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This article deals with an innovative wireless charging system for an implanted capsule robot. The transmitting coil is given by a combination of a Helmholtz coil and a birdcage coil. This coil configuration generates a magnetic field with all nonzero field components for any location within the human torso. Therefore, a single axis receiving coil wound around a cylindrical shaped ferrite core is able to receive a significant quantity of electrical energy for any capsule orientation and position. Design guidelines are provided and illustrative examples are given. Assuming a capsule of 2 cm length and 1 cm diameter we can transfer at least 1 W to the load with a minimum power transfer efficiency larger than 10% without considering electronic losses. Finally, compliance with electromagnetic field safety limits is assessed by a numerical dosimetric analysis. [ABSTRACT FROM AUTHOR]

The electric vehicles (EVs) have played an important role in people's traveling due to the clean energy and friendly environment. Considering the endurance issue of EVs, wireless charging is regarded as a convenient and effective solution. However, the charging power and the efficiency would be greatly affected when the transmitting coil (TC) and the receiving coils are nonaligned. In this article, we present a flexible and high-accuracy positioning device based on electromagnetic balance, which could automatically achieve wireless charging and two-level positioning without communication between TC and EVs during the location. Besides, a six-coil cross-coupled circuit model has been built to optimize the key parameters that affect the positioning accuracy. The theoretical analysis and experimental results show that the proposed structures and location method have certain advantages in positioning accuracy, operation complexity, and practicability. Within the range of first-level positioning, the accuracy could achieve 1 cm. There is a high fitting performance between the simulation and experimental results, which verify the correctness of the theoretical analysis and the validity of the structures. Moreover, an additional comparative experiment has been designed to verify the correctness of the proposed method used in the wireless charging positioning system with ferrite cores and a magnetic shielding layer. [ABSTRACT FROM AUTHOR]

Wireless charging coupled with computation offloading in edge networks offers a promising solution for realizing power-hungry and computation intensive applications on user-devices. We consider a multi-access edge computing (MEC) system with collocated MEC server and base-station/access point (AP), each equipped with a massive MIMO antenna array, supporting multiple users requesting data computation and wireless charging. The goal is to minimize the energy consumption for computation offloading and maximize the received energy at the user from wireless charging. The proposed solution is a novel two-stage algorithm employing a nested descent algorithm, primal-dual subgradient and linear programming techniques to perform data partitioning and time allocation for computation offloading and design the optimal energy beamforming for wireless charging, all within MEC-AP transmit power and latency constraints. Algorithm results show that optimal energy beamforming significantly outperforms other schemes such as isotropic or directed charging without beam power allocation. Compared to binary offloading, data partition in partial offloading leads to lower energy consumption and more charging time, resulting in better wireless charging performance. The charged energy over an extended period of multiple time-slots both with and without computation offloading can be substantial. Wireless charging from MEC-AP thus offers a viable untethered approach for supplying energy to user-devices. [ABSTRACT FROM AUTHOR]

The prerequisite for adjusting the transmitting and receiving coils to alignment is the accurate coil offset angle measurement. There is still a gap and lack of specific research on angle offset. Meanwhile, current technology is acquired in a two-dimensional (2D) plane while the inclination angle is rarely considered. This paper proposes a multi-degree of freedom accurate offset angle measurement based on three-dimensional (3D) electronic compasses. In addition, to obtain the offset angle which contains the direction, a method based on vector dot product and cross product is proposed. In addition, this paper analyzes, models and corrects the different errors to improve further accuracy. Finally, the experimental prototype is built and the results reveal that the proposed strategy can successfully complete the accurate offset angle measurement with an error of less than 1° under the 3D freedom condition of ±60° inclination angle, even if the two coils have the translational offset at the same time. [ABSTRACT FROM AUTHOR]

This article presents a 2.4 GHz and high-efficiency wireless power receiver (Rx) integrated with a low-power transmitter (Tx) for wireless charging of the Internet-of-Things (IoT) or wearable devices. A single pole double throw (SPDT) circuit isolates the operation of the Rx from Tx, thereby offering the capability of sharing antenna between them. The Rx employs a high-efficiency radio frequency (RF)-dc converter, which is facilitated with threshold voltage cancellation technique for enhancing the efficiency, and adjustable internal impedance matching network to compensate the nonlinear behavior of the input impedance with respect to input power level. In addition, it includes a boost dc-dc converter to charge the storage element with a fixed voltage and current. The Tx utilizes a low-power phase-locked loop (PLL) and a class-D power amplifier (PA). Several techniques are adopted to achieve low power consumption. The chip is implemented in a 180 nm CMOS process with a die size of $2.3\,\,\mathrm {mm} \times 5\,\,\mathrm {mm}$. The Rx shows the measured RF to dc maximum power conversion efficiency (PCE) of 53.8% at the input power level of 0 dBm. The Tx achieves a variable output power range of −10 to 10 dBm, while consumes 4 and 23 mA at 0 and 10 dBm output power, respectively. [ABSTRACT FROM AUTHOR]

