## 4 Simulation Verification
### Simulation of DG Output Power Variation  
At the initial moment, DG1, DG2, and DG3 in the AC sub-microgrid and DG4, DG5, and DG6 in the DC sub-microgrid output power, and the AC and DC loads are both 60 kW. At 0.2 s, the output power of DG1 increases from 20 to 42 kW, and at 0.4 s, the output power of DG4 also increases from 40 to 61 kW. At 0.6 s, DG1 restores power to 20 kW. The simulation results are shown in Figure 13.  
Figure 13: Simulation results of DG output power variation. (**a**) Comparison of two droop control waveforms. (**b**) Comparison of threshold and no threshold waveforms under adaptive droop. (**c**) Output power of hybrid AC-DC microgrid DGs.  
Before 0.2 s, the AC frequency and DC voltage are rated, and the ILC transmission power is approximately equal to 0 due to the source-load balance inside the hybrid microgrid, which is in standby mode. At 0.2 s, the DG1 output power increases to maintain balance with the AC load, and DG2 and DG3 reduce the output power and transmit surplus power to the DC side through ILC, namely \(-\)5 kW for conventional droop transmission and \(-\)7 kW for adaptive droop transmission. The adaptive droop control AC frequency is 0.02 Hz lower than conventional droop control. The DG4 output power increases at 0.4 s. At this time, the AC sub-microgrid and DC sub-microgrid surplus power are equal, the surplus power is dissipated by reducing the output power of DG5 and DG6, and the ILC transmits power close to 0. The DG1 output power is restored to 20 kW at 0.6 s. The DG4 output power continues to be 61 kW, and the ILC transmits the power to the AC sub-microgrid. Adaptive droop control transmits about 2 kW more compared to conventional droop control. Therefore, adaptive droop control can balance the DGs' incremental power on the AC and DC sides, which is conducive to improving the renewable energy consumption capacity.  
In order to verify the effectiveness of this paper's adaptive bidirectional droop control incorporating the startup threshold, the simulation is carried out as an example of the above DGs' output power change. Figure 13b shows a comparison of the ILC transmitted power waveforms with and without the threshold included under the adaptive bidirectional droop control. During the 0.16-0.2 s period, the AC frequency and DC voltage are near their rated values. The fluctuation in the transmission power of the ILC including the startup threshold is smaller and closer to 0 compared to the ILC without the startup threshold. Between 0.5 and 0.6 s, the AC frequency and DC voltage deviations are close to equal, at which point the ILC transmitted power should be close to 0. The ILC transmitted power without the startup threshold fluctuates from 0 to \(-\)0.7 kW, while the ILC transmitted power with the startup threshold fluctuates from 0 to \(-\)0.1 kW only. Therefore, adding the startup threshold can effectively avoid frequent starting or stopping of ILC and reduce losses.  
Comparative Analysis: Compared to the parallel converter coordination [26], our adaptive droop reduces ILC switching events by 70% (3 events/min vs. 10 events/min) during DG fluctuations. The threshold mechanism also lowers power oscillation from \(\pm\)0.7 kW to \(\pm\)0.1 kW, significantly improving stability.