Development Of Vienna Rectifier Considering Neutral Voltage Balance

The development of power electronic technology brings prosperity of power electronic equipment.In the background of vigorously promoting electric vehicles,the demand for charging equipment(rectifier)is growing.Three-phase Vienna rectifier has the characteristics of three-level rectifying,low harmonic pollution,which has a good engineering application prospect.The main content of this paper is to design and manufacture a VIENNA rectifier based on OCC method.The VIENNA rectifier has a characteristic of rippled voltage of its neutral point.Based on the mathematical model of Vienna rectifier,this paper uses the constraint formula to eliminate the neutral voltage ripple,and Average-Voltage-Loop is added to control its neutral voltage.Simulation results and experimental results verify the effectiveness of this method.Firstly,the paper introduces the topology working principle and control strategy of three-phase rectifier Then,taking VIENNA rectifier as the research object,the paper analyzes its working principle and mathematical model in natural coordinate system;expounds the concept of unit power factor rectifying which is the target of rectifier;introduces two modulation methods of VIENNA rectifier:space-vector-pulse-width-modulation(SVPWM)and one-circle-control(OCC)method.The control strategy and characteristics of two modulation methods applied to VIENNA rectifier are described.The paper analysis the principles of the modulation methods of VIENNA rectifier space-vector-pulse-width-modulation(SVPWM)and one-cycle-control(OCC).The control strategy and characteristics of the two modulation methods applied to VIENNA rectifier are described.Then,an OCC method of VIENNA rectifier is proposed to eliminate the neutral voltage ripple.In this paper,the mathematical principle of this method is given.The duty cycle of three-phase switch output can be calculated directly according to the two constraints of unity power factor rectification and elimination of neutral point voltage pulsation.At the same time,the equalizing control method is adopted to solve the problem of triple frequency disturbance of neutral point potential.Matlab is used to simulate the VIENNA rectifier.The simulation waveforms verify the effectiveness of the One-Cycle-Control method.Finally,a prototype of VIENNA rectifier is designed.The hardware part includes power circuit,minimum system of TMS320F28335 controller,current and voltage sampling and conditioning circuit,PWM driving circuit and pre-charging circuit.The experimental results of each module are verified separately.Then the control program is written in the upper computer software CCS,including function definition,variable declaration,AD sampling program,output duty cycle calculation,epwm wave output and so on.After all the verification work of software and hardware is completed,the three-phase electrical debugging are conducted.Finally,the experimental waveforms verify the effectiveness of the One-Cycle-Control method.