Data Driven Optimal Energy Flow Calculation And Operational Risk Assessment For Integrated Electric-Gas Systems

The integrated electric-gas systems is one of the important exploration directions for China’s energy transformation and transformation under the "dual carbon" goal.The model of an integrated electric-gas systems is the basis for operational optimization and safety control.However,accurate modeling still faces the following challenges:the dynamic process of a natural gas system is characterized by a set of partial differential equations,and the model is complex and difficult to solve;Both the optimal energy flow model and the safety assessment model are affected by the distribution parameters of the gas network,and this parameter is difficult to measure;The safety assessment model has integer variables and is difficult to solve.For this reason,this dissertation proposes an optimal energy flow calculation model and a safety evaluation model for the integrated electric-gas systems based on the surrogate model of the gas network dynamics.The main work is as follows:(1)A surrogate model for natural gas systems dynamics is proposed.Based on historical operating data of natural gas systems,neural networks are used to fit the flow and pressure relationships of the gas network,and neural network parameters are extracted to construct a surrogate model for the gas network dynamics;Based on the time domain two-port gas network model,the concept of the maximum time constant of the gas network is proposed.Using the constant as a reference,the historical operation data of the gas network is cut and reused,which improves the effective sample number,reduces the size of the surrogate model,and obtains a rolling surrogate model for the gas network.Taking the gas distribution network as an example,the accuracy advantages of the proposed model compared to the physical model based on the assumption of pipeline parameter homogenization and the full-time surrogate model for the gas network are verified.(2)A method for calculating the optimal energy flow of an integrated electric-gas systems considering the dynamic process of a natural gas system is proposed.Taking the minimum operating cost of the integrated electric-gas systems as the objective function,the surrogate model of the gas network dynamics containing a nonlinear activation function is equivalently transformed into a mixed integer linear programming model,and combined with the power flow model of the power system,the optimal energy flow model of the integrated electric-gas systems is established;Taking a distribution network level integrated electric-gas systems as an example,the advantages of the proposed model over the physical model based on the assumption of pipeline parameter homogenization and the full-time surrogate model for the gas network are verified.(3)A security evaluation method for an integrated electric-gas systems considering the dynamic process of natural gas is proposed.Based on the surrogate model of the gas network dynamics,the minimum load shedding in the worst case is taken as the security evaluation index,and the node energy flow uncertainty is considered as an attacker.An attacker-defender model is constructed to evaluate the security of the solution of the optimal energy flow model in the presence of load uncertainty.A column and constraint generation algorithm is used to solve the attacker-defender model.Finally,the evaluation accuracy of the proposed method compared to the physical model based on the assumption of pipeline parameter homogenization is verified.In summary,this dissertation proposes an optimal energy flow calculation method and security evaluation method based on the surrogate model of the gas network dynamics,analyzes the dynamic process of the gas network,proposes the concept of the maximum time constant of the gas network,improves the number of effective samples,reduces the size of the model,and improves the accuracy of the model.In combination with the power system flow model,an optimal energy flow model for the integrated electric-gas systems is established,an attacker-defender safety evaluation model is proposed to meet the safety and economic operation of the electricity gas integrated energy system.