Abstract：In the real world, the energy crisis and environmental pollution problems are prominent. Traditional fossil energy has been unable to meet the rapidly growing energy demand of human society. The regionally integrated energy system came into being to meet the distribution network's green and low-carbon development needs. However, the development form of multi-energy complementation of regionally integrated energy systems brings incredible difficulties to its reliability assessment. In recent years, some reliability assessment methods for regional integrated energy systems have been proposed, but they lack practicality, and the calculation accuracy and efficiency are out of balance. A reliability assessment method for a regionally integrated energy system based on sequential Monte Carlo simulation considering multiple thermal inertias was proposed to solve this problem. A practical evaluation method is suggested by improving the calculation accuracy and efficiency from three aspects of the component outage model, system modeling, evaluation method, and fault state analysis. Firstly, the typical structure of the CHP unit was constructed. The operating states of the CHP unit, such as normal operation, power-heat reduction, power supply reduction, and system shutdown, are analyzed. A four-state reliability model for the CHP unit was developed based on Markov chains. Secondly, the effects of heat source start-up inertia, heat network transmission inertia, and building thermal inertia on system reliability were analyzed. Based on differentiated energy flow modeling, an operation optimization model for steady-state and a dynamic optimal load-cutting model considering multiple thermal inertias were proposed. The optimization models were established with the objectives of operation economy and equivalent load loss amount, respectively. Finally, the heat network loss of load indices was corrected by counting user comfort characteristics. A sequential Monte Carlo simulation is used to evaluate the reliability of the regionally integrated energy system. The simulation results show that compared with the traditional two-state model, the four-state reliability model of components based on the Markov chain analytic method improves the modeling accuracy of power supply and heating by 26.22% and 12.89% respectively, and reduces the probability index of system load loss. It has higher evaluation accuracy. Under the multi-energy complementary mechanism, coupling the gas grid and power grid improves the power grid's reliability by 0.51%. The cogeneration unit undertakes 53.44% of the energy supply of the power grid and heat supply network. Therefore, increasing the capacity of coupling equipment and making each subsystem have certain source side redundancy can bring noticeable reliability gain. The reliability index of heating based on heating temperature is proposed. The reliability of the heating network can be improved by 11.76% by using building thermal inertia. Although the heat source inertia and heat network inertia reduce the system reliability due to the extension of the time for heat energy transmission to users, using the difference between photovoltaic output and user demand time and the configuration of heat storage at the heat source can convert the heat load into translatable load during operation, which can improve the system operating economy. The following conclusions can be drawn from the simulation analysis: (1) The detailed description of the reliability model of CHP units can effectively improve the reliability evaluation of regionally integrated energy systems. (2) Analyzing the difference in energy flow in different subsystems and the idea of differential energy flow modeling in normal and fault phases can effectively improve the calculation accuracy and efficiency. (3) Full use of the multiple thermal inertias of the source, grid, and load in the thermal system can effectively reduce the frequency and duration of the system load loss event under fault conditions.
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