Research On Position Sensorless Control Of Permanent Magnet Synchronous Motor For Battery Electric Vehicle

In recent years,with the popularity of the Internet of things and intelligentization,new vitality has been injected into the automobile industry.The automobile industry is in the era of great change.Automobile electrification is the basis of intelligent cars,and it is also an effective measure to mitigate atmospheric pollution.Developing electric vehicles vigorously is not only in line with the national strategy but also conforms to the trend of the transformation and upgrading of the automobile industry.The driving motor used in BEV(battery electric vehicle),is the heart of it.Because of its advantages of simple structure,high power density and wide range of high efficiency,PMSM(permanent magnet synchronous motor)has become the main choice of driving motor used in BEV.The high dynamic performance and high efficiency control of PMSM used in automobile is crucial to the driving range,dynamics and safety of BEV,and also it is important to get the angle of the rotor position accurately.Generally,for the PMSM used in BEV,a resolver is installed to obtain the rotor position angle and rotation speed of it.At the same time,the use of mechanical sensors increases the cost and installation space,and it can also lead to poor system reliability,etc.In order to solve the above problems,position sensorless control technology of PMSM has become a research hotspot.This thesis studies the position sensorless control of permanent magnet synchronous motor for battery electric vehicle.First of all,the advantages of BEV are analyzed and then gives an overview of the drive system for BEV.Meanwhile,the common drive system forms of BEV are compared,and make an investigation and selection of driving motor of BEV.The current research status of position sensorless control for low speed,zero speed and medium to high speed of permanent magnet synchronous motors is reviewed in this section.In order to realize vector control of PMSM,the basic principle of SVPWM(space vector pulse width modulation)is elaborated in detail.What's more,the SVPWM algorithm of inverter is analyzed in detail and simulated by matlab/simulink.Then the mathematical model of PMSM in static three phase coordinate system and synchronous coordinate system is established,and the principle of vector control of PMSM is analyzed in depth.Subsequently,several vector transformation matrices and their variants are compared.According to the requirements of power and efficiency for BEV,the maximum torque current ratio(MTPA)is used to distribute the d/q axis current.The parameters of the current regulator and the speed regulator are adjusted.Finally,the simulation model of vector control system of PMSM is built.To solve the problem of poor accuracy or even failure of position sensorless control method based on the permanent magnet synchronous motor fundamental wave model in low speed or zero speed,pulsating high frequency current injection method is used.In this part,the advantages and disadvantages of various position sensorless control methods are discussed firstly.Then the basic principle of pulsating high frequency current injection method is deduced and analyzed.Also current regulator and position tracking observer are reconstructed and designed.To make a compensation of rotor polarity by the saturation characteristic of rotor permanent magnet,the voltage response of the pulsating high frequency current injection method based on the nonlinear saturation characteristic of the permanent magnet chain is analyzed and deduced.Furthermore,the rotor initial estimation system was designed and its convergence was analyzed in depth.Finally,the simulation model of the algorithm is built to verify the feasibility and effectiveness of the algorithm.The position sensorless control method based on pulsating high frequency current injection has the problem of poor estimation accuracy and the hysteresis is obvious at medium to high speeds.While the back EMF is large enough,so the model reference adaptive principle based on the fundamental wave model is used to solve the accuracy and dynamics of estimation system.In this part,the characteristics of model based position sensorless control methods are analyzed and compared.The basic principle of the model reference adaptive system and the system stability determination method are expounded.The reference model and the adjustable model are derived and then the nonlinear feedback system is constructed.The appropriate adaptive rule is constructed and the stability analysis of the nonlinear feedback system is carried out by the Popov hyperstability theory.To achieve position sensorless control over the full speed range of PMSM,a weighted hysteresis loop switching hybrid observer is designed.Finally,the algorithm simulation model is built and verified.A motor test bench is built ? Then the theoretical analysis,simulation research of sensorless control method and weighted hysteresis switching hybrid observer are verified by experiment in this thesis.