UL Publishes Long-Awaited Advanced Inverter Standard

Posted by Joseph Bebon on September 08, 2016 No Comments

Following months of anticipation, global safety science organization UL has published a new inverter standard update that is expected to significantly help with solar integration onto the grid, UL 1741 Supplement A (SA).

UL has announced a new Advanced Inverter Testing and Certification Program, which the group says will utilize UL 1741 SA to test and certify inverters and other utility-interconnected distributed generation (DG) equipment for grid-support functions enabling smarter, safer, reactive grid interconnection.

“Brownouts or blackouts have demonstrated the far-reaching impacts of utility grid instabilities,” said Jeff Smidt, vice president and general manager of UL’s energy and power technologies division. “We are pleased to now publish the latest updates via UL 1741 SA for grid-support utility-interactive inverters to meet the current market need for a more stable utility grid.”

As UL explains, advanced inverter testing is smart, reactive control of DG for support of ongoing modernization of grids utilizing increasing levels of DG and renewable energy resources. UL says traditional utility interconnection requirements (IEEE 1547) require DG devices to disconnect when the grid is experiencing stability issues. The UL 1741 SA specifies the test methods needed to build the foundation enabling DG devices to stay online and adapt their output and overall behavior to stabilize the grid during abnormal operation, rather than simply disconnecting.

The State of California previously announced that inverters installed in the state will be required to comply with the Rule 21 grid-interconnection requirements within one year of publication of the UL 1741 SA. Other states are considering adopting similar installation requirements, especially in areas with high levels of DG and solar penetration.

Rule 21 is the inverter-related revision to the State of California Electric Tariff Rule 21 made by the California Public Utility Commission (CPUC). UL says Rule 21 is a source requirement document (SRD) to be used with the UL 1741 SA. SRDs set the specific parameter settings to be used with the test methods of the UL 1741 SA. Other SRDs may also be used with the UL 1741 SA as other markets look to build smart grid functionality into the modernization of their electrical power system.

(For more information about what UL 1741 SA means for solar and the future of the grid, check out a related article in Solar Industry‘s September 2016 issue here.)

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