In view of the shortcomings of current image detection methods for icing thickness on power transmission lines, an image measuring method for icing thickness based on remote online monitoring was proposed. In this method, a Canny operator is used to get the image edge, in addition, a Hough transform and least squares are combined to solve the problems of traditional Hough transform in the parameter space whereby it is easily disturbed by the image background and noises, and eventually the edges of iced power transmission lines and un-iced power transmission lines are accurately detected in images which have low contrast, complex grayscale, and many noises. Furthermore, based on the imaging principle of the camera, a new geometric calculation model for icing thickness is established by using the radius of power transmission line as a reference, and automatic calculation of icing thickness is achieved. The results show that proposed image recognition method is rarely disturbed by noises and background, the image recognition results show good agreement with the real edges of iced power transmission lines and un-iced power transmission lines, and is simple and easy to program, which suggests that the method can be used for image recognition and calculation of icing thickness.

A radial-flux rotational wireless power transfer (RF-R-WPT) system with rotor state identification function has been proposed to provide power to the devices mounted on a rotating shaft in this article. It can not only transmit electric power from the stationary side to the rotating side but also monitor the rotor state at the same time, improving the stability, security, and service life of the traditional brushes and slip rings. First, the topology and operation principle of the RF-R-WPT system have been proposed. Second, the radial-flux coupler has been designed and optimized. Third, the rotor state identification algorithm has been proposed. Fourth, the voltage and current variation of the primary side and the secondary side of the S--S compensation topology and LCC-S compensation topology have been studied separately, while the coupling degree of the coupler changes. A mutual inductance identification model has been proposed. Fifth, a prototype has been built and tested. From the experimental results, it is verified that the system can realize the power transmission of 13.5 W with a comprehensive efficiency of 74.1% and measure the rotor speed stably to determine its state at the same time.

As a key factor in the design of a voltage-adjustable LLC resonant converter, frequency regulation range is very important to the optimization of magnetic components and efficiency improvement. This paper presents a novel optimal design method for LLC resonant converters, which can narrow the frequency variation range and ensure high efficiency under the premise of a required gain achievement. A simplified gain model was utilized to simplify the calculation and the expected efficiency was initially set as 96.5%. The restricted area of parameter optimization design can be obtained by taking the intersection of the gain requirement, the efficiency requirement, and three restrictions of ZVS (Zero Voltage Switch). The proposed method was verified by simulation and experiments of a 150 W prototype. The results show that the proposed method can achieve ZVS from full-load to no-load conditions and can reach 1.6 times the normalized voltage gain in the frequency variation range of 18 kHz with a peak efficiency of up to 96.3%. Moreover, the expected efficiency is adjustable, which means a converter with a higher efficiency can be designed. The proposed method can also be used for the design of large-power LLC resonant converters to obtain a wide output voltage range and higher efficiency.

In order to solve the problem of increased system weight and cost of current wireless power transfer (WPT) systems with ferrite, a Halbach-type coupler WPT system with flux-shielding function for linear motor has been proposed in this article. It is characterized by high transmitting efficiency, better shielding ability, and antioffset ability. First, the topology and working mechanism of the proposed coupler have been analyzed. Second, considering the coupling ability and magnetic flux density, the parameters of the proposed Halbach-type coupler have been optimized. Third, the prototype of the proposed system has been built and tested, compared with the current DD-type coupler WPT system. Fourth, the magnetic field shielding ability and antioffset ability of the proposed Halbach-type coupler and DD-type coupler have been analyzed, respectively. The experimental results have verified that the WPT system based on the Halbach-type coupler has more promising magnetic field shielding ability and better resistance to the $z$ -axis offset, compared with the WPT system based on the DD-type coupler. The efficiency of the WPT system based on the proposed Halbach coupler can achieve 80.5% and the maximum output power reaches 69.5 W at 11 mm.

In order to improve poor anti-offset capability of rotary transformer in electric excitation motor, a coaxial nested rotary wireless power transfer (CNR-WPT) system has been proposed in this paper. Firstly, considering the spatial geometric relationship of the coils and the power transmission efficiency of the CNR-WPT, the preliminary coil structure has been proposed. Secondly, through theoretical derivation, the specific relationship between the mutual inductance of the coils and the offset have been studied to verify the feasibility of the preliminary design. Thirdly, aiming at the problem that the CNR-WPT is susceptible to steel interference, the magnetic field has been optimized by adding ferrite and introducing a protective casing in this paper. Finally, an experimental platform for CNR-WPT system has been built. The experimental results verify that the power transmission efficiency of the CNR-WPT system can reach 90% when the radial offset and axial offset are below 5 mm, and the angular offset is below 5°. The energy losses can be reduced by adding ferrite and protecting the casing. The CNR-WPT system thereof can also be applied to other rotary power transmission occasions.

A rotating wireless power transfer system based on a mixed flux coupler and dual-path parallel compensation is proposed in this article. It can achieve stable and efficient wireless power transmission as well as accurate speed monitoring without adding an additional excitation, solving the problems of voltage instability and low efficiency in existing solutions. First, the system topology and working principle are presented. Then, the working characteristics of the mixed flux coupler are analyzed and optimized. The power, efficiency, and voltage gain formulas are derived for the system based on a dual-coupled inductor–capacitor–capacitor-series compensation. Based on these theories and the functions that need to be achieved, a number of key design criteria are discussed. Practical experiments on rotating wireless power transmission, speed measurement, and dual-load interference have been carried out. The experimental results show that the proposed system can achieve accurate speed monitoring and stable wireless power transmission. The maximum power of the system can reach 163.59 W, and a maximum efficiency of more than 80% can be achieved. The proposed technique has the potential to significantly contribute to the further development of wireless power transfer technology for rotating machines, such as wind turbines, machining equipment, and robot joints.