The increasingly severe global climate problem has not only brought the trend of multi-energy coupling but also put forward higher requirements on the ability of energy systems to resist the impact of extreme disasters. To improve the resilience of integrated electricity and natural gas distribution systems (IEGDS)

this paper proposes a two-stage distributionally robust expansion planning model considering dual-fuel units and tie lines. Firstly

a deterministic expansion planning model is established

in which the sum of the system's operation and planning cost is taken as the objective function. The planning model considers the deployment of gas turbines

power-to-gas equipment

power storage equipment

gas storage equipment and the upgrades of lines and pipelines. In terms of improving resilience

the paper considers combined gas and electricity islands with tie lines to enhance the resilience of the IEGDS

given that dual-fuel units can replace fuel supply loads when natural gas is insufficient during disasters

and the construction of tie lines can increase the flexibility of distribution network reconfiguration. Therefore

the construction of dual-fuel units and tie lines is modeled. Operation constraints such as reconfiguration of the distribution network are also considered in the model. Secondly

using distributionally robust optimization method based on Kullback-Leibler (KL) divergence to model the uncertainty of extreme disasters' impact

the paper establishes a two-stage distributionally robust expansion planning model. In the first stage

the model calculates the most economical planning decision of IEGDS in the basic case. In the second stage

the optimal planning decision is obtained using the resilience threshold set by the system operator to form the resilience constraint. Finally

through case study

the paper demonstrates how the proposed model improves the economics of IEGDS operation under normal conditions and enhances resilience during extreme disasters.