This article presents an optimal multivariable control (OMC) strategy for the LCC-LCC compensated wireless power transfer systems. To mitigate reactive power and achieve higher efficiency, the proposed OMC method incorporates dual-side hybrid modulation and primary-side switch-controlled-capacitor (SCC) tuning into the triple-phase-shift (TPS) control. First, the impact of hybrid modulation and SCC tuning on the system characteristics is investigated. The inverter and rectifier zero-voltage-switching (ZVS) conditions are then analyzed to achieve dual-side ZVS with minimal reactive power. Furthermore, a multivariable optimization problem is established based on the power loss analysis. The solution to this problem provides optimal control variables that minimize the overall system loss. Through collaborative modulation and control of the inverter, rectifier, and SCC, the proposed method reduces the rms values of the currents and lowers the turn-off currents for the converters. As a result, this approach improves efficiency in both light- and heavy-load conditions, enabling wide output regulation and full-range efficiency optimization simultaneously. Finally, the proposed method is benchmarked with the existing TPS method. Experimental results demonstrate that the proposed method achieves higher dc-to-dc efficiency in the power range of 0.2-2.2 kW, with a maximum efficiency improvement of up to 6.3%.

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Due to the urgent desire for a fast, convenient, and efficient battery charging technology for electric vehicle (EV) users, extensive research has been conducted into the design of high-power inductive power transfer (IPT) systems. However, there are few studies that formulate the design as a multiobjective optimization (MOO) research question considering both the aligned and misaligned performances and validate the optimal results in a full-scale prototype. This article presents a comprehensive MOO design guideline for highly efficient IPT systems and demonstrates it by a highly efficient 20-kW IPT system with the dc-dc efficiency of 97.2% at the aligned condition and 94.1% at 150-mm lateral misalignment. This achievement is a leading power conversion efficiency metric compared to IPT EV charging systems disseminated in today's literature. Herein, a general analytical method is proposed to compare the performances of different compensation circuits in terms of the maximum efficiency, voltage/current stresses, and misalignment tolerance. An MOO method is proposed to find the optimal design of the charging pads, taking the aligned/misaligned efficiency and area/gravimetric power density as the objectives. Finally, a prototype is built according to the MOO results. The charging pad dimension and total weight, including the housing material, are 516∗552∗60 mm3/25 kg for the transmitter and 514∗562∗60 mm3/21 kg for the receiver. Correspondingly, the gravimetric, volumetric, and area power density are 0.435 kW/kg, 581 kW/m3, and 69.1 kW/m2, respectively. The measured efficiency agrees with the anticipated value derived from the given analytical models.

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Resonant circuits are commonly used in inductive power transfer (IPT) systems for the charging of electric vehicles because of the high power efficiency. Transient behaviors of the resonant circuits, which play a significant role in the design and analysis of IPT systems, are cumbersome to model analytically because of the high-order. This article develops a reduced-order continuous dynamic model based on the energy interactions among the resonant tanks. By applying the proposed energy balancing method (EBM), the order of the dynamic model is reduced to half of the number of the passive components in the resonant circuits. To show the accuracy of the EBM, the dynamics of a series-series (SS) compensated IPT system are modeled using Laplace phasor transformation (LPT) and EBM separately and the results are compared. The order of the EBM is found to be one-fourth of that of the LPT method. The sensitivity of the EBM to the switching frequency is discussed when the zero voltage switching turn-on operation is attained. Besides, to prove the advantage of reducing the order of the dynamic model, model predictive controls (MPCs) based on EBM and LPT are developed. The transient performances of the MPC controllers are simulated and the control inputs are applied to an experimental setup. Finally, experiments are conducted to verify the accuracy of the proposed EBM under zero and nonzero conditions and the effectiveness of the developed MPC controller.

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When considering EV wireless charging that uses inductive power transfer with magnetic resonance, the coils’ current distortion must be minimized to guarantee compliance with the electromagnetic compatibility limits on the radiated magnetic field set by the relevant industrial standards. This paper analyzes the current distortion caused by switch-controlled capacitors (SCCs) used as series compensation to achieve constant optimum load (COL) matching at different coils’ alignments. First, the proposed COL charging method is explained where the SCCs have either the half-wave or the full-wave modulation. Their impact on the measured coils’ current distortion has been analyzed up to 30MHz by computing the fast Fourier transform (FFT). Additionally, the currents’ FFT from the half-wave modulation has been compared to those resulting from the conventional series-series compensation with fixed capacitance. The SCCs using the half-wave modulation result in the highest total-lumped distortion. However, the individual amplitudes corresponding to the critical frequencies of the radiated magnetic field’s limit from SAE J2954 are comparable or lower than those resulting from the other implementations. Finally, the radiated magnetic field resulting from each strategy has been evaluated using the finite element method. All results are well within the SAE J2954 recommended limits at 10 m. Moreover, a minimum distance of 25 cm from the outer sides of the coupled coils ensures a safe exposure to both the general public and implanted medical devices according to the ICNIRP reference levels.@en

