## 3 Simulation Results
### Grid-Connected Mode
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Condition**} & \multicolumn{6}{c}{**Power (W)**} & \multirow{2}{*}{**Efficiency (\%)**} \\ \cline{2-2} \cline{4-6}  & **Grid** & **Load** & **Fundamental** & **5 th Harmonic** & **7 th Harmonic** \\ \hline Normal Load (1 kW) & 1015 & 999.2 & 685.1 & 185.4 & 144.1 & 98.44 \\ Load Increase (1.5 kW) & 1513 & 1499 & 1002.1 & 277.9 & 233.7 & 99.07 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Power distribution and efficiency under different load conditions. Figure 5: Load voltage and current. (red: phase a, green: phase b, blue: phase c, purple: phase a, olive green: phase b, cyan: phase c). The power transfer efficiency during the increased load condition reached approximately 99.07%, calculated from a total sent power of 1513 W and a received load power of 1499 W. The system maintains excellent efficiency at the higher transfer level, validating the capability of multi-frequency power boosting without compromising performance. The DC bus voltage measurement in Figure 7 shows a load increase at t = 1.2 s, resulting in a transient voltage dip. The voltage drops from its nominal value of approximately 400 V to a minimum of around 375 V, then begins to recover. The system successfully stabilizes the DC voltage within approximately 300 ms (by t \(\approx\) 1.5 s), demonstrating fast and reliable dynamic response. This confirms robust system performance under load transients and harmonic-rich grid conditions, with effective DC-link voltage regulation throughout the event. Figure 6: Dynamic power sharing of fundamental and harmonic components during load increase. Figure 7: DC bus voltage during load increase. The step increase in power demand results in the grid voltage and current waveforms, which are displayed in Figure 8. The voltage waveform shows no change in amplitude or shape while maintaining its harmonic content and staying within peak limits. The grid current shows an increase in magnitude after the load change because the system starts transmitting more power. The proposed method demonstrates an essential benefit because it allows power transfer increases through current amplification without changing the voltage envelope structure or exceeding peak constraints. The system operates safely through changing loads because voltage-sensitive components remain within safe limits. The inverter load voltage and current responses to the load increase are depicted in Figure 9. The voltage remains sinusoidal and stable, which means that the inverter maintains a clean 50 Hz output. The current increases smoothly in response to the higher load, which confirms that the system delivers more power without affecting voltage quality or waveform shape. Figure 8: Power increase reflected in grid current with voltage held constant. (red: phase a, green: phase b, blue: phase c). According to the simulation results, the proposed LVDC-link control system transfers the total power from the multi-frequency grid to the load as standard signals. This proves that this device can precisely play the role of the frequency changers when connecting the multi-frequency systems to the loads that are not addressed so far in the multi-frequency power transfer system research topic.