testbed is configured so that the IBR works in four operating conditions expressed by real power and reactive power. For per-unit (p.u.) values, the base power is 1 MVA. Case 1: real power at 0 MW and reactive power at 0 Mvar Converter GSC V Battery C1 vabc P Q GSC Control abc/dq i1,abc vPCC,abc id 100 50 -50 -100 0.01 0.02 0.03 Response in Current 0.04 1 0.5 -0.5 -1 0.01 0.02 0.03 Perturbed Voltage 0.04 figure 4. The measurement testbed for a 2.3-MVA inverter. GSC: grid-side converter; PCC: point of common coupling; CGI: controllable grid interface. iq vd vq dq/abc 1 MVA 400 V: 13.2 kV RC Filter 13.2 kV Grid I1 L1 R1 PCC VPCC T1 Vg P Q Case 2: real power at 500 kW or 0.5 p.u. (-6 dB), reactive power at 0 Mvar Case 3: real power at 0 MW and reactive power at 500 kvar or 0.5 p.u. (-6 dB) Measurement Point CGI Grid-Side Output Transformer Transformer (a) Voltage Source Converters (b) (c) figure 5. The CGI and sensors. (a) The 7-MVA grid simulator. (b) and (c) Medium-voltage sensing. (Source: Mark McDade, National Renewable Energy Laboratory; used with permission.) 70 ieee power & energy magazine may/june 2022