Multi-Energy Flow Calculation And Analysis In Multi-Energy Carrier Systems

With the advancement of technology and the improvement of people’s living standards,a single energy structure can no longer meet the needs of human production and life.In order to promote better conversion,use and improve energy efficiency between various energy sources,people began to explore a new energy system structure-multi-energy system.Calculating the energy flow of a multi-energy system is an important process for understanding the state of the network.The calculation result of the energy flow is an important basis for the process of network control and planning analysis.Therefore,this paper mainly studies the deterministic and uncertain energy flow calculation of the multi-energy system.The specific research contents are as follows:(1)According to the physical structure and operation mechanism of the multi-energy system,the interconnection relationship between networks is fully studied,and the mathematical models of electrical,natural gas,thermal network and coupling equipment are established.In addition,the classification of node types is proposed from the perspective of each sub-network and network components,and several new slack types are proposed to lay the foundation for energy flow calculation.(2)Using the Newton-Raphson method for unified energy flow calculation,it has the advantages of fast convergence speed and high calculation accuracy.Based on the sensitivity of the Newton-Raphson method to the initial value,a convergence theorem is proposed.It can be judged before the iteration whether the initial value can make the energy flow obtain a convergence result.Based on the convergence theorem,the initial value selection strategy is further proposed,and a set of initial guesses to ensure the convergence result is selected to make sure the accurate energy flow results of the complex and closely coupled integrated energy network can be obtained by using the Newton-Raphson method.(3)Using fast decomposing strategy to calculate energy flow,this method has the advantages of simple and fast calculation compared to Newton-Raphson method,especially for large-scale integrated energy network and the calculation speed of energy flow is higher than the result accuracy.This strategy can be divided into the holomorphic embedding method,the linear pressure method and the linear mass flow method.The simulation proves that the method has moderate accuracy and fast calculation speed,and has obvious applicability and superiority.(4)Because of the existence of probabilistic uncertainty and possibilistic uncertainty in the actual multi-energy systems,the traditional pure probabilistic method and pure possibilistic method are no longer suitable for dealing with multiple uncertainties.This paper considers the uncertainties from the perspective of the source,network and load of multi-energy systems,and proposes a hybrid possibilistic-probabilistic energy flow assessment method,which can achieve higher computational efficiency and reduce overestimation of uncertainty.This can help system operators and planners betrter evaluate the technical performance of multi-energy systems.