The Research Of Performance And Efficiency Optimization Control Of IPMSM Driven System Using Bidirectional Quasi-Z Source Inverter For Electric Vehicle Applications

With the rapid development of electric vehicles in the world,as the core part,the motor drive system has become a hot research at home and abroad.Electric vehicles are generally powered by batteries,due to the factors of battery technology,cost and volume constraints,the DC bus voltage in the conventional permanent magnet synchronous motor(PMSM)driven system for electric vehicles is usually low,and frequent fluctuations occur under complex conditions,large current discharged or even causes the battery terminal voltage drops,the power performance and system efficiency of driving motor are influenced seriously.Quasi-Z source inverter(QZSI)with unique impedance source network,can achieve the function of boost and inverter at the same time.Thus,in this thesis,the bidirectional quasi-Z source inverter(BQZSI)is applied to the permanent magnet driven system of electric vehicles,the performance and efficiency optimization control strategy of BQZSI-IPMSM system are studied deeply.Firstly,the research background and significance of the topic are described,and the research status of QZSI and efficiency optimization control are introduced.The mathematical model of PMSM and the working principle of QZSI are analyzed.The bidirectional QZSI is used to solve the abnormal working state,and the bidirectional energy flow is realized.Finally,the parameter design method of quasi-Z source network is given.Secondly,the small signal model of BQZSI is derived by means of the state space averaging method,the influence of quasi-Z source network parameters on the dynamic characteristics and stability of BQZSI is analyzed.The DC bus voltage control strategy based on input voltage feedforward and capacitor voltage feedback is proposed,a closed loop PID controller for capacitor voltage is designed,and the performances of the control strategy and controller are verified by simulation.Thirdly,on the basis of studying the traditional SVPWM and the shoot-through segmentation SVPWM modulation strategy,an improved 2 segmentation shoot-through SVPWM modulation strategy is proposed.The output limit of inverter and the typical operation curves and control strategy of IPMSM are analyzed in detail.According to the running characteristics and the actual demands of IPMSM driven system for electric vehicles,a simple and practical regulation strategy for DC bus voltage of BQZSI is proposed,to enlarge the speed range of constant torque of motor.The correctness and effectiveness of the proposed method are verified by simulation results.Finally,the efficiency optimization integrated control of BQZSI-IPMSM driven system for electric vehicles is used,when the system is in steady state,the optimal ratio method of loss model is used to obtain the sub-optimal value of direct axis current first,then with this value as the searching initial value,an improved golden section algorithm is used to find the best system operating point.The dynamic current distribution is also added to improve the torque response speed of the motor.Simulation results show that efficiency optimization integrated control can effectively improve the dynamic performance and steady-state efficiency of system.