As a type of energy system with bright application prospects

the integrated energy system (IES) is environmentally friendly and can improve overall energy efficiency. Tight coupling between heat and electricity outputs of combined heat and power (CHP) units limits IES operational flexibility significantly. To resolve this problem

in this paper

we integrate operating mode optimization of the natural gas combined cycle CHP unit (NGCC-CHP) into dispatch of the IES to improve flexibility of the IES. First

we analyze operational modes of the CHP units from the perspectives of thermal processes and physical mechanisms

including the adjustable extraction mode

back-pressure mode

and switching mode. Next

we propose an explicit mathematical model for full-mode operation of the CHP units

in which the heat-electricity feasible region

switching constraints

and switching costs are all formulated in detail. Finally

a novel economic dispatch model is proposed for a heat and electricity IES

which uses the full-mode operation of CHP units to improve operational flexibility. The Fortuny-Amat transformation is used to convert the economic dispatch model into a mixed-integer quadratic programming model

which can then be solved using commercial solvers. Case studies demonstrate the proposed method can reduce operational costs and obviously promotes wind power utilization.