## 5 Simulation and Experimental Verification
### Experimental Results  
To verify the proposed VDCC method for fast transient response and no backflow power, the experimental prototype has been built, as shown in Figure 11. For experimental comparison, steady-state and transient experiments using the traditional constant compensation control method and the proposed VDCC method are conducted. The steady-state experiments are divided into four groups with the same output voltage \(U_{\text{o}}\) = 50 V, as shown in Table 2, i.e., \(U_{\text{in}}\) = 80 V, \(R\) = 50 \(\Omega\); \(U_{\text{in}}\) = 100 V, \(R\) = 50 \(\Omega\); \(U_{\text{in}}\) = 130 V, \(R\) = 50 \(\Omega\); \(U_{\text{in}}\) = 100 V, and \(R\) = 45.4 \(\Omega\). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Symbol** & **Value** & **Symbol** & **Value** & **Symbol** & **Value** \\ \hline \(U_{\text{in}}(1)\) & 80 V & \(R_{\text{(1)}}\) & 50 \(\Omega\) & \(k_{\text{(1)}}\) & 1.25 \\ \(U_{\text{in}}(2)\) & 100 V & \(R_{\text{(2)}}\) & 50 \(\Omega\) & \(k_{\text{(2)}}\) & 1 \\ \(U_{\text{in}}(3)\) & 130 V & \(R_{\text{(3)}}\) & 50 \(\Omega\) & \(k_{\text{(3)}}\) & 0.77 \\ \(U_{\text{in}}(4)\) & 100 V & \(R_{\text{(4)}}\) & 45.4 \(\Omega\) & \(k_{\text{(4)}}\) & 1 \\ \(U_{\text{o}}\) & 50 V & \(N\) & 2 & \(f\) & 10 kHz \\ \(L\) & 1.15 mH & C\({}_{1}\) & 220 nF & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Main experimental parameters. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Symbol** & **Value** & **Symbol** & **Value** & **Symbol** & **Value** \\ \hline \(L\) & 1.15 mH & \(f\) & 10 kHz & \(U_{\text{in}}\) & 100 V \\ \(N\) & 2 & \(C_{1}\) & 220 nF & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Main simulation parameters. Since the performance of backflow power elimination is mainly affected by the value of \(d\), the traditional constant compensation control method and the proposed VDCC method have no obvious effect on the steady-state results of the backflow elimination. Therefore, for a unified comparison, the steady-state waveforms are obtained with the two control methods, as shown in Figures 12 and 13. In Figure 12, \(d\) is set to 0.38, which is an inappropriate value of the outer phase shift ratio to achieve no backflow power operation according to the above analysis. It can be observed from Figure 12a to Figure 11d that the direction of currents and voltages sometimes are opposite at both sides of the LCL resonant tank, representing that the backflow is not eliminated in the input and output of the converter. In Figure 13, \(d\) is set to 0.22, which is an appropriate value of the outer phase shift ratio. According to these four figures, the currents are always reversed at zero voltage, so the backflow power is eliminated for both bridges of the converter. The elimination effectiveness of backflow power for an appropriate \(d\) matches the above simulation results, and, in addition, the current stress also decreases correspondingly. Figure 11: Photo of the experimental platform. To verify the transient response of the proposed VDCC method, the starting process, the transient response against input voltage disturbance, and the transient response against load disturbance are observed and compared with the traditional constant compensation control method. Figure 14 shows the starting process of the two control methods, which indicates that the settling time with the proposed VDCC method is 121 ms, shorter than that with the traditional control method. Figures 15 and 16 compare the transient response with two control methods under input voltage and load disturbances, and the steady-state waveforms before and after disturbances are the same as those in Figure 13b-d. As shown in Figure 15, when input voltage \(U_{\text{in}}\) is changed from 100 V to 130 V, the output voltage with the traditional constant compensation method first increases, and then is adjusted to the reference value while the output voltage with the proposed VDCC method remains stable.