Research On The Power And Efficiency Optimization Of WPT System Based On The Phase Control Of Receiver

Wirelss Power Transmission(WPT)can use microwave,laser,ultrasonic wave,and electromagnetic coupling to achieve non-contact energy transmission.The microwave and laser suit for long-distance applications,but their efficiencies are relatively low.And the transmission power of ultrasonic wave is low.The electromagnetic coupling method is the most widely used technic currently.Based on electromagnetic induction principle,it inputs alternating current in the transmitting terminal to generate alternating magnetic field,so the induced electromotive force is generated in the coil of receiving terminal generate,and finally the power transmission can be realized.Compared with wired energy transmission,wireless energy transmission has the advantages of safe operation,good user experience,and it is suitable for bidirectional energy transmission.In addition,the transmission power can reach several kilowatts with the maximum efficiency of more than 90%.Therefore,it is an effective approach to charge electric vehicles.With regard to the application of wireless energy transmission in electric vehicles,the most commercial issue is concentrated on the optimization of its efficiency and maximum transmission power,which is also focused in this thesis.The influence of different parameters on the transmission efficiency and power is discussed,and the active phase control algorithm for receiving terminal is proposed to further improve the transmission power and efficiency.In this paper,a voltage source(active power source),which has the same frequency as the transmitting terminal and adjustable phase and amplitude,is introduced at the receiving terminal of the wireless energy transmission system.Based on this voltage source,the current phase of the receiving terminal circuit can be changed accordingly,so currents phase angles of both the receiving and transmitting coils are controllable.When the phase difference between the active and the transmitting power supplies is within a certain range,the transmission power and efficiency can be improved simultaneously.In the experiment,two full-bridge inverter circuits are employed,the trigger signals are four PWM waves with synchronous phase,frequency,and continuously adjustable duty cycles,which are generated by the Atmel SAM3X8 E single-chip.The center frequency of the experiment is 85 kHz.The experimental results show that the active receiving terminal method proposed in this paper can improve the transmission efficiency and power simultaneously.In addition,when the excursion is more than half of the coil radius,the transmission efficiency can be increased to 90%,therefore the proposed method can be used in wireless energy transmission applications.