Influence On Power Oscillation By Wind Power And Supplementary Damping Control

With the increasing requirements of renewable energy and the development of wind power technology, the scale of wind power integration into power systems has become larger in recent year. Therefore, the influence of wind power has also been more severe. Due to characteristics of wind turbines, large-scale trip-off problems of wind turbines are likely to happen, which may result in serious power outage. The study on the influence of power oscillation by wind power integration and the strategy of damping the oscillation are launched in this thesis. The domestic and overseas research progress is summarized. The eigenvalue analytical method, Prony analytical method, controller parameter optimization and power system simulation technology are used to research the oscillation in power systems by wind power integration and design damping controller for power oscillation. The main contributions and results of this thesis are as follows.Firstly, the theory of eigenvalue analysis in power systems is described, the meaning of participation factor and electromechanical mode are explained. The wind speed models including the basic wind, the gust, the gradient wind and the random wind are introduced. The mechanical models and generator models of doubly fed induction generator and permanent magnet synchronous generator are established for dynamic stability study. The mechanical model includes aerodynamic model, the equivalent generator, converter model, shaft model, the pitch angle control model and the converter control system model. The generator model includes the equivalent generator, converter and the converter control system. The equivalent model of wind farms is also discussed.Secondly, forced power oscillation theory and the Prony analytical method are introduced. A simulation of two area test system with DFIG is made based on forced power oscillation theory. The gust which is imposed on the wind turbine is in different frequency and with various speed. Therefore different kinds of forced power oscillation on the power transmission lines may occur. This phenomenon proves that the frequency and speed of wind affect the power oscillation. In the simulation of Weihai power grid, a wind farm powered by composite wind may also result in forced power oscillation. The concrete conditions which may lead to power oscillation are finally discussed with the analysis on different composite wind.Finally, a damping controller model based on both the operating principles and the DC/AC control dynamic mathematical models of SVG is built. In order to improve the system damping ratio and suppress the power oscillation, input signals and parameters are optimized. With supplementary damping control, the system damping improves significantly and the amplitude of forced power oscillation is reduced in the simulation of two area test system and Weihai power grid. It is observed that the supplementary damping control on SVG and parameter tuning can enhance the system dynamic stability and decrease oscillation amplitudes.