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This paper reviews the present situation of the application of wind turbines generator system(WTGS) at home and abroad, describes the strategic significance and the value of sustainable development of the wind power in the country, illustrates the problems, a variety of reasons and responses on large-scale off-grid of WTGS, compares the advantages and disadvantages of various methods, gives full consideration to the actual demand for WTGS works and characteristics and points out the further research.

In this paper, the steady state and transient model of the DFIG system are analyzed. It is concluded that the PI controller parameters and stator transient current are influenced by different parameters of the system, including resistance value, generator rotor inductance or sag magnitude of power grid voltage , etc. Then the steady state and transient model of doubly fed wind power generation system are analyzed. It is concluded that there are two ways to improve the low voltage operation of the doubly fed wind power generation system.One is to use the optimal control strategy to improve the control of the current inner loop of the doubly fed wind power generation system;The other is that when the power grid voltage has the drop fault, it can be considered to increase the Crowbar protection circuit to consume excess energy in the DC side, this way can solve the problem of high DC bus voltage caused by unbalanced power. Structure of double fed wind power generator Firstly, the double fed wind power generator rotor is connected to the converter. Secondly, it is connected to the power grid through the converter. In the end, the stator is directly connected to the power grid. The structure of doubly fed wind power generator is shown in Figure 1.