Research On Fault Ride-through Control Strategy Of Doubly-fed Wind Power Generation System

Wind energy as an inexhaustible, environmentally friendly and renewable clean energy, has become the fastest growing green energy in power system of our country, the influence of large-scale wind power on power grid stability can't be ignored. Wind power technology and industry has become a focus of electrical technology research and the mechanical and electrical products production.The doubly-fed wind generator is widely used due to its excellent operating characteristics and the topology structure. Therefore, this article mainly launches the research for the doubly-fed wind power generation system control strategies and its fault through research. The main work is as follows:(1)Based on the the analysis of the situation of the development of wind power at home and abroad,the importance of research on wind power grid-connection control strategy is put forward. The composition and characteristics of the doubly-fed induction wind power system and permanent magnet direct-drive synchronous wind power system which used variable speed constant frequency operation technology is briefly introduced. Based on double-fed induction wind power converter control strategy, sliding mode variable structure control is proposed to improve the control strategy.(2)Double-fed induction wind generator and the operation principle of dual PWM converter are analyzed in detail. Having studied the structure of doubly-fed wind power generation system, and built the mathematical model of DFIG and its control system in this paper. Based on matlab/simulink to build the DFIG system grid-connection model, DFIG grid-side converter based on grid voltage oriented vector control, the rotor-side converter based on the stator voltage oriented vector control.Researching the situation of the DFIG no-load grid-connection and realize maximum wind energy tracking under the conventional PI control strategy.(3)In order to study the promotion of system performance when sliding mode variable structure control strategies are used in doubly fed wind power generation system, a sliding mode variable structure control strategy based on exponential reaching law is proposed. The control rate of different objects is analyzed and calculated, and based on the simulation model built in SIMULINK, the control strategies used in dual-PWM converter control, MPPT control and the application of the no load on the grid-connected control are studied systematically. Compared with the PI control method, the simulation result show that the proposed sliding mode variable structure control strategies no only simplify the system control structure, but also improve the response speed, control precision and robustness of the system, which approved to be effective and feasible.(4)Base on the reserch of the improved control strategy of doubly-fed wind power generation system incluede the stator flux linkage dynamic process in low voltage ride through, evaluat the transient behavior of DFIG using high-order sliding mode variable structure control strategy and the traditional PI control in power grid voltage sags, the comparison results show that the sliding mode variable structure control strategy is better than traditional PI control for DFIG to pass the LVRT.