The Study On Key Technology Of Bidirectional Converter For Variable Speed Constant Frequency Wind Power Generation System

With the high-speed development of world's economy, the shortage of energy sources and the environment pollution are being serious. The exploitation of renewable power is one of the methods for solving the problems above. The wind power resource is the most rapidly developing renewable power in recent years; the Variable Speed Constant Frequency (VSCF) wind generation technology becomes the main trend of nowadays wind power generation technology for its advantages of high efficiency and small volume of converter needed.Firstly, the actuality of the wind power generation industry and the wind power generation technology are introduced in this paper; the basic principle of VSCF wind power generation system and the technical actuality of the bidirectional converter applied in VSCF wind power generation system are analyzed.Secondly, the principle of the rectifier and inverter in dual PWM and three-level converter are analyzed and their relevant mathematical models are founded in this paper. Then the principle of traditional Space Vector Pulse Width Modulation (SVPWM) method for the three-level topology is researched detailedly. Based on above, a SVPWM method based on 60o coordinate is researched that can omit the judging process of the sectors, reduce the calculating quantity. The simulation results prove the high efficiency of new SVPWM method based on 60o coordinate.At the same time, based on the analyse of the reason that voltage unbalance in neutral-point between capacitances of dual PWM and three-level converter, a control strategy that changing the voltage adjusting coefficient to adjust the working time of positive and negative small vectors in SVPWM is advanced to maintain the approximate balance of neutral-point voltage between capacitances through computing the electric charge in the neutral-point between capacitances, and it is applied with the design of three-level rectifier. Then, a unisonous control strategy is researched for dual PWM and three-level converter that the voltage unbalance in neutral-point between capacitances is controlled by three-level rectifier.Finally, the simulation of dual PWM and three-level transducer is accomplished. And based on above, the control programs are designed based on the chip of DSP2812, and part of the flowchart are given.