The Research Of SSR For DFIG In Series Compensation

For wind power in today’s energy crisis and the increasing demand for electricity, more and more attention paid by countries in the world. Wind energy unstable characteristics made many stability problems still need further research in the development of the scale enlargement. In this paper, a wind power widely used models: double-fed induction generator (DFIG) based on the analysis of the self-excited oscillations in series compensated lines.Departure from the characteristics of the DFIG distinction of the ordinary asynchronous motors in its rotor windings to the grid through an AC-DC converter connected. The AC side of the converter can be equivalent to the controlled voltage source, the power flow to adjust the rotor slip by adjusting the voltage of the controlled voltage source, which makes DFIG in the equivalent circuit of the access lines has controlled voltage source. To expresses the equivalent circuit diagram, we need study the control method.This paper studies the transfer function of the converter control system, and the correctness of its transfer function is verified by simulation. Then the transfer function can expresses how the controller of DFIG influences the system stability. Due to the PLL controller, the transfer function firstly expresses the power frequency of the relationship between the amounts.This paper analyzes the change of transfer function after the DFIG connected in series compensated line. In the analysis, the amount of non-power frequency is also present in the entire system, and will vary with the control system and the level of series compensation. The initial model parameter was found in40%SC of the lines in the analysis of the transfer function, which has positive half-plane poles. So the next job from the following points of departure:1:how control parameters affect the oscillation;2: how series compensation levels affect oscillation;3:how the fan output level influence the oscillation.Finally, a damping control system is designed to suppress signal. The sub-synchronous oscillations caused by a different wind turbine output and different level of series compensation in a fixed converter control parameters, the design can be used to suppress down the sub-synchronous oscillation. In addition to simulation in the last paragraph, the pole-zero analysis of the system transfer function, you can see the damping inhibitory signal pole.