The Study Of Doubly-fed Induction Generator's Excitation Control Based On Space Vector Technology

Nowadays, energy sources consume increasingly daily and environmental pollution becomes serious gradually. People pay more and more attention to the use of regenerated, green and clean energy, 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.In recent years, with the great development in manufacture of power electronic converter and its application technology, the variable speed wind turbine (VSWT) with large capacity has become one primary technology directions of wind turbines. The doubly-fed induction generator (DFIG) which can flexibly connect to power system has turned into mainstream machine in the field of exploring wind energy in the world. Comparison with the general wind energy generation system,because of equipped transducer of DFIG system located at rotor loop,it not only possesses the characteristics of small cubage, light weight and low cost but also realizes flexible connection of mechanical- electric system,which only deals with slip power in two-way flow. DFIG system and its control technology are studied in this paper. Firstly, the article summarizes the development situation of wind power course abroad, and especially in our country. Then, the paper analyzes the classification of the wind power technology, and explains the advantages of variable speed constant frequency technology. Based on the above basis, give out the paper's main content and investigation significance.Secondly, this paper select the dual PWM converter as a doubly-fed motor Excitation converter, analyzes the wind power system and DFIG operation principle in detail, and then, explains the flow characteristics of power and operating characteristics of the DFIG at different status. Combined with reasonable simplified conditions, the paper establishes the model of the DFIG system. Then, under the principle of coordinate transformation, the paper deduces the Mathematical model of DFIG in the abc and dq coordinates.Then, emphasis is paid to introduction about the space vector control theory. we can simplify the converter which is near to the Power Grid and motor's formula by the alternation from three phrase still axis to two phrase rotating axis with the same speed of the magnetism, then we should select a special direction for the axis, that is, stator field orientation, which really makes us go further to simplify the model.Finally, the simulation research is carried out on the platform of MATLAB/Simulink to validate the proposed strategy. The simulation results indicate that the system has good dynamic performance, DC bus voltage is stable and has small fluctuations, and it satisfies 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 to realization. Obviously, the system has some important practical value.