In order to have an accurate knowledge of systemwide operation states

it is necessary to perform state estimation for the integrated energy system (IES) as the basis of energy management and control. Centralized state estimation is practically infeasible for IES due to the unreliability of communication

the barrier on privacy

and the large scale of integrated systems. This paper proposes a distributed state estimation algorithm based on the alternating direction method of multipliers (ADMM) for IES containing electricity

heat

and natural gas. Various coupling units are taken into full consideration in modeling of IES state estimation to reflect the harmonization of multi energy. On the basis of bilinear measurement model

the state estimation considering nonlinear measurements can be replaced by an equivalent three-stage problem containing two linear state estimations and an intermediate transformation to avoid nonconvex optimization. The three-stage procedure for IES state estimation can be further decoupled over three sub-systems with coordination on coupling units

yielding a fully distributed scheme based on ADMM. A modified ADMM with the self-adjusting penalty parameter is also adopted to enhance the convergence. Simulation results demonstrate the validity and superiority of the proposed algorithm.