Research On The Power Control Of Doubly-fed Nduction Wind Generator

Energy is an important material foundation of the national economic development. Because of the gradual depletion of fossil energy resources and the increasingly serious problem of environmental pollution, it has become the inevitable choice to develop renewable energy represented by wind energy and solar energy for the sustainable development of human society. Among many renewable power generation methods, wind power generation is one of the methods which are the most mature and suitable for large-scale development in the field of electronics. In this thesis, the trends of the wind power generation industry and the development status of the doubly-fed induction generation (DFIG) based on the variable-speed-constant-frequency (VSCF) wind turbines are given. The control of PWM convertor for VSCF wind energy generation system with DFIG.studies is studied.At first, the VSCF operation principle of the DFIG is introduced. The Mathematical model of DFIG and the coordinate transformation method are derived, which are the theoretical basis for the research.Secondly, the thesis studies the direct power control (DPC) of DFIG grid-side converter. The block diagram of the DPC is implemented by the model of the grid-side converter. Then the expression of active and reactive power and the ways of DPC based on fixed frequency are given. The thesis applied the Matlab/Simulink to build the model in order to research deeply.The thesis studies the control strategy of DFIG rotor-side converter on basis of researched the grid-side converter. The mathematical model of the DFIG is established.Then the controller of the vector control and the direct power control based on fixed frequency are designed. This paper proposes a new direct power control strategy based on the nonlinear state observer, which introduces the tracking-differentiator (TD) and the nonlinear state observer on the basis of direct power control. The simulation results validate that direct power control of DFIG based on the nonlinear state observer can solve the contradictory between overshoot and rapidity, which achieves fast control without overshoot and improves dynamic performance of the system.Finally, the experimental system uses2.2KW DFIG as a prototype. This thesis introduce the design ideas and schematics of the system’s hardware and software module.The experiment of DFIG grid synchronization control is completed.