| Integrated Energy System(IES)can realize the coordinated supply of electric energy,natural gas energy and thermal energy,effectively improve the local absorption capacity of distributed renewable energy,and reduce the dependence on external power grid on the premise of meeting the needs of users,which has received extensive research and attention.The electricity-gas regional integrated energy system is composed of power system,natural gas system and energy center,which realizes the complementary support among distribution network,gas distribution network,regional energy center and other regional energy systems within the regional scope.Deterministic multi-energy flow calculation is an important basis for IES analysis and operation,which can provide basis for equipment location and capacity determination,operation decision and fault analysis.In this paper,the multi-energy flow calculation and its convergence adjustment for the electricity-gas regional integrated energy system are studied.The main work is as follows:1)Perform energy flow calculations for the electricity-gas regional integrated energy system.Based on the idea of decomposition solution,the node type processing of energy hub(EH)is carried out,and the node power equation of power system,node pressure equation of natural gas system and loop flow equation are analyzed based on the conventional energy flow calculation mechanism.Establish the conventional energy flow model of power system and natural gas system,and the mathematical model of compressor and gas turbine.The Newton-Raphson(NR)method is used to decompose and solve the energy flow of the electricity-gas regional integrated energy system.Finally,a numerical example is given.2)An method for energy flow differentiation of the electricity-gas regional integrated energy system is proposed.In view of the diversity of EH operation mode in electricity-gas regional integrated energy system and the difference of energy flow characteristics between power system and natural gas system,this paper decomposes and solves the power system and natural gas system,recursively solves the energy flow of power system based on analytic function,and uses linear approximation method to solve the energy flow of natural gas system.In solving the energy flow of the power system,the analytic function equation of the power node is established based on the power equation of the power node.The analytic function of the quantity to be solved is expanded into the form of power series.The coefficient of the finite term power series is calculated by the recursive method,and the Pade approximation of the finite term power series is constructed to judge the feasibility of the solution.Finally,an example is given to verify the correctness and effectiveness of the proposed method.3)A method for diagnosing and adjusting the energy flow convergence of power system and natural gas system is proposed.The algorithm and physical mechanism of non-convergence of energy flow calculation in power system and natural gas system are analyzed.On this basis,the unbalance types and main nodes that lead to non-convergence of energy flow calculation in the system are identified by using the variation characteristics of modified values in the iterative calculation process of NR method.For the power system,considering the strong coupling characteristics of active power and reactive power,the voltage amplitude adjustment method of balance nodes and the power node type conversion method are adopted to solve the problem of non-convergence of energy flow calculation.For natural gas system,considering the flow characteristics of the system,the pressure adjustment mode of natural gas node is adopted to solve the problem of non-convergence of energy flow calculation by adjusting the outlet pressure of gas source or compressor.Finally,an example is given to verify the correctness and feasibility of the proposed method,which provides a theoretical basis for the convergence analysis and adjustment of multi-energy flow in the electricity-gas regional integrated energy system.4)A decoupling adjustment method for multi-energy flow convergence of the electricity-gas regional integrated energy system is proposed.Based on the multi-energy flow decoupling calculation method of the comprehensive energy system,the convergence judgment of the energy flow calculation of the power system and the natural gas system is carried out separately,and the unbalance type and the main nodes are identified,and then the convergence decoupling adjustment is made.In view of the non-convergence of energy flow calculation caused by the system active power imbalance,the multi-EH power balancing machine adjustment mode is adopted.EH in the working mode of electric constant heat is used as the power balancing machine to share the active power imbalance of the system.Finally,an example is given to verify the correctness and effectiveness of the proposed method. |
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