## 5 Experimental Results
### Load Transient Testing for the Proposed DAB Converter  
Experiments on the step load response of the proposed converter in bidirectional power conversion are shown in Figures 20 and 21. Figure 20 shows the experimental waveforms in the forward power conversion mode. According to Figure 20a, the distortion level of battery voltage is approximately 12 V when the step load changes from 10 W to  
Figure 19: Experimental waveforms of the prototype converter operating in backward power conversion mode (at 1 kW output power): (**a**) waveforms of gate signals \(V_{GSI}\), \(V_{GS3}\), \(V_{GS5}\) and \(V_{GS7}\); (**b**) waveforms of gate signals \(V_{GSS}\), \(V_{GST}\) and inductor current \(i_{LK}\).  
Figure 17: Experimental waveforms of the prototype converter operating in backward power conversion mode (at 100 W output power): (**a**) waveforms of gate signals \(V_{GSI}\), \(V_{GSS}\), \(V_{GSS}\) and \(V_{GS7}\); (**b**) waveforms of gate signals \(V_{GSS}\), \(V_{GST}\) and inductor current \(i_{LK}\).  
Figure 18: Experimental waveforms of the prototype converter operating in backward power conversion mode (at 200 W output power): (**a**) waveforms of gate signals \(V_{GSI}\), \(V_{GSS}\), \(V_{GSS}\) and \(V_{GS7}\); (**b**) waveforms of gate signals \(V_{GSS}\), \(V_{GST}\) and inductor current \(i_{LK}\).  
1 kW, and it takes about 300 ms to reach a steady state. Conversely, the distortion level of battery voltage is approximately 2 V when the step load changes from 1 kW to 10 W, and it takes about 200 ms to reach a steady state, as shown in Figure 20b. Figure 21 shows the experimental waveforms in the backward power conversion mode. When the step load changes from 10 W to 1 kW, the distortion level of the DC bus voltage is approximately 5 V, and it takes around 10 ms to reach a steady state, as shown in Figure 21a. Conversely, when the step load changes from 1 kW to 10 W, the distortion level of the DC bus voltage is around 5 V, and it takes about 120 ms to reach a steady state, as shown in Figure 21b.  
Figures 22 and 23 are waveforms of the mode switching of the proposed DAB converter. This paper sets the mode switching point at 200 W for forward power conversion, so the output power is selected from 150 W to 300 W for measurement. According to Figure 22a, it takes approximately 60 us for the converter to reach a steady state without oscillation when the output power increases from 150 W to 300 W. Conversely, when the output power changes from 300 W to 150 W, the converter takes approximately 100 us to reach a steady state without oscillation, as shown in Figure 22b.  
For backward power conversion, the mode switching point (threshold value) is set at 100 W, so the output power is selected from 10 W to 200 W for measurement. A steady state of about 60 us is observed when the output power increases from 10 W to 200 W in Figure 23a. Conversely, when the output power decreases from 200 W to 10 W, the converter reaches a steady state after 120 us, as shown in Figure 23b. It is worth noting that under the above test conditions, the converter does not oscillate. Therefore, the dual-mode control strategy proposed in this paper is feasible.  
Figure 21: Step load response of prototype converter operating in backward power conversion mode: (**a**) load change from 10 W to 1 kW; (**b**) load change from 1 kW to 10 W.  
Figure 20: Step load response of prototype converter operating in forward power conversion mode: (**a**) load change from 10 W to 1 kW; (**b**) load change from 1 kW to 10 W.