A new parallel transmission method of power and data is proposed for peer-to-peer wireless power transfer (WPT) systems. Essentially, data are modulated and transferred via high-frequency electric field generated by the parasitic capacitances of the coupling coils and the metal shield plates, while power is transferred through relatively low-frequency magnetic field generated by the coupling coils. Coupling structure and operation principle are illustrated and analyzed. Besides, the signal to noisy ratio performance is studied and optimized. With the proposed method, a 40 W prototype is built and the data transmission rate reaches 230 kbps. Experimental results have verified that the proposed method is valid and has the advantages of good flexibility and large spatial position offset redundancy. Because the method does not do any modification on the main circuit of the WPT system, it also has advantages of low cost and easy to implement.

In the electric vehicle dynamic wireless charging (EVDWC) system, when the electric vehicle (EV) drives from one track to the next, it will produce output power fluctuation. This article proposes a multicoupling LCC-compensated method for EVDWC system based on an integrated magnetic coupler to suppress the power fluctuation. The magnetic coupler includes three couplings. The first coupling is between the main coils. The second coupling is between the adjacent compensation inductor coils integrated into main coils. The third coupling is between the primary compensation inductor coils and the secondary compensation inductor coil. The main coils are unipolar and the compensation inductor coils are in a double D structure. The parameter matching rules and optimized design process considering the additional cross-couplings are given. The main advantage of the proposed method is to realize compensation inductance using coupling coils, thereby adding two cross-couplings, and to suppress output power fluctuation based on system normal operation without adding new components. A prototype is designed and implemented to validate the proposed magnetic coupler and parameter design rules. Experimental results show that the output power fluctuation is within ±4% during dynamic charging at a power level of 12 kW, and the maximum efficiency reaches 92.3%.

This paper proposes the design and implementation of a 60kW electric vehicle dynamic wireless power transfer (EV-DWPT) system. The system utilizes a dual transmitter dual receiver (DTDR) structure, and one inverter to active two transmitter coils, which enables it to achieve high output power with low power electronic modules and reduce the numbers of inverters. In the proposed scheme, a unipolar inductor is integrated into the receiver coil, which has the advantage of higher power density. Additionally, a protection circuit is added to protect the charging circuit and the battery, improving the reliability of the system. In the EV-DWPT system with DTDR structure, based on the system modelling and analysis, the coupler design method is given, while taking into account both power and magnetic field exposure time. Moreover, a 54m long dynamic charge path was constructed and a 60kW EV-DWPT system was tested to evaluate system performance while presenting the practical implementation challenges encountered during the construction of the demonstration. The system operates at 85kHz with a 20cm air gap from the transmitter coil to the electric bus chassis. The DC/DC efficiency reaches 87.5% when the transfer power is 62kW.

For a general multi-coil magnetic coupling wireless power transfer (MC-WPT) system with different coil properties and non-negligible cross couplings, there is no analytical solution which connects the resonant frequencies of the system to its electric parameters. Establishing such a generalized analytical solution not only permits quantitative analysis of resonant points but also provides a generic platform for the physical interpretation of resonance. For this purpose, a novel modeling and analysis method of integrating time-domain and frequency-domain is proposed in this paper, with that all possible resonant points of arbitrary coil MC-WPT systems can be quickly and accurately determined. Firstly, an accurate state space model of a general MC-WPT system with arbitrary number of transmitters, repeaters and receivers is established and the analytical current response on each circuit is derived. Then several key system concepts about resonance are elucidated, based on which the generalized analytical expressions of resonant points of MC-WPT systems, including resonant frequencies and corresponding powers and efficiencies, are derived. Further, the physical interpretation along with the mathematic relationships of several key easy-confusing concepts are deduced, which provides systematic theoretical criteria for the selection of operating frequency to achieve the resonant states for MC-WPT systems.

This article proposes a magnetic integrated method for the coupler of the electric vehicle dynamic wireless charging system to suppress power fluctuation by transforming the problem into designing a stable equivalent mutual inductance between the receiving coil and transmitting coils on the road. Both primary-side and secondary-side couplers adopt a magnetic integrated design. The primary-side coupler integrates a reverse coil inside the transmitting coil, and the secondary-side coupler integrates a coil in the LCC resonance compensation inside the receiving coil. Two advantages are unveiled through theoretical analysis of system characteristics: the original single mutual inductance is replaced by the mutual inductance difference between the two reverse series transmitting coils and the receiving coil to determine the power transmission, which suppresses output power fluctuation; the secondary-side integrated inductor coil replaces the external bulky compensation inductor in the LCC resonance compensation network and additionally realizes better zero-voltage switching conditions. The optimized design process considering the additional couplings is given based on circuit analysis. A prototype is implemented to validate the proposed design. Experimental results show that the output power fluctuation is within ±4% during dynamic charging at a power level of 4.5 kW, and the efficiency reaches 91.6%.

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.