Controllable Grid Interface

Engineers have developed a cross-cutting approach to evaluating grid integration using the Controllable Grid Interface (CGI) that provides grid operators with the performance information they need for a fraction of the time and cost it would take to validate a turbine in the field.

Photo of a man walking towards several long buildings.

NREL's 7-megavolt amperes CGI system can reduce certification time and costs while providing system engineers with a better understanding of how marine energy systems, wind turbines, photovoltaic inverters, and energy storage systems react to disturbances on the electric power system. NREL's CGI system is the first validation facility in the United States that has fault simulation capabilities, and has the following capabilities:

  • Allows manufacturers and system operators to certify renewable systems in a controlled environment
  • Fully integrated with two dynamometers, turbines in the field, and to a matrix of electronic and mechanical storage devices
  • Validates renewable energy generation systems offline from the grid
  • Verifies compliance with standards
  • Previously recorded data from various power systems or from data generated by models allows for accurately-produced inertial and primary frequency response controls validation.

Learn more about the CGI.


Engineers at the Flatirons Campus have the ability to connect the CGI to a number of facilities, including the 5- and 2.5-MW dynamometers, grid integration research pads, individual or marine energy systems, and the Energy Systems Integration Facility. These connections allow for the following capabilities:

  • Balanced and unbalanced over- and undervoltage fault ride-through evaluations
  • Frequency response assessments
  • Continuous operation under unbalanced voltage conditions
  • Grid condition simulation (strong and weak)
  • Reactive power, power factor, and voltage control validation
  • Protection system assessment (over- and undervoltage and frequency limits)
  • Islanding operation
  • Subsynchronous resonance conditions
  • 50-Hz evaluations.