Influence Of A Large Proportion Of Intermittent Energy Sources On Frequency Stability Of Power Grid

Affected by environmental pollution,energy conservation and other issues,modern power grid must be organically integrated into a large number of distributed clean energy power generation,users and energy storage as a whole,to provide the required energy when users needing.When a large proportion of green energy with randomness and "uncontrollability",e.g.,solar and wind power,is connected to the grid,it can seriously affect the power quality of the power grid,and even cause the voltage and frequency collapse.From the perspective of network structure,modern（future）power grid has become a highly heterogeneous,non-autonomous,time-varying complex network,which makes the traditional stability analysis methods will be difficult to apply.Therefore,it is of great theoretical and practical value to study the frequency stability of power grid and ensure the reliable transmission of electricity in this case.Firstly,the frequency analysis model of power grid with wind/light/energy storage node is established according to the rotation equation of the rotor.Then,based on the Lyapunov inverse theorem,this paper proves the admissible variant capacity of intermittent energy sources to keep the frequency stability of power grid,which takes the network topology,the initial load of nodes,and the type of nodes into account.In terms of optimal scheduling,the optimal power scheduling method of grid considering maximum capacity constraint is proposed.The method gives the optimal power generation plan of conventional generators and the charging/discharging plan of energy storage units by rolling calculation,which is based on the prediction value of wind,photovoltaic power and load,so that the active output of all the power stations can be safely operated in the stable area.The optimal power scheduling method is beneficial for the grid to accept wind power,photovoltaic and other intermittent energy power generation to the maximum extent under the premise of ensuring the safe and stable operation of power grid.A large number of intermittent energy grid-connected operation will also lead to the changes of grid in the spatial and temporal structure.Therefore,it is very important to study the stable operation of the variable topology power grid.This paper presents the relationship between network variant capacity and network topology,which provide theoretical guidance for the optimal access location of clean energy grid-connected operation.In addition,the method is applied to the problem of critical line identification of power grid.The new identification method is established by judging the maximum eigenvalue λ_max（L_b）of the matrix L_b.In the aspect of power grid control,the method of grid frequency stability control is given based on the agent model.The control algorithm has the advantages of being independent of the main control station,and with fast frequency response.Motivated by the situation of high intermittent energy penetration,some beneficial theoretical exploration for future grid stability analysis and control has been provided in this thesis.