"Sags and power outages have demonstrated the far-reaching impact of instability in electric utility grids," said Jeff Smidt, Vice President and General Manager of UL's Power and Electricity Technologies Division. "We are pleased to now publish the latest updates through AA UL 1741 for utility grid-support interactive inverters to meet today's market need for a more stable utility grid.".
Advanced inverter testing is smart, reactive control of distributed generation to support the ongoing modernization of grids using increasing levels of distributed generation (DG) and renewable energy resources. Traditional utility interconnection requirements (IEEE 1547) mandate that DG devices disconnect when the grid is experiencing stability issues. AA UL 1741 specifies the testing methods necessary to develop the foundation for DG devices to remain online and adapt their output and overall behavior to stabilize the grid during abnormal operation, rather than disconnecting.
The State of California announced that inverters installed in the state must comply with Rule 21 grid interconnection requirements within one year of the publication of AA UL 1741. Other states are considering adopting similar installation requirements, especially in areas with high levels of distributed generation and solar penetration.
Rule 21 is the investor-related revision of Rule 21 of the California State Electricity Tariff, issued by the California Public Utility Commission (CPUC). Rule 21 is a Source Requirements Document (SRD) for use with AA UL 1741. SRDs establish specific configuration parameters for use with the AA UL 1741 test methods. Other SRDs may also be used with AA UL 1741 as other markets seek to develop smart grid capabilities in the modernization of their electric power systems.
UL has taken the lead by working with industry to develop AA UL 1741, which establishes guidelines for modern smart grid interconnection. In addition, UL has built two state-of-the-art testing laboratories for advanced inverters. These laboratories use automation to minimize time to market for inverters, reducing average testing times to less than three weeks. Alternatively, UL has an expert engineering team that can oversee testing at customer sites already equipped with laboratories capable of executing the required test plan.
