Modeling And Control For Variable Speed Constant Frequency Doubly-fed Wind Power Generation System

Nowadays, energy shortage becomes an urgent problem that human survival and international development has to confront with. To ease the situation of energy shortage by using renewable energy resource as the clear energy source in the future means a lot. Wind energy is the most fast-growing renewable clear energy resource, which is also among the most promising renewable resources that can be exploited in large-scale. Compared with traditional energy resources, wind energy is widely distributed all over the world, the cost of power generation is stable and there is no environmental pollution. With all these unique superiorities, wind energy has gradually become an important part of sustainable development strategy in many countries and has been growing fast. Meanwhile, the control methods of wind power generation system have been greatly improved. More and more attentions are being paid to a series of key problems such as how to maximize the captured wind energy and how to improve the reliability of the wind power generation system.The nonlinear mechanism model of wind energy generation system including wind turbine, drive train, DFIG and blade servo is established. Also the nonlinear characteristic of wind power generation system is analyzed.According to the multi-time scale characteristic of wind speed, the wind speed is divided into low-frequency component and high-frequency component. Then the two-frequency model is established for wind power generation system based on the nonlinear mechanism model. Below the rated wind speed, maximizing captured wind energy and decreasing the generator oscillation are taken as the control objectives, and the two-frequency-loop optimal controller is designed. On-Off control is adopted in the low-frequency-loop, and H∞output feedback control is introduced in the high-frequency-loop. Simulation results show that the two-frequency-loop optimal control is feasible, and a trade-off can be achieved between the two control objectives by selecting different H∞performance index.Further based on the established two-frequency model, the LPV model of normalized error for wind power generation system is established. And the LPV controller for wind power generation system is designed. In order to maximize the captured wind energy below the rated wind speed, the LPV controller is taken as a dynamic compensation on the basic of PI control strategy. Experiment results which are based on hardware-in-the-loop simulation platform for wind power generation system via dSPACE show that the LPV controller is effective.