The Study On The Control Strategy For The VSCF Double-Fed Wind Power Generator

Nowadays, under the serious problem of energy and environment, people pay more and more attention to the use of energy regenerated green and cleanness such as wind energy, water energy and solar energy etc. By virtue of its outstanding merits, wind power has drawn great attention in exploiting renewable energy resource, and the wind power technology has become tremendous scholars' research hotspot. Now it is a real hot topic to research the control strategy of wind energy conversion system.Firstly, this article summarizes the development situation of wind power course abroad, and especially in our own country, gave out the paper's main content and investigation significance. The Variable Speed Constant Frequency (VSCF) wind power generation system using Doubly-Fed Induction Generator (DFIG) improves the utilization ratio of wind power. The system can adjust the active and reactive power separately, and improves the stability of electric power system.Secondly, this paper analyzes the wind power system and DFIG operation principle in detail, including mathematic model of DFIG and DFIG operation characteristics. The dynamic mathematical model and coordinate transformation of DFIG are studied with theoretical deduction. A general control model based on stator flux oriented vector control strategy is established and the dual-closed-loop PI adjusters are designed to realize the speed control of DFIG and decoupled control of the active and reactive power.Then, the paper analyzes the excitation control of VSCF wind power generation. The dual PWM converters have better input and output performances, less harmonics and bidirectional energy-transform. The theory of SVPWM and the model of grid-side converter are analyzed. The control strategy of grid-side converter, the function of which is to adjust the in put power factor at grid side and to control DC bus voltage is proposed on the basis of the field oriented vector control.Finally, the simulation research is carried out based on the platform of MATLAB/SIMULINK to validate the proposed strategy. The Simulation results indicate that the system has good dynamic performance. And the grid side converter has many advantages, such as low harmonic, high power factor, fast dynamic response and energy bidirectional flow, could satisfy the demand of DFIG excitation.The method of stator-flux-oriented vector control combining the dual PWM converters harmonious control provides an excellent theoretical foundation of realization. Obviously, the system has some important practical value.