Simulation And Analysis Of Doubly-fed Induction Generator Transient Response During Voltage Dip

Global climate change and security of energy supply are serious challenges we are facing in the world today, and vigorously develop of the renewable energy is an important way to deal with these challenges. Wind power is currently the main large-scale commercial application of renewable energy, doubly-fed induction wind generator (DFIG) currently has been widely used in the wind power industry due to its excellent operating performance. In the face of common fault types such as the grid voltage sags, it is extremely sensitive to the grid fluctuations because of its unique structure. Therefore, it has very important significance to study the transient response of the DFIG that is in dealing with the voltage sags fault to improve low voltage ride through (LVRT)ability of wind turbines.The main research contents of this paper include:First, for the special structure of doubly-fed induction wind power generation system, the stator side directly connected with the grid, the rotor side connected to the grid through converters, introduces the basic principle of variable speed constant frequency, starting from the equivalent circuit, then on the basis of the fundamental electromagnetic equations,derived5order mathematical model and3order mathematical model of two-phase synchronous rotating coordinate system; Secondly,built models of a wind power generation system in the MATLAB/SIMULINK, simulated the transient process of these two kind of models of DFIG under the grid voltage sag fault, the results show that the5th order model can provides more clear and detailed transient responses when the voltage drops, it can more accurately characterizes the transient response process under the voltage dip faults; DFIG under traditional control strategy has good output performance in constant grid voltage, but the voltage sags in the power grid will cause the negative impact of the severe fluctuation of transient response and restricting its low voltage ride through operation, for this reason, proposed the feed-forward compensation control for the converter side, and corrected the control strategy considering the change of the stator excitation current for the rotor side, the simulation results show that, as compared with the conventional control methods,improved strategy can effectively suppress the rotor over-current oscillation, improve the output performance of the active power and reactive power, testified the effectiveness of the improved control strategies.