| As a non-contact energy transfer technology,wireless power transfer(WPT)technology gets rid of power wires,and has the advantages of safety,convenience,easy maintenance,and suitable for extreme working environments,so it has a broad application prospect.Especially,the magnetic-coupled WPT system demonstrates the characteristics of wide power levels,low electromagnetic radiation,and low dependence on transmission media,which has become the mainstream research direction of WPT in recent years.Compared with single-load WPT technology,multi-load WPT technology can easily power multiple free-placed load devices simultaneously,so it is suitable for charging wireless sensor networks,wearable smart devices,and distributed medical implants.However,there are still lots of key technical issues in multiload WPT technology that need to be solved: 1)The complicated coupling mechanism between coils causes the system detuning,resulting in the degradation of system transfer performance;2)The output control strategy is complicated due to the mutual influence of loads in different receivers;3)It is difficult to realize the power distribution between loads as required.To solve the above issues,dynamic decoupling and power distribution methods of multi-load WPT systems are studied in this paper,which provides theoretical and experimental bases for the practical application of multi-load WPT technology.Since the cross-coupling between receivers is an important factor leading to the coupling of various loads,and the method of effectively compensate the cross-coupling is a key technical issue in realizing load-decoupling control.Therefore,this article will study the cross-coupling compensation as the point of realizing load decoupling.The main research contents of this article are as follows:(1)Aiming at the issue that the cross-coupling compensation strategy of multi-load WPT system is difficult to be applied under the condition of variable parameters,which leads to the degradation of system transfer performance,a dynamic cross-coupling compensation method of multi-load WPT system is proposed.A multi-load WPT system model based on LCC-S topology is built,and the phase relationship between symbolic currents which can be used for dynamic cross-coupling compensation is analyzed.A phase synchronization method for the multi-load WPT system is proposed to avoid the phase synchronization failure caused by the cross-coupling effect.Based on variable switching capacitors,a dynamic cross-coupling compensation strategy is proposed which is not limited by mutual inductance polarities.A 40 W experimental prototype is built for verification.Compared with the system without crosscoupling compensation,the efficiency and output power of the proposed system are increased by 69% and 14.3 times,respectively.(2)Aiming at the issue that the output control strategy of multi-load WPT system is complicated due to the interference of different loads,a constant-current output control method for multi-load WPT system based on cross-coupling compensation is proposed.The method of constructing cross-coupling compensation reactance and realizing constant-current output control based on a PWM rectifier is explored.A constant-current closed-loop control strategy based on dynamic cross-coupling compensation is proposed to eliminate the influence of the cross-coupling effect on load current control.The phase synchronization method is optimized,the circuit structure is simplified and the modulation mode of the synchronous signal is improved.A 70 W experimental prototype is built for verification.Compared with the constantcurrent output control system,the efficiency of the proposed system is improved by 22%.(3)Aiming at the issue that the power distribution between loads of multi-frequency multiload WPT system is limited by the resonant frequency of the transmitter,an adaptive tuning method of multi-frequency multi-load WPT system is proposed.The influence of transmitter resonant frequency on power distribution between loads is analyzed.Based on Selective Harmonic Elimination(SHE)phase-shift control,a multi-frequency source with suppressed non-target harmonic components is constructed.A multi-frequency adaptive tuning circuit with free target tuning frequency is proposed,the adaptive tuning mechanism of the tuning circuit is analyzed,and the redundancy issue of the passive tuning circuit is solved.A 50 W experimental prototype is built to verify the theoretical analysis,and the maximum efficiency of the proposed system reaches 80%.(4)Aiming at the issue that the multi-load WPT system is difficult to provide sufficient power for distant receivers,which leads to the degradation of the transfer performance of the system,a multi-load WPT repeater system topology with constant-current/constant-voltage output characteristics is proposed.Based on the transfer characteristics of the dual-load WPT repeater system,a multi-load WPT repeater system is constructed,and the topology of realizing the constant-current/constant-voltage output of each load is deduced.The transfer characteristics of the system are discussed.A 100 W experimental prototype is built for verification.When the distance between the transmitter and the furthest receiver reaches 0.4 m,the overall efficiency of the system reaches 83%. |
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