## 6 Experimental Results
Figure 12: Control methods (Ver 1 and Ver 2) for IPT-based 3-phase single-stage AC-DC converter. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Motor** & **Gear** & **Generator** & **V\({}_{\mathrm{LL}}\) (V)** & **P\({}_{\mathrm{ac}}\) (W)** & **Freq(f\({}_{\mathrm{G}}\)) (Hz)** \\ \hline
650 & 10.3 & 63.11 & 112.6 & 150 & 20.99 \\
750 & 10.3 & 72.82 & 127.8 & 268 & 24.85 \\
950 & 10.3 & 92.23  
Firstly, this paper describes the experimental setup for controlling the secondary-side output voltage (V\({}_{\rm o}\)) of the three-phase single-stage AC-DC converter designed for a small wind power generation system based on IPT technology, aiming to maintain a constant output voltage of 400 V\({}_{\rm DC}\) via wireless sensing of V\({}_{\rm o}\). Figures 14-16 illustrate the performance characteristics under various load conditions, ranging from a light load of 150 W to a rated load of 998 W. Specifically, these figures present the waveforms of the boost inductor current (I\({}_{\rm B1}\)), AC phase voltage (V\({}_{\rm AN}\)), phase current (I\({}_{\rm A}\)), link voltage (V\({}_{\rm Link}\)), and the terminal voltages and currents of the contactless coupler in the DC-DC stage: primary-side terminal voltage/current (V\({}_{\rm P}\)/I\({}_{\rm P}\)) and secondary-side terminal voltage/current (V\({}_{\rm S}\)/I\({}_{\rm S}\)). The generator line-to-line voltage (V\({}_{\rm LL}\)) was varied from 110 Vac to 250.2 Vac during these experiments. Figure 14: Experimental waveforms of (**a**) the PFC stage (V\({}_{\rm Link}\), V\({}_{\rm AN}\), I\({}_{\rm A}\), I\({}_{\rm B1}\)) and (**b**) the DC/DC stage (V\({}_{\rm P}\), I\({}_{\rm P}\), V\({}_{\rm S}\), I\({}_{\rm S}\)) obtained by control of the constant output voltage (V\({}_{\rm o}\): 400 V\({}_{\rm DC}\)) in conditions of wind generator voltage V\({}_{\rm LL}\): 110 V\({}_{\rm rms}\) and load P\({}_{\rm O}\): 150 W.  
Figure 13: Experimental setup for performance testing in IPT-based small wind power generation system. The experimental waveforms show that the boost inductor current (I\({}_{\text{BI}}\)) in the PFC stage operates in discontinuous mode for the controlled output voltage (V\({}_{\text{o}}\): 400 V\({}_{\text{DC}}\)). This operation improves the power factor and makes the phase current waveform (I\({}_{\text{A}}\)) align with the AC phase voltage (V\({}_{\text{AN}}\)) as a sinusoidal wave through filtering. Additionally, examining the waveforms of the primary-side square wave voltage (V\({}_{\text{P}}\)) and current (I\({}_{\text{P}}\)) applied to the S-S compensation circuit for wireless power transfer shows that the output voltage (V\({}_{\text{o}}\)) is controlled in response to variations in the link voltage (V\({}_{\text{Link}}\)) according to phase control (D\({}_{\text{1}}\)T). Due to the resonance current (I\({}_{\text{P}}\)) being delayed relative to the square wave voltage (V\({}_{\text{P}}\)) at the a-b terminals, all primary-side switching devices are confirmed to operate with zero-voltage switching (ZVS). In particular, as illustrated in Figure 17, during the control of the secondary-side output voltage (V\({}_{\text{o}}\): 400 V\({}_{\text{DC}}\)) via wireless communication, the primary-side link voltage (V\({}_{\text{Link}}\)) was observed to vary from 557 V\({}_{\text{DC}}\) to 573.2 V\({}_{\text{DC}}\), resulting in a variation rate of 2.87%. The experimental results demonstrate that the primary-side link voltage (V\({}_{\text{Link}}\)) exhibits minimal variation across the entire range of generator line-to-line voltages (110 V\({}_{\text{ac}}\) to 250.2 V\({}_{\text{ac}}\)) and varying load conditions. Based on these findings, the feasibility of controlling the output voltage (V\({}_{\text{o}}\): 400 V\({}_{\text{DC}}\)) without sensing the secondary-side output voltage and without relying on wireless communication solely through the control of the primary-side link voltage (V\({}_{\text{Link}}\)) was also assessed.