The Analysis And Design Based On Wireless Power Transfer Via Strongly Coupled Magnetic Resonances

Wireless power transfer is a kind of advanced technology in the area of power transmission, which represents the most leading edge of theories and the latest ideas. Compared to power transfer with wires, it has the advantage of flexibility and safety. The wireless power transfer via strongly coupled magnetic resonances comes more recently in comparison with other wireless power transfer technologies. It fills the blank of wireless power transfer with higher power in middle range and has great potential and vast development prospects.The paper introduces several wireless power transfer technologies including their transmission mode, transmission range, history of development and directions in future.The coupled mode theory and near field theory which are involved in technology are stated. The process of power transformation of resonators’self-resonance and coupled resonance is analyzed in a mathematical form. The mathematical model for wireless power transfer system is developed. The major factor which affects the transmission efficiency mostly is achieved and the diagram which illustrates the influence of the factor to transmission status is given.To improve the efficiency and reduce the harmonic of simple oscillating circuit, the power conversion circuit in the wireless power transfer system is introduced. It includes Boost PFC circuit, DC/DC converter and high frequency DC/AC inverter. Boost PFC circuit uses average current control strategy to suppress the harmonic. DC/DC converter uses phase-shifted ZVS full bridge control strategy to decrease the switching loss. DC/AC inverter can change the duty cycle and frequency through regulator to meet requirements of research. The’design of hardware and software for power conversion circuit is elaborated. The power circuit, sensors and driver circuit are designed. DSP and CPLD are used to constitute the digital control system. Software is programmed according to specific control strategy.The equivalent diagram for the coil of wireless power transfer is proposed. The operation condition of coil is analyzed and the adaptive range of working frequency is achieved. After the design of transmission coils, wireless power transfer via strongly coupled magnetic resonances is accomplished. Several experiments are carried out to discuss the effects that the distance, direction, voltage, frequency and size of coil influence the characteristic of wireless power transfer. The research lays the foundation for further applications.