The Research Of Frequency And Power Control In Wireless Energy Transfer System

In recent years, with the development of high frequency and a variety of disciplines, wireless power transfer technology has been widely attented again. It overcomes the shortcomings of traditional power transfer, and starts a new way of power transfer and has important value of research. Due to the stability of frequency, frequency bifurcation phenomenon, and different power for different different load in the process of transmitting power, so the frequency tracking and power control in the wireless power transfer system have important research significance.The resonant network, and the influence of coupling coefficient and the quality factor to voltage gain, current gain, and the efficnency of transfer for the bilateral compensation in wireless power transfer system are studied in detal in this paper. On the basis of comparison with different topological structures, the topological structure of this paper is determined. And the results of PSPICE simulation demonstrate the validity of the theory. In addition, bilateral compensation will increse the order of system, and it will result to have multiple resonance frequency points in the system, that is, the phenomenon of frequency bifurcation occurs. The formula of frequency bifurcation of four structures has been deduced, it can avoid the stability problems of the system due to frequency bifurcation.The main circuit of system is determined in this paper. And the main ciucuit consists of rectifier filter circuit, the phase shifting full bridge inverter circuit, the primary resonant network and the secondary resonant network. On the basis of calculating the parameter of the system, the schematics of the whole system is designed, and simulation is carried to prove the rationality of the design. Besides, phase-shifting control chip UCC3895 is used in the inverter, and it can achieve soft switching of power switch tube.Due to the influence of various factors, such as, the load, the inductance coil, the compensation capacitor, coupling coefficient, the frequency of the system and the resonance frequency is always not equal, and it results the decrease of transfer efficiency in the system. Therefore, frequency tracking is necessary in the system. The method of average current polarity is adopted, the time of currtent is greater than zero or less than zero can convert to a polarity signal. Then, based on the average value of the polarity signal, frequency tracking can be achieved.Depending on the load, the required power is different. Therefore, the control of output power is necessary. The PS-PWM technique is used to adjust the phase angle of the directional arm and phase-shifting arm to control the output power. And the output powe can be regulated. In addition, if the phase-shifting control is used, the switching tube can achieve soft switching and can make the loss less.