Reliability evaluation of electric-gas-thermal coupling systems considering the post-fault operation modes of user-level integrated energy system

The distribution network with user-level integrated energy systems (UIESs) represents a new form of future energy systems. Traditional reliability evaluation methods for distribution networks with multiple UIESs are no longer applicable due to their multi-energy coupling and island operation. To address this, a reliability evaluation method for electric-gas-thermal coupling systems with UIESs is introduced. Post-fault operation modes of UIESs are proposed considering the multi-energy cooperation and joint island operation. The criteria of fault correlation matrixes are further established to quickly determine the energy supply state of the loads and the operation mode of the UIESs. Moreover, a static island division model and a dynamic load reduction model for the UIES are embedded in the reliability assessment. The effectiveness and practicality of the proposed reliability evaluation method are verified, as the results accurately calculate reliability indices and offer guidance for micro-energy grid operations under various fault conditions.