Research On High Frequency Transmitter Topology Theory And Control Strategy Of Wireless Power Transfer Via Coupled Magnetic Resonances

Wireless power transfer(WPT)via coupled magnetic resonances has more advantages:longer transmission distance,higher transmission efficiency,less medium dependence and strong environment adaptability,which has become a research hotspot in colleges and universities at home and abroad.However,there are still many problems that have not been solved,such as the large losses of its transmitters,low-frequency output current of its transmitters,poor robustness of system resonance frequency and so on.In order to solve these issues,a novel Z-source inverter is proposed firstly,which is as the transmitter of wireless power transfer systems via coupled magnetic resonances.Its topology structure and operation principle are analyzed.Then,a frequency doubler control strategy is proposed to achieve high-frequency current.The bus voltage ratio,voltage stress,current stress and efficiency of proposed inverter are analyzed in detail.The proposed inverter has the advantages of large bus voltage ratio,frequency doubler,low capacitors voltage stress,and low inrush current.In order to break through the constraints of the switching frequency and switching losses on high-frequency resonance,a unidirectional active energy injection transmitter with soft switching is proposed.Its topology structure and operation principle are analyzed.The constraints of the zero-voltage switching,voltage stress and current stress of the switch,and expressions of transmission power are deduced.To improve power transmission capabilities,a bidirectional active energy injection transmitter and its optimized phase shift control strategy are proposed based on this.And a power regulation strategy and its maximum power point tracking algorithm for above active energy injection transmitters are proposed.The principle of power regulation strategy and the algorithm flow of maximum power tracking algorithm(MPPT)are introduced.The resonance frequency of the proposed active energy injection transmitters depends on practical parameters of circuit,hence,adaptive resonances with high operation frequency can be achieved even at relatively low switching frequency.Meanwhile,soft switching can be realized,resulting in lower switching losses further.More importantly,the bidirectional active energy injection transmitter has lower voltage stress on switches,higher energy injection rate and higher emssion intensity.Finally,the hardware and software of wireless power transfer systems based on active energy injection transmitters are designed.Especially,transmitter and receiver coils are optimized and designed.The simulation model on Saber and experimental prototype are built to verify the transmitters,control circuit and control strategies.Meanwhile,the effects of transmission distance,radial offset and angle offset on the systems transmission characteristics are studied.