Operational Risk Assessment For Power System With Consideration Of Wind Farm Forecast Errors

With the goal of carbon peak and carbon neutrality are proposed,the development of high proportion of renewable energy has become a trend.The share of renewable energy power generation has been increased to achieve carbon neutrality.As more and more renewable energy is integrated into power system,which brings new challenges.The grid structure and operation mode of the power system have been changed because of the renewable energy is connected.The uncertainty of the system is significantly increased due to the volatility of renewable energy,which has impacts on the static and dynamic security operation of the power system.Therefore,it is particularly important to carry out operational risk assessment for power grid.Based on the background hereinbefore,this thesis conducts research for the static and dynamic operational risks of power system with consideration of forecasting errors of wind farms.First,the impact of wind power grid integration on the power system is analyzed,and operational risk assessment indicators are established.Second,this thesis research the power system operational risk assessment methods form static and dynamic.Finally,this thesis studies the identification method of weak points of power grid on this basis.Using the proposed method to identify weak points.The main contents are as follows:(1)For static and dynamic operational risk assessment of power systems with centralized wind power,this thesis analyzes the static and dynamic impacts of wind power integrated system.The operational risk assessment indicators are proposed to quantify the impact of wind power on the system.Operational risk indicators include static(node voltage and branch flow)and dynamic(load loss)parts.(2)In the static operational risk assessment of the power system,Monte Carlo method is time-consuming and enumeration method has combination explosion problem,which cannot meet the computation time requirement of system operation.According to the above problems,this thesis proposes a fast method based on cumulant and GramCharlier series expansion to calculate the static operational risk.With consideration of forecasting errors of multiple wind farms,the problem of large linear errors of the calculation result is solved and the fluctuation of input samples is reduced by using Kmeans.Subsequently,Cumulants and Gram-Charlier series expansion theory are applied in each cluster to compute the cumulative distribution of node voltage and branch flow.According to the cumulative distribution,this thesis proposes an operational risk calculational method based on integral theory.Case study on a practical power system demonstrates that the proposed method meets system operation’s accuracy and time requirements.(3)In the dynamic operational risk assessment of the power system,the direct method application model is single.The stability margin cannot be calculated by using the time domain simulation method.A dynamic operational risk assessment method of power system is proposed based on Dynamic Security Region(DSR).First,according to DSR theory,the DSR of a certain disturbance event is established.Second,the transient stability and the minimum load loss of power system are determined based on the relative position of system operating point and DSR.Finally,dynamic risk indices are computed by the product of the system state probability and the load loss.The feasible and the effectiveness of the proposed method is verified by IEEE-39 test system.(4)Based on the aforementioned research of static and dynamic operational risk assessment of power system,this thesis proposes a computational method to identify the root causes and weak points of power system.In the proposed method,the formulas of calculating the indices of root causes and weak points are derived,which are used to identify the root causes components and weak points(weak buses and weak branches)of the system respectively.Subsequently,the efficacy of the proposed method is tested on IEEE 39-bus system.The proposed method can effectively help system operators to monitor weak points and root causes of power grid.This thesis with consideration of the static and dynamic aspects of the power system to evaluate the real-time operational risk.The studies can provide operators effective reference to improve the security of power grid operation.