| Autonomous Underwater Vehicles(AUVs)have been widely used in the field of ocean exploration with the advantages of safety,flexibility and wide working range.However,due to its size and battery capacity,the AUV is unable to perform long underwater missions and needs to return to base to recharge.Traditional wired charging technology are greatly limited in the underwater environment,but Inductive Power Transfer(IPT)technology has been the optimal solution to the underwater charging dilemma due to its ability to achieve non-contact charging between the power supply side and the power consumption side.When IPT technology is used for wireless charging of AUV,due to ocean currents and other factors in the seabed environment,AUV inevitably rotates and shifts,resulting in transmission power fluctuations.In addition,the internal space of AUV is limited and there are many power electronic devices,so the magnetic field distribution of the wireless charging system cannot be concentrated in the center of the ship,otherwise strong electromagnetic field may interfere with the normal operation of the power electronic devices or control circuits inside the AUV,leading to the failure of the AUV system.In this paper,In this paper,a three-phase IPT system with a new coupling structure is proposed.The coupler is composed of three transmitting coils and four receiving coils alternately connected in reverse.The structure is beneficial to suppress the central magnetic field and improve the anti-rotation misalignment performance simultaneously.The main research of this paper is as follows:1.The characteristics of typical topologies S-S,S-P,LCC-S and LCC-LCC are studied,and LCC-S topology is selected as the basic topology of three-phase IPT system.The characteristics of three-phase LCC-S topology are analyzed.In order to simplify the analysis,the concept of "equivalent mutual inductance" is proposed and its relationship with system output power is deduced.2.The influence of cross coupling between the primary transmitting coils on the transmission characteristics of three-phase IPT system is deduced.The results show that the cross coupling will introduce reactive power into the system and increase the required capacity of the system.In order to eliminate cross coupling between primary coil,a decoupling method based on passive element is proposed.Finally,the topology and parameter design method of three-phase LCC-S based on passive element decoupling method is presented.3.According to Biot-Savart’s law,the basic analysis method of magnetic field distribution is clarified.A new coupling structure is proposed,and the influence of the transmitting coil and the receiving coil on the distribution of the central magnetic field is qualitatively analyzed by the above-mentioned magnetic field analysis method,and the suppression mechanism of the central magnetic field is further clarified.The suppression effect of the proposed coupling structure on the central magnetic field is verified by the finite element analysis software ANSYS Maxwell,and compared with the traditional single-phase system.In addition,the variation of self-inductance,mutual inductance and other coupling parameters with the rotation offset angle of the simulation model is obtained,and the influence of these parameters on the transmission power and sensitivity of the system is analyzed.The simulation results show that the new three-phase coupling structure can take into account both the anti-rotation misalignment capability and the low magnetic field intensity in the central region.4.In order to verify the feasibility of the proposed scheme,an experimental prototype of600 W was built,and the changes of system output power and efficiency were measured when the system was shifted from 0° to 60°.The experimental results show that the output power fluctuation range is 536～595W,the maximum power fluctuation is 59 W,and the maximum fluctuation rate is 9.91%.The maximum DC-DC efficiency of the system is 86.28%,the lowest is 85.24%. |
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