Grid Modernization

PNNL Creates Model For Integrating Grid-Forming Inverters Into The Grid

Researchers at Pacific Northwest National Laboratory (PNNL) have developed a model for a device that could improve how well renewable power sources can be integrated into the bulk power system.

The device, a grid-forming inverter, converts direct current (DC) electricity produced by sources such as solar, wind or batteries, to alternating current (AC).

The model devised by PNNL engineers is designed to allow utility operators to test how to safely add new power sources to the grid in a way that increases power system resiliency and stability.

PNNL’s grid-forming inverter modeling work started in the development of microgrids. With support from the Department of Energy’s (DOE) Office of Electricity Microgrid Program, PNNL led and participated in multiple grid-forming inverter modeling projects for microgrid studies. That research showed it is possible to run a 100 percent inverter-based microgrid using grid-forming inverters, which can operate on their own without the reliance on conventional synchronous power generators.

Building on that work, Wei Du, a PNNL senior researcher, and his team have been investigating how grid-forming inverters affect large-scale transmission and distribution systems.

The PNNL researchers developed the generic droop-controlled, grid-forming inverter model for transmission system studies. That model specification was recently approved by the Western Electricity Coordinating Council’s Modeling and Validation Subcommittee, making it available to be integrated into commercially available grid simulation tools used by thousands of utilities in North America and other parts of the world.

“Grid-forming inverters will become more and more important to power systems in the future,” Song Wang, who chairs the WECC Modeling and Validation Subcommittee, said in a statement. “The existing inverter models in the WECC model library are all grid-following-based and cannot represent grid-forming inverters. The new model developed by PNNL enables WECC to study how grid-forming inverters will impact power grids at the transmission level. Our preliminary simulation studies based on the model show that grid-forming inverters can impact power system stability in a very positive way. We believe the work done by PNNL will greatly help the utility industry better understand grid-forming inverters and their potential impacts on power systems.”

PNNL’s research into the grid-forming inverter model was internally funded with further support from the DOE’s Solar Energy Technologies Office (SETO) and Wind Energy Technologies Office (WETO).

SETO and WETO recently awarded $25 million to the Universal Interoperability for Grid-Forming Inverters (UNIFI) Consortium to further investigate grid-forming technologies.

UNIFI is a multi-year effort to create an ecosystem for grid-forming inverters that is led by National Renewable Energy Laboratory, the University of Washington, and the Electric Power Research Institute.

The PNNL researchers’ goal is to work with UNIFI to unify the models of various grid-forming technologies and their diverse applications in power systems.

“To achieve the national targets of clean electricity and decarbonized economy, inverter-based renewable generation will be an essential part of the future energy mix,” Henry Huang, a PNNL fellow, said in a statement. “The inverters will fundamentally change power system dynamics and thus require new approaches to model and simulate such a system.”