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The integration of renewable energy sources into existing electric power systems is connected with an increased interdependence between natural gas and electricity transmission networks. To analyse this interdependence and its impact on security of supply, we developed a novel quasi-dynamic simulation model and implemented it into the simulation tool SAInt (Scenario Analysis Interface for Energy Systems), the first published software application that allows the combined simulation of gas and electric power systems in a single time frame and simulation environment. The model is composed of a transient hydraulic simulation model for the gas system and an augmented AC-Optimal Power Flow model for the electric power system, which includes a model for dispatchable power system loads and considers time transitional constraints, such as the ramp rate and the start-up time of generation units. Both models take into account the control and constraints of the most relevant facilities present in both systems. The bidirectional interconnection between both systems is considered and established by coupling equations describing the fuel gas offtake for power generation in gas fired power plants, and the electric power supply to LNG terminals and electric driven compressors in gas compressor stations. The resulting system of equations for the combined model are solved in a single simulation time frame. In order to quantify the impact of different contingencies on the operation of the combined system, a number of security of supply parameters are proposed, which can be utilised to compare the impact of different contingencies on security of supply and the effectiveness of countermeasures to mitigate this impact. The capabilities of the combined model and the functionality of the simulation tool SAInt are demonstrated in a case study of a sample gas and power transmission system. Results indicate how the combined simulation of gas and electric power systems can give insight into important and critical information, such as the timing and propagation of contingencies cascading from one system to the other or the grace period to react to these contingencies. Such information can contribute to improving the coordination between gas and power transmission system operators in the event of a disruption, thus, increasing the resilience and the level of security of supply in the combined energy system. The information provided by the combined model cannot be obtained by the traditional co-simulation approach, where both systems are solved in different time frames. Furthermore, the studies stress the importance of using transient gas simulation models for security of supply analysis instead of steady state models, where the time evolution of gas pressure and linepack are not reflected appropriately.

Power systems worldwide are becoming more reliant on energy from natural gas, wind, and solar, posing potential reliability and coordination challenges from the tighter coupling of these infrastructure systems. This paper proposes a framework for the market-based coordination of electricity and natural gas system operations. The proposed framework includes a power system model that accounts for flexibility in the commitment of power plants with short start-up and shut-down times, coupled with a dynamic gas model that simulates when gas cannot be delivered to generators. The capabilities of the framework are illustrated using real-world electric power and gas systems, including scenarios around wind and solar penetrations and the analysis of time-variant, “shaped flow” gas nominations. Our results indicate that coordination between power and gas systems improves total gas delivery and reduces out-of-merit order dispatch in the electricity system, and that shaped flows may reduce unserved gas in systems with high penetrations of wind and solar energy sources. Coordination can have mixed effects on carbon-dioxide emissions, with emissions increasing with coordination for current systems during high load weeks but decreasing for systems with high renewable penetrations, particularly during periods of high variability.

This paper presents an integrated transient hydraulic model that describes the dynamic behavior of natural gas transport systems (GTS). The model includes sub models of the most important facilities comprising a GTS, such as pipelines, compressor stations, pressure reduction stations, underground gas storage facilities and LNG Terminals. The submodels are combined to an integrated network model and the algorithm for solving the resulting system of equations is detailed. The accuracy of the model is confirmed by benchmarking the model against results from the scientific literature and the commercial software SIMONE. Finally, the ability of the model to simulate the normal operation of a real world gas system and the operation in case of a supply disruption from a major entry point is demonstrated. Crown Copyright (C) 2015 Published by Elsevier B.V. All rights reserved.

Increasing renewable energy penetrations and low natural gas prices have increased the reliance of U.S. power systems on natural gas-fired generation. Increased reliance has sparked concerns over and resulted in natural gas deliverability constraints. To mitigate these constraints, research and regulatory reform have tried to improve coordination between power and gas systems. The U.S. Federal Energy Regulatory Commission (FERC) issued Order 809 in 2015 to improve day-ahead and intra-day coordination of power and gas systems. Given little research on intra-day coordination and FERC's recent action, we quantify the value of improved intra-day coordination between gas and electric power systems. To do so, we co-simulate coordinated day-ahead, intra-day, and real-time operations of an interconnected power and natural gas test system using a dynamic natural gas simulation model and a power system optimization model. We find intra-day coordination reduces total power system production costs and natural gas deliverability constraints, yielding cost and reliability benefits. Sensitivity analysis indicates improved intra-day renewable energy forecasts and higher renewable energy capacities increase intra-day coordination benefits for gas network congestion. Our results indicate FERC Order 809 and other policies aimed at enhancing intra-day coordination between power and gas systems will likely yield cost and reliability benefits.

The operation of electricity and natural gas transmission networks in the U.S. are increasingly interdependent, due to the growing number of installations of gas fired generators and the penetration of renewable energy sources. This development suggests the need for closer communication and coordination between gas and power transmission system operators in order to improve the efficiency and reliability of the combined energy system. In this paper, we present a co-simulation platform for examining the interdependence between natural gas and electricity transmission networks based on a direct current unit-commitment and economic dispatch model for the power system and a transient hydraulic gas model for the gas system. We analyze the value of day-ahead coordination of power and natural gas network operations and show the importance of considering gas system constraints when analyzing power systems operation with high penetration of gas generators and renewable energy sources. Results show that day-ahead coordination contributes to a reduction in curtailed gas during high stress periods (e.g., large gas offtake ramps) and a reduction in energy consumption of gas compressor stations.

Gas and power networks are tightly coupled and interact with each other due to physically interconnected facilities. In an integrated gas and power network, a contingency observed in one system may cause iterative cascading failures, resulting in network wide disruptions. Therefore, understanding the impacts of the interactions in both systems is crucial for governments, system operators, regulators and operational planners, particularly, to ensure security of supply for the overall energy system. Although simulation has been widely used in the assessment of gas systems as well as power systems, there is a significant gap in simulation models that are able to address the coupling of both systems. In this paper, a simulation framework that models and simulates the gas and power network in an integrated manner is proposed. The framework consists of a transient model for the gas system and a steady state model for the power system based on AC-Optimal Power Flow. The gas and power system model are coupled through an interface which uses the coupling equations to establish the data exchange and coordination between the individual models. The bidirectional interlink between both systems considered in this studies are the fuel gas offtake of gas fired power plants for power generation and the power supply to liquefied natural gas (LNG) terminals and electric drivers installed in gas compressor stations and underground gas storage facilities. The simulation framework is implemented into an innovative simulation tool named SAInt (Scenario Analysis Interface for Energy Systems) and the capabilities of the tool are demonstrated by performing a contingency analysis for a real world example. Results indicate how a disruption triggered in one system propagates to the other system and affects the operation of critical facilities. In addition, the studies show the importance of using transient gas models for security of supply studies instead of successions of steady state models, where the time evolution of the line pack is not captured correctly.