Research On The Resilience Assessment And Improvement Method Of Urban Integrated Energy System Based On Multi-Source Coordination

Since energy such as coal and oil are not renewable,and burning will generate a good deal of damaging gases such as carbon dioxide and contaminate the environment,under double pressures of energy deficiency and rising global temperature,it is urgent to improve energy utilization,decrease energy consumption,and regulate the energy construction.The urban integrated energy system（UIES）can consort and optimize various energy sources such as wind,light,cold,and heat,and effectually decrease the usage of fossil energy and carbon discharge.In the integrated energy system（IES）,the UIES is a typical existence and occupies significant development place in urban energy network.As coupled units are widely used in UIES,the degree of coupling of electricity/gas/heat networks has been deepened,and the research on the safe and reliable operation of UIES has become more and more important.Typhoons,floods and other extreme natural disasters have greatly endangered the safe operation of UIES and caused heavy losses to the national economy.The ability of UIES to deliver electricity,heat and natural gas uninterrupted to users during high-influence,low-possibility events like extreme disasters is critical to the security and life quality of urban population and the economy of urban areas.Thence,this paper put forward a load recovery strategy in view of multi-source coordination to improve the UIES’s resilience based on the principle of prioritizing the restoration of important loads for energy supply.The principal contents are as shown below:1)To assess the resilience level of urban energy systems,this paper constructs a resilience evaluation index for IES.The resilience assessment index can not only provide the resilience assessment of a single energy form system,but also can synergistically consider the load recovery of different energy systems,and provide the resilience assessment results of the whole UIES.This index takes the weight coefficients of loads in different energy forms in the system into consideration,considers the priority of loads in their respective systems,quantifies the recovery of loads in different energy forms,and can be widely used in the evaluation of other load recovery methods.The greater the resilience evaluation index value,the greater the recovery of important loads,and the stronger the system’s ability to resist extreme natural disasters.2)After extreme natural disasters,there are three stages for load power supply level of the system: no load recovery strategy is adopted,during the load recovery strategy,and load recovery strategy is completed.After extreme disasters,the multi-power-source coordination load recovery strategy is adopted,so that the load power supply level of the system can maintain the original or reach a new state.The load recovery strategy of multi-power-source coordination forms the final area after extreme natural disasters based on the minimum diameter spanning tree（MDST）method by controlling the tie switches in the urban power grid.Taking the minimum important load reduction in the final area as the objective function,and all the static safety constraints in the area are considered,the optimal power flow calculation is carried out.At this time,the area can maximize the use of various power sources in the urban power grid to achieve power supply to important loads in the system,thereby the urban power grid’s resilience is promoted.3)In order to improve the resilience of UIES,this paper presents a multi-energy coordination method apply to the UIES based on the multi-power-source coordination method for improving the resilience of the urban power grid.The recovery strategy is divided into two stages: the first stage determines the topology of the final area after the failure based on the MDST method,and reconnects each energy "island" after an extreme natural disasters to ensure that the operating radius of the area is minimal,and reducing power grid loss and voltage drop,gas network pipe storage and pressure drop,heat network temperature transmission delay and temperature drop.In the second stage,based on the obtained final area after the fault,taking all the static safety constraints in the area into consideration,and the objective function is to minimize the sum of important load reductions in the system,and compute the optimal multi-energy flow in this area.The restoration strategy proposed in this paper is able to take full advantage of energy complementarity by coordinating all sources（power,gas,and heat）in the area to ensure uninterrupted energy supply for critical loads in the system.At last,analyze and validate the proposed method through UIES E33-G14-H6 test system and UIES E123-G48-H32 test system.According to the case study: the proposed load recovery strategy can realize the priority recovery of critical loads in the system after the disaster and effectually heighten the system’s resilience.