基于磁共振的水下非接触式电能传输系统建模与损耗分析

文章对基于磁共振的水下非接触式电能传输系统在海水中的传输机理以及电涡流损耗进行了分析. 首先基于互感模型, 建立了空气中磁共振非接触式电能传输系统的数学模型, 分析了系统的频率特性, 从理论上对频率分裂现象进行了解释. 然后针对海水环境, 通过麦克斯韦方程组建立系统的数学模型, 通过级数展开, 略去高阶项, 得到计算电涡流损耗的近似公式, 分析了电涡流损耗与线圈半径、谐振频率、传输距离、磁感应强度的关系, 为水下非接触式电能传输系统的总体设计提供了理论依据. 最后通过实验验证了在空气中和海水中进行非接触式电能传输的异同, 以及电涡流损耗与各项参数的关系. 实验表明: 在空气中当传输距离为50 mm、传输功率为100 W时, 效率在80%以上; 在海水中当传输距离为50 mm、传输功率为100 W时, 效率约为67%, 说明基于磁共振的水下非接触式电能传输系统在海水中也有很好的应用前景.

Modeling and analysis of eddy-current loss of underwater contact-less power transmission system based on magnetic coupled resonance

In this paper, we investigate the transmission mechanism and eddy-current loss of the contact-less power transmission (CPT) system in seawater environment. Contact-less power transfer could be achieved in the three following ways: magnetic coupling, magnetic resonance coupling, and microwave radiation. When the primary and secondary coils are in resonance, a channel of low resistance in the magnetic resonance coupling system is formed. Therefore, it is used for medium-distance power transmission and it has less restrictions on orientation, which means that it has wide applications in many scenarios. Moreover, contact-less power transfer is safer and more concealed than traditional plug power supply, especially in underwater vehicles. Firstly, the mathematical model based on the mutual inductance model is proposed for the CPT system in the air, then the frequency analysis of the CPT model as well as theoretical explanation of the splitting phenomenon is conducted, after that we consider the seawater effect on the mutual inductance coefficient. Secondly, we build a mathematical model of the eddy-current loss in seawater circumstance according to the Maxwell's equations, where we introduce an average magnetic induction in cross section, then derive an approximate formula through Taylor expansion, and analyze the relations between eddy-current loss and the physical parameters including coil radius, resonance frequency, transmission distance, and magnetic induction. According to the theoretical results, we optimize these physical parameters and then design a 754 kHz CPT system, thereafter we validate the CPT system both in the air and in seawater and find the difference between these two circumstances, and verify the relations between eddy-current loss and the physical parameters which are proposed in our theory. It can be learned from the experiment that when transmission distance is 50 mm and transmission power is 100 W in the air, the transmission efficiency is over 80%, and when transmission distance is 50 mm and transmission power is 100 W in seawater, the transmission efficiency is over 67%. Apparently, our magnetic-resonance-coupling-based CPT system has potentials serving as an underwater vehicle.