The integrated energy system(IES) is of great significance to promoting the complementary use of energy and improving the comprehensive energy utilization rate. The analysis of multi-energy flow is related to the planning

operation and control of the IES. In this paper

the research status of power flow and optimal power flow in IES is explored

and the calculation models and methods are summarized. It introduces the development

structure and the models of multi-energy flow calculation of the IES. Moreover

it summarizes the problems and solutions of the power flow and the optimal power flow in the IES

respectively. Generally

it points out the shortcomings of the current multi-energy flow calculation of the IES and the future research trends and prospects. The result shows that

there is a lack of in-depth research on multi-energy flow modeling and calculation methods of electricity-heat-gas IES at present

without fully considering the quasi-stationary and transient models and the interaction of multienergy. It is necessary to deepen the energy hub's modeling method actually to describe the coupling link uniformly. The current models of IES seldom consider the energy storage devices

which is beneficial to improve the energy efficiency further and dispatch energy more flexibly. Finally

the existing algorithms are not enough for power flow and optimal power flow involved few multi-objective optimal power flow calculations. The safety and reliability evaluation system of the IES needs to be further improved.