Research On The Field Weakening Control Algorithm Of Spmsm For Wheel Motor Application

When operated in the constant power area, the PMSM need to raise rotor speedand reduce torque output by taking Field weakening control algorithm, which hasimportant influence on the PMSM system for wheel motor application. The systemdynamic response depends on the accuracy of the armature magnetic field controlledby field weakening control module and the ability to produce toque depends on theutilization of dc bus voltage. Current oscillation and lack of load capacity oftenoccur by taking traditional field weakening algorithm, especially for SPMSM. Thesystem can obtain very good robustness when taking traditional field weakeningmethods based on dc side voltage feedback or current lead phase angle control.This paper firstly introduces the principles of the PMSM system for wheelmotor application and analyzes the relationship between the motor parameters whenoperated in field weakening area. It provides a theoretical basis for proposing thefield weakening algorithm with current oscillation elimination function and toqueoutput increases function. By combining direct toque control and SVPWM method,a field weakening method is investigated which contains a flux estimation module toget the stator flux to calculate the expected voltage vector. The method is verified byusing Simulink software.Secondly, three adaptive field weakening control algorithms which caneliminate the current oscillation and have good dynamic response are investigated,including the fast adaptive method, voltage phase angle control method and feedforward predetermined method. This paper analyzes their principle and realizationmethods, set up the simulation model and conducts some experiments. Thepresented fielding weakening algorithms are verified.Thirdly, traditional current lead angle control method cannot obtain rapidlycurrent response and make full use of motors’ ability of torque output. An improvedmethod is proposed by taking an easy modulation method and a new way to obtaincurrent angle, considering the low utilization of dc bus voltage and the low accuracyof current lead angle. This paper analyzes the relationship between the current angleand motor parameters, sets up a simulation module and conducts a few simulationexperiments. It proves that this method can improve dynamic response and increasetorque output.Finally, a DSP-based PMSM system is designed and set up to verify andvalidate the effectiveness of the proposed field weakening algorithms. The hardwareconsists of the control circuit, power circuit and position decoding circuit. Thedesign of software includes the main routine and the main interrupt program. Based on the experimental platform, the feed forward control method and improved currentlead angle method based on minimum amplitude error of voltage vector are realizedrespectively. It shows that the field weakening algorithms investigated in this papercan effectively suppress current oscillation and increase torque output during thefield weakening control.