Routing and Controlling the Grid With Advanced Electronics, Solid-State Transformers
Here at Greentech Media, we’ve been covering the emergence of a new class of power electronics that could revolutionize the way the world’s electric grids work, mainly by replacing one of the cornerstone devices of the grid: the transformer. Now from Japan comes a new nonprofit group with a plan to get the revolution underway.
That’s the Digital Grid Consortium, a group officially launched in December with member companies including Japan’s ORIX Corp., NEC Corp. and National Instruments, as well as Cupertino, Calif.-based business development consultant Kyumaru Pacific Alliances.
David McQuilkin, managing director of Kyumaru, told me in a December interview that three Japanese electrical equipment manufacturers are planning to join the consortium, though he wouldn't name them. One could imagine that a short list of likely contenders might include Hitachi, Toshiba or Mitsubishi, to name a few.
The concept relies on a key piece of technology that the consortium calls a “Digital Grid Router,” McQuilkin said. Simply put, it’s a device that replaces today’s coil-based transformers with solid-state AC-to-DC-to-AC converters, allowing voltages to be ramped up and down at frequencies that can change on the fly, while also managing power quality, reactive power and other functions -- all via digital control.
While such “solid-state transformers” are still very much on the drawing boards today, their usefulness in managing a future grid of two-way power flows from lots of distributed sources (solar panels, local energy storage devices, smart building systems, etc.) could make them worth the extra cost and complexity.
Indeed, much of Greentech Media’s 2010 Networked Grid event was dedicated to discussing the potential for new technological developments to bring that promise closer to reality, with companies including Cree, ABB and Gridco Systems contributing to the discussion. Demonstrating real-world models of the insulated gate bipolar transistors (IGBTs), metal-oxide semiconductor field-effect transistors (MOSFETs) and other devices that can perform these functions at grid-scale reliability is still a long ways off, however.
Presumably, the as-yet-unnamed equipment makers planning to join the Digital Grid Consortium would be rolling out such devices to test. Right now, however, the consortium is starting out with simulations to demonstrate a working model of the grid router concept, which was developed by Rikiya Abe, a University of Tokyo professor and former engineer and researcher at Japanese wholesale electric utility JPower.
Part of the benefit of the Digital Grid architecture would be to “tag” power from different generation sources so it can be identified as it flows across the power grid. That kind of technology is being developed by startup Power Tagging, which has developed technology to allow powerline carrier (PLC) data to travel across the grid’s existing transformers in a way that could allow, say, power from a renewable resource to be identified as such at the point where it’s used.
But McQuilkin told me that getting the system to work doesn’t necessarily rely on using the power lines to communicate -- and that power tagging is just the first in a number of transformations that the Digital Grid concept envisions.
Eventually, the consortium’s goal is to plan, design and implement a new way to architect the power grid as a collection of independently operating “cells,” rather than the synchronously managed grids of today, he said.
“Since most electrical design these days is done through simulation, that’s a certain level of validation,” he said. “But we actually want to be able to build the devices -- and then you need to take internet routing technology and apply that to these devices.”
That’s why the consortium uses the term “digital grid router” to describe the devices that control the frequency and voltage of power at the point at which each individual grid “cell” connects to the next, he said. Those digital grid routers, in turn, will communicate and respond to a “digital grid controller” device that could be located at each power generation source, or at utility central control, he added.
At small scale, that concept could be applied to so-called “microgrid” systems: military bases, campuses or other local entities that can generate, store and balance their own power to keep themselves running or help balance the grid they’re attached to.
On a larger scale, the Digital Grid concept could be applied to help entire regions or nations balance grids facing unprecedented levels of new intermittent renewable power generation sources and unstable power demands. Japan, which has two separate national grids operating at different frequencies, is an obvious first target for this kind of flexible and resilient power architecture, particularly amidst the country’s post-Fukushima power shortages, he noted.
But the Tres Amigas project in the United States, which will connect the nation’s three independently operated power grid systems, is another example of the usefulness of the concept. The U.S. utility research group Electric Power Research Institute (EPRI) is also working with the Digital Grid Consortium, and plans to set up demonstration tests in the coming months.
There’s no doubt that the consortium has a long road ahead of it. McQuilkin said that the initial simulation and modeling work is targeting a completion date of mid-2012. Proving that the technology and business cases behind the model can work is another step, however.
“None of the technology is new or risky in any way,” he said. “What’s new is power semiconductors that can do this at much reduced costs.”
At the same time, the consortium has another project devising business models that could justify the cost of deploying digital grid routers and controllers in a real-world setting. We’ll be keeping a close eye on these concurrent technical and business model developments as one way to track the progress of this solid-state grid revolution.
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