| The traditional urban energy system planning is dominated by a single network,and there is no connection between the networks,and no overall planning.This paper conducts an in-depth study on the co-planning problem of the distribution electricity-gas-heating network of the urban integrated energy system,and elaborates the connotation of the urban integrated energy system planning.This paper makes an in-depth study on the joint planning of electricity-gas-heating distribution network of urban integrated energy system,expounds the connotation of urban integrated energy system planning,and studies the related theories and methods of urban integrated energy system planning from the perspective of multi-network coupling and reliability.The research covers the key technical problems of the multi-network coordination planning,control objects,multi-network relaxation,large data application and N-1 reliability,N-k reliability in urban integrated energy system planning,and forms a relatively perfect basic research method and technical scheme of urban integrated energy system.The research priorities and related achievements mainly reflect the following aspects:(1)An extended planning model of electricity-gas-heating distribution network with hourly-level distribution network reconfiguration is proposed.The similarities and differences between the grid-gas network and the heat network are analyzed.Three common network planning general models are extracted with reference to relevant literatures.Based on the detailed study of distribution network reconfiguration,radial structure constraints and power flow trends,a power flow stripping distribution network planning method with reconfiguration is proposed.The method is analyzed from three levels:planning layer,operation layer and reconstruction layer.A three-network energy hub model is established,and a planning method suitable for heating network is proposed.The centralized modeling of the three networks is realized,which can simplify the complexity and adapt to large-scale network planning.The correctness and effectiveness of the proposed model are verified by the 54-node test system of the distribution network,the 50-node test system of the gas distribution network,the improved 38-node test system of the heating network and the joint test network of 5 energy hubs.(2)Areconfigurable distribution network and natural gas distribution network planning model for electricity storage and natural gas storage in energy hubs is proposed.Based on the basic structure of energy hub and the analysis of Electricity-Gas energy storage model,the energy hub with Electricity-Gas energy storage and the operation mechanism of hourly charging and discharging are analyzed theoretically,and the essence of energy hub and Electricity-Gas energy storage operation is revealed.Simulation results on three energy hubs and twelve energy hubs systems show that reconfiguration can transfer load and make full use of the capacity of existing lines,energy storage devices can smooth load fluctuations and delay or even avoid new equipment installation.The results verifying the correctness of theoretical analysis.The conclusions obtained can provide useful guidance for the promotion and application of urban integrated energy system control resources such as energy storage devices and reconfiguration.(3)An active distribution electricity-gas network joint expansion planning model based on mixed integer second-order cone is proposed.Based on the analysis of power flow equations of active distribution networks,auxiliary variables are introduced into the nodal power balance equations,and the nodal power balance equations and the voltage drop equations of power lines are relaxed to obtain the form of mixed integer second-order cones.At the same time,based on the analysis of the flow equation of the gas distribution network,the steady-state equation of the nonlinear non-convex and difficult to solve gas network pipeline is studied,and the relaxation method of the second-order cone is proposed.A moderately loose second-order cone programming model based on mixed integers is established to takes full account of the changes in the running state,and provide theoretical guidance for urban integrated energy system planning.(4)A method for urban multi-energy system planning considering energy supply reliability and wind-photovoltaic generators uncertainty is proposed.This paper studies the problem that the traditional scene reduction technology deviates too much when a large number of historical data is not good.Based on the analysis of the inherent mechanism of clustering algorithm,an improved DBSCAN algorithm is proposed to obtain the typical scene and the probability of fault occurrence closer to the actual working condition.At the same time,by separating the magnitude and direction of power flow and introducing virtual variables of load state,a reliability evaluation method of N-1 power supply is proposed,which is suitable for radial network and can be solved integratively without cyclic checking.And the correctness of the algorithm is illustrated from the planning level,the operational level and the N-1 failure level.An integer quadratic programming model for urban multi-energy systems with the goal of maximizing total profit is established.It provides a theoretical reference for the application of big data in the actual urban integrated energy system planning and the calculation of N-1 energy supply reliability.(5)A electricity distribution network and natural-gas network expansion planning model considering the reliability of electrical-to-gas coupling and radial network energy supply is proposed.Firstly,the physical structure of the model to be planned is described,and the electrical gas is modeled.For the volatility problem of renewable energy,the DBSCAN density clustering algorithm is applied to generate typical scenarios and their probabilities.Then establish a fault outage model,calculate the expected fault time of N-k occurring in any k energy distribution channels,and obtain the expected fault set.Then,by separating the magnitude and direction of the power flow and introducing the dummy variable of the load state,a radial network energy supply reliability algorithm considering N-k is proposed.The hybrid integer quadratic programming model is established with the minimum total cost of the distribution-gas system as the target..The test system uses a 24-node to-be-planned distribution network and a modified 30-node to-be-designed gas distribution network and is coupled through three electrical converters.The case study results prove the correctness of the radial network energy supply reliability evaluation algorithm proposed in this paper,which shows that N-k can obtain appropriate planning results compared with N-1.It shows that the two networks connected by PtG can effectively improve the system energy supply reliability and increase the capacity of renewable energy. |
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