Study On Flux-weakening Control Strategy Of PMSM For Electric Vehicles

As a common means of transportation,small fuel vehicle is greatly convenient to people's lives,but the fossil fuels used in their power systems have also brought about certain environmental pollution problems.As a kind of clean energy that is economical,practical,easy to convert and control,electric energy can act as an alternative energy source for fossil fuels in theory.However,due to the insufficiency of battery energy storage technology,it can't accord with the requirements of long-term operation of electric vehicles.Therefore,it is imperative to find a low-power motor to reduce the consumption of electric energy.PMSM have many special advantages such as low power consumption and low power density,which meet the requirements of electric vehicle drive control systems.In this paper,the PMSM used in electric vehicles is considered as the research object,besides the control method of which is studied.A flux-weakening control strategy for PMSM used in electric vehicles is proposed.The main work of this thesis is as follows:1.The developing background and research status of PMSM in electric vehicle field are introduced.The control strategy and application field of PMSM for electric vehicle mainly include the development of motor selection and control method,and include its flux-weakening control.The significance of the system research and research status at home and abroad of the PMSM about flux-weakening control and the position sensor-less key technology are summarized.2.The structure,dynamic mathematical model and coordinate transformation principle of PMSM is explained.The mathematical model of PMSM under distinctive coordinate structures is established,and the principle of space vector pulse width modulation(SVPWM)technology is briefly analyzed.The vector control system of PMSM is established,and the corresponding simulation model is built in MATLAB/simulink for analysis.3.The principle of flux-weakening control for permanent magnet synchronous motor is studied.A method of flux-weakening control for built-in permanent magnet synchronous motor is proposed,which includes the maximum torque-current ratio below the base speed and the judgment of two flux-weakening regions above the base speed.The methods of estimating rotor position by sliding mode observer under sensorless permanent magnet synchronous motor are analyzed and compared.4.According to the proposed flux-weakening control method and sensorless sliding mode observer control method of permanent magnet synchronous motor,a simulation model is built in MATLAB/simulink.The simulation results of permanent magnet synchronous motor with position sensor and without position sensor are compared to verify the feasibility of the control method.5.The hardware structure and software realization process of PMSM are determined.The hardware part mainly includes control board,power drive board,switching power supply and PMSM.The software part includes main program,vector control subroutine and flux weakening interrupt subroutine.According to the control strategy,the hardware experiment platform of the control system is built.The software part of the control system is programmed in the CCS integrated development environment is implemented,and the research content of this thesis is verified according to the experimental results.