Research On Maximum Torque-Current Ratio Control Method Of Permanent Magnet Synchronous Motor For Light Electric Vehicle

Permanent Magnet Synchronous Motor(PMSM)is widely used in high performance motor drive applications such as high speed train drive systems and electric vehicle drive systems because of its good controllability,wide speed range,high power factor,high torque at low speed and high energy utilization.In this paper,we analyze and study the improved control strategy of EV permanent magnet synchronous motor by combining PMSM mathematical model and Vector Control(VC)principle,and mainly carry out the experiments of PMSM vector control based on feedforward current compensation and motor control based on least squares parameter identification.Firstly,the background and significance of the research topic are explained,several structures and operation principles of permanent magnet synchronous motors are introduced,the mathematical models of motors in different coordinate systems are derived,the principle of Space Vector Pulse Width Modulation(SVPWM)for driving motors is explained,and the implementation and improvement of control algorithms for permanent magnet synchronous motors are The foundation is laid.The traditional double closed-loop vector control system for permanent magnet synchronous motor has a long adjustment time when the load changes because its speed loop cycle is much larger than the current loop,resulting in a large sudden change in speed.By observing the load torque,the current loop current is adjusted by the relationship between torque and current when the load torque changes,speeding up the response of the current regulator to the load.In both id=0 vector control and Maximum Torque Per Ampere(MTPA),the load feedforward compensation can reduce the speed fluctuation after the load changes.The feedforward current compensation based on the observed load torque can greatly reduce the speed fluctuation,but it cannot suppress the electromagnetic torque pulsation,which affects the positioning accuracy and servo performance of the motor,especially when the motor is running at low speed.Therefore,a compensation method based on the difference between the electromagnetic torque and the observed load torque is proposed,which can reduce the torque pulsation under different load conditions and take into account the suppression effect of load feedforward compensation on the speed pulsation.During the operation of the motor,the internal parameters of the motor may change due to the influence of the operating environment,resulting in deviations in the control algorithm of the MTPA formula method that relies on the motor parameters,and the problem of inaccurate control,the internal parameters of the motor are identified by the Recursive Least Square(RLS)method,and the accurately identified motor The MTPA algorithm control accuracy is improved by continuously inputting the identified motor parameters into the MTPA control,which has good dynamic response in the motor load addition and reduction experiments.In the MTPA vector control,the iterative MTPA control formed by the parameter identification is combined with the control strategy based on the torque difference to generate the compensation current to form the composite control,which reduces the speed pulsation when the load torque changes and the electromagnetic pulsation under different loads,and at the same time ensures the accuracy of the control algorithm.Experiments are conducted in RTU-BOX,a real-time digital control system,and the results are corroborated with Matlab/Simulink simulations to verify the effectiveness of the improved vector control algorithm.