Frequency-Based Virtual-Admittance Tuning For Grid-Forming Converters

Grid-forming (GFM) converter control is a key technology enabling stable operation of converter-dominated electric power grids, which makes the converter behave as a slowly varying voltage source behind an impedance. The utilization of a virtual admittance (VA) in the converter control allows to choose this impedance at frequencies above the active range of the power controllers. Moreover, employing a decoupled GFM controller allows to choose the VA parameters freely without introducing power coupling. This paper proposes a VA parameter tuning approach that bases the parameter selection on the desired frequency response of the controller, either specified as gain limits for the input admittance at two chosen frequencies, or as a decay time constant for the VA’s synchronous frequency resonance. Finally, the impact of the parameter choice on the converter’s response to grid disturbances is investigated.