The Sensorless Control System Of Air Conditioner Permanent Magnet Synchronous Motor For Electric Vehicle

With the increasing consumption of oil and energy by conventional fuel vehicles and the growing problem of exhaust pollution,most countries around the world have issued declarations to ban the sale of conventional fuel vehicles from around 2025.New energy vehicles are gradually being pursued by the car-making forces,and from the perspective of green sustainability,pure electric vehicles are undoubtedly the best choice.In this study,the air conditioning motor of a pure electric vehicle is chosen as the object of research.As the internal working environment of the air conditioning compressor of an electric vehicle is at high temperature and strong corrosion,and the vehicle is prone to bumps when driving under poor road conditions,it is difficult to detect the rotor position and speed by installing various sensors inside the motor,so a sensorless control algorithm is used to carry out the research.Firstly,the thesis introduces the structure and operating principle of modern permanent magnet synchronous motors,defines the basic mathematical model of PMSM(Permanent Magnet Synchronous Motor)in different coordinate systems,elaborates the control theory of the SVPWM(Space Vector Pulse Width Modulation)algorithm and constructs a vector control model of PMSM for verification.Then,in order to address the problem that the permanent magnet synchronous motor for pure electric vehicles is subject to frequent changes in operating conditions,limited installation space and harsh working environment,which leads to the reduction of the accuracy of mechanical sensors in detecting the motor rotor signal,the thesis proposes the method of injecting high frequency voltage signals into the straight shaft of the motor during the low speed phase of motor operation,detecting the high frequency signals in the system and analysing them to achieve The results show that the method can accurately estimate the rotor position information in the low speed stage and the system runs smoothly.In the medium and high speed stages of motor operation,a modified SMO control system is proposed,in which the discontinuous switching function is improved and the rotor position information is estimated using a phase-locked loop technique,and a fuzzy PI algorithm is used to control the rotor speed loop in the PMSM vector control system to further improve the stability of the system.A simulation model is then constructed to verify the rotor position and speed information in the medium and high speed operation stages.The results show that the method is more accurate in estimating rotor position and speed information during the medium and high speed operation phases.Finally,a weighted algorithm is proposed to achieve smooth switching of the motor under the joint control of the high-frequency voltage injection method and the improved SMO control method,so that the motor can accurately estimate the rotor position information during the full-range running phase;secondly,an experimental platform based on the STM32F407ZGT6 microcontroller control is constructed,and the design of the hardware and software modules is completed;finally,the simulation model and the experimental platform are used to The results show that the proposed composite control algorithm can effectively achieve smooth switching of the motor in the full-speed running phase,and the system has good stability.