Study On Current Source Inverter Applied To Electric Vehicle

Motor drive system is the core of electric vehicle research,and most of previous researches are focusing on voltage source inverter.However,with the improvement of electric vehicle performance,the requirements are becoming higher and higher on the speed output range,motor high-speed drive characteristics,drive system efficiency,and automotive-grade reliability.The defects on voltage source drive system’s structure cannot meet the demands.Therefore,the studies on current source inverter with boost characteristics have become hotter in the word.It can adapt to the occasions that input voltage changes.Current source inverter uses inductor as energy storage components to achieve over-current protection and short circuit protection.Besides,it allows the same bridge upper legs and lower legs to conduct at the same time for obtaining higher reliability.But,while the current source inverter is used in electric vehicle motor drive system,there are still some new problems need to paying attention.In this paper,the current source inverter used in electric vehicles has been deeply studisd:Based on the vector control method of voltage source inverter,a mathematical model of current source inverter has been founded in three-phase stationary coordinate system,two-phase stationary coordinate system and synchronous rotating coordinate system.On the base of rotor field orientation control method,the dynamic mathematical model of induction motor is established and modified to adapt to the current source type power supply,which lays the theoretical foundation for further research on current source motor drive system.Secondly,a three closed loop control system is designed for the characteristics of current source motor drive system.Based on rotor field orientation control,the feedforward decoupling compensation terms are calculated.In order to ensure the dynamic response and steady state performance of the system,this paper designs voltage loop,current loop and velocity loop.According to the requirements of each loop,the parameters of the controller of each loop are set up by using the standard of typical type I system and typical type II system respectively,and the performance of the control system in wide range is improved.In order to avoid the parallel resonance produced by the filter capacitor and the motor stator inductance,and to improve the stability of the system,this paper uses active damping method to correct the voltage loop regulator parameters.Thirdly,a direct SVPWM modulation algorithm for current source inverter is designed,which avoids the complicated function operation and greatly improves the calculation speed.Aim to solve the problem that the DC inductor current is not controllable in the current source inverter modulation strategy,this paper analyzes the instantaneous state of the inductor current,improves the current source type motor drive system topology,and deduces the stable conditions of the DC bus given current.By the requirements of system performance,this paper designes the value range of DC side inductance parameters and filter capacitor’s parameters.Then,by simulation analysis of the influence of different filter capacitor’s values on the system performance.This paper verifies the correctness of the designed parameters.On the basis of simulation analysis,the experiment is carried out with the induction motor with rated power of 3kW.Simulation and experimental results demonstrate the correctness and feasibility of the modulation strategy and control scheme described in this paper.The research results have strong guiding significance for the application of current source PWM inverter in the future electric vehicle market.