Operation Control And Analysis Of Micro Grid Based On The Double-Fed Wind Generator

As the energy and environmental problems become increasingly prominent, and there are several problems of the existing power system, such as power supply quality, reliability and economy and so on. Therefore, the distributed power generation technology which is mainly based on renewable energy is developing rapidly. Undoubtedly, the wind power is the most representative distributed power (DG) which has great prospect. However, a large number of DG accessing to the tradition power grid brought impact on grid and a lot of negative effects, so the development of distributed power generation technology is also restricted. Micro grid make use of DG is the most effective way to solve this problem. Micro grid integrates a great deal of micro grid power sources and loads as a whole, it can either be connected to distribution grid, or can operate independently. it effectively provide the power grid of the future supplement and effective support. It represents the new developing trend, as a frontier area of research, it becomes a research focus of power system.This paper made fully studies on the control strategy of doubly fed wind Power generation (DFIG) system which is connected to the micro grid, the vector-oriented control should be adopted for the wind power generation system both in grid connected and islanded state of the micro grid, to ensure it can run in the maximum point power tracking; When the micro grid is running in islanded mode, it is need other controllable micro sources adopted coordinate control, so that the output power volatility of the wind power generation system can be balanced.The details are as follows:(1) The concept of micro grid,topology structure,operation mode,micro source of different kinds and its characteristics are expounded, and the controllable micro source grid inverter control strategy are introduced. When the grid run in parallel operation state, the controllable micro adopts the PQ control according to the needs of the dispatching to output constant active power and reactive power; when the grid run in isolated operation state, the controllable micro adopts the droop control, so that the output power volatility of the wind power generation system can be balanced.(2) The two typical micro grid control strategies which consist of PQ and V/f were established in Matlab/Simulink separately. According to the simulation results in different operating modes, the dynamic characteristics of system are analyzed, it verify that the validity of control strategy for inverters. The simulation results show that, using reasonable control method can guarantee the voltage of loads and frequency within acceptable limits from a standard.(3) The basic principle and mathematical model of double fed wind generator is expounded, and the model of control system of rotor-side converter is established on the basis of the voltage and flux linkage equations of stator and rotor, by adopting the stator flux linkage-oriented vector control, which makes DFIG run in the maximum point power tracking, in addition, the active and reactive current in rotor are decoupled, thereby, the active and reactive power in DFIG can be regulated independently.(4) The detailed simulation model of DFIG is built and simulated the dynamic response of doubly fed machine when DFIG operates in sub-synchronous, synchronous and super-synchronous condition, the simulation results shows that the speed of doubly fed machine can trace wind speed quickly, realizing the maximum point power tracking, the frequency of rotor current is satisfied with the operating condition of variable speed constant frequency (VSCF) operation, further more, the active and reactive power in DFIG can be regulated independently.(5) The micro grid composed of DFIG,the controllable micro power and load, it is need for other controllable micro sources to be adopted coordinate control, so that the volatility of the wind power generation system's output power can be balanced, however, the voltage amplitude and the frequency need to control in the reasonable scope. When the micro grid run in islanded mode, the output power of DFIG is change due to the speed of the volatility, in order to guarantee the balance of the micro grid system of power supply and the demand, it is need for other output power of the controllable micro change. The simulation results show that the control strategy designed is effective and feasible.