Research On PDM-based Control Strategy For Wireless Power Transfer System

Magnetic coupled resonant wireless power transmission(MCRWPT)technology,an comprehensive use of basic and applied research of cross disciplines,have the advantages of high transmission efficiency,flexibility,penetrability,safety,non penetrating radiation,wide application prospect and other superiority,which is also suitable for long distance transmission.With the development of transmission requirements and the modem power electronics technology,domestic and international researchers have made great progress in the research and application of the MCRWPT technology,but there are still many problems to be solved urgently,such as load matching and voltage regulation,the sequence to be optimized based on pulse density modulation(PDM)control,the discontinuity of the output power regultation,the efficiency of the system to be improved under parameter detuning and other many related problems.Based on these issues,in-depth research and analysis are carried out,the specific research contents are as follows:First of all,based on the working principle of MCRWPT system,a control method is proposed to realize impedance transform and output voltage regulation of the receiver of the MCRWPT system based on PDM.A receiver rectifier topology is developed by replacing the lower diodes of the rectifier with MOSFETs and anti-parallel diodes.The impedance transform systems and the output voltage regulation are analyzed using Fourier series.The method is verified by the theoretical derivation and experiments,and it simplifies the power and control of the receiver.The impedance transform circuit is also applicable to the situation with variable frequency.Furthermore,in the rectifier filter control,the sequence optimization is carried out.The mathematical model of the MCRWPT system is constructed and analyzed by ZVZCS according to the PDM mode and the synchronous switch mapping method.The analytical function of steady state response of the system is derived,and the Fourier series is used to prove the phenomenon of beat frequency.And then the optimal sequence is found by the improved genetic algorithm to reduce the total harmonic distortion.Also the simulation and experimental results show that the proposed method is feasible.Finally,the power control and tuning strategy of MCRWPT system based on complex hybrid modulation is proposed and analyzed to achieve the desired power regulation and maximize the efficiency.Firstly,the power control strategy based on PDM/PWM hybrid control is proposed to implement power continuous adjustment or adjust as needed,which is controlled by the duty cycle and the controllable delay.Then,the maximum efficiency point of the MCRWPT system based on PDM/PWM/phase shift hybrid control is proposed,and the tuning direction is determined by the phase detection method to find the maximum efficiency point.Experiments show that the control strategy proposed can achieve the required power regulation and the maximum efficiency by active parameter detuning which also can be applied to the situation with variable load and variable distance.