## 4 Simulation Verification
### Simulation of DC Sub-Microgrid Is Stronger than AC Sub-Microgrid  
AC and DC hybrid microgrids with different sub-microgrid output power will change the strength of the microgrid load-carrying capacity, and load changes in a sub-microgrid with lower output power are more likely to cause large deviations in frequency and DC voltage, or even overrun the limits. In this case, more power support is needed from the sub-microgrid with higher output power to the sub-microgrid with lower output power.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Values** \\ \hline Rated DC voltage \(U_{\rm dc}^{*}/\rm V\) & 600 \\ DC voltage, upper and lower & 630, 570 \\ limits \(U_{\rm dcmax}\), \(U_{\rm dcmin}/\rm V\) & 60 \\ DC rated power \(P_{\rm dc}^{*}/\rm kW\) & 60 \\ DC bus capacitor \(C/\rm\upmu F\) & 1100 \\ Droop coefficient \(k_{\rm dc}\) & 0.0006 \\ Rated AC voltage \(U_{\rm ac}^{*}/\rm V\) & 380 \\ AC rated frequency \(f_{\rm ac}^{*}/\rm Hz\) & 50 \\ AC frequency, upper and lower & 50.5, 49.5 \\ Limits \(f_{\rm acmax}\), \(f_{\rm acmin}/\rm Hz\) & 60 \\ AC rated power \(P_{\rm ac}^{*}/\rm kW\) & 0.00007, 0.003 \\ Drop coefficient \(k_{\rm p}\), \(k_{\rm q}\) & 0.00007, 0.003 \\ Filter inductor \(L_{\rm f}/\rm mH\) & 3 \\ Filter capacitor \(C_{\rm f}/\rm uF\) & 20 \\ Droop coefficient \(k\) & 20,000 \\ Activation threshold \(\eta\) & 0.05 \\ \hline \hline \end{tabular}
\end{table}
Table 2: System simulation parameters.  
At the initial moment, the AC and DC loads are both 60 kW, and only DG1 and DG2 of the AC sub-microgrid output power, while DG4, DG5, and DG6 of the DC sub-microgrid output power. At this time, the AC sub-microgrids and DC sub-microgrids are balanced in terms of internal source loads. At 0.2 s, the AC load increases to 80 kW, and at 0.5 s, the DC load also increases to 80 kW. The simulation results are shown in Figure 11.  
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. During the 0.2-0.5 s period, the AC loads increase, and the load carrying capacity is weak due to only two DGs outputting power in the AC sub-microgrid. According to the conventional droop control regulation, the AC sub-microgrid frequency is maintained at 49.76 Hz, and the ILC transmission power is about 6.8 kW, whereas with adaptive droop control, the AC sub-microgrid frequency is maintained at 49.79 Hz, and the ILC transmission power is about 8.5 kW, which transmits 1.7 kW more power than the conventional droop. The DC loads also increase to 80 kW after 0.5 s. At this time, although the AC sub-microgrid and the DC sub-microgrid have equal power deficits, the AC sub-microgrid is weaker and has more frequency dips, and adaptive droop control increases the power delivered by 0.8 kW compared to conventional droop control.  
Comparative Analysis: To provide a fair benchmark, the proposed strategy is compared with the adaptive power ratio control in [13]. Under identical conditions (AC load +20 kW), [13] achieves frequency stabilization at 49.76 Hz with 6.8 kW transfer, while our  
Figure 11: Simulation results showing that DC sub-microgrid is stronger than AC sub-microgrid. (**a**) Comparison of two droop control waveforms; (**b**) output power of hybrid AC-DC microgrid DGs.  
method maintains a value of 49.79 Hz with 8.5 kW transfer (25% higher). This demonstrates enhanced support capability for weaker subgrids.