A Testing Framework for Grid-Forming Resources

This paper presents a testing framework for grid-forming (GFM) resources. First, it analytically derives in the frequency domain the active and reactive power response of an ideal voltage source with a reactor. These transfer functions are then used to quantify the voltage source behavior expected from a GFM inverter within subtransient timescales (5-15 cycles) following a grid disturbance. The paper also shows that the testing of a GFM inverter might require a reactor of an appropriate size between the inverter and the grid simulator used for the inverter testing. Finally, the paper presents a systematic approach for developing specifications for GFM resources using active and reactive power response frequency scans. The testing framework and results presented in this paper are demonstrated using EMT-PSCAD simulations of a 1-MW GFM inverter.