电动汽车无线充电系统异物检测装置设计与实现

  电动汽车无线充电技术以其场地资源利用率高，操作便捷、友好等显著优势，有望在未来成为促进电动汽车推广普及的重要因素。为推动技术平稳快速发展，开展相关技术风险问题的研究具有紧迫性。在实际场景中，由于充电环境较为开放，金属异物容易落入充电区域。异物的侵入不仅会影响充电效率，而且异物本身在交变磁场作用下会产生剧烈温升现象，极易引起火灾风险。为了以准确、可靠和低成本的方式实现金属异物检测，消除潜在的风险隐患，本文设计并验证了基于耦合线圈空间磁场分布特征的金属异物检测方案。

  本文的主要工作内容包括：首先，基于电磁学基础理论，研究金属异物与耦合磁场的相互作用机理，分析金属异物对无线充电系统能量传输和安全运行产生的不良影响；其次，针对表现为非极化场的圆形线圈和极化场的DD形线圈，分别提出与二者空间磁场分布特征匹配的异物检测方案。为解决金属异物检测面临的两大痛点，即低灵敏度区和盲区问题，本文创新性地提出了部分区域多匝绕制方法，可调制C形检测单元和补丁线圈设计。现实充电场景中，车辆与地面发射端存在不对准的情形。立足实际，本文进一步提出了适用于偏移情形的金属异物电磁感知方案。该方案所需的位置偏移信息，可通过复用同一套阵列检测线圈得到。前述工作均通过大量仿真案例和实验研究进行了验证。基于圆形耦合线圈和DD形耦合线圈，各自搭建集成了金属异物检测功能的3 kW无线充电系统。结果表明，对异物可能侵入的充电区域，所提出方案实现了全域可检。在行业标准允许的±75 mm偏移范围内，所提出方案能够适应不同工况下的异物检测需求。

Taking the solid advantages of high utilization rate of land resources and user-friendly characteristics, wireless electric vehicle charging (WEVC) technology is expected to be a key factor enhancing electric vehicle adoption in the future. To promote steady and rapid development of this technology, it is important and urgent to study risk-related issues. In practical scenarios, some metal objects may fall into the charging area since it is not totally enclosed. For one thing, the intrusion of metal objects will affect the charging efficiency. For another, the temperature rise of metal objects will be very high due to the electromagnetic interaction between them and high-frequency coupling field, which is easy to cause fire risk. To detect metal objects in an accurate, reliable and cost-effective way for the elimination of potential risks, a metal object detection (MOD) scheme based on the characteristics of magnetic field established by the coupling coils is designed and verified in this paper.

The main contents of this paper include: Firstly, based on the fundamentals of electromagnetics, the mechanism of the interaction between metal objects and coupling field is studied, and the adverse effects of metal objects on the power transmission and safe operation of WEVC systems are analyzed. Secondly, for the circular coils with non-polarized field and DD coils with polarized field, corresponding MOD schemes matching the field characteristics are proposed. To solve the two major pain points of MOD, viz., low-sensitivity zone and blind zone, a method of multi-turn winding in partial regions, a C-shaped detection unit with size modulation and a design of patch are innovatively proposed in this paper. In practical charging scenarios, the spatial misalignments between EVs and the power transmitter is inevitable. On this basis, this paper further proposes a MOD scheme suitable for the misaligned scenarios. The misalignment information required by this scheme can be obtained by reusing the same set of detection coils. The above works are comprehensively verified by a large number of cases in simulation and experiments. Employing circular coils and DD coils, the two 3-kW WEVC systems integrated with MOD function are built, respectively. The results show that the proposed MOD scheme can stably detect the whole charging area where metal objects may intrude. Within the ±75-mm misalignment range allowed by the standards in the WEVC industry, the proposed MOD scheme can be applicable under working conditions of WEVC systems.

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