Research On Modulation Strategy For Three-Phase Vienna Rectifier Zero-Crossing Distortion

The energy crisis and environmental pollution have been two great problems perplex the car industry.To overcome the issue,vigorously promoting electric vehicle has become an effective solution.As a basic equipment of the electric vehicle’s energy supply,the performance of charging pile has a significant impact on the development of the electric vehicle industry.Nowadays,the DC charging pile has been widely used owing to its fast-charging speed and high output power.But there are still some problems need to be solved,for example,the front-stage rectifier has the disadvantages of low-power factor as well as serious harmonic pollution and so on.Therefore,it is of great significance for improving the DC charging pile performance to increase the power factor of the front-stage rectifier and reduce the harmonic distortion.Because of its high efficiency,high power density and low cost,the three-phase Vienna rectifier has become the key equipment which is used to convert AC power to DC power in the DC charging system.However,the rectifier has the inherent problem that the zero-crossing distortion of ac-side input current,if this problem is not to be solved,the harmonic content of input current will be increased and the power quality will be deteriorated.Hence,this paper has focused on the three-phase Vienna rectifier and discussed the key aspects,including the operation principle,modulation strategies as well as the ac-side current distortion and so on.Firstly,this paper has presented the research status and technical features of the PWM rectifier,then the advantages and disadvantages of various types of PWM rectifiers are compared.The operation principle of three-phase Vienna rectifier and two kind of modulation strategies which are CBPWM as well as SVPWM have been emphatically analyzed.In this paper,the zero-crossing distortion of input current of three-phase Vienna rectifier based on CBPWM modulation has been studied.Firstly,the mechanism of zero-crossing distortion of input current and its concrete performance in this modulation method have been analyzed.In order to reduce the switching loss,the intermittent mode control of CBPWM modulation is realized by zero sequence component injection which will aggravate the zero-crossing distortion of input current.Therefore,based on continuous mode and intermittent mode of CBPWM modulation,the methods of eliminating zero-crossing distortion of input current are presented.This paper has analyzed the performance of zero-crossing distortion of input current in SVPWM modulation.In order to solve the problem of zero-crossing distortion caused by wrong vector action,a five-segment control method has been proposed to avoid the wrong vector action,by which way solving the phenomenon of zero-crossing distortion of input current.A hybrid control mode of five-segment and seven-segment control has been further proposed,which not only can eliminate the zero-crossing distortion of input current,but also enable the Vienna rectifier to balance the neutral point potential.Finally,the paper has designed simulation and experiment based on VIENNA rectifier.An engineering prototype of VIENNA rectifier is developed by MATLAB/SIMULINK,and the specific design methods of hardware and software have been given.Simulation analysis and experimental verification have been carried out for the proposed zero-crossing distortion improvement method,and the zerocrossing distortion phenomenon has been eliminated.