SnoPUD's Arlington Microgrid. Courtesy of SnoPUD.
SnoPUD's Arlington Microgrid. Courtesy of SnoPUD.

One Microgrid + Multiple DERs = Flexibility

Sept. 28, 2022
The edge of the grid is becoming the center of attention.

The 2022 Atlantic hurricane season is in full swing. There’s a lot of speculation about how many above-normal storms this season will have produced. Experts are reminiscing about past years, and Hurricane Sandy is one of their favorites. After all, October is the tenth anniversary of that infamous storm. The authorities like to use it as an example of a late season hurricane and its potential.

From the power grid’s perspective, Sandy was a major influencer when it came to microgrid technology. According to several accounts prior to Sandy’s impact, the average person didn’t know much if anything about microgrids, but that changed. Sandy caused extensive damage to the power grid resulting in prolonged blackouts in many areas. It was reported that in midst of these blackouts, there were islands of light and comfort.

Once power was restored, investigations found that those oases everyone was so interested in came from microgrids. This quickly focused the national attention on microgrid technology and why there weren’t more of them. Suddenly microgrids moved from the grid’s edge to centerstage, or so it seemed.

Energy from the Edge 

We have come a long ways in the ten years following Sandy. Microgrid technology and distributed energy resources (DERs) appear to be the go to technology on both sides of the meter. It has been an interesting genesis for our industry. It started with the customer adopting rooftop solar and ended with widespread microgrid adoption. The acceptance of rooftop solar beat all the odds and has exceeded our expectations. It’s estimated the global capacity of rooftop solar installations was approximately 59 gigawatts in 2021.

Then another unexpected technology caught everyone’s attention, energy storage.  Customers added energy storage to extend their green solar power beyond sundown. Renewable energy producers added it to make their power more dependable. On the behind-the-meter segment solar-plus-storage was a gamechanger. Unfortunately, it didn’t help the customers with those increasing numbers of power outages. Solar-plus-storage needed the energized grid to work.

It didn’t take long, however, for enterprising suppliers to offer conversion kits that turned these solar-plus-storage applications into carbon-free microgrids. This adaptation changed the energy landscape and redefined the boundaries of the edge of the grid. Bi-directional power flows became commonplace, and industrial, commercial, and residential customers could control their own power supplies.

More than Backup Power 

Microgrid technology continued evolving to the point that modern microgrids are more than just a source of backup power. Depending on their design, modern microgrids can island themselves from the main grid when needed, but they can also operate in parallel to the energized grid. In this mode, these smarter microgrids make the power delivery system more flexible, reliable, and resilient ancillary services.

Their paralleling ability is a powerful tool in the control and management of the power grid during major and minor operational fluctuations. For the customer, they can provide a revenue stream while taking the pain out of outages. These smarter devices provide utilities with dynamic energy management, ensure power stability with voltage and reactive power control along with frequency support.

According to a recent report from DOE’s (Department of Energy) Office of Electricity the next-gen of microgrids will serve as an effective platform for integrating DERs. DOE continues saying these devices will achieve optimal performance from the DERs by reducing costs and emissions while bolstering the resilience of the nation’s electricity system.

Mixing DER technologies for multiple power sources for individual microgrids seems to be the next logical technological progression, but there are some major hurdles to overcome to get there. Different DERs operate in vastly dissimilar ways, which means manufacturers are taking more innovative approaches for control and management systems. It has been described as the leveraging of benefits and many see it as a transformational shift in grid architecture that is still being defined.

Real World Application 

Snohomish County Public Utility District (SnoPUD) and Hitachi Energy have been working together for over five years on such a system. Early this year their work culminated in the successful commissioning of SnoPUD’s new Arlington Microgrid. Talking with Scott Gibson, principal engineer, SnoPUD, and John Glassmire, senior advisor, Grid Edge Solutions, Hitachi Energy revealed some interesting aspects of assembling such a microgrid with the next-gen microgrid management platform.

