Near Field Electromagnetic Energy Flow Regulation Method for WPT System via Frequency Adjustment

DOI link: 10.1109/JESTPE.2024.3455378

Keywords: Wireless Power Transfer (WPT), Magnetic Field Coupled Power (MFCP), Electric Field Coupled Power (EFCP), Frequency Adjustment, Energy Flow Regulation.

What - Clarification of the Core Content:

• This study proposes a method to regulate the near-field electromagnetic energy flow in a wireless power transfer (WPT) system by adjusting the system’s working frequency, aiming to improve power transfer capability and efficiency under misaligned conditions.
• The research focuses on the comprehensive utilization of both magnetic field coupled power (MFCP) and electric field coupled power (EFCP) in the near-field WPT system to enhance its grid interaction capabilities.
• The paper describes the energy flow process of the near-field WPT system using Poynting vector analysis and proposes a reduced-order evaluation method to assess the transmission levels of MFCP and EFCP.
• The study aims to provide a new method for realizing complementary output and ratio regulation of the two types of coupled power using couplers made of simple materials.

Why - Analysis of the Purpose:

• The integration of large-scale WPT systems into the power grid poses challenges due to the decrease in output characteristics caused by coupling misalignment.
• The study seeks to address this issue by exploring a method to regulate the electromagnetic energy flow in the near-field WPT system, thereby improving its stability and efficiency under misaligned conditions.
• The research aims to enhance the grid interaction capabilities of electric equipment equipped with near-field WPT systems by utilizing both MFCP and EFCP.
• The goal is to provide a practical solution for improving the output characteristics of WPT systems using simple materials and minimal coupler size.

How - Description of the Methods Used:

• The paper employs Poynting vector analysis to describe the electromagnetic energy flow process in the near-field WPT system, considering the effects of distributed parameters.
• A reduced-order evaluation method is proposed to assess the transmission levels of MFCP and EFCP.
• The study uses an equivalent circuit model of the WPT system with coils as transmission carriers to analyze the transmission ratio between the two types of coupled power.
• Simulations and experiments are conducted to verify the effectiveness of the proposed method for regulating the near-field electromagnetic energy flow by adjusting the working frequency.

Key Findings and Insights:

• The transmission ratio between MFCP and EFCP is proportional to the square of the working frequency, and the EFCP transmission channel is less sensitive to positional misalignment.
• By increasing the working frequency, the proportion of EFCP in the total electromagnetic power transmitted by the system increases, enhancing the system’s misalignment tolerance.
• The experimental results show that the system efficiency (AC-AC) improves with increasing working frequency, and the misalignment resistance is enhanced by up to 13.2% when the working frequency is increased from 100 kHz to 400 kHz.
• The proposed method effectively regulates the near-field electromagnetic energy flow, ensuring optimal output characteristics under coupling misalignment.

Examples of Critical Solutions Proposed:

• The study proposes a method to regulate the near-field electromagnetic energy flow by adjusting the system’s working frequency, which actively changes the transmission ratio between MFCP and EFCP.
• The introduction of EFCP compensates for the decreased total electromagnetic power due to coupling misalignment, improving the system’s output characteristics.
• The use of a coupler consisting of simple materials (e.g., planar coils) allows for the complementary output of MFCP and EFCP, enhancing the stability of the WPT system under misaligned conditions.

Research Gaps and Future Work:

• While the study provides a method to regulate the electromagnetic energy flow using frequency adjustment, further research is needed to explore other potential methods and their effects on system performance.
• The impact of different coupling materials and their properties on the transmission ratio and system efficiency should be investigated in future work.
• The study’s results offer a foundation for further exploration into the optimization of coupler design and system control strategies to enhance the overall performance and reliability of WPT systems under various operating conditions.

Recommended citation: Fengxian Wang, Qingxin Yang*, Xian Zhang*, Ting Chen, Guangyao Li. Near Field Electromagnetic Energy Flow Regulation Method for WPT System via Frequency Adjustment. IEEE Journal of Emerging and Selected Topics in Power Electronics. Early Access.
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