Session: 09-06-01: Decarbonization with Hybrid Energy Systems

Paper Number: 173954

Rapid Load Transition of a Solid Oxide Fuel Cell – Gas Turbine (Sofc-Gt) Hybrid System and Its Impact on Power Grid Resiliency: A Geographically Distributed Co-Simulation Study 

Renewable energy generation (mainly solar and wind power) on power grids has increased significantly in the past decade. However, due to the intermittency of renewable energy generation, it has become challenging to maintain a demand-supply balance, which deteriorates the stability and reliability of power grids. Mitigation approaches (e.g., dispatchable generation with improved flexibility, grid-scale electric energy storage, and controllable loads) have been proposed to address these stability issues; however, the interplay between these approaches and the power grid dynamics has not been well researched.

In the present study, we established a geographically distributed co-simulation platform that connected the solid oxide fuel cell–gas turbine (SOFC-GT) hybrid system at the National Energy Technology Laboratory (NETL) in Morgantown, West Virginia, with the grid simulation capability at the Idaho National Laboratory (INL) in Idaho Falls, Idaho. This telecommunication was established using the Energy Science Network (ESnet) and a Virtual Private Network (VPN), with a round-trip latency of approximately 80 milliseconds.

NETL’s SOFC-GT hybrid is a tightly coupled hybrid system that integrates an SOFC with a gas turbine to maximize the synergies from both components. This cycle was realized through an advanced cyber-physical simulation approach, with the SOFC being a real-time cyber-physical model and the balance of plant (i.e., turbine, compressor, and bypasses) being hardware. This cyber-physical simulation approach represented the actual cycle at high fidelity and low risk.

NETL’s SOFC-GT was remotely interfaced to INL’s Power and Energy Systems Real-time Simulation Lab (PERL). NETL’s SOFC-GT hybrid served as a generation node in this grid simulation. The generation capacity was scaled and interconnected to Bus 816 of the IEEE-34 Node Test Feeder on the RTDS® Simulator. This distribution test feeder represented an actual one in Arizona.

Leveraging both unique assets for this geographically distributed co-simulation, rapid load transition of the SOFC-GT hybrid was demonstrated. SOFC-GT load ramp-down from 373.5 kW to 192.3 kW (approximately 48.5% turndown) was achieved in 10 seconds upon grid demand change from INL (for the scenario of sudden load drop). Later, the SOFC-GT hybrid ramped up from 192.3 kW to nominal power (373.7 kW) in 10 seconds (for the scenario of sudden load increase). The gas turbine load, hot-air bypass valve opening, and pre-combustor fuel mass flow were controlled to manipulate the SOFC cathode inlet air process flow for SOFC thermal management without violating its solid temperature gradient constraint (<10 K cm^-1). More importantly, nonlinear transients in the air process flow were observed as caused by the interplay between the SOFC and the balance of plant. This highlighted the need for adaptive control strategies to enable automated load turndown as the hybrid system underwent several control states during load transitions.

The grid simulation performed at INL studied the penetration of solar generation to the rest of the 34-Node Test Feeder at 1%, 10%, 25%, and 50% with and without the rapid load transition capability of NETL’s SOFC-GT hybrid. The power ramp-up and down commands were sent to the SOFC-GT via the Giga Transceiver Socket (GTNET-SKT), and associated acknowledgments were recorded to tune the dynamic rate limiter for responding to emulated load fluctuations. For each penetration level, frequency and voltage transients at Bus 816 were observed in relation to dynamic load fluctuations. It was observed that the presence of SOFC-GT improved both the frequency and voltage nadir, and such a trend was more pronounced at higher penetration of inverter-based resources such as solar generation.

This research applied a geographically distributed co-simulation platform in advancing the development of hybrid systems in response to grid events. In addition, this joint research also demonstrated how a federated testbed can address challenges related to grid resilience, flexibility, and modernization.

Presenting Author: Biao Zhang U.S. Department of Energy, National Energy Technology Laboratory

Presenting Author Biography: Biao Zhang has been a researcher at NETL since 2019. His research at NETL mainly focuses on
the grid demand response of hybrid energy systems and cyber-physical simulation of solid oxide
cells (SOFC/SOEC)-based hybrid energy systems. Prior to joining NETL, Biao was an assistant
professor at Chongqing University in the research area of transport phenomena in fuel cells
and multi-energy systems. Biao Zhang has diverse expertise and experience in cyber-physical
simulation, including real-time model development, system analyses, and geographically
distributed co-simulation.

Authors:

Biao Zhang U.S. Department of Energy, National Energy Technology Laboratory
Shafiul Alam U.S. Department of Energy, Idaho National Laboratory
Anudeep Medam U.S. Department of Energy, Idaho National Laboratory
Nor Farida Harun U.S. Department of Energy, National Energy Technology Laboratory
Nana Zhou U.S. Department of Energy, National Energy Technology Laboratory
David Tucker U.S. Department of Energy, National Energy Technology Laboratory
Rob Hovsapian U.S. Department of Energy, National Renewable Energy Laboratory
Ning Kang U.S. Department of Energy, Idaho National Laboratory
Danylo Oryshchyn U.S. Department of Energy, National Energy Technology Laboratory