基于多线圈阵列的单管无线电能传输电路优化

Optimization on Single-Switch Wireless Power Transfer Circuit Based on Multi-Coils Array

针对多线圈的单管无线电能传输系统提出一种P#型LCC-S补偿网络和输入电流纹波抑制方法,以改善输入电流波形、降低输入电流THD及纹波,从而提高系统效率。该文首先分析P^(#)型LCC-S补偿网络的工作模态和波形,同时给出P^(#)型LCC-S补偿网络参数的计算方法;其次推导了三线圈在非均衡耦合情况下输入电流与输入电压、线圈互感、负载阻抗等参数间的解析关系,利用傅里叶变换分析了输入电流的构成,并对交流分量进行移相抑制;最后搭建实验平台并进行相关实验验证。实验结果表明,在额定传输功率下,纹波抑制后系统效率最高达88.2%,验证了该方案的有效性。

In wireless power transfer technology,full-bridge or half-bridge topology is mainly adopted for the multi-coil parallel transmission system.However,its control and peripheral circuits are complicated,and two switches in series in the inverter turn-on simultaneously will cause a short circuit.In contrast,the single-switch resonant inverter circuit has the advantages of high reliability,simple control,low cost,and easily realizing zero-voltage turn-on.It also has the disadvantages of limited transmission power and significant input current ripple.Hence,by connecting multiple transmitters in parallel and controlling the angle of the input current of the system,the conducting current ripple is suppressed,and the transfer power is increased.It is an effective way to overcome the deficiency of the single-switch resonant inverter.Moreover,the control scheme of the system is simpler than the full-bridge topology if the transfer power is equal.Because of the particularity of the single switch resonant inverter WPT system,the conventional LCC resonant topology can only be used indirectly.The compensation network of the single switch resonant inverter on the side of the transmitter is usually a P-type structure.The resonant frequency of the PP type and PS type is determined by the transmitter L_(t),the receiver L_(r),mutual inductance M and the load R_(L).However,when the magnetic coupler is misaligned,the mutual inductance M will be varied,which will significantly change the resonant frequency of the system.Eventually,it will affect the transmission power and efficiency of the WPT system.In addition,the voltage gain and the quality factor of the P-type compensation network are low,the DC input voltage in normal operation is high,and the filtering effect of the system on high-order harmonics is poor.The LCC topology has the following advantages when working normally:(1)Adjusting the compensation network parameters to make the system constant voltage output.(2)The mutual inductance and load do not affect the resonant frequency of the system.It is just related to the self-inductance of the transmitter.Meanwhile,the system works stably and is hardly prone to detuning.(3)As a high-order network,it has an excellent filtering effect on high-order harmonics for the nice quality factor.In addition,the voltage gain is adjustable,and the requirement of the input voltage level is low.The proposed P-type LCC-S compensation network is suitable for the single-switch resonant inverter.It increases the transmission power of the system by adopting the approach of three-coil parallel input.In order to improve the THD of the input current of the system,firstly,this paper analyzed the working modes of different resonant circuits and parameters and the input current waveform to determine the P#LCC-S compensation network.Secondly,to reduce the ripple of the system input current,the relationship between the coil input current and the input voltage,mutual inductance,and load impedance in the case of three-coil unbalanced coupling was deduced.After analyzing the input current frequency domain,the RMS of fundamentals and each harmonic was obtained.The ripple is suppressed by vector analysis which improves the system's efficiency.The experimental results indicate that when the rated power is 150 W and the phase-shifting suppression strategy is adopted,the Vpp of the input current is reduced from 8.7 A to 2.76 A when the power transfer distance is 50 mm.In addition,the Vpp of the input current is reduced from 6.98 A to 1.6 A when the power transfer distance is 40 mm,50 mm,and 60 mm.Among these situations,the highest efficiency is 88.2%.