Inverter sizing guides grid connection, rules US court


From pv magazine USA

The US Court of Appeals for the District of Columbia Circuit has ruled that a solar power facility’s alternating current (AC) size is the technical consideration that matters when determining “Qualifying Facility” status under PURPA. The case was filed by the Solar Energy Industries Association (SEIA).

The case focused on Broadview Solar’s facility in Montana, which applied for an 80 MW (AC) Qualifying Facility electricity contract with the state under PURPA guidelines. The facility was sized at 80 MW (AC)/160 MW (DC) of solar power, and 50 MW/200 MWh of batteries. Broadview Solar says the site will feature 20 inverters, rated at 4 MW (AC) each.

An initial ruling from the Montana Public Utilities Commission in September 2020 stated that the solar power facility should be based upon its direct current (DC) rating, which is the same way in which solar panels are rated. Broadview Solar argued that its peak grid output, determined by its inverters, is what should be considered. The commission realized this was a departure from previous logic, but they went with it anyway. Broadview Solar appealed.

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The Montana Supreme Court has ruled against the commission’s apparent anti-solar biases in the past. In March 2021, the commission vacated its prior ruling, instead stating that the facility’s peak grid output was the motivation for PURPA’s legislation.

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