Research On Safety And Stability Characteristics And Control Of Power Grid Frequency Under The Condition Of New Energy Sources

With the limitation of the energy resources and the requirements of environmental protection,more and more attention has been paid to it,the scale of China’s wind power and photovoltaic new energy access is increasing,At the same time,it is affected by the reform of electric power system,the separation of plant and network and the diversification of management subjects,The security and stability control of power grid is facing great challenges.On the one hand,the new energy and thermal power,water and electricity compared to conventional power,lack of inertia effect,and volatility,do not have the function of primary frequency modulation.Therefore,after access to new energy grid frequency dependence on conventional units increase,need to strengthen the research of primary frequency for thermal power and hydropower unit,and clear difference between traditional and digital electro-hydraulic control system of the two class,to provide guidance for the accurate simulation and scientific strategy.On the other hand,the new energy and power grid access system between the splitting fault is an important scene research on safety and stability of frequency,should fully take into account the power side frequency protection and grid side safety control measures,the problem of high frequency or low frequency and control strategy.This thesis firstly introduces the mathematical model of new energy and conventional units are used,and summarizes the tolerance range of each frequency,the characteristics and differences of the two types of units are analyzed.Then,the characteristics and differences of thermal power and hydropower units of traditional and digital electro-hydraulic speed control system is two compare,focuses on two types of speed control system structure,dead zone,the dynamic frequency characteristic three aspects,analyze the characteristics of two kinds of typical governor.On this basis,the new energy access system after splitting problems caused by high frequency research,established with multiple types of power supply end of typical example analysis of OPC thermal power unit protection fixed value difference setting effect;It is pointed out that the high frequency protection setting value of the new energy is too low and the disordered network will result in the serious consequence of the original high frequency problem into the low frequency problem;The scheme of chain cutting machine for high frequency problems is studied,the different effects of the removal of conventional units and the removal of wind turbines on the frequency fluctuation and the maximum power angle difference are compared,a comprehensive cutting strategy considering both frequency and power factor is proposed.Finally,the problem of low frequency in the new energy access system is studied,and a provincial power grid with large scale new energy access is taken as an example,the influence of the voltage control of dynamic reactive power compensation,the reserve capacity of the conventional units,the proportion of new energy sources and the proportion of the grid on the frequency regulation characteristics of the power system is studied,and for the new energy access is easy to cause the UFLS round the problem of increasing the Underfrequency Load Shedding Scheme Optimization strategy.