Improved Voltage Flux-Weakening Strategy of Permanent Magnet Synchronous Motor in High-Speed Operation

Abstract

This paper presents an improved voltage flux-weakening strategy of a permanent magnet synchronous motor (PMSM) in a high-speed operation. The speed control performance using voltage flux-weakening control is not affected by the motor parameters, so it is used in various motors for high-speed operations. In general, the voltage flux-weakening control uses voltage references to generate a flux axis current reference. However, there may be errors between the voltage reference and the actual voltage flowing into the motor. This causes an error in the current reference generation and reduces the efficiency of the inverter and motor due to the use of more current. In this paper, the problems that can occur due to voltage errors were analyzed through theoretical approaches and simulations, and improved voltage flux-weakening control to resolve these problems was presented. This method’s advantage is that the error between the voltage reference and the voltage applied to the motor can be minimized, and the target speed can be reached with minimum current. As a result, it was possible to increase the energy efficiency by reducing the amount of current flowing through the motor. The effect of the improved voltage-based flux-weakening control method was verified through simulations and experiments. As a result, the voltage errors were reduced by approximately 2.16% compared to the general method. Moreover, the current used in the field-weakening control region was reduced by up to 27.17% under the same torque condition.