UL launches advanced inverter testing and certification program

UL (Underwriters Laboratories), a global safety science organization, announced the launch of a new advanced inverter testing and certification program. As utilities continue to upgrade their grids by using large amounts of distributed generation and renewable energy, UL's service portfolio is expanding to meet the changing needs for safety, performance and grid support functions. This new program uses the new UL 1741 Supplement A (SA) standard to test and certify the grid support functions of inverters and other utility grid-connected distributed generation equipment to achieve a more intelligent and safe responsive grid interconnection.

“The impact of utility grid instability is profound, as brownouts and outages are a testament to this,” said Jeff Smidt, UL’s vice president and general manager of Energy and Power Technologies. “We are pleased to now release the new UL 1741 SA standard for testing and certifying inverters for utility grid support, as the market is demanding a more stable utility grid.”

Advanced inverter testing is the intelligent, responsive control of distributed generation to support the grid upgrades currently underway through the adoption of higher levels of distributed generation and renewable energy. Traditional utility grid interconnection requirements (IEEE 1547) require that distributed generation equipment be disconnected in the event of grid stability issues. UL 1741 SA defines the test methods needed to build the foundation upon which distributed generation equipment can remain operational during abnormal conditions, by adjusting their output and overall response to achieve grid stability rather than simply disconnecting.

It is reported that California has announced that inverters installed in the state need to meet Rule 21 grid interconnection requirements within one year of the release of UL 1741 SA. Other states are also considering adopting similar installation requirements, especially in areas with high penetration of distributed generation and solar power generation.

Rule 21 is an inverter-related amendment to California Electric Tariff Rule 21 developed by the California Public Utilities Commission. Rule 21 is an original requirement interpretation document used in conjunction with UL 1741 SA. It specifies specific parameter settings used in conjunction with the UL 1741 SA test method. As other markets also look to incorporate smart grid capabilities into power system upgrades, other original requirement interpretation documents may also be used in conjunction with UL 1741 SA.

UL is a leader in providing modern smart grid interconnect specifications. In addition to working with the industry to develop the UL 1741 SA standard, UL has also built two first-class advanced inverter test laboratories. These laboratories use automation to shorten product time to market and reduce the average testing time to less than 3 weeks. In addition, UL also has an experienced team of engineers who can test products in customer factories with well-equipped laboratories that can meet the required testing conditions.