Tuning Strategy Research On Magnetically Coupled Resonant WPT System

Magnetic coupling resonant wireless power transmission(MCR-WPT)technology is a new power transmission technology,it use alternating magnetic field generated by coils to achieve electromagnetic coupling,and will be free from the shackles of conventional cables.Compared with other traditional wireless energy transmission scheme,this way achieves effective balance in the transmission power,transmission efficiency,and transmission distance.Because this type has a broad prospect in the research value and practical value,so it gets a lot of attention.The key of magnetic coupling resonant wireless power transmission is resonance,that is,the system must ensure that the transmitter resonant frequency,power excitation frequency,receiver resonant frequency are the same in the transmission process,so the system can transfer energy efficiently.Due to environmental changes,load changes,external interference and other factors,the system easily lead to the transmitter or receiver resonant frequency offset,resulting in detuning.Non-resonant will cause a sharp decline in system transmission performance,so more and more research pay attention to solve the detuning problem.In this thesis,the coupled-mode theory and circuit theory were used to analyze the magnetic coupling resonant WPT principle.Through analysis of the system transmission performance,it is concluded that only when transmitter and receiver resonant frequency are the same,the transmission efficiency of system is highest.Through analysis the relationship of the system resonant state and impedance angle,the system resonant state could be recognized through impedance angle.The advantages and disadvantages of several tuning strategies are compared,and the tuning control strategy of based on phase-controlled capacitor was put forward in this paper。According to mismatch problem in magnetic coupling resonant WPT system,this thesis adopts a phased capacitor tuned circuit,and an adaptive tuning control algorithm is put forward.Phased tuning principle of capacitor is given in this paper,and listed the relationship between impedance angle and tuning range,and according to the impedance angle,designing the tuning algorithm enables the transmission resonant frequency to follow the resonance frequency of the receiver,solved the problem of low system transmission performance which caused by the different transmitter and receiver resonance frequency.And use of MATLAB simulation to verify the validity of the tuning strategies.In order to verify tuning strategies proposed in this thesis,a magnetic coupling resonant WPT prototype was designed.Experimental results show that when the system is in resonance state firstly,remove some compensation capacitors of receiver,and model non-resonant state,the tuning control strategy can adjust the non-resonant WPT system,so that the transmitter and receiver of the system can return back to the resonant working state,and make the system of the transmitter and the receiver in resonance state,to verify the feasibility of the tuning strategy.