Flexibility of Integrated Power and Gas Systems: Gas Flow Modeling and Solution Choices Matter

TL;DR

This paper develops a unified framework for modeling gas flow in integrated power and gas systems, highlighting how different modeling choices impact the accuracy of flexibility provision estimates from gas networks to power systems.

Contribution

It harmonizes existing gas flow modeling approaches and analyzes how solution choices affect the assessment of system flexibility, revealing potential overestimations by certain methods.

Findings

Relaxation-based approaches can overestimate flexibility by allowing physically infeasible linepack rates.

The unified framework enables consistent comparison of different modeling and solution methods.

Accurate modeling of gas flow physics is crucial for reliable flexibility assessment.

Abstract

Due to their slow gas flow dynamics, natural gas pipelines function as short-term storage, the so-called linepack. By efficiently utilizing linepack, the natural gas system can provide flexibility to the power system through the flexible operation of gas-fired power plants. This requires accurately representing the gas flow physics governed by partial differential equations. Although several modeling and solution choices have been proposed in the literature, their impact on the flexibility provision of gas networks to power systems has not been thoroughly analyzed and compared. This paper bridges this gap by first developing a unified framework. We harmonize existing approaches and demonstrate their derivation from and application to the partial differential equations. Secondly, based on the proposed framework, we numerically analyze the implications of various modeling and solution choices on the flexibility provision from gas networks to power systems. One key conclusion is that relaxation-based approaches allow charging and discharging the linepack at physically infeasible high rates, ultimately overestimating the flexibility.