目前，基于磁场能量收集系统、多中继无线供电系统及绝缘子相结合的新型供电装置为高压杆塔在线监测设备提供了全天候、不间断的电能供给。然而，集成于绝缘子的分立式谐振电容极易损毁，严重威胁了供电装置的寿命。自谐振线圈利用内部寄生电容进行自补偿，能够无需外部分立电容，有效地提高供电装置的可靠性。然而，传统双层线圈的自谐振频率不稳定，导致系统的输出特性易发生改变，难以在实际中适用。因此，本课题将针对上述问题，围绕系统的电路模型、线圈自谐振模型等方面展开深入研究，明晰线圈自谐振频率不稳定的主要原因，研究提高线圈自谐振频率稳定性的方法。在线圈自谐振频率稳定、系统输出特性稳定的前提下，提出系统效率提升方法。本课题具体开展的研究工作如下：
首先，针对传统双层线圈自谐振频率高，线圈自谐振频率易受外部填充材料影响的问题，建立了多中继无线供电系统电路模型，从频域上分析了自谐振频率变化对系统输出特性的影响规律，明晰了系统输出特性稳定时自谐振频率范围。然后建立了计及匝间电容的自谐振线圈电路模型，揭示了线圈匝间电容变化是线圈自谐振频率变化的主要原因。基于此，研究了线圈外部填充材料对匝间电容及其自谐振频率的影响规律，发现了传统双层自谐振线圈的不足。设计了四层双绕向自谐振线圈结构，通过增加了线圈层间电容以及降低线圈匝间电容的变化，来降低线圈自谐振频率受外部填充材料的影响，提高线圈自谐振频率的稳定性，确保系统具有稳定的输出特性。
其次，在四层双绕向自谐振线圈结构基础上，研究了系统效率提升的方法。分析了趋肤效应、邻近效应、介质损耗对线圈内阻的影响，研究了线圈参数与线圈内阻的数学关系，建立了自谐振线圈Q值模型。基于此模型，在保持线圈自谐振频率稳定的前提下，研究了自谐振线圈Q值优化方法，给出了线圈设计的详细流程。此外，建立了功率变换器的损耗模型，分析了开关损耗、导通损耗对系统效率的影响规律。通过设计系统的工作频率来实现功率器件零电压开通(Zero Voltage Switching, ZVS)，有效降低了系统的开关损耗，并采用了基于GaN的高频逆变器，进一步提高系统效率。
最后，搭建了自谐振多中继无线供电实验平台。测试并记录了线圈的谐振特性、自谐振频率一致性、系统的输入输出特性及损耗分布等数据，同时在外部填充材料变化的条件下，对比分析了基于四层双绕向自谐振线圈结构与传统双层自谐振线圈结构的多中继系统输出特性的变化情况。实验结果表明，四层双绕向线圈结构的自谐振频率具有更好的稳定性，在外部填充材料变化以后，其谐振频率仅变化了0.2%，系统依然保持较好的CV输出特性，此时系统的最高传输效率可达71.36%。
 

Currently, a novel power supply device, combining magnetic field energy harvesting technology and multi-relay wireless power transfer technology, offers continuous power for high-voltage online monitoring devices. However, the discrete resonant capacitors are easily destroyed, which seriously threatens the lifetime of the power supply device. Self-resonant coils utilizing the internal parasitic capacitance to compensate can eliminate the discrete capacitors and enhance the devices’ reliability. However, when the coil's self-resonant frequency is high, the coil is extremely susceptible to the insulator-filling material. At this point, the system is prone to losing its original output characteristics. Conversely, a low self-resonant frequency in the coil results in a diminished quality factor (Q), leading to lower transfer efficiency. Therefore, the primary purpose of this work is to ensure that the system maintains stable output characteristics. The output voltage characteristics of the system and the self-resonant frequency characteristics of the coil are established to improve the resistance of the system to interference from external filling material changes. The specific research carried out in this work is as follows:
Firstly, to address the problem that the output of the system is easily susceptible to the external filler material when the coil self-resonance frequency is high, a frequency domain model of the output voltage of the multi-relay wireless power supply system is established. The influence of self-resonance frequency change on the system output is analyzed, and the range of self-resonance frequency to satisfy the system output characteristics is clarified. Then, a lumped circuit model considering the turn-to-turn capacitance is established to reveal the influence of the coil's external filling material on the coil turn-to-turn capacitance and its self-resonant frequency. Based on this, a four-layer antisymmetric planar self-resonant coil structure is proposed, which reduces the self-resonant frequency by increasing the interlayer capacitance of the coil. The resistance of the coil's self-resonant frequency to external filler material is improved, ensuring a system with stable output.
Secondly, to address the problem of low transmission efficiency of multi-relay system when the coil self-resonance frequency is low, the Q value model of the self-resonant coil is established. The influence of coil parameters on the internal resistance is investigated. On the premise that the output of the system is not easily disturbed, the Q-value optimization method is proposed, and the detailed flow design is given. In addition, the influence of switching loss and conduction loss on the system efficiency is analyzed by establishing the loss model of the power converter. The operating frequency of the system is designed to achieve the zero voltage switching (ZVS) of the power device, which effectively reduces the switching loss. GaN inverter is adopted to further improve the system efficiency.
Finally, a multi-relay wireless power supply experimental platform based on self-resonant coils was built. The resonant characteristics of the coil, the self-resonant frequency consistency, the input and output characteristics of the system, and the loss distribution were tested and recorded. Comparing the double-layer high-frequency self-resonant coils, the self-resonant frequency stability of the coils designed in this project is tested under the change of external environment. The experimental results show that the self-resonant frequency of the coil designed in this project only changes by 0.2% under the change of external environment, and the system has stable output characteristics. The output characteristics of the proposed coil structure are compared with those of a double-layer high-frequency self-resonant coil structure under variations in the external filler material. Compare the output characteristics of the proposed coil structure with that of a dual-layer high-frequency self-resonant coil structure under variations in external filling materials. The experimental results show that the self-resonant frequency of the proposed coil structure varies by only 0.2%, and the output characteristics of the system are free from external interference. Under this condition, a maximum transmission efficiency of 71.36% can be achieved.