As the rapid growth of gas-fired generators and the development of power-to-gas(P2G)technology intensify the interdependency between electricity and natural gas system

it is imperative to co-optimize the two systems synergistically. In China

the electricity system and natural gas system belong to different investment and decision makers

which means the two systems can only share little information with the help of an isolated coordinator. To adopt this situation

a distributed co-planning method of integrated electricity and natural gas system is proposed based on the alternating direction method of multipliers(ADMM). Firstly

a collaborative co-planning model of integrated electricity and natural gas system coupled by gas fired generators and P2G is proposed. The operation constraints of power system and natural gas system are taken into account to establish the planning model. Secondly

an co-planning subproblem of power system source-network and a planning subproblem of natural gas network are presented via the ADMM theory. With the information transfer of coupling variables

the mechanism of alternating iterative solution for two subproblems is developed. Finally

the effectiveness and feasibility of the proposed model is verified by an integrated electricity and natural gas system which consists of modified IEEE 39-node power system and Belgium 20-node gas system.