In an integrated energy system (IES), such as electricity-heating-gas system, remarkable difference in response time among multiple energy subsystems make the overall energy scheduling a challenging issue. Meanwhile, storage capabilities, such as inherent storage capability of gas pipelines, provide a potential way to improve system scheduling flexibility. In this paper, an optimal scheduling approach for IES operated in an islanded mode is developed, while covering inter- and intra-hour timescales simultaneously. Specifically, in inter-hour timescale, steady-state models of individual energy subsystems are used, and the heuristic particle swarm optimization (PSO) is integrated into the decomposition-based sequential multi-energy flow (MEF) calculation to derive optimal scheduling of CHPs and flow rates of gas sources with respect to forecasts of renewable energy sources (RESs); While in intra-hour timescale, with the dynamic model of gas flows, the optimal range of pressure of gas source node is scheduled to ensure robustness against RES uncertainties while leveraging storage capabilities of gas pipelines. An integrated energy test system is studied to demonstrate effects of integrated inter-hour and intra-hour schedules in handling different dynamic response time and effects of storages capabilities of gas line pack in achieving robust operation against uncertainties. (C) 2019 Elsevier Ltd. All rights reserved.