Can Microinverters Stabilize Hawaii's Shaky Grid?

Img source:cheap portable storage unitsHawaii 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.This is the kind of basic "smart inverter" functionality that Germany has already introduced for its solar-impacted grid. In the United States, Hawaii and California are the furthest along in putting together advanced inverter features to be included in new solar installations.

But Enphase already has nearly 8 million inverters worldwide, all designed with software-defined functionality to provide flexibility in how they"re used, he said. That, along with a dedicated, two-way communications channel, allows Enphase to do remote firmware upgrades, monitor grid conditions, and ask inverters to provide reactive power or ramping mitigation as a "virtual power plant," all from the company"s Petaluma, Calif. headquarters, Nahi noted."We are talking about a distributed resource that is on tens of thousands -- and soon to be millions -- of roofs," he said. "You need a robust, sophisticated, bidirectional communications technology that allows us not only to know what is happening with the solar systems and the grid, but what to do about it."In the case of Hawaii, Enphase"s systems are connected to an estimated 140 megawatts of peak power generation capacity, he noted -- a significant share of energy in a state whose largest fossil-fuel-fired power plant generates 180 megawatts.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.As more utilities start to see Hawaii-like penetrations of customer-owned solar on their distribution circuits, they"re likely to look to the inverters already installed as possible tools for managing the resulting disruptions, Nahi noted. "Because the density of solar in Hawaii is unique, they"re the first to enable these functions," he said. But "the trend we"re talking about is absolutely a global trend."see more at:solar grid storage