Research On Impact Of Low-frequency Oscillation Characteristics In Power System With Wind Power Generator Integration

With the growing of the global energy crisis, and the development of wind power technology, and the enlargement of the power interconnected system, thus the influence of the power system stability when wind power is connected to the grid have received much attention. The low frequency oscillation of power system often occur when the wind power is connected to the grid, at the same time the low frequency oscillation take some potential risks to the stability of the power system. Therefore researching the impact of low frequency oscillation characteristics in power system with wind power integration, and researching the measures to suppress the oscillation have become hot issue in practical engineering. This paper use the double fed induction generator(DFIG) as the research object and analysis the impact of low frequency oscillation characteristics of the power system when the wind farm under different working condition.Adding the DFIG-PSS to the DFIG rotor side converter control system, at the same time using the unified power flow controller(UPFC) with additional damping controller to suppress the low frequency oscillation.Specifically, the main contents of the dissertation are as follow:(1) The detailed mathematical model of the double fed induction wind generator. The model includes wind turbine model, mechanical transmission model, DFIG model, DFIG converter model, converter control model and the wind farm equivalent model. The converter model and converter control model are the pivotal models.(2) The generation mechanism and analysis method of the low frequency oscillation have been described. This paper introduce the theory and parameter selection of eigenvalue analysis method, HHT and Prony algorithm. An algorithm than combining HHT and Prony is proposed to extract the low frequency oscillation modes, and use the example analysis to prove the availability of associated algorithm.(3) The damping characteristics of simple interconnected system and system with wind farm have been analyzed. From the analysis, getting the related factors about low frequency oscillation of the power system with wind farm. Then using the four machines and two areas power system simulation model to analyze the low frequency oscillation characteristics of power system when the wind farm and power system in different working condition.(4) The basic theory and parameter setting principle of PSS are introduced, and the model and control system of UPFC have been described in this paper. Then adding the DFIG-PSS to the DFIG rotor side converter control system and using the unified power flow controller(UPFC) with additional damping controller as the suppression strategy to improve the low frequency oscillation characteristics. At last, using the simulated analysis and data comparison to prove the availability of suppression strategy.