Research On Electric Vehicle Drive System Based On Bidirectional Quasi Z Source Inverter

In recent years,problems such as global warming and air pollution have become increasingly prominent.The exhaust emissions of fuel-fueled vehicles are one of the main sources of air pollution.Therefore,accelerating the development of new energy vehicles is a key measure to solve the problem of air pollution.Among them,electric vehicles have become a promising research area in the field of new energy vehicles due to their low cost,simple structure and low noise.However,the complex working conditions such as starting,accelerating and climbing of electric vehicles will cause sudden changes of motor load torque and battery terminal voltage,which will affect motor output performance and battery service life.To solve this problem,a novel electric vehicle drive system based on bi-directional quasi-z-source inverter is designed.Aiming at the problems of large overshoot and poor robustness in the traditional PI control of the speed loop,this thesis designs an active disturbance rejection controller for the speed loop,and introduces the first-order active disturbance rejection controller into the speed loop control link to solve the problem of overshoot and rapidity.Contradiction,while having stronger anti-interference ability.Aiming at the problem of DC bus voltage oscillation of bi-directional quasi-z-source inverter,a DC side control strategy is designed to stabilize the DC bus voltage,and improves the system efficiency and reduces the switching loss by improving the space vector pulse width modulation algorithm.The main research contents of this thesis are as follows.The first part of this thesis introduces the current domestic and foreign research status of the motor control algorithm,Z-source inverter topology and control strategy in the electric vehicle drive system,analyzes and summarizes the application of the control strategy in the electric vehicle drive system.The second part explains the principles of the DC side and the AC side of the drive system,namely the bidirectional Z inverter and permanent magnet synchronous motor,and establishes a mathematical model.Firstly,the mathematical model of permanent magnet synchronous motor mathematical modeling and coordinate transformation is introduced,which lays the foundation for the realization of the following permanent magnet synchronous motor vector control;then,the converter suitable for electric vehicle drive system—bidirectional quasi-Z source inverter is selected.,Analyzed its structure and working principle in detail,and established the small signal model of the bidirectional quasi-Z-source inverter using the state space averaging method;finally introduced the principle and mathematical model of the active disturbance rejection controller,and established the simulation model of the three modules(tracking differentiator,extended state observer and nonlinear state error feedback control law)are simulated and verified.In the third part,the control strategies for the DC side and AC test are designed for the drive system.First,the vector control and direct torque control are compared and analyzed,and the principle and framework of id=0 vector control are explained.Secondly,the traditional SVPWM modulation algorithm is explained,and an improved SVPWM modulation algorithm is proposed based on this.Then based on the small signal model of the bidirectional quasi-Z-source inverter,the dynamic characteristics of the bi-directional quasi-Z-source inverter are analyzed,and the DC bus voltage control strategy suitable for the battery pack terminal voltage feedforward of the drive system is designed.Finally,for the PI controller to control the permanent magnet synchronous motor,which cannot meet the operating problems of electric vehicles under complex operating conditions,a first-order active disturbance rejection controller of the speed loop is designed,so that the speed can reach the desired value quickly without overshoot,and improving disturbance rejection significantly.The fourth part is the simulation verification of the control strategy of the drive system.A MATLAB/Simulink simulation model is established to verify the proposed control strategy.Through the analysis of the simulation results,the simulation results of the improved SVPWM are consistent with the theoretical analysis results.The dynamic response speed and anti-interference ability of the speed loop active disturbance rejection controller are significantly better than the PI controller,and the DC bus voltage control strategy has achieved good control The effect proves the superiority of the designed drive system control strategy.Moreover,under the same conditions,the DC side voltage control system with the active disturbance rejection controller has a better control effect and strong anti-interference ability,which can effectively ensure the driving stability of the electric vehicle.This thesis provides new and higher-quality solutions for the design of electric vehicle drive systems,and has important theoretical value and engineering practical significance.