Power System Frequency Emergency Control Strategy Considering Dynamic Characteristics Of Wind Power

Large scale of new energy, such as wind power, transmitted through long-distance and large-capacity HVDC, is the main mode of China's new energy development, which will make the frequency characteristics become more complex. So the adaptability analyses and improvements of frequency emergency control strategies need further studies. When the DC block fault occurs, there will be a lot of redundant power back to the sending grid, resulting in grid frequency rising over the limit, which will threaten the security of power grid. High-frequency generator tripping strategy, which belongs to the third defense-line of power grid, is an important measure of frequency emergency control strategies to solve problems under extremely serious faults. Based on Ningxia wind-thermal-bundled power transmitted through AC/DC system, and on highfrequency issue in the provincial grid caused by DC block and system separation cascading faults, wind-thermal power-united high-frequency generator tripping strategy adaptive to new fluctuant power is in this paper.In this paper, the mathematical models of doubly fed induction generators(DFIGs)are presented firstly, and the operation characteristics and control strategies are analyzed.Then a DFIG-based power system is simulated by MATLAB/Simulink, and the characteristics of wind turbine in operation are explained under the change of wind speed and load disturbance.Secondly, impacts of wind power integration on system dynamic frequency characteristics are analyzed from generator's three responding links of synchronizing,inertia and speed regulating, and a typical wind-thermal-bundled power transmitted through AC/DC system is simulated by PSD-BPA. Then a variety of typical operation modes are presented to analyze the applicability of existing high-frequency generator tripping strategy, and some simulation comparisons on frequency characteristics of Ningxia sending power grid with wind-thermal bundled power after its separation to Northwest power grid are done under different operation modes. Furthermore, the reason why the exiting strategy is not suitable after the integration of large-scale wind power is analyzed.Thirdly, on the strong-fluctuation, low-inertia and weak-bracing characteristics of wind power, problems of secondary disturbing, tripping amount increasing and stability worsening caused by wind-thermal power disorderly tripping are assessed, and the wind-thermal power united generator tripping principles considering security and economy are proposed.Finally, under operation mode without wind power, based on “principle of minimum lacking-tripping”, an initial high-frequency generator tripping strategyadaptive to different faults is made. Furthermore, under operation mode with 60% wind power, based on principles of “tripping new energy power first”, initial generator tripping strategy is replaced by round, and three improved wind-thermal power-united high-frequency generator tripping strategies adaptive to the fluctuant new energy power are proposed, whose adaptabilities are simulated in Ningxia Grid.