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NREL's PRECISE Helps Interconnect SMUD Customers' Solar PV for Better Performance, in Half the Time

July 26, 2018

Preconfiguration, quasi-static time series, and autonomous operation are all features contributing to the expansion of distributed energy systems, thanks to advanced inverters and an NREL- and Sacramento Municipal Utility District (SMUD)-developed platform called PRECISE.

Neighborhood of houses with rooftop solar panels.

PRECISE, a tool that allows the preconfiguration of advanced inverter settings, can dramatically reduce the time it takes to receive approval to install and connect rooftop solar onto a utility's distribution feeder. Photo by Dennis Schroeder

The tool, PREconfiguring and Controlling Inverter SEtpoints (PRECISE), is a technology that evolved from NREL’s work at the Energy Systems Integration Facility (ESIF) with Hawaiian Electric Companies (HECO), inspired by the surge in customer interest to connect home-installed solar to Hawaii’s grid. Like HECO, SMUD began to see a surplus in solar photovoltaic (PV) interconnection applications from residents in Sacramento in 2016, challenging the utility’s ability to respond to each request in a timely manner while considering voltage control and grid reliability.

During this time, and as an outgrowth of the inverter studies performed in Hawaii, NREL Engineer Adarsh Nagarajan had been exploring the idea of preconfiguring advanced inverters based on residents’ locations, clusters, and seasonal weather patterns.

“I realized we could assume that even if an inverter has communications, we are not really trying to communicate with it every 10-15 minutes,” said Nagarajan. “We could preconfigure the inverter and set modes for seasons. Then it would be done before it’s even installed. You turn on the inverter, and it knows what to do.”

With support from SMUD, Nagarajan and the PRECISE team began developing a planning and real-time operation platform that would enable distribution utilities to identify optimal inverter modes and settings, ultimately to maximize the cost-effective use of installed PV systems. The team found that the tool can dramatically reduce the time it takes to receive approval to install and connect PV systems onto the utility distribution feeder, from 10-15 days down to 5. PRECISE is now helping the Sacramento utility—and utilities in India—to seamlessly interconnect and integrate high penetrations of PV onto today’s grid in a safe, cost-effective, secure, and reliable way.

“The PRECISE platform expands upon our work that involved the quasi-steady state modeling of Hawaii’s distribution systems,” said Martha Symko-Davies, Laboratory Program Manager of Energy Systems Integration. “The exciting part of this project is seeing how the work leverages a technology that we developed in a more automated way, scaling to other regions in the United States and beyond.”

With PRECISE, as soon as a customer applies for rooftop or ground-mount PV system installation, a utility operator can identify exactly where the correct feeder is located based on the customer’s interconnection address. The operator can then use PRECISE to model the distribution feeder and preconfigure advanced inverter modes that help provide grid support, enabling seamless interconnection with much less wait time.

Beyond the United States, this kind of immediate service and fast access is exactly what’s needed in places like India where some utilities are installing PV systems at the gigawatt scale.

As Nagarajan explained, solar is booming in India at an extraordinary rate, but distributed energy in India is still, in a sense, the “Wild West.” Without decades of refinement to interoperability standards and advanced grid technologies like PRECISE, too much deployment could lead to reliability concerns. The country’s fast growth in solar—teamed with the opportunity for PRECISE to add significant value—is why Nagarajan has already begun discussions with utilities in India about the tool.

“PRECISE can help fast-forward to best practices,” he said. “The utilities in India are aware of how quickly the industry is changing. They want to provide active power support. They know that advanced inverters are the way to achieve that, but they aren’t sure where to start.”

Nagarajan expects that his team will start to model an Indian feeder this August or September and plans to attend the Distribution Utility Meet in Mumbai this November. By bringing PRECISE to India, his hope is that the country’s regulation agency will also gain the benefit of taking the U.S. Institute of Electrical and Electronics Engineers (IEEE) interconnection standard 1547-2018, adopting it to work with their grid infrastructure, and achieving active power support through advanced inverter standards, pre-configured settings, and greater access to distributed energy.

“Moving these technologies from West to East is truly a high-impact achievement for our researchers and partners,” said Symko-Davies, adding that with hardware-in-the-loop capabilities at the ESIF, she sees the PRECISE platform extending to any region where there’s opportunity to better manage high penetration PV. “With PRECISE, it will be much easier for people to integrate their PV onto the grid.”

Learn more about PRECISE.