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For the wireless power supply of on-line monitoring equipment for HVTL (high voltage transmission lines), a multi-relay WPT (Wireless Power Transfer) system with double-sided LCC resonant network is proposed to improve the system output power and constant voltage output characteristic. In order to reduce the influence of frequency splitting on system output characteristic, three working modes are analyzed. A numerical simulation analysis has been carried out to prove that the working modes proposed can improve the system’s constant voltage output capability.

When wirelessly supplying electric power to movable devices using capacitive power transfer (CPT) technology, the sudden move in and move out of the pickup 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 pickup is removed. To address the issues, this paper proposes an F-type compensated CPT system based on the characteristics of the inductor–capacitor–inductor resonant network. A steady-state model of the proposed CPT system is established, and a set of design equations is 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 pickup is removed, and restore to deliver the required power (>25 W) to the load at a high power efficiency (>80%) after the pickup 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.

This paper proposes a method to transfer power across a metal barrier wirelessly by combined capacitive and inductive coupling. At the primary side of the power transfer system a two plate coupling interface is designed to allow for a current flow in the metal barrier, which generates a magnetic field for transferring power via an inductive coil at the secondary side. The current distribution in the metal barrier is analyzed by taking the skin effect into consideration, based on which the magnetic field distribution around the metal surfaces is determined. A three-dimensional (3-D) model is established using a computer simulation technology (CST) package to simulate the magnetic field distribution, which gives consistent results compared to theoretical analysis. Finally, a wireless power transfer system is constructed, and practical measurements show that the magnetic flux density near the edges of the metal barrier is higher than that in the middle region. The output power around the edge is also higher although it is more sensitive to the variation of the distance and positioning of the receiving coil. It has demonstrated that more than 11 W of power can be transferred across an aluminum plate with a thickness of 2 mm when the power pickup is placed at an edge of the plate along the current path.

This paper proposes a fast soft-starting method based on phase-shift control strategy for electric vehicle dynamic wireless charging (EV-DWC) system. Firstly, the AC impedance model of the EV-DWC system is established based on the double-sided LCC compensation network. The overshoot suppression method for the output current of the inverter is presented. Then the control method combining phase-shift and fuzzy PID of full-bridge inverter is adopted to achieve fast dynamic response of the system. Finally, an experimental prototype of the EV-DWC system with the output power of 15kw is built, which archives 5ms settling time of the output current of the inverter. The simulation and experimental results proves the feasibility and effectiveness of the proposed method.

In order to improve the power transmission capacity of wireless charging system, a dual-transmitter wireless power transfer (DT-WPT) system with a repeater is presented in this paper. On this basis, in order to avoid the cancellation of the power injected by dual transmitters into the repeater, a method to keep the synchronization of the output voltage phases of the dual primary inverters is proposed in this paper. The method is achieved by adding a current-phase detection module in the system and it does not need communication between the two transmitting units.

To make the pickup coil and its compensation network more compact and efficient, an integration method is proposed to make the traditional bulky compensation inductance integrated into the center of the pickup coil in a form of planar coil. The mutual inductances among the primary coil, the pickup coil and the integrated compensation coil are investigated with finite element analysis method. Then the equivalent circuit is analyzed and the power transfer characteristics of the system are further investigated. It has been shown that the influence of the integrated coil can be ignored and the system keeps the constant current characteristics of the primary coil current and the equivalent load current. Finally, a 10kW prototype system is built up. The experimental results have verified the validity of the proposed integration method. The system is tested to be able to output 9.3kW with an efficiency of 93%.

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.

Capacitive power transfer (CPT) systems based on high-frequency electric field coupling have attracted much attention recently due to their simplicity and low eddy-current losses. This paper proposes a mixed-resonant topology consisted of a Π- CLC resonant circuit on the primary side and a T- CLC circuit on the secondary side for multiple pickups constant current output applications. The voltage gain, current gain, and zero phase angle frequency at different operating modes of Π- CLC and T- CLC circuits are analyzed by fundamental frequency approximation, and the conditions leading to a constant output current independent of loads are determined. Based on the analysis, a design method to determine the resonant network parameters is proposed according to the required output current of each pickup. A prototype with three pickups has been designed and built, and both simulation and experimental results have demonstrated that the proposed multiple-pickup CPT system can output a constant current at each operating power pickup against the load variations of itself and others.

