There’s been a lot of news lately around the emergence of a new class of grid power electronics -- devices meant to replace today’s electromechanical gear with semiconductor-based, digitally enabled control of the distribution grid. Some noteworthy startups in this field include Varentec and Gridco Systems, both of which have brought technologies to market and onto the grid in real-world utility trials.
Add GridBridge to the list of startups to watch. In the past month, the quiet North Carolina State University spinout, founded in 2012, has emerged from stealth, laid out some details on its technology, and revealed that it’s trialing the first versions of its grid equipment with hometown utility Duke Energy.
The company, so far funded via grants and undisclosed early-stage funding, is also one of eighteen companies involved in the Next Generation Power Electronics Institute, a White-House-backed effort to boost the commercialization of wide-bandgap (WBG) semiconductor technologies. The new institute will be receiving a $70 million U.S. Department of Energy grant, to be matched by companies and institutions in the Raleigh, N.C. region, for projects including solid-state LED lighting, variable speed motors, electric vehicle drivetrains, and power grid applications.
Raleigh is already a hotbed of research in the field through NC State’s FREEDM Systems Center. And Dr. Alex Huang, the director of the National Science Foundation-backed center, is also GridBridge’s chief scientist. While GridBridge hasn’t learned what slice of that new funding will be coming its way, it’s working on those contracts right now, as well as seeking private investment, CEO Chad Eckhardt told me at last week’s DistribuTECH conference.
As for what form its devices are taking, “What we’ve been able to do is package those systems inside a solution -- a Grid Energy Router platform,” he said.
The concept of an “energy router” isn’t a new one. Indeed, it’s an idea that underlies many grid roles for digital power electronics. Just how GridBridge plans to put this concept into practice is a more complicated matter, however, involving both current versions that could provide a range of traditional distribution grid functions, and future versions that stretch the boundaries of how power is managed at the edge of the grid.
The grid energy router as multipurpose tool
So, what’s a Grid Energy Router? Eckhardt declined to give too many specifics on the technical functions and features of GridBridge’s device, but he did lay out how its first iteration is being tested by Duke Energy.
“At this stage, it’s going onto a live circuit, located downstream of the substation...at the transformer,” he said. The first test for the device will be to show it can provide conservation voltage reduction (CVR) and volt/VAR optimization (VVO) on individual circuits by inserting either capacitive or inductive reactive power. That can be done either to meet conditions preset into each device, or under commands coming from the utility via a variety of communications links, he said.
Digital devices that can alter voltages on individual sections of the grid without impacting the system as a whole could be a boon for VVO schemes, which otherwise face limitations on how much efficiency they can squeeze out of the grid based on their “weakest” feeders. That’s made VVO a use case that both Varentec and Gridco have targeted along with GridBridge. In fact, Duke is testing devices from all three of these vendors right now, which could put the utility in the position to do some head-to-head comparisons.
Beyond core reliability and durability testing, GridBridge is targeting a wide range of additional functions its Grid Energy Routers could provide once they’re deployed. “These are inherent to utilizing power electronics at this key location on the grid,” and range from power quality management services like harmonic cancelation and transient mitigation, to sensor functions like theft detection and aggregate metering, said Eckhardt.
Here’s a broad description of features pulled from a white paper available at the GridBridge website:
Advanced microprocessor capabilities combined with revolutionary hardware and innovative decentralized software offers the flexibility to expand alongside the utility’s needs. Breakthroughs in power electronics are being harnessed to introduce GERs for...sensory, communications, [and] decision-making [needs], and control downstream of the substation. Heuristics can even be utilized to offload centralized decision-making from the substation. Intelligence is complemented by the GER’s hardware capability to directly modify many components of power.
These, again, aren’t unique concepts to GridBridge -- both Varentec and Gridco have highlighted how their devices, coupled with the computing power built into them and the software platforms they run on, could serve a range of tasks. Part of Duke’s testing process will include measuring the economic value to be derived from these combinations of services, Eckhardt noted.
Nanogrids, green energy hubs, and new semiconductors on the roadmap
Other concepts for putting GridBridge’s technology to use are a bit more visionary. For example, Eckhardt laid out the idea of placing a Grid Energy Router at a transformer serving several homes or buildings with a complement of renewable energy resources, most likely solar PV, or perhaps energystoragesystems.
“These are primarily DC [direct current]-based devices,” he noted, and each requires an inverter to convert that DC to alternating current (AC), with a small but significant loss in conversion efficiency -- something a single GER at the transformer could reduce. What’s more, while today’s inverters aren’t necessarily designed or set up to optimize power quality for the grid, GERs are meant to do just that, he said.
Setting up a local grid this way would require using DC throughout a number of buildings and up to the local transformer, which would be a radical departure from the way electricity is managed today. Even so, DC-powered buildings and even DC-powered microgrids are starting to appear in pilot projects around the world. In the meantime, utilities may want to cluster DC-based renewables and energy storage behind GERs to reduce integration complexity and inefficiencies, he noted.
Finally, Eckhardt laid out the concept of “nanogrids,” or smaller-scale iterations of campus or facility-wide microgrids, that could be linked via GERs into a more resilient collection of nodes within a larger grid. On this point, it’s worth noting that the high-voltage direct current (HVDC) systems that carry massive amounts of electricity across regions and oceans use large-scale power electronics to manage their interface with AC grid systems.
Similar concepts, but on a sub-transmission or distribution grid scale, are being explored by Japanese companies participating in the Digital Grid Consortium group, as well as companies like Varentec, ABB and Cree. The latter two companies have a big presence in Raleigh.
They’re also deeply involved in R&D aimed at solving the key problems of efficiency, thermal management, durability and cost-effective manufacturing of devices using the next generation of semiconductor technologies, such as silicon carbide and gallium nitride. That makes Raleigh a good place for a startup like GridBridge to be, Eckhardt said.
“GridBridge is chartered with utilizing some of these next-generation semiconductors in grid-scale devices,” he said. While the company’s current products are using “off-the-shelf type” semiconductor components, “I can say that we, at the center of the power electronics technology development in Raleigh, have access to the latest advances in semiconductor technology.”