Power And Natural Gas Network Co-optimization Based On Energy Circuit Theory

Gas turbine is an essential part of the power system because of its rapid response ability and low-emission characteristic.With the continuous access of renewable energy power generation in the future,the power system will need more peak-shaving power plant to cope with the randomness and volatility in order to ensure its safety.Gas turbine will be a good choice.However,if only the operating constraints of gas units are considered and the natural gas network constraints are not considered,it may happen that the gas units cannot execute the dispatch instructions as required.But at present,adding natural gas network constraints to the dispatch model will face two major difficulties.First,most of the current gas network models are only suitable for describing steady state changes,ignoring the intermediate dynamic transition stage from one steady state to another steady state,resulting in a large gap between the model and the actual system.Second,the nonlinearity of the gas network model greatly increases the difficulty of solving the scheduling model.In response to this problem,this thesis first introduces the dynamic model of the natural gas network based on the Energy Circuit theory.Based on the flow quality equation and momentum equation of the natural gas one-dimensional pipeline,the model uses the distributed parameter theory to establish the model of the natural gas transmission line,and then combines the node branch correlation matrix of the natural gas network to establish the gas network node parameter admittance matrix equation in the frequency domain.Using this equation combined with the Fourier forward and inverse transformation,the time-varying curve of the gas network node parameters can be solved.Then,in order to apply the dynamic gas network model to the power-gas network cooptimization model,this thesis simplifies the mentioned solving method of the gas network node parameters.According to the linear superposition theorem,the complex changes of the gas network parameters are decomposed into a basic state and multiple simple changes.And the influence factors of the simple changes of the nodes on the gas network are extracted.Using this influence factor,the node parameters of the gas network can be calculated linearly.A numerical example verifies the effectiveness and convenience of using this influence factor to calculate the parameters of the gas network nodes.Finally,the influence factor solution method is used to linearize the dynamic gas network constraints,thereby reducing the difficulty of solving the power-gas network co-optimization model.In addition,based on the current situation that the information of the power network and the gas network are not interoperable,two methods are considered to make the power dispatching results satisfy the constraints of the gas grid as much as possible,and the feasibility is tested through calculation examples.