Research On Impact And Control Methods Of Low Frequency Oscillation In Power System With Wind Power Integration

With the worsening of the global energy crisis, the development and utilization of new energy and renewable energy has become a trend. Wind power is currently the most technologically mature, within one of the most large-scale development conditions and business conditions for the development of power generation. But along with the grid-connected wind power growing proportion in the grid, and a great challenge due to the randomness of the wind speed, wind energy has brought instability to the safe and stable operation of the entire grid. Low-frequency oscillations often occurs in large interconnected power system. The growing grid size, especially large-scale wind power grid may lead to low-frequency oscillation of the grid, to bring hidden dangers to the security and stability of operation of the system. The impact of wind power access to low-frequency oscillation has also become the current research topic. As the most widely used, variable speed constant frequency doubly-fed wind generators are studied. The impact of the wind power integration leading to low-frequency oscillation is proposed. Additional damping controller based on the unified power flow controller (UPFC) is used to suppress low-frequency oscillation in the power system with wind power. The main work of this paper is as follows(1) The detailed mathematical model of a doubly-fed wind turbine is studied. A simulation model of a doubly-fed wind turbine in the grid-connected system is designed in MATLAB/SIMULINKA. Using the traditional PI control theory, simulation and analysis of the performance of the system is realized.(2) The generation mechanism, analysis methods and the main suppression strategies of low frequency oscillation are described. The principles and parameter selection of the Prony algorithm are introduced. The simulation results demonstrate the effectiveness of the algorithm applied to low-frequency oscillation pattern recognition. Based on through-domain simulation and Prony analysis, the impact of the access of wind power on the grid low-frequency oscillation is studied.(3) Detailed description of the system structure and working principle of UPFC is given. The operating principle of UPFC parallel side and serial side is introduced. A detailed mathematical model of UPFC is developed in MATLAB/SIMULINK simulation. The control of the UPFC series side and parallel side strategy is designed. Simulation results verify the validity of the model of UPFC.(4) The principle of UPFC suppressing low-frequency oscillation is introduced. A mathematical model of UPFC with additional damping control and the MATLAB/SIMULINK model are proposed. UPFC with additional damping control is used to restrain low frequency oscillations in the4machine system with wind power integration. The application of UPFC additional damping controller can effectively suppress the low frequency oscillation.