Gridco Systems, a startup offering next-generation power electronics devices to actively manage voltage and reactive power at the distribution circuit level, has raised $12 million in a funding round that includes existing investors, as well as an intriguing new strategic investor -- German power transformer regulation company Maschinenfabrik Reinhausen GmbH (MR).

The new round brings the Woburn, Mass.-based startup’s total financing to date to $54 million. The investor group included previous investors General Catalyst, Lux Capital and North Bridge Venture Partners, as well as “one of the world's largest private family investment offices,” according to Thursday’s announcement.

As for MR, it’s a global leader in power regulation equipment, like tap changers and voltage regulators, which serve to help grid voltages stable -- the same kind of things that Gridco’s devices are doing on an even more distributed scale.

Gridco is one of a small set of companies using the latest technology advances in inverter and power conversion electronics to design, build and deploy grid-hardened devices that can actively manage voltage and reactive power at the distribution-circuit level. Others with similar, though technically distinct, devices include Varentec and GridBridge for the low-voltage grid, and Smart Wires for the transmission grid.

The difference between these devices and the previous generation of load-tap changers, voltage regulators and power transformers is that they’re digitally altering the waveform of the alternating current humming through the grid. That makes them more flexible in terms of the control they can achieve over specific portions of the grid.

That also makes them particularly useful for circuit-specific problems, such as the voltage fluctuations caused by lots ofsolarPV on a single distribution circuit. Both Gridco and Varentec have pilot projects underway with Hawaiian Electric, in a territory where one in nine customers has rooftop solar, and some circuits actually feed back solar power at midday. GTM Research predicts a $320 million U.S. market by next year for these kinds of devices, built largely on this business case.

At the same time, Gridco has been expanding its product line over the past year to tackle other use cases. Its core unit, the in-line power regulator, is now deployed with utilities ranging from Hawaiian Electric and Sacramento, Calif.’s municipal utility district, to Duke Energy in North Carolina and Sudbury Hydro in Quebec, Canada.

The company has also launched a Static VAR Compensator, a 150 kVA three-phase Inline Power Regulator, and a 50 kVA integrated Power Regulating Transformer over the past year. These are designed less as standalone boxes, and more as stand-ins for the existing types of equipment now deployed for distribution grid voltage management.

That makes MR’s investment of particular interest. While the two companies didn’t announce any specific projects or products they might be working on, Michael Rohde, managing director at MR, said the two are "looking forward to jointly exploring synergy potentials for the benefit of our customers in the U.S. and internationally."