Research In The Control Strategy Of Three Phase Tri-Level PWM Rectifier

In order to reduce the harmonious pollution in power net caused by none control or half control rectifier, we introduce the PWM technique to rectifier to totally eliminate the harmonious pollution in power net, making current to sin wave at the AC side so as to be the state of unity power factor, furthermore, it can sent the energy to the power net. So the research in rectifier becomes hotspot.The content I research is three phase three level rectifier, which fit for commuting system or speed governing system of the middle of high voltage level. Through analyzing the three level topology and control method, the three phases three level diode-clamped rectifier based on the three level SVPWM is confirmed finally. It proved by simulation and practice on a small power set.By analyzing the traditional strategy based onθand modulation proportion m ,a new strategy based on V_α,V_βis proposed. The strategy is easy to practice which only content the simply operation, the addition, the subtraction and the multiplication. Quite fit for programming on DSP 2407.According to the waveform, specially, the issue about the balance of the two capacitances voltage is exists. The balance control by various proportion genes is proposed, validated by simulating and the experiment.Finally, through analyzing the neutral point at DC side influenced by the center vector, a new space vector modulation is proposed, the technique is radial state space vector modulation and improves the divisions of the area of vector composition and the issue is solved better which confirmed by the comparison between the two vector modulation simulating.