VIRTUAL IMPEDANCE CURRENT LIMITING CONTROL FOR GRID FORMING INVERTER-BASED RESOURCES

A method for controlling an inverter-based resource (IBR) connected to a power grid during a grid event includes operating the IBR based on a first virtual impedance reference prior to the grid event, the first virtual impedance reference being used for determining a first virtual impedance of the IBR defining a first virtual reactance and a first virtual resistance. The method also includes receiving an indication of a start of the grid event that causes a change in the first virtual impedance reference to a second virtual impedance reference. Immediately after the change in the first virtual impedance reference, the method includes activating a soft activation module for outputting a second virtual impedance defining a second virtual reactance and a second virtual resistance that maintains a magnitude of the second virtual impedance at or above a magnitude of the second virtual impedance reference so as to reduce current in the inverter-based resource. At a certain time period after activating the soft activation module, the method includes transitioning the second virtual reactance and the second virtual resistance to a virtual reactance and a virtual resistance defined by the change.