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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 long gray building surrounded by energy boxes and gravel with a man approahing it from the left.

NREL's 7-megavolt amperes CGI system can reduce certification time and costs while providing system engineers with a better understanding of how wind turbines, photovoltaic inverters, and energy storage systems react to disturbances on the electric power system.

  • The first validation facility in the United States that has fault simulation 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 wind turbines 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 NWTC 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 multiple MW field-research wind turbines, 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.

An illustration showing the full spectrum of grid integration in the National Wind Technology Center, including the dynamometers, wind turbines, controllable grid interface, and grid research test pads.