Ameren and S&C test microgrid islanding
August 29, 2017
St Louis utility Ameren Corporation and Chicago-based smart grid company S&C Electric conducted a successful 24-hour islanding test this month at the recently deployed microgrid in Champaign, Illinois.
The microgrid – said to be one of the most technologically advanced utility-scale microgrids in North America – has been operational since May and has now proven it can provide a seamless transition from grid-connected to island mode.
The test focused on the 50kW microgrid at the site, which powers an Ameren research facility. The complete microgrid includes 225kW of renewable generation (PV solar and wind) and 250kW or 500kWh of battery energy storage.
The test began with the battery's state of charge at 97 per cent capacity. Once the battery was depleted to 90 per cent capacity, solar and wind generation kicked in, simultaneously carrying the load and charging the battery. This pattern continued throughout the day, never letting the battery fall lower than 88 per cent capacity. In short, the microgrid functioned without any human interaction, automatically coordinating resources and ensuring power never faltered.
The chart shows when the battery was being discharged, and when renewable generation was used. Upon conclusion of the 24-hour test, the microgrid successfully moved back into grid-connected mode without any loss of power for end users.
"We have one of the few microgrids in the world that operates at utility-scale voltages and can seamlessly transition from grid-connected to islanded mode," said Ron Pate, senior vice president at Ameren Illinois. "This successful test provided tangible proof that the system can accomplish what it was designed to do. The microgrid isn't theoretical and our tests don't need to be lab simulations. We were able to prove that this technology works and can provide key benefits to our customers."
During the test, the microgrid functioned on 100 per cent renewable energy throughout the day. Many microgrids of this scale need to rely on rotating machines or generators, which prevent 100 per cent penetration of renewable energy. At this microgrid, when the generation exceeds the load, the excess powers the battery. With a rotating machine, the influx of generation would have caused the system to trip due to penetration limits.
"When designing this microgrid, we were confident that the seamless transition and the ability to run solely on renewable generation would be two of the biggest features to this system," said David Chiesa, senior director at S&C. "Microgrids are becoming more commonplace on the grid, and this test continues to prove how impactful they can be for energy users."
Ameren has 2.4 million electric customers and more than 900,000 natural gas customers in a 166,000-square-kilometre area through its Missouri and Illinois rate-regulated utility subsidiaries. Ameren Illinois provides electric distribution and transmission service, as well as natural gas distribution service, while Ameren Missouri provides vertically integrated electric service, with generating capacity of over 10,200MW, and natural gas distribution service. Ameren Transmission of Illinois develops regional electric transmission projects.