Abstract: This paper optimizes the integrated energy system （IES） at the time of grid connection on the basis of considering energy supply to the important loads after unplanned off-grid. Firstly， taking economic scheduling as the goal， considering different energy conversion efficiency and energy constraints， we establish a day-ahead economic optimization scheduling model with multiple forms of energy sources including cooling， heating and electric power. On this basis， a dynamic constraint method for the SOC of energy storage is proposed according to the energy demand of important loads after unplanned off-grid， and the energy storage capacity is fully utilized on the basis of ensuring important loads. Finally， using the particle swarm optimization algorithm to solve the model and determining the multi-energy flow coordinated optimization scheduling scheme. The analysis of the example shows that the SOC of energy storage can be constrained dynamically according to the scheme proposed in this paper， which can fully exert the role of “peak load shifting” of energy storage within the constraint range， and has obvious economic advantages compared with the traditional distribution method. At the same time， the established grid-connected economic optimization scheduling model can ensure that energy supply requirements of important loads can be met after unplanned off-grid at any time.

Key words: integrated energy system, unplanned off-grid, important load, independent energy supply, optimal scheduling