The Windurance 90 kW Inverter at Sandia National Laboratories undergoing UL 1741 SB experimentation. Photo Credit: Jay Johnson.
By Jay Johnson, DER Security Corp; Rachid Darbali-Zamora, Sandia National Laboratories; and Paul Rowan, Windurance
A large and growing number of the United States jurisdictions have adopted IEEE 1547-2018 as their interconnection standard for Distributed Energy Resources (DER). With this change, all newly interconnected Distributed Wind (DW) converters are required to incorporate a specified set of grid-support functions and communication interfaces. Proof that a product contains these functions and interfaces is established by a Nationally Recognized Testing Laboratory (NRTL) which certifies the product to UL 1741 SB. Authorities Having Jurisdiction (AHJs) confirm products are UL 1741 SB listed prior to approving them for interconnection.
The challenge for DER manufacturers is that, unlike compliance for previous versions of the IEEE 1547 standard, testing for IEEE 1547-2018 is far more expensive and time consuming. Long before engaging with a NRTL, which itself has become more time consuming, manufacturers must perform months of pre-testing to validate that the electrical and interoperability behaviors of the equipment are within allowable tolerances for safe and accurate grid operation. The result is that costs have ballooned, and the market entry times are dramatically longer than before.
Fortunately, there has been a decade-long effort to reduce test times, improve accuracy, and establish precise repeatability of UL 1741 SB testing. This effort has been led by an international community of research laboratories, the non-profit interoperability standards developer, SunSpec Alliance, and other strategic partners. The result of the effort is an open-source certification platform known as the Open System Validation Platform (Open SVP). A commercial version of this software, DER Security LabTest Pro, provides greater test coverage and automation, supports a wider array of laboratory test equipment, and incorporates additional interoperability and cybersecurity certification capabilities. These software offerings provide a new approach to certification testing that can drastically reduce the test time by automating test execution and results analysis.
NRTL test beds typically include a DC power supply, AC grid simulator, data acquisition system (DAQ), and the Equipment Under Test (EUT). With this equipment, test sequences are executed, data is logged, and the results are processed to assess the pass/fail performance of the EUT. This is done by communicating with the EUT and laboratory hardware through APIs, Ethernet, serial, or GPIB programmatic interfaces to run different tests—e.g., ride-through and trip, enter service, limit active power, constant power factor, voltage-reactive power, active power-reactive power, etc.
The Department of Energy (DOE), Wind Energy Technology Office (WETO) and Office of Technology Transition (OTT) Wind Interconnection Standards Platform (WISP) Project has funded Sandia National Laboratories, the DW industry, and DER Security Corp to validate this experimental testing approach using the Windurance 90 kW inverter.
As a first step, the Windurance SunSpec Modbus communication interface was tested in accordance with the “SunSpec Modbus for 1547” test procedure to resolve communication interoperability issues. With that step completed, the converter hardware was installed in the Sandia National Laboratories’ Distributed Energy Technology Laboratory (DETL) to validate the electrical performance of the equipment by coordinating the UL 1741 SB tests using a combination of a real-time simulations and wind turbine emulator technologies. With the bugs worked out, the final step will be to run an automated test sweep—that takes less than 48 hours to perform—of all UL 1741 SB electrical and interoperability compliance tests with a NRTL.
This collaboration has shown the power of automated interconnection standard certification testing for the DW industry and highlights Sandia National Laboratories’ commitment to advancing sustainable energy solutions. The Wind Interconnection Standards Platform (WISP) project is designed to increased adoption of DW in the U.S. and reduce barriers for converter vendors to enter the market in jurisdictions that have adopted IEEE 1547-2018. If you would like to learn more about this research, reach out to Rachid Darbali-Zamora at rdarbal@sandia.gov and if you would like to learn more about the DERSec LabTest Pro software, contact sales@dersec.io.