Research On Low Voltage Ride Through Of DFIG Wind Turbine Based On DIgSILENT/PowerFactory

Nowdays, wind energy, one of the popular renewable energy, has gained rapid development. And the doubly fed induction generator (DFIG) is one of the main commercial wind-turbines.And the basic data of connecting to the grid of one generator can be get by testing. However the testing method can not get the data of all the generators in one wind farm.In this paper, According to the basic circuit of the DFIG wind farm, the mathematical models of DFIG and its converters are discussed respectively in the three phase stationary reference frame and two phase refernec frame rotating at synchronous speed. Based on these mathematical models, the vector control scheme is given. The grid side converter is two control loops, DC voltage control and AC current control loops. And the rotor side converter is power control loop and rotor current control loop respectively.In order to satisfy the low voltage ride through (LVRT) of the grid code of wind power, control strategies have been proposed during grid voltage dips. And the model in DIgSILENT/PowerFactory will test these control methods. When the voltage of the Grid drops, the voltage of the DC-link and the current in the rotor will become bigger in short time. The crowbar circuit will start work to absorb the energy. Almost 20 milliseconds later, The generator start injecting reactive power to the grid.With the analysis above and for the simulation of all the generators in the wind farm, a feasible method of DFIG based on static generator has been developed. This generator can satisfy all the static and dynamic behaviors of the DFIG connecting to the grid, The most important is the low voltage ride through of the wind turbine. Also, with the help of China Electric Power Research Institute, the output data during LVRT of the model have been tested with the testing data. The results of the analysis tells that the simulation model can staisfy the requirements of the wind power code of China.The traditional fifth order of DFIG model brings lots of inconvenience to the analysis of power system. And the third-order model of the DFIG has been developed and the related work are also down in DIgSILENT/PowerFactory. And the results have been compared with the five order DFIG model, and we derive that the simulation curves of the two have much similarities.