  We propose a hidden convexity-based method to address distributed optimal
energy flow (OEF) problems for transmission-level integrated electricity-gas
systems. First, we develop a node-wise decoupling method to de-compose an OEF
problem into multiple OEF subproblems. Then, we propose a hidden
convexity-based method to equivalently reformulate nonconvex OEF subproblems as
semi-definite programs. This method differs from any ap-proximation and
convexification methods that may incur infeasible solutions. Since all OEF
subproblems are origi-nally convex or equivalently convexified, we adopt an
ADMM to solve the hidden convexity-based distributed OEF problem with
convergence analysis. Test results validate the effectiveness of the proposed
method, especially in handling a large number of agents.
