed implies a big electromotive force and requires flux-weakening. Usual control algorithms do flux-weakening by adding negative Id current when the required voltage by the current regulation exceeds the maximum voltage depending on the battery. If the magnet can be totally defluxed then it is better to use a Maximum Torque Per Volt (MTPV) strategy. Furthermore there is no speed regulation in the control and the driver gives a torque reference that has to be limited to the reachable operating points; the battery power limit has to be taken into account in addition to the voltage and current limits. The d-q current reference are calculated to minimize the total current magnitude required to reach the reference torque. This paper presents a salient pole PMSM control that calculates the minimum magnitude current references to obtain the reference torque while respecting the voltage, current and power limits with a flux-weakening strategy and including MTPV operation in a unified algorithm. The effectiveness of the proposed method is observed through simulations.