## 2 Three-Phase Single-Stage AC-DC Converter in Inductive-Power-Transfer-Based Wind Power Systems
### Operation Modes of Inductive-Power-Transfer-Based Three-Phase Single-Stage AC-DC Converter
Additionally, in the secondary voltage doubler rectifier, the secondary resonant load current (I\({}_{\text{S}}\)) flows through the path of the secondary winding of the contactless coupler (N\({}_{\text{S}}\)) \(\rightarrow\) secondary resonant capacitor (C\({}_{\text{r2}}\)) \(\rightarrow\) output rectifier diode \(\rightarrow\) output capacitor (C\({}_{\text{o}}\))/load \(\rightarrow\) doubler capacitor (C\({}_{\text{o}2}\)) \(\rightarrow\) secondary winding of the contactless coupler (N\({}_{\text{S}}\)), delivering power to the load. **MODE 3 (t\({}_{2}\)-t\({}_{3}\)):** The period t\({}_{2}\) to t\({}_{3}\) is the dead time for the switching devices (Q\({}_{1}\), Q\({}_{4}\)). At t\({}_{2}\), switching device Q\({}_{1}\) turns off, and the boost inductor currents (I\({}_{\text{B1}}\), I\({}_{\text{B3}}\)) and the primary resonant current (I\({}_{\text{P}}\)) begin to charge and discharge the parasitic capacitors (C\({}_{\text{P}}\)) of switching devices Q\({}_{1}\) and Q\({}_{4}\), as well as the parasitic capacitors (C\({}_{\text{ip}}\)) of circulating diodes D\({}_{1}\) and D\({}_{2}\). The voltages of the parasitic capacitor (C\({}_{\text{P}}\)) of switching device Q\({}_{1}\) and the parasitic capacitor (C\({}_{\text{ip}}\)) of circulating diode D\({}_{2}\) are charged to V\({}_{\text{Link}}\)/2. In contrast, the voltages of the parasitic capacitor (C\({}_{\text{P}}\)) of switching device Q\({}_{4}\) and the parasitic capacitor (C\({}_{\text{ip}}\)) of circulating diode D\({}_{1}\) are fully discharged to 0. Afterward, when the negative current flows through the anti-parallel diode of switching device Q\({}_{4}\), if Q\({}_{4}\) turns on at t\({}_{3}\), it operates with zero-voltage switching (ZVS). **MODE 4 (t\({}_{3}\)-t\({}_{4}\)):** At t\({}_{3}\), switching device Q\({}_{4}\) turns on, and the energy stored in the boost inductors L\({}_{\text{B1}}\) and L\({}_{\text{B3}}\) is reset due to the differential voltage between the filter capacitor voltages (V\({}_{\text{CFA}}\), V\({}_{\text{CFC}}\)) and the link capacitor (C\({}_{\text{1}}\)) voltage, which is half of the link voltage (V\({}_{\text{Link}}\)). Consequently, the reset slope of the boost inductor currents (I\({}_{\text{B1}}\), I\({}_{\text{B3}}\)) gradually decreases, flowing through the path of filter capacitors (C\({}_{\text{FA}}\), C\({}_{\text{FC}}\)) \(\rightarrow\) boost inductors (L\({}_{\text{B1}}\), L\({}_{\text{B3}}\)) \(\rightarrow\) input rectifier diode \(\rightarrow\) link capacitor (C\({}_{\text{1}}\)) \(\rightarrow\) circulating diode (D\({}_{\text{1}}\)) \(\rightarrow\) switching device (Q\({}_{\text{2}}\)) \(\rightarrow\) filter capacitors (C\({}_{\text{FA}}\), C\({}_{\text{FC}}\)) \(\rightarrow\) boost inductors (L\({}_{\text{B1}}\), L\({}_{\text{B3}}\)). At this time, a quarter of the link voltage (V\({}_{\text{Link}}\)) is applied to the primary resonant circuit terminals (a-b), allowing the primary and secondary resonant currents (I\({}_{\text{P}}\), I\({}_{\text{S}}\)) to flow. The primary resonant current (I\({}_{\text{P}}\)) follows two distinct paths. The first path flows through the voltage divider capacitor (C\({}_{\text{B1}}\)), the switching device (Q\({}_{\text{2}}\)), the resonant capacitor (C\({}_{\text{r1}}\)), the primary winding of the contactless coupler (N\({}_{\text{P}}\)), and returns to the voltage divider capacitor (C\({}_{\text{B1}}\)). Concurrently, the second path involves the flying capacitor (C\({}_{\text{B}}\)) or the link capacitor (C\({}_{\text{2}}\)), passing through the switching device (Q\({}_{\text{2}}\)), the resonant capacitor (C\({}_{\text{r1}}\)), the primary winding of the contactless coupler (N\({}_{\text{P}}\)), the voltage divider capacitor (C\({}_{\text{B2}}\)), and subsequently either the flying capacitor (C\({}_{\text{B}}\)) or, alternatively, the switching device (Q\({}_{\text{4}}\)) leading to the link capacitor (C\({}_{\text{2}}\)).