This paper proposed a novel wireless power transfer system with full-duplex communication on a shared channel for capacitively coupled power transfer systems. For the analysis of power and signal transmission, a frequency-domain model of the power and signal channels is established. Based on this model, the signal transfer characteristic of the channel and the influence of power flow on the signal channel are analyzed. Moreover, to ensure the power and signal transfer without unacceptable interference or attenuation, a parameters selection method of the communication channel is developed. In addition, an interference suppression strategy by taking the interference from the ipsilateral channel into consideration is proposed. To suppress the interference effectively, an estimation of the ipsilateral channel output signal is made. Then, the signal from the opposite channel is demodulated by removing the estimated values of the interference. Both simulation and experimental results showed have proven the correctness and effectiveness of the proposed wireless power and signal transfer method. Finally, it has demonstrated that the designed channel can transfer 100 W of power, and a full-duplex communication can be well achieved with different data rates in two directions when both two data rates are set within 200 kb/s.

A novel interference isolation method is proposed by using several designed coils in capacitive power transfer systems as isolation impedances. For each designed coil, its stray parameters such as the inter-turn capacitance, coil resistance and capacitance between the coil and the core, etc. are taken into account. An equivalent circuit model of the designed coil is established. According to this equivalent circuit, the impedance characteristic of the coil is calculated. In addition, the maximum impedance point and the corresponding excitation frequency of the coil are obtained. Based on this analysis, six designed coils are adopted to isolate the interference from power delivery. The proposed method is verified through experiments with a power carrier frequency of 1MHz and a data carrier frequency of 8.7MHz. The power and data are transferred parrallelly with a data carrier attenuation lower than -5dB and a power attenuation on the sensing resistor higher than -45dB.

In the applications of wireless power transfer for mobile devices, the pick-up of the wireless power transfer system often needs to be moved in and moved out. A sudden change in the system structure will cause high transient voltages or currents, which could damage the power electronic device of the capacitive power transfer (CPT). In addition, the standby power of the system will be too high to work after removing the pick-up. A CPT system with double T-type resonant networks has been proposed to address these problems. The steady-state models of the system without the pick-up and normal state conditions of it are established. The relationships between the resonant network parameters are analyzed, and a systematic circuit parameter design method is provided. The proposed CPT topology and the parameter design method have been verified by simulation and experiment. The system not only achieved self-protection under severe load change but also entered standby mode automatically after the pick-up was moved out. Besides, the system is restored to the normal state condition when the pick-up is moved in without additional detection and control circuitry.

Capacitive power transfer (CPT) has been investigated as an alternative wireless power transfer technology based on electric field coupling. The coupling interface of CPT is formed by a pair of “capacitors” in series with the power source and load. The effective capacitance ranges from tens to a few hundreds of picofarads, yielding high impedance. Therefore, in most CPT systems, a tuning inductor is connected in series with the coupling interface for circuit compensation and power transfer capability enhancement. However, this compensation method suffers from high voltage spikes from the inductor if the secondary side load is removed suddenly causing electrical and health hazards. To address the issue, this paper proposes a CPT system based on a Z-impedance compensation network with inherent open-circuit and short-circuit immunity. It also has the voltage boost capability as a Z-source inverter. Its operating principle is described and a set of design equations are given. Both simulations and experimental results from a 5 W low power design have demonstrated that the proposed compensation method using the Z-impedance matching network exhibited open-circuit and short-circuit immunity, could boost up the output voltage by 50% with power efficiency exceeding 80%.

Transmitter coil is one of the most critical part in an inductive power transfer (IPT) system for electric vehicles (EVs) application. For the traditional transmitter coils, due to the switch process between the adjacent coils, two serious problems of pick up voltage fluctuation and high power loss on the windings affect the stability and efficiency of the wireless EV charging. In order to solve these problems, this paper proposes a novel segmented transmitter coil for wireless power transfer on EV. A mutual inductance model is established based on the Neumann's Formula, moreover, a key parameters selection method and turns ratio optimization method of the proposed segmented transmitter coils are also presented to keep the mutual inductance in a constant level while the transmitter coils switching one by one. Both of the simulations and experimental results verify the validity and effectiveness of the proposed transmitter coils and its key parameters selection method.

Electric-field coupled power transfer (ECPT) systems have been proposed as an alternative wireless power transfer (WPT) technology in recent years. With the use of capacitive plates as a coupling structure, ECPT systems have many advantages such as design flexibility, reduced volume of the coupling structure and metal penetration ability. In addition, wireless communications are effective solutions to improve the safety and controllability of ECPT systems. This paper proposes a power and signal shared channel for electric-field coupled power transfer systems. The shared channel includes two similar electrical circuits with a band pass filter and a signal detection resistor in each. This is designed based on the traditional current-fed push-pull topology. An analysis of the mutual interference between the power and signal transmission, the channel power and signal attenuations, and the dynamic characteristic of the signal channel are conducted to determine the values for the electrical components of the proposed shared channel. Experimental results show that the designed channel can transfer over 100W of output power and data with a data rate from 300bps to 120 kbps.

