Research On Control Strategies Of Converter In Direct-Driven Wind Generation System

Currently, the worldwide energy crisis and environment deterioration have been the major issues which influence the development of human society. Development and utilization of renewable clean energy has become the consensus of mankind. People have attached greate importance to the wind generation which is rapidly unprecedented developing, because the wind generation is a new renewable clean energy and can be large-scale commercial developed. Direct-driven wind generation system is considered to be an important research direction in wind generation technology area due to its superiotities of energy conversion efficiency, flexible power control ability, safe and reliable, etc. The developed wind power is abundant, and there will be also a great developing potentiality in our country. Compared with the international levels, technology of mainstream MW level direct-driven wind generation is in backward status, we still have a long way to go. Therefore, this paper gives control stategies study on full-power grid-connected power converter in direct-driven wind generation system, is of great practical significance.Firstly, the development of wind generation at home and abroad is elaborated, describing the development process of wind generation technology, on which basis the development of direct-driven wind generation system at home and abroad is analyzed.Secondly, around the study of modeling and control of the direct-driven wind generation system line-side converter, on which basis we determined the voltage oriented control strategy of the line-side converter, and the design of line-side system parameters is given.Thirdly, study on the generator-side converter control technology of the back-to-back double PWM converter topology, taking the zero d-axis current control for an example, analysis vector control strategy based on rotor flux oriented control of the permanent magnetic synchronous generator based on its mathmatical model and wind turbine's maximum power point tracking. On the basis of analyzing the line-side converter and generator-side converter control system, control model of direct-driven wind generation system is built, and the design of generator-side system parameters is given.Fourthly, study on the low voltage ride-through operation property of the permanent direct-driven wind generator system. Analyze the control stategies on power grid fault conditons, and study the LVRT property and STATCOM model operation principle on power grid fault conditions.Fifthly, simulation model of 1.5MW direct-driven wind generation system based on full-power back-to-back PWM converter has been built under PSCAD/EMTDC simulaiton environment, which demonstrates the steady and dynamic performance of control strategy of generator-side and line-side converter system.And the simulation result also shows that full-power back-to-back PWM converter has a good isolation effect. Generator-side system seems to be immune to power grid fault. And when the power grid voltage drips, the line-side converter can work in the STATCOM model and provide reactive power that needed for power grid, then pass the area of low voltage, it indicated that direct-driven wind generation system has a better capability of low voltage operation.Finally, the part hardware and software design of direct-driven wind generation system is given, to provide a basis for experimental studied on the platform.