## 5 Experimental Results
### Forward Power Conversion Mode  
According to the load conditions, the proposed DAB converter operates in PWM mode at light load (output power below 200 W), as shown in Figures 12 and 13. In PWM mode control, the gate signals \(V_{G51}\) and \(V_{G53}\) on the high-voltage side are synchronized with gate signals \(V_{G55}\) and \(V_{G57}\) on the low-voltage side. Thus, the DAB converter has the switching characteristics of a synchronous rectifier, as shown in Figures 12a and 13a. In addition, it can be seen from Figure 12b that when the output power is 10 W, the duty cycle of gate signal \(V_{G51}\) is approximately 45.7%, and the RMS value of inductor current \(i_{LK}\) is 278 mA.  
Figure 11: Experimental platform of DAB in laboratory.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Primary voltage, \(V_{D\text{clus}}\) & 400 V \\ Secondary voltage, \(V_{\text{int}}\) & 50 V \\ Transformer turns ratio, \(n\) & 24:3 \\ Maximum output power, \(P_{o,max}\) & 1 kW \\ Switching frequency, \(f_{\text{zav}}\) & 100 kHz \\ Maximum phase-shift, \(D_{max}\) & 0.2 \\ Magnetizing inductance, \(L_{M}\) & 1.2 mH \\ Leakage inductance, \(L_{K}\) & 57 uH \\ High-voltage side capacitor, C\({}_{1}\) & 100 uF \\ Low-voltage side capacitor, C\({}_{2}\) & 360 uF \\ \hline \hline \end{tabular}
\end{table}
Table 3: Specifications of the proposed DAB converter prototype.  
When the output power increases to 200 W, the duty cycle of the gate signal \(V_{GSI}\) increases to 47.1%, and the RMS value of inductor current \(i_{LK}\) is 739 mA, as shown in Figure 12(b).  
When the output power increases above 200 W, the operating mode of the proposed DAB converter changes from PWM mode to SPS mode, as shown in Figures 14 and 15. The SPS controls the turn-on time of switches, causing the phase-shift between the high-voltage side switches and low-voltage side switches, thereby controlling the direction and magnitude of power flow. When \(V_{GSI}\) leads \(V_{GSS}\), power flows from the high-voltage side to the low-voltage side, as illustrated in Figures 13(a) and 14(a). When the output power is 300 W and 1 kW, the RMS value of inductor current \(i_{LK}\) is 852 mA and 2.81 A, respectively, as shown in Figures 13(b) and 14(b).  
When the output power increases above 100 W, the operating mode of the proposed DAB converter changes from PWM mode to SPS mode. Note that at this time, gate signal V\({}_{\text{GS1}}\) lags behind gate signal V\({}_{\text{GS5}}\), as shown in Figures 18a and 19a. When the output power is 200 W and 1 kW, the RMS value of inductor current \(i_{LK}\) is 595 mA and 2.84 A, respectively, as shown in Figures 18b and 19b.  
Figure 16: Experimental waveforms of the prototype converter operating in backward power conversion mode (at 10 W output power): (a) waveforms of gate signals \(V_{\text{GS1}}\), \(V_{\text{GS3}}\), \(V_{\text{GS5}}\) and \(V_{\text{GS7}}\); (b) waveforms of gate signals \(V_{\text{GSS}}\), \(V_{\text{GS7}}\) and inductor current \(i_{LK}\).  
Figure 14: Experimental waveforms of the prototype converter operating in forward power conversion mode (at 300 W output power): (a) waveforms of gate signals \(V_{\text{GSI}}\), \(V_{\text{GS3}}\), \(V_{\text{GSS}}\) and \(V_{\text{GS7}}\); (b) waveforms of gate signals \(V_{\text{GSI}}\), \(V_{\text{GS3}}\) and inductor current \(i_{LK}\).  
Figure 15: Experimental waveforms of the prototype converter operating in forward power conversion mode (at 1 kW output power): (a) waveforms of gate signals \(V_{\text{GSI}}\), \(V_{\text{GS3}}\), \(V_{\text{GSS}}\) and \(V_{\text{GS7}}\); (b) waveforms of gate signals \(V_{\text{GSI}}\), \(V_{\text{GS3}}\) and inductor current \(i_{LK}\).