Research Of Three Phase High Power Rectifier Based On PWM Technology

In realization of controlled and uncontrolled rectifier using diodes and thyristors, a lot of harmonics and reactive power are injected into the system because of the current wave form distortion. This consequently causes serious power pollution. With the development of power electronics technology, researchers begin to study PWM rectifying technology. The voltage style PWM rectifier has a lot of advantages, such as low current wave harmonics, high power factor on the AC side and stable voltage output on the DC side. Thus, it's becoming one of the hotspots in the contemporary power electronics area. The PWM rectifier is getting more and more wide use in power system active filter, reactive power compensation, flow control, solar power, as well as AC-DC transmission system and other areas. In this dissertation, the three-phase PWM rectifier has been studied, mainly to complete the following:First of all, this dissertation introduces the principle of the PWM rectifier, gives out the three-phase PWM rectifier topology structure, analyses the rectifying process of the PWM converter, gives out the mathematical model of the PWM rectifier, designs the AC side inductors and the DC side capacitors.Secondly, three control methods, which include current hysteresis control, current PI control and voltage space vector control, are introduced and corresponding models are built for the simulation analysis. The sub-PI control method is added into the DC voltage control in order to restrain overshoot and keep steady-state error in a very small scope. Meanwhile, the current can be limited in an allowed scope by a series-wound limiting resistance during the start period.At last, on the basis of simulation, the strategy of leading given current leading given and the voltage space vector controlled basing on rotating coordinate system are adopted. Thus, the problem of current error is solved. The simulation results show that, the three-phase voltage style PWM Rectifier designed in this paper has run with a high power factor and realized the stable control of direct current voltage. The issues such as high harmonics and low power factor, which existed in the traditional rectifying circuits, have been solved. It will prove to be a practical and useful design.