Research On The Neutral-Point Voltage Balancing Control And Input Current Distortion Suppressing Technology Of The Vienna Rectifier

The application of electric vehicle(EV)becomes more and more widely because of its zero emissions,low noise,high energy efficiency and other advantages.The charging facility is an important part of EV,thus the rapid development of electric vehicles will accelerate the increase of demand for the charging facilities market.For the EV charging equipment,it is essentially an AC to DC converter.The three-phase Vienna rectifier has a series of advantages such as high performance,high power factor,high power density and high efficiency,and has been widely used in EV charger.However,the neutral-point voltage fluctuation and the current distortion of Vienna rectifier will seriously affect the performance of the rectifier.So this article analyzes the operating principle of Vienna rectifier,establishs the mathematical model and equivalent circuit,and then puts forward the control strategys of suppressing neutral-point voltage unbalance and improving current distortion,and finally by the simulations and experiments verifies the effectiveness of these strategys.In this paper,the topologies and control techniques of three-phase rectifier at home and abroad are briefly reviewed.And then the main research methods of the modulation methods and the neutral-point voltage balance control technology of Vienna rectifier are investigated.And the background and purpose of research are introduced,and the basic structure of this article is also presented.Secondly,the operating principle of three-phase/wire/level Vienna is analyzed,and mathematical models are established in both natural coordinate and the d-q synchronous reference frame.The expressions of main variables are deduced.The voltage and current stress of the switching device are calculated,which provides guidance for selecting the appropriate switching device.Thirdly,the space vector pulse width modulation principle of Vienna rectifier is analyzed.The traditional three-level space vector modulation(SVM)method and the two-level space vector modulation method are researched,and the intrinsic relationship between these two is analyzed.The reason of the neutral-point voltage oscillation is analyzed qualitatively,and the fluctuation caused by the small vector and the medium vector are calculated quantitatively.A control strategy for suppressing the fluctuation of the neutral-point voltage is proposed,and the effectiveness of the strategy is verified by simulations and experiments.Finally,a conventional dual-carrier pulse width modulation(CB-PWM)method of Vienna rectifier is studied.A carrier pulse width modulation strategy with voltage compensation is proposed to solve the distorted input current waveform.The correctness of the theoretical analysis and the validity of the proposed strategy are verified by constructing the simulation model and experiments.