*5.5. Experimental Validation in Scenario #5 (SC-GS)*

In this test, the Split-pi converter was operated as a current-controlled source exchanging power with a stiff microgrid. The external voltage generator still had a no-load voltage of 180 V but no droop resistance. The same combination of output current and load variations as in scenario #4 (SC-GD) was applied; however, the stepwise variation of load resistance occurred at about t = 1 s in scenario #5. Therefore, the output current reference was again changed with a stepwise variation from −1.37 A to 1.37 A at t = 0 s. Instead, the load resistance was varied from 130 Ω to 65 Ω at about t = 1 s, corresponding to nominal load current (power) levels of 1.385 A (250 W) and 2.770 A (500 W), respectively.

The most relevant among the acquired waveforms are presented in Figure 14. They are coherent with the simulation results and show that the converter's control system was also stable in this challenging condition. Furthermore, they are nearly identical to those of Figure 13; the main difference is the even smaller voltage variation, which determined slight differences in the load current and the external generator current. Before t = 0 s, the converter was controlled to draw −1.37 A from the DC microgrid recharging the emulated storage system. The external generator delivered 1.37 A to the converter and 1.385 A to the load for a total of 2.755 A. At t = 0 s, the current reference for the converter was increased to 1.37 A. Thus, the converter almost entirely supplied the load, and the current of the external generator automatically approached zero. Finally, at about t = 1 s, the load requested a current of 2.770 A. Since the converter's output was kept constant, the external generator automatically provided the additional current contribution of 1.385 A.

**Figure 14.** Experimental results in scenario #5 (SC−GS): (**a**) grid−side currents; (**b**) input inductor current; (**c**) duty cycle; (**d**) percentage variation of microgrid voltage.

In this scenario, the theoretical voltage variation was 0% because the DC microgrid was stiff. However, a small resistance was present due to cable connections. Nonetheless, the actual voltage variation was −0.1%, as shown in Figure 14d. Again, the system exhibited good dynamic behavior with fast aperiodic transients, as expected based on the simulation results.
