An Underwater Non-contact Power Transmission System Design Based On Magnetic Resonance

In recent years,various kinds of underwater vehicle have played an important role in such areas as marine exploration survey,rescue and salvage,military detection and anti-mine,as a result,many countries in the world begin to actively explore and develop underwater vehicle.Electric power transmission is a problem that must be solved for underwater vehicle to work in deep sea.At present,contact electric power transmission method is widely adopted in deep-sea work,complex sealed structure designed in order to adapt to the poor deep-sea environment will make the interface wear out severely and will also cause leakage problem.Based on the electromagnetic induction,contactless power trans-mission(CLPT)technology is an energy supply way.The good insulation,simple structure brings good prospects to the CLPT technology with a use of underwater energy supply for AUV.Due to its unique advantage,contactless electric power transmission has the potential to be an effective measure to solve the problems above.Under this background,In this article,We study the underwater non-contact charging technology system,which mainly include:1.Through the both theories of Coupled modes and Mutual inductor model,We study the underwater non-contact charging technology system,including the frequency characteristics of the system,transmission power,transmission efficiency.Also,We explain the frequency splitting phenomenon in theory and introduce the effective distance of the system.Using frequency tracking technique,We can get a high transmission efficiency in the effective distance of the system.2.Based on the Maxwell’s equations,We accurate calculation the electric field strength of the round coils with the sinusoidal alternating current.We give the formula for calculating the electric field intensity and magnetic induction intensity,analyzing the electric field strength and magnetic induction intensity in theory.Finally,the numerical solution is obtained,We study the distribution of electric field intensity amplitude and phase in space.3.Based on the Maxwell’s equations,We study the relationship between the eddy loss and the transmission distance,conductivity,coil current,resonant frequency and so on,By series expansion,neglecting the higher-order terms,we give the approximate eddy current loss mathematical expressions and by experiments it was verified that our conclusion is right.Which can give the theoretical basis for our design of CLPT system in the future.4.By comparing the difference of time-harmonic electromagnetic field between in the sea and in the air,the effects caused by eddy current is introduced to the Wirelss Power Transmission(WPT)system in the form of equal impedance,which results in the revise of mutual inductance model.It would simplify the analysis of the WPT system in the sea.The revised mutual inductance model has proved to be correct with experiments.5.This thesis calculates the total impedance of the rectifier and Buck-Boost convert and design a impedance regulation circuit,which adjust the WPT system to deliver power in highly efficient way as the load changes.According to the research in this thesis,a prototype of WPT system is fabricated.The experiment shows that the efficiency is over 80% in the air and it drops to approximate 67% in the sea while the gap is 50 mm and the power delivered is 150 W.