Study On Converter Control Strategy For Permanet Magnet Directly Driven Wind Power Generator System

Increasingly along with the traditional energy sources dried up, represented by wind power new energy technology obtained the rapid development and application. Wind power generation with its advantages of no pollution,recycled,has been favored by countries around the world. Wind power generation system with variable speed constant frequency and constant speed constant frequency included. Variable speed constant frequency system mainly include doubly-fed type and direct drive type .In past decades, direct drive type has been great developed,gradually becomes the mainstream in the development of wind power technology. In this paper, with permanent magnet direct drive wind power system as the research object, with the "back-to-back" structure of variable flow system as the main research contents, Converter Control Strategy is been focused.In permanent magnet direct drive wind power system, Convert plays an important role.Which convert the instability alternating current (AC) generated by generator into stability AC power in the way of electrical energy transformation in "pay - straight - to pay" mode,and then transformed to power grid. The quality of control strategy will directly affect the quality of AC and the performance of the whole power system, and even affect the stability of the power grid. In consequence, the control strategy of convert and rectifier has been studied in this paper.Firstly, the topological structure of variable flow system is determined, which is"back-to-back" full power active topology. Three-phase voltage source PWM rectifier is adopted in the converter. Which can works not only onrectifier state but also on active inverter state. so the energy bi-directional flow is realized and wind power system control becomes easy.Secondly, the mathematical models of the parts are established, in the models,Converter, wind turbine, Generator.etc. are included. On the basis of mathematical models theory, the Zero d axis control strategy of permanent magnet synchronous generator is used,the climbing search method was adopted to achieve the tracking control of maximum wind speed, which improved the efficiency of the wind turbine. SVPWM technology was used to achieve the rectifier’s control.Then, Inverter control strategy was put forward, the direct power control and double closed-loop control method. The two methods are all built on Voltage oriented control strategy, but the control ideas and implementation methods are different, so the control effect. Based on the analysis of each principle and method,it was given of respective control block diagram. The simulation was done to analyzed for the different wind conditions, which can be result of the corresponding conclusions.Finally, related simulation models based on MATLAB were built based on the controlling strategy and mathematical models referred and simulation was analysed in every part module. Power curve was given under different pitch angle and tip speed ratio, which proved that the wind turbine can achieve the maximum capture of wind energy in different wind speed. In addition,simulation and theoretical analysis of the entire wind turbine was taken in the article.