Aiming at the power supply solution of online monitoring equipment for high-voltage transmission lines, a dual-frequency dual-load multirelay magnetic coupling wireless power transfer (MC-WPT) system using a shared power channel has been proposed. The proposed MC-WPT system provides the selective power distribution for different loads and has the constant current output characteristic. First, a dual-frequency inverter is introduced to provide the ac voltage of two frequencies. The compensation network that includes the band-stop filter can reduce the cross interference of the nontarget frequency from another power channel. Second, the system is modeled and analyzed based on the quadratic eigenvalue problem. Considering the cross-coupling mutual inductance, operating frequencies that make the system have constant current output characteristics are obtained. Finally, three evaluation indices are proposed: average current gain, load-independent index, and average sensitivity index of operating frequencies. Optimized operating frequency is selected according to these evaluation indices. The experimental results verify constant current output characteristics and the selective power distribution of two power channels.

In order to solve the problem that the output voltage of bilateral LC-compensated CPT system varies with the variation of load and equivalent coupling capacitance, this paper presented a parameter design method which maintained the output voltage constant and guaranteed a high power factor. The mathematical model of the bilateral LC-compensated CPT system was established. The characteristic of the primary and secondary LC-compensated network were analysed, then the conditions remaining a constant output voltage with varying load and coupling capacitance were determined. The relationship between the power factor and the load versus equivalent coupling capacitance was given. With the proposed parameter design method, a 100 W bilateral LC-compensated CPT experimental setup was constructed. The output voltage changes from 55.0 V to 58.7 V and the power factor varies from 0.902 to 0.977, when the load and coupling capacitance vary from 30.2 Ω to 70.8 Ω and from 310 pF to 1490 pF respectively. Both simulation and experimental results have verified the characteristic of constant output voltage and the effectiveness of the proposed parameter design method.

In magnetic coupling wireless power transfer systems, air gap and load changes are very common. Due to the presence of ferrite cores, changes in the air gap can lead to variations in coil parameters (mutual inductance and self-inductances), particularly in small air gap applications. This article proposes a constant current (CC) output method for LCC-LCC compensated WPT system with variable parameters. The proposed method utilizes an integrated magnetic coupler to provide a variable compensation inductance to offset output fluctuations caused by mutual inductance changes. In addition, compensation parameters for maintaining a CC output versus air gap and load changes are obtained through a particle swarm optimization (PSO) algorithm. An 800 W experimental setup is constructed to validate the effectiveness of the proposed method. The experimental results show that, when the output power varies from 400 to 800 W, within the air gap range of 15 to 50 mm, with a maximum self-inductance variation range of 23% and a maximum coupling coefficient variation range of 0.71 to 0.32, the system has a CC output characteristic with a maximum current fluctuation of only 4% and a maximum efficiency of 90.8%. A video demonstrating the variations in system key waveforms during air gap changes is attached to this article.

When wirelessly supplying electric power to movable devices using capacitive power transfer (CPT) technology, sudden move-in and move-out of the pick-up will cause a sudden change to the system structure. As a result, the current and voltage of the inverter may increase dramatically, which may destroy the semiconductor switches or other circuit components, and the system may consume a lot of power after the pick-up is removed. To address the issues, this paper proposes an F-type compensated CPT system based on the characteristics of the LCL resonant network. A steady state model of the proposed CPT system is established, and a set of design equations are provided. The feasibility and validity of the proposed topology and its parameter design method have been verified by the simulation and experimental results. It has demonstrated experimentally that the CPT prototype can be self-protected and automatically enter standby mode after the pick-up is removed, and restore to deliver required power (>25W) to the load at a high power efficiency (>80%) after the pick-up is moved back to the primary circuit, which are the inherent features of the proposed system rather than relying on any additional detection and control.

The data communication always needs to be implemented in application of the Wireless Power Transfer (WPT) technology. However, there are also some problems need to be dealt with in practical applications. For example, the interference between power transfer and communication is serious, when the power and data are transmitted through the same coupling coil. A simple design is presented to implement bidirectional communication through the power transmission channel in this paper. The main idea is that the high-frequency signal can be sent via a single antenna. The power is transferred in the frequency range of 20 KHz to 100 KHz, the data is transferred by employing carrier at around 10MHz. The interference between the two function is analyzed. In order to demonstrate the effectiveness of the proposal, a hardware experiment prototype platform is built up in the project. In the experiment, the transmission gap distance is 10mm, the power transfer is reached 30W, and the data transmission rate is capable of up to 80 Kbps.