Research On Current Distribution Strategy Of Permanent Magnet Synchronous Motor

With the development of industrialization,people’s living standards are increasing day by day,but people have to face the environmental protection problems.In response to the increasingly serious air pollution problem,various countries have taken relevant measures to reduce the emission of polluting gases,and vigorously developing pure electric vehicles is one of the most important measures.Pure electric vehicles are also favored by various countries because of their advantages of high energy efficiency,relatively simple structure and zero emissions.As the power source of pure electric vehicles,the driving motor’s control performance directly determines the overall performance of electric vehicles.Therefore,it is very important to study the control strategy of electric motors.Due to the characteristics of simple structure,small size and higher power factor of Permanent Magnet Synchronous Motors,they are widely used in China with the largest reserves of rare earth resources in the world.This article takes the built-in PMSM as the research object,the main purpose is to improve the speed regulation performance of the motor,widen the speed regulation range of the motor,and improve the torque output capability of the motor.In order to achieve the above purpose,this thesis focuses on the analysis and research of the Maximum Torque per Ampere control strategy of the built-in PMSM and the control strategy of the motor in the field weakening region.First of all,this thesis introduces the mathematical model of PMSM in three different coordinate systems,tells the principle of coordinate transformation and the basic principle of Space Vector Pulse Width Modulation,and briefly introduces several different control strategies of vector control,and analyzes the advantages and disadvantages of different control strategies.Secondly,the thesis compares with different control strategies of the motor under the base speed,and chooses MTPA control strategy for the control below the motor base speed.Based on this,the thesis analyses the shortcomings and deficiencies of the traditional MTPA control strategy,and choose the segmented fitting method to optimize it.This way meets the requirements of fitting accuracy,reduces the calculation difficulty of the system.In order to avoid the influence of parameter changes on the current distribution during motor operation,the current is compensated using variable step search,and these all achieve the application of the MTPA control strategy in engineering practice.At the same time,this thesis also studies the field weakening control technology of the PMSM,and introduces the speed-up process after the motor terminal voltage is saturated.When the output torque is maximized,the fieldweakening control strategy such as Maximum Torque per Volt and iq-axis voltage feedback performs field-weakening control is adopted to control the motor,which widens the operation area of PMSM and increases the current utilization ratio.At last,the motor control system model is built in MATLAB/Simulink and the system is simulated,and it shows that the method adopted in the thesis is feasible.