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How Many Ways Can We Control a Microgrid?

Peter Asmus
Apr 17, 2018

How to control a microgrid? Let me count the ways. In the Guidehouse Insights Leaderboard: Microgrid Controls report, all energy storage and smart inverter companies were excluded. This was done to have an apples-to-apples comparison since controls encompass many different technologies. Among the available solutions, microgrids are controlled with digital relays, smart switches, traditional automation products, and increasingly, new sophisticated software algorithms.

This blog traces the evolution of one battery vendor—EnSync Energy—and acknowledges how key microgrid control innovation has flowed from the energy storage community. The story illustrates how battery vendors have evolved over time, turning many early assumptions about microgrids upside down. Whereas in the past microgrids were designed to minimize or eliminate the need for battery storage due to cost, today the vast majority of microgrids include some form of energy storage, especially systems that incorporate renewables.

The roots of what is now EnSync focused first and foremost on a unique flow battery chemistry, with its control architecture as a secondary feature. “The original company had significant intellectual property in power controls. That was one of the key reasons I joined the company,” said Dan Nordloh, executive vice president. “I believed there was peril ahead in remaining a flow battery supplier,” he noted, referencing the recent bankruptcy of ViZn Energy in validation of his concerns.

In contrast, EnSync is no longer focused on flow batteries and has an agnostic approach to battery type. It now boasts over 22 current projects in Hawaii alone, and these represent $35 million in electricity sales over the term of the power purchase agreements (PPAs). The company is deploying a modular, scaleable, off-grid system in East Africa that will likely link up with a larger village nearby. EnSync has also added to its list of partnerships by entering into a strategic relationship with Schneider Electric.

Is Plug and Play the Way to Go?

The key to EnSync’s success? “We decided to move away from single application cul-de-sac designs and instead shift[ed] to a more modular, rack-mounted plug-and-play approach, which future-proofs microgrids. Adding a new resource? Just slide a new drawer in,” said Nordloh. Picking up on a trend also evident among energy storage vendors such as Greensmith, companies that started out with a focus on battery optimization have expanded their reach to generation and loads. In short, they now offer microgrid controllers.

“I like using the analogy of Lego blocks. Remember, a small microgrid is just as complex as a large microgrid. But with our direct current (DC) bus as a backbone, it is easier to add to the microgrid over time, reducing the need to re-engineer the microgrid every time you want to expand the distributed energy resources (DER) mix. And with their integrated cloud-based DER Flex controls package, microgrids can be changed to enable export of grid services with a simple software adjustment,” continued Nordloh. He pointed to the Palama Holdings meat processing plant on Oahu that is installing a microgrid under a self-financed PPA. At present, the microgrid reduces costs by enabling demand charge abatement strategies. Yet state regulators are considering creating markets for grid services. This microgrid could provide demand response and frequency regulation through EnSync’s DER Flex controller with a simple software switch.

An advantage of EnSync’s DC-centric approach is that users do not need to control variable solar PV. Instead, voltage algorithms keep the microgrid in balance. This approach is the corollary to the droop in frequency of the alternating current controls approach known as CERTS. Both control schemes shy away from the common master/slave control protocol, moving the market closer to plug and play.