Providing Resilient Power

A Novel Demonstration
The Kirtland demonstration project is novel in several ways. The main power bus is based on direct current rather than traditional alternating current. Additionally, it is a hierarchical microgrid, meaning that control and integration occur at multiple levels and enhance the ability to provide resilient power under a variety of circumstances. This hierarchical nature means parts of the installation can run independently, in combination with each other, or in connection with the traditional power grid. This project also ties into the central grid, which uses alternating current, making it a hybrid direct-current grid. Sandia is studying this hybrid direct-current structure to better understand the advantages, optimize the design and seek out cost savings. This makes the system more resilient than even a traditional microgrid, investigator Jack Flicker said. The functionality is enabled by power electronic interfaces, an area of research for Sandia.

“Since we started operations in December 2019, we’ve been concentrating on evaluating microgrid operations in three areas,” said Jack. “The first area concerned operations that all microgrids can do, such as provide power to all nodes and island when needed. We then moved on to operations that are more difficult for traditional microgrids to do, such as black start and maintaining full operations through fault events.”

Black start is the process of restoring power after an outage. “We’re now looking at operations that typical microgrids cannot do, such as — in resilience events — being able to arbitrarily route power to critical nodes that are dynamic in both space and time as the situation evolves,” Jack said. Coupled with the Distributed Energy Technologies Laboratory, the installation allows researchers to simulate varied scenarios and observe how well the microgrid performs.

While much of the power transported and delivered across the U.S. is alternating-current power, recent advances and changes to the composition of the grid have revived interest in direct-current grid installations. According to a 2015 study that examined the potential benefits of direct-current microgrids relative to an alternating-current microgrid, it was noted that direct-current microgrids might have cost, reliability and efficiency advantages for certain applications. Seven national laboratories, including Sandia, participated in the study. The study identified potential areas of imminent and future study to verify and better understand any potential advantages.

The connection between the direct-current microgrid and Distributed Energy Technologies Laboratory provides researchers with information about the microgrid’s performance. Meanwhile, the demonstration project contributes renewable energy to the base facilities’ footprint. Increased use of renewable energy, which emits no greenhouse gas emissions, will be a key part of achieving the nation’s ambitious goals to tackle climate change, a DOE priority.

Strengthened grid stems from strong partnership

“The project is, for me, the embodiment of all the things that microgrids have promised to deliver, especially the modularity and resilience,” said Gerro Prinsloo, project manager with Emera Technologies for the demonstration. “We have been able to integrate new technologies and test rapidly, doing so with little additional engineering effort post-commissioning. The rate at which it was done would have been difficult to achieve had it not been for the flexible nature of this microgrid architecture and the excellent resources Sandia brought to the table.”

Emera Technologies and Sandia formed a Cooperative Research and Development Agreement after Emera Technologies approached Sandia to work together on making clean, community-scale direct-current microgrids mainstream. Sandia researchers had already been studying the control and stability of direct-current microgrids for military applications, aiming to optimize design and performance at a lower cost.

Adding local control to energy distribution systems through microgrids can mean added resilience to the nation’s existing energy infrastructure.