Gibson open the discussion saying, “The Arlington Microgrid uses a solar powered energy system as the primary energy source. It also has a PowerStore battery energy storage system (BESS), electric vehicles (EVs), and an advanced microgrid controller technology. All of these components work together to enhance grid reliability, resiliency and improved disaster relief. You might say it’s an advanced microgrid test lab that will power SnoPUD’s Clean Energy Center, a local data center, and when built, SnoPUD’s North County Community Office building. I like to think of it as an emergency solar power supply with a day job.”

Gibson continued, “In addition to the 500 kW (kilowatt) community solar photovoltaic (PV) array, a 1 megawatt/1.4 megawatt hour grid-forming Lithium-ion BESS was installed to tame the variability of the PV array. The microgrid also has two SnoPUD fleet Nissan Leaf electric vehicles (EVs) providing mobile energy storage to the microgrid. They are connected to the grid via two Mitsubishi  bi-directional 6 kW EV charging stations making this one of the first V2G (vehicle-to-grid) installations in the U.S. There is also a 350 kW emergency generator adding to the complexity of the backup power arrangement.”

At this point Glassmire added, “Having a PV array, a stationary BESS plus mobile energy storage with two independent EV bi-directional charging systems and a backup generator gave the microgrid a great deal of flexibility. It also required taking the control arrangement of the system to the next level of microgrid management to make this group of DER technologies operate as a single entity. The Hitachi Energy state-of-the-art e-mesh control system assures the seamless integration of renewable energy assets with traditional energy assets. Together with an advanced SCADA (supervisory control and data acquisition) layer, it forms a microgrid controller that is designed to take advantage of the full potential of all the DER devices connected to the microgrid, but interoperability was critical.”

Glassmire explained, “Interoperability requires guidelines, standards, and extensive modeling to make everything play nicely together, but the industry hasn’t gotten that far yet. There isn’t a mature standard like IEC-61850 when it comes to this type of operation. After all, this was the first application for a facility with this variety of components, and each from a different supplier used in a single coordinated microgrid. It required a step-by-step approach and when an issue was found it was addressed. It builds on a solidly engineered solution portfolio, but even so adjustments to the control and automation scheme were needed to enable the microgrid to take shape.”

Glassmire continued, “Once this was achieved, the operation of the microgrid was rock solid offering substantial benefits. Loads could be transferred from the grid to the microgrid and back again seamlessly, while the microgrid regulated voltage and frequency. All of this happened without so much as a flicker from the lighting or any of the connected systems.”

Gibson added, “Building this microgrid has been one challenge after another and one continuous learning process. Grid-forming solar arrays and BESS are cutting-edge technologies and tricky to operate, particularly when combined with other innovative technologies like V2G. SnoPUD has learned a lot about designing and building advanced microgrids. We are convinced this knowledge will be valuable in all future microgrids SnoPUD is involved with in the coming years.”

Shape of the future  

Recently Duke Energy announced a program to evaluate V2G using five Ford F-150 lightning electric trucks. The announcement said Duke would be using these trucks and their bi-directional charging equipment in Florida. Also, Con Edison reported they have successfully completed their V2G pilot program using five Lyon EV school buses. Con Edison said they had injected power into the grid from the buses and distributed it to White Plains customers directly.

When it comes to modernizing the grid infrastructure, microgrids and DERs lead the list of technologies being applied. The edge of the grid is significantly changing the power delivery system. Back in the day, microgrids were easy to ignore and expensive to build, but modern microgrids have changed that. They have become user friendly and even our customers have installed them successfully.

Mixing different types of DERs to individual microgrids have added more benefits. With the various DERs and sophisticated controls, these next-gen microgrids offer ancillary services. Now these devices are more of a virtual power plant than merely a backup power supply.

These non-wires alternatives work independently of the power grid and provide a non-traditional approach that offers flexibility to improve the grid’s resiliency. We can’t get rid of grid hazards, but we can minimize them with fast acting technologies like these next-gen microgrids!

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