Field-weakening Control of PMBM Based on Instantaneous Power Theory

Since high density permanent magnet brushless motor (PMBM) used in electric vehicle (EV) takes the specialty of permanent magnet synchronism motor (PMSM) in high speed range and brushless DC motor (BLDC) in low speed range, there are similar trapeziform back EMF in PMBM. To complete real-time and reliable control for EV, it is impossible to use complex control strategy. Because of the limitation of DC bus, it is difficult to obtain perfect performance in high speed with traditional square current advanced. This paper presents a method of field-weakening control with square current based on instantaneous power theory, in order to handle difficulty of high density PMBM in high speed. Differ to traditional phase advance of square current for field-weakening control of PMBM, instantaneous power theory for field-weakening control can easily obtain wider speed range and good performance, without change current wave and without complex vector transform. This method takes control strategy includes two sides: maxim torque per ampere control method in low speed field and constant power field-weakening control in high speed Held. Experiment result shows that there are higher performance in all speed range and high reliability and safety used in EV.