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Research Highlight: Virtual Oscillator Control Maintains Grid Operations with High Inverter Penetrations

June 21, 2016

Today's power grids rely on massive generators rotating at the correct speed to produce power at a certain frequency: 60 cycles per second in the United States. These generators give inertia to the entire power grid, which enables it to absorb disturbances with minimal deviations in frequency. Under such high-inertia grid conditions, inverters are designed to lock onto the grid's frequency and follow it.

However, as the world shifts to more inverter-based, distributed energy sources, the grid could lack mechanical inertia -- and stability of such a vast number of inverters is uncertain. To address this issue, NREL, the University of Minnesota, and the University of California Santa Barbara are examining virtual oscillator control as a new strategy for inverters to help ensure stability of the grid.

Virtual oscillator control (VOC) makes each inverter behave electronically like a spring, "bouncing back" to its normal operating range when disturbed. Inverters electrically coupled this way would tend to converge to the same frequency, resulting in a stable grid. Any change in voltage or frequency will induce an inverter response that maintains them within the nominal range. VOC also offers faster response times, because the inverter controls are streamlined.

To learn more about this research, read the NREL Science and Technology Highlights fact sheet

—Wayne Hicks