Research On Class Synchronous Machine Damping Control Of DFIG Connected To The Grid

Wind is a clean energy source and has little impact on the environment in recent years, so a growing number of countries around the world began to develop wind energy resources. A sustainable development strategy has been submitted in China and wind power capacity grew year after year. As the proportion of wind power grows, the wind turbine will replace part of the synchronous generator, which will undermine the adjusting ability of power grid. The imbalance of load center and energy center makes it difficult for wind power to dissolve on the spot, and the wind power base is built at the end of grid to output power. Randomness and intermittency of wind power will directly affect the reliability of power systems and wind power will also have an impact on low-frequency oscillation characteristics of power system. In order to make the best use of wind power and guarantee the stability of power system, it’s hoped that the wind turbine may be able to provide some damping for power system.This paper starts from the wind turbine structures and researches the effects of damping on power system. With doubly-fed wind power generator as the object of study, it’s designed to enhance the small disturbance stability by adding damping control in converter control system.First of all, based on the structure and working principle of doubly-fed induction generator, mathematical modeling of doubly-fed wind generator parts has been finished. By establishing the model of doubly-fed wind turbine mechanical transmission shaft, generator model, converter model and the overall control model, the overall small-signal linearized state equations is obtained. Then stability analysis of systems in different running states is studied by eigenvalue analysis. On the basis of the research, damping control of synchronous machine method is proposed to improve damping of power system. This method uses the synchronous generator voltage controller (PSS) as a reference target, selects the target eigenvalue and makes pole assignment.Then, the mechanism and analysis methods are researched in power system of low frequency oscillation. The simulation analysis of 3-unit 6-node system is conducted for doubly-fed wind turbine in the MATLAB/Simulink condition. The paper does The experiment by characteristic value method and the numerical analysis method in time domain. Effects on low frequency oscillation and damping characteristics of power system are researched under different conditions of grid-connected wind turbine capacity. It verifies that damping control method can enhance small disturbance stability and restrain low frequency oscillation of power system.