Transient Stability Analysis And Control Research Of Large-scale Wind Power Connected Power System Based On Network Energy

In recent years,large-scale grid connection of new energy represented by wind power is becoming the main trend of grid development.With continuous expansion of grid-connected scale of wind power in our country,the fluctuation and randomness of its output and its weak inertia support ability have brought challenges to ensure the safe and stable operation of power system.Therefore,it is of great significance to study the impact of wind power grid-connected on the transient stability of power system and to provide a transient stability emergency control strategy suitable for large-scale wind power grid-connected power system.On the basis of summarizing the current research status of transient stability of wind power grid-connected power system,this paper focuses on the following four aspects: the construction of transient energy function of wind power system,the construction of network energy analysis method of wind power system,the analysis of the influence of wind power on the transient stability of power system,and the strategy of wind-fire coordination.The main research work is as follows:1)From the perspective of external characteristics of wind power,the transient energy function of the wind power grid-connected power system is established by considering the damping coefficient of the synchronous machine and the network resistance,and the branch potential energy,node energy,resistance loss energy and load energy in the network energy system are defined.It provides a theoretical basis for the subsequent construction of transient stability analysis methods based on network energy.2)Establish a network energy analysis method suitable for the transient stability problem of wind power grid-connected power system.First,establish the branch energy index,which can screen the key links in the network and reflect the transient stability of the power system through the branch energy index of the key link,and then establishes the node energy index,which can be used to evaluate the inertia support capacity of the system,and study the influence of the inertia change of the wind turbine on the transient stability characteristics of the power system after the wind turbine is connected to the grid.3)The influence of different wind power models and different grid-connected positions on the transient stability characteristics of the power system is explored from the perspective of the network.The influence of inertia change on energy distribution and stability margin is studied.Secondly,the influence on energy distribution and stability margin when wind turbines of the same capacity are connected to the sending end and receiving end in a dual-machine system is studied.4)On the basis of clarifying the influence of wind power grid connection on the transient stability of power system,the correlation between the active power output of wind power and thermal power units and the branch energy index is deduced,and the sensitivity index of the active power output of wind power and thermal power units is constructed.Through the sensitivity index of wind power and thermal power active power,the optimal control unit when wind power grid-connected power system is unstable is screened.On this basis,taking the minimum cutting amount as the optimization goal,using the gray wolf optimization algorithm,the optimal cutting scheme is constructed to realize the quantitative control of transient stability of power system.Finally,the feasibility of the proposed wind-thermal coordination quantitative control scheme is verified in ten-machine system.