Research And Design On Three Phase Three-level VIENNA Rectifier Of 7.5kw Charger

With the increasingly higher proportion of rectifiers in the power electronic devices, its strong nonlinear characteristics caused serious harmonic pollution to the power grid, how to manage the harmonic, improve power quality and purify grid environment effectively becomes a hot research field in Power Electronics, PWM rectifier has become a common rectifier topology of distributed power electronic devices because it controls the harmonic from the very beginning. The traditional three-phase six-switch PWM rectifier has more switching elements and more difficult to design the driver, however the three-phase three-level VIENNA rectifier this article has studied has fewer switching elements, lower switching stress, lower total harmonic distortion, higher power factor advantages with good practical engineering application future.The working principle of VIENNA rectifier is analyzed in this thesis, the system running status at each switching state is introduced. Then modeling the system based on the principle, a system model of mathematics are given both in the natural coordinate abc and rotating coordinate dq. Then the paper analyzes VIENNA rectifier control algorithms in depth, studies the traditional three-level space vector pulse width modulation(SVPWM) algorithm and describes the problem of its application to VIENNA rectifier that is it requires a complex judgments of current sector, and then propose a current sector judgment with the expected voltage auxiliary, and with the combination of some general term, these methods make the SVPWM algorithm applied in VIENNA rectifier has been simplified.A detailed design principle of power devices in VIENNA rectifier is presented in this paper, and the power elements were calculated and selected based on the 7.5k W charger prototype. Because the system uses double closed-loop control method of voltage and current, this paper analyzes how to decouple the control of current and presents the overall structure of the dual-loop control. On the basis of the system design and control method of the research, this paper set up a control system simulation on Matlab/Simulink platform based on VIENNA rectifier, the simulation verifies the correctness of the parameters of the system design and control algorithm.Finally, this paper presents the design parameters, control system block diagram and hardware design principles of the 7.5kW charger, and build an experimental platform prototype, with the debug and test of the prototype, an in-depth research was conducted. Experimental results illustrate that, the VIENNA rectifier and its control algorithm designed in this paper which is based on the research and analysis is feasible, the system can achieve stable operation of at unity power factor.