====================================================================== UL 1741 SB Certification Evidence Package Guide (PDF) ====================================================================== DEFINITION ---------------------------------------- The UL 1741 SB Certification Evidence Package Guide is a structured technical document published by Underwriters Laboratories (UL) that outlines the evidence requirements, test methodologies, and documentation needed to demonstrate compliance of inverters and distributed energy resources (DERs) with IEEE 1547-2018 and UL 1741 Supplement B (SB) for advanced grid-support functions—including ride-through, reactive power control, frequency-watt, volt-var, and anti-islanding. It serves as a roadmap for manufacturers to prepare certification submissions to UL or other Nationally Recognized Testing Laboratories (NRTLs). The guide ensures DERs operate safely, reliably, and interoperably within modern inverter-dominated microgrids and utility-scale grids. OVERVIEW ---------------------------------------- UL 1741 SB represents a critical evolution in DER interconnection standards, mandating dynamic, grid-responsive behaviors beyond basic safety and isolation requirements. The Evidence Package Guide provides manufacturers with prescriptive instructions on how to compile and present technical evidence—including test plans, lab reports, firmware versioning records, functional block diagrams, and verification matrices—to substantiate conformance to each SB requirement. It emphasizes traceability: every functional capability (e.g., 'LVRT at 0.5 pu for 2 seconds') must be mapped to specific test cases, configuration settings, and validation data. The guide also addresses cybersecurity considerations introduced in SB (e.g., secure firmware update mechanisms), software lifecycle documentation, and the role of third-party validation. Crucially, it supports microgrid protection coordination by ensuring inverters respond predictably under fault conditions and during islanded/grid-connected transitions—enabling selective coordination with upstream breakers, relays, and microgrid controllers without unintended tripping or instability. KEY COMPONENTS ---------------------------------------- 1. Compliance Verification Matrix 2. Test Plan and Execution Reports 3. Firmware and Configuration Documentation 4. Functional Architecture Diagrams 5. Cybersecurity Validation Artifacts APPLICATIONS ---------------------------------------- - Certification submission for solar PV inverters, BESS inverters, and wind converters - Design verification and validation (V&V) during product development - Microgrid integration testing and interconnection approval with utilities KEY FORMULAS ---------------------------------------- Voltage Ride-Through (LVRT) Threshold: V_{min} = 0.5 \times V_{nom} \text{ for } t \leq 2\,\text{s} -> Defines the minimum allowable AC voltage during low-voltage events for inverter continued operation per UL 1741 SB Table SB4.1 Reactive Power Support (Q-V Curve): Q = Q_{max} \times \left(1 - \frac{|V - V_{ref}|}{\Delta V}\right) -> Calculates reactive power output based on measured voltage deviation from reference, per UL 1741 SB Section SB6.2.1 RELATED CONCEPTS ---------------------------------------- - IEEE 1547-2018 - Grid-Forming Inverter (GFM) Controls - Microgrid Protection Coordination - NRTL Certification Process - Cybersecurity for DERs (NIST SP 800-82) REFERENCES ---------------------------------------- UL 1741 SB Certification Evidence Package Guide (v2.0, 2023) (https://www.ul.com/sites/default/files/2023-09/UL_1741_SB_Evidence_Package_Guide_v2.0.pdf) IEEE Standard 1547-2018: Standard for Interconnecting Distributed Resources with Electric Power Systems (https://standards.ieee.org/ieee/1547/4212/) UL 1741 Supplement B: Inverters, Converters, Controllers and Interconnection System Equipment for Use With Distributed Energy Resources (https://standardscatalog.ul.com/standards/en/ul-1741sb/) TAGS ---------------------------------------- UL1741SB, DERCertification, MicrogridIntegration, InverterTesting, GridSupportFunctions