Permanent Magnet Synchronous Motors For Vehicles Are Based On Efficient Control Of Optimal Flux Linkage

Permanent magnet synchronous motor is widely used in the field of electric vehicles because of its simple structure,light weight,small size,high power density and high efficiency.The operation performance of vehicle permanent magnet synchronous motor is affected by many factors,such as large load variation,more external interference and time-varying system parameters.In order to improve the system performance of vehicle permanent magnet synchronous motor,the control technology of PMSM needs to be further improved.Direct torque control has the advantages of simple structure,fast torque response,direct control method,etc.Sliding mode variable structure control is a kind of nonlinear control technology.It has certain anti-interference ability to the change of internal parameters and external disturbances of the control object.Therefore,this paper adopts a control method combining direct torque control and sliding mode theory to reduce the torque ripple of vehicle permanent magnet synchronous motor and improve its control performance.Then,combining the search method with motor loss model,an efficiency optimization strategy based on model search is proposed to further improve the control performance of vehicle permanent magnet synchronous motor(PMSM).The main contents of this paper are as follows:(1)Firstly,the general situation and development status of vehicle PMSM drive system are introduced.Several schemes of PMSM under vector control strategy and direct torque control are briefly described,and several commonly used methods to optimize the efficiency of PMSM system are given.Then based on the mathematical model of PMSM in ABC three-phase stationary coordinate system,according to the principle of space coordinate transformation,the mathematical model of permanent magnet synchronous motor is simplified by Clark and Park coordinate transformation.Then the basic theory of DTC and the traditional DTC implementation process are expounded.Explain its advantages and disadvantages;then study the principle of SVPWM and build its simulation model.(2)Subsequently,the basic idea and design requirements of sliding mode variable structure control are studied and analyzed.The design process of sliding mode surface function,basic satisfying conditions and sliding mode reaching law in sliding mode variable structure are described in detail.The sliding mode variable structure control idea is introduced into permanent magnet synchronous motor control system,and a direct torque controller based on sliding mode is designed.The stator flux linkage and electromagnetic torque of the control motor are connected.This method eliminates the decoupling problem in traditional vector control,and also solves the shortcomings of traditional DTC such as unstable switching frequency and large torque ripple.The validity and correctness of the proposed strategy are proved by the simulation experiment of MATLAB/Simulink.(3)Then,on the basis of sliding mode direct torque controller,an efficiency optimization control strategy of permanent magnet synchronous motor based on search method is proposed.The principle of golden section algorithm and the process of how to select the optimal flux linkage are introduced in detail.This method does not need motor parameters,and the control accuracy is not affected by the time-varying parameters of the motor.At the same time,it also covers the analysis of the loss of the inverter.The purpose of optimizing the efficiency of the whole electric drive system of permanent magnet synchronous motor is achieved by using these methods.Similarly,the feasibility of the proposed method is verified by the simulation experiment of MATLAB/Simulink.(4)Finally,aiming at the efficiency optimization control method of permanent magnet synchronous motor(PMSM),an efficiency optimization control method based on model search is proposed,which combines the efficiency optimization control strategy of PMSM based on search method with the loss model of PMSM.This method eliminates the tedious parameter tuning process of the traditional minimum loss control strategy,and does not need to rely on sampling feedback value to search like the search method control strategy.It speeds up the search process.At the same time,it not only has the rapidity of the minimum loss control strategy,but also considers the system efficiency,so that the vehicle permanent magnet synchronous motor drive system achieves the requirements of high efficiency and fast response.Finally,a simulation model is established by using MATLAB/Simulink to verify the effectiveness of the proposed strategy.