Improvement Strategy Research Of Double Current Closed Loop Based On Doubly-Fed Induction Generator

Due to worldwide energy crisis, the research and development of new energy becomes a hot spot. As a a renewable resource, wind power’s reserve is very rich. The wind power is a distributed power generation, and it can pose impact to power grid when connected to power grid. What’s more, the safe and stable operation of wind turbine can in reverse be affected by the power grid when there exists a failure in the power grid. In the case of he power grid failure, if wind power generator has superior control performance, the generator’s capability of low voltage ride-through (LVRT) can be greatly enhanced, so as to ensure the stable operation of power grid..The common control strategy of doubly-fed asynchronous wind power generator (DFIG) under symmetrical grid fault is introduced in this dissertation. As the most commom failure appeare in the power grid is asymmetric, which produces negative sequence component and a double ripple component in the DFIG dc side. As the the benchmark of control model has been changed, the control algorithm obtained by using the symmetric power grid failure control strategy is not accurate enough, and the control error is a bit large, so as to influnce the generator’s operation.The static ABC coordinate DFIG mathematical model and rotating dq coordinate DFIG mathematical model are deduced in this dissertation. Then, the DFIG web-side converter mathematical model under asymmetric power grid failure is constructed. By using the MATLAB software, the correctness of the proposed model is verified. The process to set up double current loop control strategy by this model is shown in detail. Based on the simulation test of DFIG net-side performance under asymmetric power grid failure, it’s demonstrated that the performance of DFIG net-side PWM converter is changed after joining "double loop strategy". And the simulation results show that although double loop strategy can effectively improve the DFIG "low voltage through" performance, the control effect is limited.Finally, the paper presented a PID controller strategy based on fuzzy adaptive (Fuzzy PI D), The strategy adjusts the parameters of PID controller by fuzzy adaptive technology and pu ts forward the double current closed-loop control (NNS-DCLC) strategy based on neural netw ork, meanwhile, This strategy also adjusts the parameters of PID controller for real-time adapt ive adjustment by using neural network technology. Through the simulation of DFIG converte r grid side test asymmetric fault, After joining the improved strategy, the performance of DFI G grid side PWM converter has changed, The simulation results show that thw improves strat egy has a better control performance than the traditional "double loop strategy", Compared wi th "NNS-DCLC strategy", "Fuzzy PID" has a higher precision of control current and dynamic response time is shorter and also more effectively to eliminate the DC side voltage fluctuation.