This article proposes a mode-switching-based phase shift control (MS-PSC) for wireless power transfer (WPT) systems, which is able to achieve power regulation, load matching, and wide ZVS operations simultaneously without using additional dc-dc converters. Based on the mode transitions between the full-bridge, mixed-bridge, and half-bridge modes of both the inverter and the rectifier, the MS-PSC method guarantees a wide-range ZVS with minimized circulation of reactive power. Therefore, the system efficiency is improved over a wider power range compared to the conventional triple-phase-shift (TPS) control and the existing hybrid modulation control. The principles of different operating modes are analyzed. Then, the implementation of the proposed MS-PSC method and the mode selection strategy are presented. Finally, the effectiveness of the proposed MS-PSC method is validated in a WPT prototype. Experimental results show that the proposed MS-PSC method can achieve a high overall efficiency in a wide power range. Compared with the conventional TPS control, the MS-PSC method further optimizes the efficiency in 10%-63% of the rated power, with efficiency improvements ranging from 1.5% to 6%. As a result, the system efficiency remains at 93.5%-96.1% in the power range of 1-10 kW, with the transformer coupling coefficient k = 0.19.

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This paper aims to investigate the dynamic charging performance of an 11 kW dynamic inductive power transfer (DIPT) system. First, a multi-objective optimization (MOO) method is proposed to find the Pareto front of the DD charging pad. Then, the optimal design with a 96.82% efficiency is selected as the target design for the DIPT system. Based on the coupler mutual inductance at different misalignment, the orientation of the transmitter (Tx) and receiver (Rx) pads and the distance between Tx pads are studied and optimized. To obtain the dynamic characteristics of the DIPT system, the impact of mutual inductance variation is investigated, and a dynamic model using Laplace phasor transformation is built to solve the waveform amplitude of electrical variables. Finally, a time-variant circuit model is built. Based on the simulations, the dynamic model is proved to be accurate, and the proposed DIPT system displays a good dynamic charging performance.

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One of the challenges with the dynamic inductive power transfer (DIPT) technique is the electric vehicle detection (EVD) that helps the DIPT system to control the power supply of the transmitter. The EVD method applying auxiliary coils is a promising candidate because the flat shape of the auxiliary coils is suitable for the compact design. However, the EVD may fail when the metallic foreign object (MFO) is present. Therefore, the desire emerges in the integration design of the EVD and foreign object detection (FOD). The FOD can ensure the reliability of the EVD as well as the highly efficient operation of the DIPT system without MFOs. In this context, this paper proposes an integrated solution to the EVD and FOD well suited for DIPT systems. The integrated solution utilizes both passive coil sets (PCSs) and active coil sets (ACSs). Additionally, a novel detection resonant circuit (DRC) is proposed to realize EVD and FOD using the same coil sets and to amplify the measurement sensitivity. The operation mechanisms, the detection coil sets architecture, the design of the proposed resonant circuits and the detection procedure are detailed. Finally, a printed circuit board based prototype is built to validate the integrated functionality of the EVD and FOD in a DIPT prototype processing 1 kW output. Experiments considering the practical DIPT application scenarios are conducted, and the proposed detection method is able to achieve advantageously high sensitivity and no blind zone.

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This paper aims to investigate the radiated magnetic field by 11 kW inductive power transfer (IPT) systems used for the charging of electric vehicles. Two reference designs suggested by SAE J2954 are studied. Both designs are analysed to obtain the coils winding currents, and 3D FEM models are built in COMSOL without considering the car chassis, which constitutes a conservative approach. The magnetic field intensity at specific distances from the IPT coupler are calculated. Finally, the simulation results are compared with the respective magnetic field limits defined in the international standards SAE J2954, IEC 61980-1 and ICNIRP. The results show that the magnetic field radiations at 10 meters points are significantly lower than the limits established in the SAE J2954, while the emissions at 0.9 meters points are only slightly below the limits defined by ICNIRP.@en

