Can Microinverters Stabilize Hawaii’s Shaky Grid?

by Jeff St John, Green Tech Media, February 2, 2015 (excerpt)

...Hawaii leads the nation in rooftop solar penetration, with nearly one in nine customers, a total of about 51,000, tying their PV systems into the state’s island power grids. About three-fifths of those Hawaiian solar systems use microinverters from Enphase, the company that leads the market for DC-to-AC devices that sit at the solar panels themselves, rather than in one big box next to the power meter.

That adds up to more than 800,000 Enphase microinverters in Hawaii, each networked to the company’s cloud-based monitoring and control systems, ready to do things beyond simple solar-to-grid power conversion. This week, Enphase is unveiling the latest use of this installed capability: reprogramming its Hawaiian microinverter fleet en masse, to help Hawaiian Electric ride through solar-influenced disruptions on the edges of its power network.

Specifically, Enphase and Hawaiian Electric have reset the frequency and voltage ride-through settings of the microinverters, which govern how and when they trip offline when grid fluctuations arise. Standard settings for low-voltage ride-through (LVRT), however, can make the original disruption worse if it leads to a majority of the solar being supplied to a solar-heavy circuit to shut off all at once.

Enphase has expanded the range of circumstances under which its inverters will trip offline, as well as extending how long each inverter waits for disruptions to correct themselves before switching off, Enphase CEO Paul Nahi said in a Monday interview....

Enphase is far from the only player in the distributed solar universe that’s had the foresight to connect its inverters to a two-way communications network. Third-party solar provider SolarCity, for example, has worked with HECO and Department of Energy researchers to show that smart inverter technologies can allow more solar per circuit -- an important concession for HECO, as it seeks to slash the net metering rates that its solar-equipped customers receive.

Importantly, Enphase’s cloud-based monitoring platform knows “not only how well the solar system is performing, [but also] how well the grid is performing in those areas as well,” he noted. “In many cases, we have more insight into the grid performance than the utility does, because we have the two-way communications network.” That’s valuable data in states like California that are demanding that their utilities start to incorporate the growth of distributed energy into their long-range grid investment plans....

read ... Stabilize?

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