Research On Voltage/reactive Power Control Strategy Of Wind Farm Integrated Power System

Due to the increasing consumption of energy and worsening environment, clean and renewable energy resources are attracting more and more interesting, especially wind energy. Wind energy, as one kind of inexhaustible, clean, renewable energy, has a promising future of being developed and used in large scale.The Variable-Speed Constant-Frequency wind generators include: DFIG and Directly-driven wind generator. In the Variable-Speed Constant-Frequency wind generators, DFIG account for a large proportion. On the one hand because the electromagnetic relationship between stator and rotor of DFIG, converters just only deal with the slip power of DFIG which can adjust the speed of the wind generator and realize the maximum capture of wind power. This greatly reduces the rated capacity of converter of Variable-Speed wind power systems. On the other hand, DFIG could realize independent regulation of active and reactive power by changing the amplitude and phase of excitation current. This can ensure wind farms runs on unit power factor and reduce power system loss.Firstly, the mathematical model of DFIG at abc static coordinate and dq rotating coordinate is established and the characteristic of power is studied, the foundation is laid for subsequent content .Secondly for the nonlinear and coupling of mathematical model of rotor side and grid side of DFIG, the strategy of feedback linearization of nonlinear control is proposed. The decoupling control of active and reactive power of DFIG is achieved. The simulation results indicate that: the dynamic characteristic is improved.Finally the characteristic of voltage stability of the power system with large wind farm integrated is studied. The reactive/voltage power sensitivities of wind farm is derived, the relationship of reactive and voltage is expressed by it. On the grid with wind farm integrated, the voltage level is maintained by dynamically regulating reactive power output of wind farm. The simulation indicates that the voltage fluctuation of the grid is restrained effectively by the proposed strategy.