Research On Modulation And Closed-loop Control Of Current Trans-quasiZ-source Inverter For Electric Vehicles

Current-fed Trans-quasiZ-source inverter(current-fed Trans-qZSI)is a single-stage inverter with buck-boost function and it can realize energy bidirectional flow.While further reducing the number of components,the use of coupled inductors can increase the output voltage range and has the advantages of improving the reliability,efficiency,and power density of the electric vehicle drive system,and has great potential for development.Firstly,the research significance and status quo of current-source inverters are introduced.The topology,principle,advantages and disadvantages of several main Z-source inverters are analyzed,and the topology and different working modes of current-fed Trans-quasiZ-source inverters are analyzed.A detailed analysis of the study was performed.Then,the modulation method of current-source inverter is introduced,and the SVPWM modulation technology of current-fed Trans-qZSI in step-up and step-down mode is deduced in detail.The modulation method of current-source inverter is introduced,and the SVPWM modulation technology of current-fed Trans-qZSI in step-up and step-down mode is deduced in detail.In order to reduce the inductor current ripple on the DC side of the current-fed Trans-Z source inverter and reduce the total harmonic distortion(THD)of the inverter output current,an optimized SVPWM modulation strategy is proposed.This strategy segments the short-circuit zero state,the open-circuit zero state,and the active time of the two active states and arranges them within each carrier cycle to reduce the maximum short-circuiting time and the maximum open-circuit time,thereby reducing the DC-side inductor current ripple and output current THD.The open circuit and short-circuit zero vector are respectively designated for each sector,so that only one switching action is performed f'or the inverter open state and the adjacent state transition.The DC side inductor ripple and output current harmonic distortion ratio(THD)were compared between the optimized SVPWM modulation strategy and the other three different SVPWM modulation strategies through Matlab/Simulink simulation model and physical experiments.Simulation and experimental results show that the use of an optimized SVPWM modulation technique can reduce the DC inductor current ripple and output current THD of the current-fed Trans-quasi-Z-source inverter and improve the performance of the inverter.Finally,the current-fed Trans-quasiZ source inverter-driven permanent magnet synchronous motor is studied.In order to solve the problem of the closed-loop system of traditional current-fed inverters under light load conditions,the harmonic distortion of the output current is large because the modulation factor M is too small.Based on the current-fed Trans-qZSI,a closed-loop control method for constraining the modulation factor at light load is proposed.When the current-dependent modulation factor is smaller than a given minimum modulation factor Mmin,the current is constrained so that the constrained current corresponds to the modulation factor as Mmin,and closed loop mode control is achieved by adjusting the open circuit duty cycle Dop.The simulation results verify the correctness of the theoretical analysis.