Study On Energy Flow Calculation Model And Method Of Integrated Energy System

The integrated energy system is one of the effective ways to improve the efficiency of energy utilization,which involves the coordinated utilization of multiple energy flow,such as electricity,heat/cold and gas.The multi-energy flow calculation is an important basic work for planning,operation and control of integrated energy systems.In this thesis,the multi-energy flow calculation model and method of integrated energy systems are studied.In terms of the model,a unified model of energy flow for the integrated energy system considering multiple working modes of compressors is established based on the traditional models of electricity network,heat network,natural gas network and coupling components.The model can consider three working modes of compressors: constant compression ratio,constant outlet pressure and constant natural gas flow.It can solve the problem of inaccurate calculation results of multi-energy flow when compressors operate in different working modes and improve the accuracy of calculation.In terms of the solution method,the integrated solution method and the decomposed solution method are used for calculation and comparative analysis.In order to improve the computational efficiency of the integrated solution,based on the derivatives of all state variables in the model,the Jacobian matrix of the model is derived,and an improved gradient descent iteration method is proposed.In order to improve the computational applicability of the decomposed method,a decomposed iteration method for solving the multi-energy flow model is proposed.Finally,by comparing and analyzing the results of the two calculation methods,a reference is provided for the system operators to choose the solution method.The proposed model and method are simulated and verified by using 14 node electricity-14 node heat-10 node gas and 1047 node electricity-32 node heat-48 node gas integrated energy systems.The results show that:(1)The compressor working modes not only affect the energy flow results of the natural gas network,but also affect the energy flow results of the electricity network and the heat network through the coupling components.(2)In terms of computational accuracy,the results of the non-gradient descent iteration method,the gradient descent iteration method and the decomposed solution method are the same;in terms of computational efficiency,the gradient descent iteration method has faster convergence speed and shorter computational time.