UL Validates Keysight Automated Anti-Islanding Grid Testing

Grid operators and regulatory bodies require grid-connected distributed energy resources and inverter-based resources to disconnect swiftly when unintentional islanding occurs, protecting utility field crews and distribution equipment from unmonitored backfeeding. Standards such as IEEE 1547.1 Clause 5.10 mandate that distributed resources detect localized power separation and cease energizing the affected distribution line within two seconds. Traditionally, certifying compliance requires manually adjusting high-power resistive, inductive, and capacitive (RLC) resonant load banks to match inverter output, a laborious procedure that introduces thermal drift, occupies large lab spaces, and typically consumes one to two weeks per full test program. Resolving these verification bottlenecks demands automated, real-time power emulation that can accurately reproduce resonant island conditions without physical load-bank tuning.

Automated Power Hardware-in-the-Loop Validation
An independent evaluation conducted by UL Solutions validated that automated Power Hardware-in-the-Loop (PHIL) testing delivers compliance results comparable to conventional test benches while significantly compressing test schedules. The evaluation compared the traditional, manually tuned RLC load-bank procedure (Method A) against a PHIL-based architecture (Method B) using the Keysight SL1200 Series Regenerative AC/Grid Emulator combined with patented RLC autotuning driven by Keysight SL1221A test automation software.

Both methodologies were tested on the same commercial photovoltaic inverter under identical operational conditions across five representative IEEE 1547.1-2020 Category B unintentional-islanding test cases. The comparative data demonstrated that both test setups yielded equivalent clearing-time metrics, with the device under test successfully meeting the mandatory IEEE 1547 anti-islanding trip threshold in all evaluated scenarios.

Operational Efficiency and Test Program Compression
Beyond measurement fidelity, the UL Solutions evaluation highlighted major operational gains. While the manual RLC bench required continuous mechanical re-tuning, physical instrumentation adjustments, and iterative logging—a workflow demanding up to two weeks of engineering effort—the Keysight automated PHIL system completed the entire five-case test series in under one day.

Thomas Goetzl, Vice President and General Manager of Keysight’s Automotive and Energy Solutions business unit, stated that expanding deployments of distributed energy resources and inverter-based resources require engineers to scale test throughput without sacrificing measurement integrity. He noted that the independent UL Solutions findings confirm that automated PHIL-based workflows match physical load-bank accuracy while drastically decreasing engineering overhead and test cycle duration.


Additional Context
This section details technical specifications and competitive benchmarking not included in the original product announcement.

In standard IEEE 1547.1-2020 unintentional-islanding evaluations, the test circuit is configured to achieve an exact resonant condition where active and reactive power balance within a resonant tank circuit characterized by a quality factor of 1.0. Under manual Method A testing, achieving this resonance demands trimming physical inductors and capacitor banks in incremental steps to match fundamental and harmonic components, during which internal thermal heating inside resistor coils causes resistance drift, shifting the resonant frequency away from the 60 Hz or 50 Hz nominal grid frequency and forcing continuous re-tuning. The Keysight SL1200 Series regenerative grid simulator overcomes this by synthesizing the reactive and active current draw dynamically in firmware, operating as a low-latency voltage or current source linked via a real-time digital closed-loop interface.

Within grid compliance testing, Keysight’s PHIL architecture benchmarks against grid-simulation and hardware-in-the-loop platforms from Typhoon HIL, RTDS Technologies, and Chroma ATE. While traditional power hardware-in-the-loop setups require separate third-party real-time digital simulators coupled to four-quadrant linear or switching amplifiers via external analog signal lines—often introducing phase delay and closed-loop instability—Keysight integrates the resonant RLC mathematical modeling directly into the regenerative amplifier's internal controller. The SL1221A compliance software operates atop the Keysight PathWave Test Automation (KS8400B) platform, automating test parameter execution, frequency-voltage trip recording, and documentation reporting required for UL 1741 SB and IEEE 1547 certification submissions.

Edited by Romila DSilva, Induportals Editor, with AI assistance.