In inductive power transfer applications, it is possible to ensure high efficiency of the main coils by operating at the optimum load. Since the optimum load depends on the coupling between the main coils, the operation needs to be adapted to match this case at different alignment conditions. This paper proposes a method to keep the optimum load constant by varying the natural resonant frequency of both the primary and secondary circuits of a S-S compensation network. This is possible by changing the value of the compensation capacitors at different alignments. This strategy differs from the ones found in the literature, where the input and the output voltage are changed to always match the optimum load. The proposed concept is proven through circuit simulations of an 11 kW EV battery charging system, and several strategies for the implementation of the variable capacitance are discussed.@en

Industrial wireless charging systems use standardized coils to guarantee interoperability between different manufacturers. In combination with these coils, the compensation network can still be designed and optimized. This paper explains the step-by-step design of the compensation network for a 7.7 kW wireless charging system (power class WPT2), which is composed of standardized coils. The compensation network must satisfy the output power and voltage requirements, the soft-switching of the inverter, and the limit of voltage and current stress on the components. The S-S compensation network is found to be unfeasible for those coils, and an optimized double-sided LCC compensation network is designed. The 3-phase grid connection is selected despite the 1-phase one because it gives the lowest total conduction losses. Finally, two parallel SiC MOSFETs C3M0075120K are chosen as inverter's switch because of their low conduction losses. This solution can achieve a payback time within a year with respect to the cheapest one.@en

This paper proposes a new method of electric vehicles detection (EVD) and foreign objects detection (FOD) for dynamic inductive power transfer (DIPT) systems. The proposed detection method applies both passive coil sets (PCSs) and active coil sets (ACSs) to achieve both EVD and FOD with a high detection sensitivity. The operation mechanisms and design of the detection coil sets topology and resonant circuits are elaborated. Finally, both circuit and magnetic field simulation are carried out. The results verify the feasibility and sensitivity of the proposed detection method.

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In high-power wireless battery charging that uses inductive power transfer, a considerable amount of power losses are located in the transmitter and receiver coils because they carry high resonant currents and typically have a loose coupling between them which increases eddy current losses. Therefore, the nominal operation needs to be chosen such that the coils' losses are minimized. Additionally, the inverter's semiconductors soft-switching improves both the power conversion efficiency and the electromagnetic compatibility of the system, thus it needs to be safeguarded for a wide operating range. However, depending on the chosen quality factor of the coils, it might happen that the minimum coils' losses and soft-switching are not satisfied at the same time. This paper defines a guideline on the parametric selection of the coils' quality factor such that the optimum operation of both the coils and the resonant converter can be achieved simultaneously. This parametric guideline is proposed for resonant converters implementing the four basic compensation networks: series-series, series-parallel, parallel-series, and parallel-parallel. Finally, circuit examples are provided for an 11 kW wireless battery charging system.

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This paper aims to identify the difference between foreign object (FO) and misalignment in terms of their influence on inductive power transfer (IPT) systems. This is performed through magnetic and equivalent circuit analysis of the mutual inductance, primary input impedance, charging pad terminal impedance and current harmonics. Experiment measurements on an IPT prototype are carried out to verify the analysis. It is found that: the charging pad terminal impedance under FO condition has a more pronounced decrement than that of misalignment; the mutual inductance under FO condition shows negative correlation with frequency, while positive for misalignment; the absolute value of the input impedance is decreased by FO and increased by misalignment; the influence of FO and misalignment on the THD of the input current is minimal. Finally, it is possible to detect FO and distinguish it from misalignment, through the variation of the primary pad terminal inductance, as well as the frequency dependence of the primary input impedance and the mutual inductance.@en

In the next decades, the number of electric vehicles (EVs) for private use is predicted to increase considerably. Charging the EVs through wireless power transfer (WPT), i.e. wireless charging, has the potential to shorten charging duration of EVs batteries through dynamic charging and it would also improve the safety of static charging in case of wet weather conditions. From 2015, standards and regulations have been released such that common constraints can be defined. Therefore, it is essential to be aware of these regulations before designing an EV wireless charging system, such that it can become an actual application. This paper focuses on the available regulations and standards on EVs charging through WPT. These regulations are explained individually and then, they are compared and discussed mainly in terms of the electromagnetic compatibility (EMC) and exposure of humans to the radiated magnetic field limits. To gain a better understanding, a quantitative and qualitative interpretation of these limits is also given.@en