Research On The Decoupled Control Strategy Of Active And Reactive Power Of Wind Turbine Doubly Fed Induction Generator(DFIG)based On The Sliding Mode Control

With the large consumption of traditional energy sources,the continuous consumption of traditional non-renewable energy such as coal and petroleum not only brings pressure on China’s energy resources,but also causes a lot of pollution to the environment.Wind energy,as the clean energy source,is being taken seriously by more and more countries.Its development and utilization are gradually becoming mature.Its annual growth is also increasing year by year.It has become the fastest growing green energy source in China’s power system,with good market prospects.The Doubly-Fed Induction Generator(DFIG)has become a popular model in the wind power market because of its adjustable power factor,wide speed range,low cost and high efficiency.The core of DFIG wind power system operation control is the control of its grid-side and rotor-side converters.This dissertation mainly focuses on the control of rotor-side converters.Based on the relevant theories of wind turbines,the DFIG’s traditional Vector Control(VC)system is constructed.Decouple the active and reactive power output from the DFIG stator by controlling the rotor-side converter.The PI controller based double closed loop control structure in the traditional vector control is improved.The integral sliding mode controller based on power function is used to replace the traditional PI controller.The following aspects are analyzed and studied in this dissertation.(1)The basic operating mechanism of wind turbine and the basic principle of variable speed constant frequency(VSCF)are analyzed in this dissertation.In addition,the principle of how to realize the maximum tracking of wind energy under the condition of wind speed and speed change is described in detail.(2)The mathematical model of DFIG in three-phase stationary coordinate system is established in this dissertation.According to the coordinate transformation,the mathematical model of DFIG in two-phase synchronous rotating coordinate system is obtained.According to the traditional vector control principle,a double closed-loop control model based on PI controller is built to realize the decoupling of the active and reactive power of the DFIG wind power system.(3)The basic principle of sliding mode variable structure is introduced.An integrated sliding mode controller based on the active and reactive current components of the reaching law of the power function is designed for the traditional sliding mode chattering problem.And it is used in the inner loop control of the rotor current to replace the traditional PI controller.(4)A simulation comparison of a wind power control system based on a power function integral sliding mode controller and a traditional wind power control system based on a PI controller is performed to verify that the designed integral-sliding mode controller based on a power function is compared with the traditional PI controller has more excellent dynamic and static performance.Finally,the robustness of the system is verified by the parameter changes of the designed control system.