NREL Evaluates Advanced Solar Inverter Performance for Hawaiian Electric Companies

NREL is providing critical information to the Hawaiian Electric Companies about the performance and impacts of today's advanced solar inverters as well as proprietary feedback to the inverter manufacturers.

The assessment is helping both the utility and its regulators plan for the future evolution of the electric grids on each of the Hawaiian Islands.

With the highest penetrations of renewable energy in the United States, Hawaii's power grid needs advanced inverters to help keep it stable. Advanced inverters include such grid-stabilizing features as riding through events that cause high or low frequencies or voltages on the grid, changing their power output to smooth voltage deviations, and ramping up their power at commanded rates both during normal operations and during reconnection following a grid fault.

NREL evaluated the performance of four advanced inverters both alone and when connected to models of the Oahu island grid through the Energy Systems Integration Facility's power hardware-in-the-loop capability. Test determined that the inverters successfully provided six grid functions—fixed-power-factor operations, volt-watt control, volt-VAR control (baseline testing only), voltage ride-through, frequency ride-through, and soft-start reconnection—during normal and abnormal conditions, and two of the inverters provided ramp-rate control during normal operation. NREL then produced a detailed technical report that describes the test results and provides recommendations for implementing grid support with advanced inverters. All four inverters are expected to pass the UL 1741 SA certification tests when Hawaii begins requiring this certification for interconnection. 

To ensure that the Hawaiian market is potentially open to all inverter manufacturers, NREL helped Hawaiian Electric develop a Source Requirements Document, a key technical standards document for UL 1741 SA certification. NREL worked with Hawaiian Electric and the Smart Inverter Technical Working Group, the utility's forum of inverter industry stakeholders, to develop the document with the goal to harmonize requirements with the ongoing revision of IEEE Standard 1547, currently in draft form, which sets standards for distributed energy resources. Such advancements in standardization requirements for grid-supportive inverters will enable greater deployment of renewable energy resources throughout the United States.