The integrated energy system (IES) has the characteristics of flexible scheduling and mutual aiding among multiple energies. Aiming at the current insufficient research on the reliability of IES energy supply, an IES reliability evaluation method considering optimal load reduction and thermal load inertia is proposed. The expected index of the total loss of the IES from power outage is established, which fully reflects the economic loss caused by the power outage of the IES. Considering energy grade, load importance, and thermal load inertia, an optimal load reduction model for IES is established, which takes into account the minimum operating cost and the minimum weighted outage load under failure scenarios. The CPLEX software is applied to solve the proposed problem in order to obtain the electric and thermal load reduction power and component equipment output. According to the principle of sequential Monte Carlo simulation, an IES reliability assessment method and its process are designed. The calculation example analysis shows that the reliability level of IES can be improved effectively by using optimal load reduction strategy and considering thermal load inertia.

%U https://www.cepc.com.cn/EN/10.12204/j.issn.1000-7229.2021.04.005