Research On Power Control Of Wireless Power Transfer System With Electromagnetic Resonance

At present, the power control of magnetic resonance wireless power transfer(WPT)system has the disadvantages of complex operation, low stability, large power loss and so on.However, the method of soft chopper can be used to make a better system of low loss, high frequency, wide range adjustment. To solve the problems of traditional two coils structure in the magnetic resonance WPT system such as low efficiency, short transmission distance and some other disadvantages, the relay coil can be joined into the system. The location of relay coil has great effects on the power transmission of magnetic resonance WPT system with relay coils. So in the situation of small range power control, directly changing the relay coil position, does not need any additional operation. In conclusion, this method which can greatly reduce the difficulty of system power control is simple and convenient.The paper derives the expression of efficiency through the coupled mode theory(CMT),and points out the key parameters which affect its efficiency through simulation. The method of capacitance matching can be used to solve the problem of magnetic resonance frequencies spliting in the WPT system with baising coils. At present, the study of power control and transfer characteristics on magnetic resonance WPT system with relay coils is simple and plain. So the researches on this area will be of very great practical value and innovative significance.The relay coil principle of power control is analyzed in detail, and the process of soft switching chopper is also described in the design of the main circuit. Chose the TMS320F2812 DSP as the core of the control circuit and design the peripheral circuits. The closed loop and incremental PID controller are used to control power transmission. The digital phase locked loop is also used to make the inverter frequency quickly follow the load resonant frequency.Based on theory research and circuit design, the pspice software is used to simulate the system, and the simulation waveforms are gotten. Finally, the article builds the prototype system of 20 k W/50 k Hz and gives the part waveforms of the experiment. The results show that the magnetic resonance WPT system with relay coil can greatly increase the transmission power and efficiency. It turned out that the theoretical values are consistant with actual values.It verifies the correctness of the proposed method of capacitance matching. The power control of soft chopper achieves the realization of soft switching, and the series resonant inverter realizes the frequency tracking, which effectively reduce the switching losses of system and improve the efficiency of the whole machine.