| Author: | NIU, Songyan |
| Title: | Analysis and assessment of security situation awareness of wireless electric vehicle charging systems under non-ideal conditions |
| Advisors: | Niu, Shuangxia (EEE) |
| Degree: | Ph.D. |
| Year: | 2024 |
| Subject: | Electric vehicles -- Power supply Wireless power transmission Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Electrical and Electronic Engineering |
| Pages: | 174 pages : color illustrations |
| Language: | English |
| Abstract: | Wireless charging is gaining popularity as a promising alternative to conductive charging for electric vehicles (EVs). It eliminates the need for physical connections, offers flexibility in charging locations, and is essential for automatic EVs in the future. Despite the advantages, charging safety remains a significant concern. While extensive research has focused on the risks of batteries and power electronics in wireless EV charging (WEVC) systems, those of magnetic couplers attract very limited attention. Moreover, early works on this issue have been mostly conducted under ideal conditions, lacking sufficient relevance to practice. As an effort to ensure reliable WEVC, this thesis conducts a systematic study, including the identification, analysis, and evaluation of risks, as well as some discussions on potential solutions to the risks. Firstly, a four-level risk evaluation framework for WEVC systems is established based on SAE J2954, meanwhile considering practical risks that are overlooked in this standard. On this basis, two main risks and factors contributing to their exacerbation are analyzed. Risk I, the overtemperature of magnetic coupler, is evaluated for WEVC systems using various types of coupling coils. Risk II, the intrusion of foreign objects (FOs), is evaluated with different materials, sizes, and positions of them, with a feasibility analysis of FO-tolerant WEVC. These evaluations adopt a dynamic perspective, with risk levels updated online throughout the charging process. Secondly, a data-driven strategy based on improved ResNet is proposed to recognize multi-type misalignments, which are considered significant factors contributing to risk I. The strategy utilizes large-scale data sampled by the proposed double-group cooperated sensing coils, which feature high sensitivity to the misalignments of all kinds. The core algorithm, adaptive channel parameter recalibration ResNet, accurately discriminates similar input data obtained from sensing coils and assigns them proper labels, which fully matches the data characteristics. The experimental verification is conducted using a 6.6-kW prototype. The proposed strategy not only helps address the overtemperature problem, but also enables foreign object detection (FOD) under misalignment conditions. Thirdly, different FOD methods targeted for varying purposes are proposed to address risk II. Two FOD methods by electromagnetic (EM) sensing are specifically devised for WEVC systems with double-D (DD) coils, a type of polarized coils. They bridge a research gap that existing EM sensing methods, originally designed for unpolarized coils, are not applicable in this context due to blind-zone issues. Specifically, the proposed cooperative FOD method can eliminate blind zones by utilizing size-modulated C-shaped coils and mitigate the central blind spot through a patch coil that exploits parallel field characteristics of DD coils. As for the proposed non-cooperative FOD method, it eliminates the blind zone by adopting a novel FOD criterion based on the voltages of individual sensing coils rather than their voltage difference, which is a fixed mindset previously employed. Additionally, this thesis also focuses on FOD under misaligned conditions. To overcome the misalignment effect on FOD accuracy, a FOD strategy employing voltage vector decomposition is proposed. This strategy remains unaffected by misalignment throughout the entire WEVC process, regardless of the resonance state of charging circuits. Experimental verification is conducted for all the aforementioned methods. |
| Rights: | All rights reserved |
| Access: | open access |
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