| In recent years, due to the pressure of energy crisis and environmental pollution, countries around the world are speeding up the pace of developing and utilizing renewable energy, so hydroelectric power, wind power and photovoltaic power generation technology are developing, especially the wind power generation technology, because of the short development cycle, cost is relatively low, it is attached great importance by the industry.In this context, as a typical representative of wind power generation technology, variable speed constant frequency doubly-fed wind power generation technology is developing by leaps and bounds, its foreground is very considerable.In this thesis, the subject which is studied is the variable speed constant frequency doubly-fed wind power generation system, the first part the author simplely introduce the component of the system and their features, and then concretely analyse the working characteristic of wind turbine, the principle of tracking maximum wind energy and the mathematical model of the drive shaft, laying the foundation to understand the important component of the wind power system- dual PWM converter;The next step the author study The mathematical model of the doubly-fed generator, including the static model and dynamic model, the control strategy of converter is obtained on the basis of the mathematical model;Then list several common power conversion circuit, compareing their advantages and disadvantages, it comes to a conclusion that the double PWM converter is the best choice; and then put forward the vector control strategy to control the dual PWM converter.In this thesis, the core of the research is the dual PWM converter, which is the main executor of the wind power system, it contains the two parts,the grid side converter and motor side converter, they are both independent and related, connected by bus capacitors which in the middle.According to the structure and characteristics of the grid side converter power system, using voltage oriented vector control strategy to guarantee the stability of busbar voltage, at the same time, make the input power factor to 1.Because of the generator are connected to the doubly-fed generator side converter, after analysing of topological structure, adopting the stator flux linkage vector orientation vector control strategy, its main task is to implement the stator active and reactive power decoupling, while ensure the robustness of the system.Finally according to the control strategy and control diagram we build the simulation model in Matlab/Simulink platform, for grid side converter, through the oscilloscope the busbar voltage that consistent with the set value can be seen, the fluctuation is not big, reactive component of the input current is almost close zero, the input power factor is 1;for generator side converter, through running the model the active power and reactive power are comparatively independent can be seen.Thus it verified the feasibility of this control method of the converter.The open loop control method is contrasted with the closed loop control method in the thesis, under the open loop control method it can satisfy the basic requirement of the variable speed constant frequency doubly-fed wind power generation system, which can realize decoupling of active power and reactive power and decoupling of mechanical and electrical system, but there is not a very good anti-jamming capability in the model,when using closed loop control method,the fluctuation of these variable is very small and more smooth, then the system have strong robustness.This is the expecte research result of this topic. |