In dynamic charging, the multi-excitation units wireless power system is used to improve the power capacity. This paper establishes the three-dimensional coordinate system of dynamic charging process to analyze the misalignment tolerance of dual excitation units charging system. By the comparison of different topology, the effectively charging area could be known. Finally, validate the effectiveness of the method through the experiments.

An online steady-state load identification method is proposed to solve the problems related to frequency drift, system robustness deterioration, difficulties in controller design due to the uncertainties in load and mutual inductance variations of an inductive power transfer (IPT) system. Take a Series-Series-type IPT system as an example, an additional capacitor is added into the system to make the system work in two operating modes, and a mathematical model is established according to the two modes for the system identification. Simulation and experimental results have verified the proposed online load identification method. It has demonstrated that the method is accurate and reliable for identifying uncertain loads and magnetic coupling variations if other system parameters are known. The method can be used to improve the system performance with precise control.

This paper introduces a new Wireless Power Transfer (WPT) system based on single pair of electric field coupling without a current return path. Such a single-contact Capacitive Power Transfer (CPT) system helps to enhance the coupling tolerance between the coupled plates. A class E converter is designed to drive an LCLC resonant circuit to boost the voltage at the primary side of the coupling plate, while a CLCL resonant circuit is used to boost the output current to the load. A practical prototype is built, and it has demonstrated that 3.8 W of power can be transferred across a single pair of copper coupling plates (100mm ×100mm) at full alignment. And it has found that the single-wire CPT system has a large coupling tolerance against both lateral and angular misalignments between the coupled plates.

Aiming at the problem of short transmission distance and low transmission efficiency, a parameter configuration method for the complementary symmetric LCC networks is proposed on the basis of the ECPT system with double-sided LC resonant network. The equivalent capacitance Cs is introduced into LC network to form LCC resonant network. Through the mechanism analysis and the parameter design of the forward LCC network, the constant voltage output of the forward LCC network is achieved; with the symmetric design of the inverse LCC network, the system characteristics including ZPA (zero phase angle) and constant current operation are obtained. The analytic relationship between the resonant operating point and system parameters is obtained by the stroboscopic map modeling method. Combining with the identification of Cs and variable frequency control, the system can still work steadily in ZPA state after Cs changes. The simulation and experimental results are in good agreement.

In energy injection resonant AC-AC converters, due to the low frequency effect of the AC input envelope and the low energy injection losses requirement, the constant and steady control of the high frequency AC output envelope is still a problem that has not been solved very well. With the aid of system modeling, this paper analyzes the mechanism of the envelope pit on the resonant AC current. The computing methods for the critical damping point, the falling time and the bottom value of the envelope pit are presented as well. Furthermore, this paper concludes the stability precondition of the system AC output. Accordingly, an optimal control method for the AC output envelope is put forward based on the envelope prediction model. This control method can predict system responses dynamically under different series of control decisions. In addition, this control method can select best series of control decisions to make the AC output envelope stable and constant. Simulation and experimental results for a contactless power transfer system verify the control method.

In order to reduce the cost and dimension of the EV's wireless power transfer coil, an efficient optimization method is presented. Based on the mutual inductance coupling theory, the analytic function of power transfer efficiency is derived. The key parameters in this function are simplified by the measures of Fourier series and linearization. With these key parameters, the expression of the power transfer efficiency is vastly predigested and the impact of the turns of coils is easily analyzed. With special examples, the turns of coil obtained from this method are verified. The experimental result shows that the efficiency is even more than 90% using the coil which dimension is 0.6 time of that of primary coil, which shows the coil optimization method is simple and valid.

Due to the constant resonant current and robust characteristic, the LCL resonant topology is widely used in the Inductive Power Transfer (IPT) system. The paper proposes an improved LCL resonant network utilizing a coupling structure between the resonant inductors in the T type network. A series of improved topologies are proposed and compared. A parameter design method is also proposed. This coupling structure will provide more freedom for adjusting the LCL network configuration either in the design stage or in the actual operation. Furthermore, it is helpful to reduce the high order harmonic components and switching losses. Experimental results verify the performance of the improved LCL network.

