This paper proposes an improved YOLOv5 deep learning algorithm to efficiently detect foreign objects in wireless power transmission (WPT) systems based on infrared images, in response to the presence or dropping of metallic foreign objects in wireless charging systems. First, the model is made lighter and the detection speed is improved by replacing the backbone network CSPDarkNet53 with MobileNetv3. At the same time, the ECA attention mechanism is added to make the network pay more attention to the parameter relationship information and localization information of the model, improving the feature extraction capability of the network. Secondly, the original loss function CIoU of the network is replaced with WIoU, which makes the model converge better and improves the precision of the algorithm detection. Finally, the improved YOLOv5 model was validated on the collected infrared image datasets for the detection of metallic foreign objects, with an increase in precision from 96.2% to 98.3%, recall from 96.5% to 98.8%, overall mAP to 99.5%, and the detection speed improved by nearly 15%, successfully enabling the detection of foreign objects in wireless power transmission systems via infrared images.

In the paper a position constraint algorithm is proposed to achieve high power density, based on the thermal resistance model of a half-bridge LLC system under natural convection. An LLC system with resonant frequency of 1MHz, input voltage of 290-330V, output voltage of 48V and power of 1kW is designed by using the third generation of power semiconductor device GaN. The electrical characteristics of the circuit are verified by simulation software. The loss of the system and the heat dissipation path of the LLC system with planar winding are analyzed, and the thermal resistance model of the system is established. Based on the thermal resistance model of the system, the heat dissipation power of each device is reduced, and the simplified thermal resistance model of each device is established. The device position constraint algorithm is established in a complex system without integration and differentiation. The simulation results show that in the LLC system under the position constraint algorithm, each device operates within the required temperature range, the error between the simulated value and the calculated value is within 5%, and the power density reaches 8.23W/cm3.

This paper presents a comprehensive analysis from a theoretical perspective, showcasing the development of a Multiphysics simulation that incorporates both electrical and magnetic components to investigate the energy conversion of a bidirectional DAB converter. Various phase shift modulation control methods are proposed and thoroughly validated through simulations. Notably, the extended phase shift modulation scheme successfully minimizes the inductor peak current and reactive power of the DAB converter. Beyond electrical circuit simulations, the study delves into the design and simulation of an 800V high-frequency transformer using COMSOL for the DAB circuit. In-depth testing, including open circuit and short circuit tests, is conducted to derive the equivalent circuit. Switching and conduction losses are also estimated based on datasheet specifications. Ultimately, the research culminates in the simulation and comparative analysis of converter efficiency across different modulation strategies. The findings shed light on the most effective approaches for optimizing the DAB converter's performance and energy conversion capabilities.

In this paper, a foreign object detection (FOD) system based on thermal infrared imaging is designed, taking advantage of its benefits, such as strong penetration in extreme weather conditions, high accuracy of non-contact detection, and no side effect on the wireless power transfer (WPT) system. Firstly, theoretical analysis and improvements are made on image processing techniques such as bilinear interpolation, Gaussian filtering, Operational Test Support Unit (Ostu) adaptive binarization, and morphological operations. Next, the processing advantages of the enhanced algorithms are confirmed using the openCV toolbox. Then, the aforementioned image processing techniques are implemented using embedded programming via the STM32 microprocessor, and the system’s foreign object detection capability is also verified by designing experiments for the location and type of foreign object under 5kW power level. Finally, the experimental results show that the WPT foreign object detection system is effective in the case of detecting and locating foreign objects that up to the size of a half yuan coin even an M4 nut, when the sensor is 15 cm away from the foreign object and the maximum viewing angle is within 110°. At this point, the minimum required temperature deviation between foreign object and background is 7°C, as well as the detection processing time is less than 0.5s, which fully satifies the demand for foreign obiect detection in the WPT system.

For metal foreign object detection (MFOD) in wireless power transfer (WPT) system, the electromagnetic induction coil detection method has the advantages of simple structure, strong environmental adaptability, and low cost. Whether it is a passive detection scheme or an active detection scheme, the detection effect is closely related to the mutual inductance between the detection coil and the metal foreign object. Thus, the structure of the detection coil needs to be optimized. It is very meaningful to optimize the structure of the detection coil for the purpose of improving mutual inductance. In this paper, a rack-shaped detection coil is designed. Firstly, theoretical analysis is used to compare the mutual inductance between the single-turn rack and the circular metal foreign object and the mutual inductance between the rectangular detection coil and the circular metal foreign object. Secondly, simulation analysis is used to compare the mutual inductance between the rack coil pair and the metal foreign object and the mutual inductance between the rectangular coil pair and the metal foreign object. Finally, experiment shows that the single-layer rack coil can effectively detect 1 RMB coin and double-layer rack coil can accurately locate the coin on the basis of effective detection when the WPT system power is 1.5kW and the vertical distance between the detection coil and the primary coil is 15mm. 1 jiao RMB coin is the minimum size of the object that can be detected accurately by the detection system.