Identifying Optimal Energy Flow Solvability in Electricity-Gas Integrated Energy Systems

Abstract

Significant growth in gas-fired generator use has strengthened the interdependence between the electrical power systems and the natural gas systems. It is therefore imperative to analyze both systems jointly as an electricity-gas integrated energy system (IES). However, peak electricity and gas demands, intermittent renewable - resource power generation, and severe contingencies can result in an unsolvable optimal energy flow (OEF). Unsolvable OEF poses a serious threat to IES because a secure operating condition is unavailable without corrective controls. Thereby, this paper proposes three models for identifying OEF solvability. Model I minimizes the square of the energy flow mismatches, and Model II maximizes the loadability. Both Models I and II add slack variables to equality constraints, while Model III relaxes inequality constraints. Meanwhile, bidirectional gas flow models are employed. Based on Models I–III, the OEF feasibility margin and the infeasibility degree are defined. Case studies integrate an IEEE 39-node system and a 48-node gas network for validating the proposed models.