This paper proposed a bidirectional contactless power transfer (CPT) system with controllers at both primary and secondary sides to regulate the power flow. By involving energy feedback mode in the converters of both sides, a backward power flow channel from load to source is achieved which helps pumping out the surplus power from the output filter capacitor to the resonant tank at the secondary side and from the resonant tank to the power supply at the primary side. Furthermore, synchronous rectifying and zero current switching technologies are involved to reducing switching losses. Therefore, with the proposed dual-side control method, rapid regulation and high efficiency can be achieved. Simulation and experimental results show that the output voltage can be controlled to be constant against load variation by regulating the power flow direction dynamically.

In inductively coupled power transfer (ICPT) system, due to load and coupling parameters dynamic variation, primary resonant system parameters often drift from inherent operating point and lead to drastic decrease of power transfer capability and efficiency. In order to identify dynamically variation of system parameters, this paper put forwards system dynamics parameters identification method based on energy analysis. The method sets up energy supply, storage and dissipation function and energy equilibrium equations in primary resonant tank. And system reflection impedance solving function is given in analytic form as well. Furthermore, with the reflection impedance identification, this paper presents load parameters identification method. The identification methods are derived from energy perspective to avoid complex system modeling and requirements of high speed sampling system. Only zero crossing points sample data of resonant variables are required in system identification process. The identification is beneficial for system controller design. The identification methods are verified by experiments results.

This paper proposes an extended stroboscopic mapping (ESM) method for analyzing soft-switching operating points of resonant inverters. The essential idea of the proposed method is treating the operating period of traditional stroboscopic mapping model as a variable and employing fixed-point theory to find the soft-switching operating points. The method consists of four simple and easy-to-implement steps and can accurately determine the periods and steady-state responses of all possible steady-state soft-switching operating points of resonant inverters. A series tuned inductively coupled power transfer (ICPT) system is taken as an example to test the proposed method. Both simulation and experimental results have proved the validation of the proposed ESM method.

In Inductively Coupled Power Transfer (ICPT) system, attribute to unidirectional energy transfer, there are many problems such as energy feedback difficultly and low efficiency brought by system open-loop running. This paper put forwards a novel contactless energy bi-directional transfer mode to realize energy exchange between transmitter and receiver. The paper presents a bi-directional energy conversion topology and set up its equivalent circuit and piece-wise state space model. The simulation results show that system resonant state have low harmonic components. It's benefit to improve system efficiency and minimize EMI interference. The bi-directional energy transfer mode can be used in energy exchange between mobile devices and energy feedback from mobile device to power grid to improve system efficiency.

In order to optimize the power transfer capability of a contactless power transfer (CPT) system with multi-load, this paper has analyzed the existence condition of the maximum power transfer capability of a CPT system with a certain topology and parameters based on impedance analysis. In addition, a procedure of optimized design is given according to the need of the power and efficiency requirement of a CPT system factually. This method has realized the optimized control of power transfer capability and efficiency by optimizing the input voltage and mutual inductance. Finally, this criterion is justified via an experiment.

The paper present comparison analysis of current soft-switched methods. Series resonant full bridge topology and parallel resonant full bridge topology were choose for their sine wave current in inductor, which meet requirement of Contactless Power Transfer (CPT) system. The paper also presents a detailed simulation and analysis between series resonant and parallel resonant full bridge topologies base on Simulink, and determine the application scope of them.

In order to improve the power transfer efficiency and ensure the space cleanliness of power transfer direction in inductive coupled wireless power transfer (WPT) system, a new U-coil WPT system is proposed. Based on the mutual inductance coupling theory, a new methodology for ensuring that a U-coil system is more energy efficient than a two-coil counterpart is presented in this paper. The theoretical proof and the conditions for meeting the objective are derived and practically verified in a practical prototype. The experimental results show: 1) comparing with two-coil system, power transfer efficiency can be improved more than ten times by using U-coil system; and 2) with the same power transfer efficiency principle, the dimension of primary and load coils in U-coil system shrinks at least 66% comparing with that of two-coil system. The U-coil system not only improves power transfer efficiency but also ensures the cleanliness of the space along the energy transfer direction.

The LCL type MCWPT system in continuous current mode is analyzed in detail. The iterative model for numerical analysis of transient dynamic response is built up with discrete time mapping modeling method. It is found that when the control frequency is equal to the inherent resonant frequency of secondary side, the inverter output current has large distortion and the switches are working in hard-switching mode. Then an effective way to find out the ideal operation frequency with the impedance analysis is proposed. A parameter optimizing process is applied to the system to realize its ideal operation mode where it has the maximum power transfer capability and efficiency. Simulation results from PSpice have verified the theoretical results.