Controllable Grid Interface

NREL's controllable grid interface is a groundbreaking apparatus for testing and demonstrating advanced controls for wind and solar power generation, energy storage systems, conventional generation, and loads at the multi-megawatt scale.

Photo of the inside of the controllable grid interface.

The rapid expansion of wind power has led some transmission system operators to demand that wind and solar photovoltaic power plants comply with strict grid interconnection requirements. These requirements involve various aspects of renewable power plant operation, including fault ride-through, power quality performance, and the provision of essential reliability services to enhance grid operations.

NREL's 7-MVA controllable grid interface, or power electronic grid simulator, enables the testing of many active and reactive power control features—including inertial response, primary and secondary frequency responses, and voltage regulation—of wind and solar generators (as well as other renewable and conventional generation technologies, including energy storage) under a controlled medium-voltage grid environment. A unique feature of the controllable grid interface is the ability to test the balanced and unbalanced fault ride-through characteristics of test articles under simulated grid conditions. In addition, power hardware in the loop allows the real-time emulation of conditions that may exist in various types of power systems.

Using the controllable grid interface, researchers can test, under controlled 13.2-kV medium-voltage conditions, the controls of any inverter-coupled or conventional generation technology (individually or in combination with others) that respond directly to grid conditions measured on plant terminals, including:

  • "Nasty" and "clean room" grid conditions
  • Inertial response (synthetic synchronous inertia)
  • Fast frequency response
  • Primary frequency response controls (governor droop-like control)
  • Direct frequency control (for islands or microgrids)
  • Black-start capability
  • Voltage fault ride-through, in accordance with grid codes and standards
  • Harmonic injections
  • Reactive power controls under weak and strong grid conditions
  • Advanced controls testing, such as interarea oscillations damping controls, sub-synchronous control interactions, damping controls, impedance characterization of inverter-based technologies, other plant-level controls using RTDS/HIL for larger plant simulation, and microgrid/islanded grid energy management systems testing.


Overview of ARIES Research Projects Involving Inverter-Based Resources, Presentation at the Power Electronic Grid Interface Platform Workshop (2020)

NREL Controllable Grid Interface (CGI): Overview of Progress and Projects, Presentation at the Fifth International Workshop on Grid Simulator Testing (2019)

Overview of CGI/Dynos/PHIL Platform, Presentation at the Fifth Annual International Workshop on
Grid Simulator Testing of Energy Systems and Wind Turbine Powertrains (2018)

NREL's Controllable Grid Interface Saves Time and Resources, Improves Reliability of Renewable Energy Technologies, NREL Factsheet (2015)

National Wind Technology Center Controllable Grid Interface, NREL Factsheet (2012)

View all NREL publications about the controllable grid interface.


Vahan Gevorgian

Chief Engineer