Static Security Assessment of Electric-gas Coupling System Using Equivalent Sign Function

A static security assessment method for electric-gas coupling system is proposed in this paper. When modeling natural gas systems, the generalized gas equations are improved by sign-function equivalent method, which simplifies the programming process for gas flow calculation. Considering the difference between the operation of the natural gas system and the electric power system, the impact of the gas system failure on the whole coupling system is transferred to the impact on the output of the coupled generation units. Therefore, the analysis of the contingency of the whole electric-gas coupling system can be focused on the N-1 analysis of the power grid, which can simplify the calculation and take into account both the failure of the gas system and power system at the same time. The proposed method was verified on a coupling test system which combined the IEEE 39-bus system and Belgium 20-node natural gas system. The results show that the static security assessment method can screen out the dangerous conditions in the electric-gas coupling system, which can provide certain guidance for the system operators and is of great significance for the security operation of the whole system.