Structure Electromagnetic Force Analysis of WPT System Under Fault Conditions

DOI link: 10.1109/ACCESS.2020.3015278

Keywords: Wireless Power Transfer, Failure Analysis, Electromagnetic Force, Stress Distribution, Smoothing Scheme.

What - Clarification of the Core Content:

• This study investigates the electromagnetic force (EMF) distribution within the coupling mechanism of a wireless power transfer (WPT) system during fault conditions, focusing on the impact of such forces.
• The study emphasizes the importance of the safe and stable operation of WPT systems, especially under fault conditions that intensify the influence of EMF.
• The series to series (SS) compensation structure is used as an example to analyze the WPT system’s electrical parameters during typical faults.
• It identifies that an open load fault affects the system the most, leading to damage to magnetic shielding structures and coil deformations.
• A mathematical model combining field-path coupling and Maxwell stress methods is established to calculate the EMF of the WPT system.

Why - Analysis of the Purpose:

• The open circuit fault is crucial to study due to its potential to cause significant current oscillations in the system, resulting in increased EMF.
• The study aims to provide theoretical support for the optimal design of the coupling mechanism in WPT systems to mitigate the adverse effects of EMF during faults.

How - Description of the Methods Used:

• A simulation model is constructed to analyze the magnetic induction strength and surface stress distribution of the system.
• Experimental validation is executed, confirming theoretical predictions of EMF distribution when subjected to faults.
• A variable-turn-pitch planar coil is introduced as a smoothing scheme to control the magnetic induction strength distribution and reduce EMF.

Key Findings and Insights:

• The study found that the magnetic induction strength and surface stress were consistent, and both were related to the distribution of the coil currents.
• The EMF amplitude ratio before and after the fault is about the square of the fault current ratio, indicating a significant increase in EMF during faults.
• The experimental results are in line with the simulated findings, substantiating the theoretical modeling approach.

Examples of Critical Solutions Proposed:

• The introduced variable-turn-pitch planar coil, enhanced using the SNOPT algorithm, had a notable effect, reducing the force on the transmission-side coupling mechanism under open circuit faults by 86.24% when compared to equi-turn-pitch planar coils.

• The study demonstrates the practicality of the proposed smoothing scheme by showing the restraint capability of the optimized coil structure.

Research Gaps and Future Work:

• While the study delves into the EMF during specific fault conditions, the analysis of other potential faults and conditions affecting WPT systems is suggested for future research.
• The study’s results offer a foundation for further exploration into structural optimization and material science to enhance WPT system resilience against EMF.

Recommended citation: Xian Zhang, Fengxian Wang*, Xuejing Ni, Yanan Ren, Qingxin Yang. Structure Electromagnetic Force Analysis of WPT System Under Fault Conditions. IEEE Access. 8.
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