The ferrite core plays an essential role in coupling enhancement and magnetic shielding for the wireless power transfer of electric vehicles. However, ferrite has apparent defects, such as a low saturation and brittleness, especially at the vehicle side. Therefore, a novel flexible nanocrystalline core is proposed in this article, which has high flexibility and high saturation limits. However, the nanocrystalline core has a large eddy current under 85-kHz excitation, so the refinement crushing process and alternating seamless stitching process are adopted to reduce the eddy loss. The feasibility of the improvement process is preliminarily verified via finite element simulations, and four nanocrystalline cores with different permeabilities are obtained. Through static parameter measurements and 7.7-kW loading tests, the modified nanocrystalline cores achieve excellent results. Based on the above, the nanocrystalline core with the best performance is further selected for an anti-saturation test and leakage measurement at 11 kW. Even when the thickness is reduced to 2 mm, the ac–ac efficiency remains 97.408%. The maximum core temperature is only 80.9 °C, and the flux leakage completely satisfies the limit requirements of ICNIRP 2010. In contrast, the ferrite core cannot withstand the impact of a strong alternating field and fails. [ABSTRACT FROM AUTHOR]

The human eye has been considered to be a promising platform for real-time diagnosis of various biomarkers in tears. The smart contact lens (SCL), as a device which directly accesses surface of human eye, is a miniaturized autonomous system integrating all the required functions on the surface of a thin film. This article presents the first implementation of a set of radio including a wake-up receiver required for SCL. The system performs RF transmission upon wake-up call using a single loop antenna. The receiver path has a baseline-tracking offset control loop to successfully detect wakeup signal in the standby state under noisy environment. The operating frequencies for uplink and downlink are 346 and 433 MHz, respectively. A magnetic-coupled wireless charging of an OFF-chip battery is also provided through the same loop antenna. The designed IC is fabricated using 0.18-μm CMOS process, consuming a power of 2.5 nW in wakeup-ready standby state. The IC is also verified with a loop antenna and a thin-film battery integrated on a substrate of SCL. [ABSTRACT FROM AUTHOR]

Edge networks offer a promising solution for satisfying the increasing energy and computation needs of user devices with new data intensive services. A mutil-access edge computing (MEC) system with collocated MEC servers and base-stations/access points (BS/AP) has the ability to support multiple users for both data computation and wireless charging. We propose an integrated solution for wireless charging with computation offloading to satisfy the largest feasible proportion of requested wireless charging while keeping the total energy consumption at the minimum, subject to the MEC-AP transmit power and latency constraints. We design a novel nested algorithm to optimally solve the resulting non-convex problem in order to jointly perform data partitioning, time allocation, transmit power control and design the optimal energy beamforming for wireless charging. The proposed resource allocation scheme offers minimal energy consumption compared to other schemes while also delivering a higher amount of wirelessly transferred charge to the users. The results also show that compared to other solutions, the energy charging beams for minimum consumption have a wider main lobe, smaller side lobes, with an absence of the back lobe. Even with data offloading, the proposed solution shows significant charging performance, comparable to the case of charging alone, hence showing the effectiveness of performing partial computation offloading jointly with wireless charging. [ABSTRACT FROM AUTHOR]

When constructing an electric vehicle (EV) wireless charging system, limited by manufacturing technology and measurement errors, the capacitance and inductance in the impedance matching network will inevitably produce parameter deviations, which will cause tuning difficulties and even burn the power supply. In order to solve these problems, this article proposes a fast and accurate tuning technique based on a double-sided L3C compensation network with a capacitor matrix. The tuning method derived from theoretical analysis can be summarized as: tuning capacitor can achieve fast matching; fine adjusting the equivalent inductance can achieve precise matching and power zero-voltage switching. After resonance matching, the capacitors on the capacitor matrix can be removed and welded together, and an inductor can be used instead of equivalent inductance, so the technology is low cost, fast, and safe. In order to verify the tuning method, a 3-kW EV wireless charging system was developed. Experimental results show that the proposed method makes the system resonate rapidly and maintain stability, and the inverter is also easy to implement zero-voltage switching. [ABSTRACT FROM AUTHOR]

This article describes a new traceable measurement system, designed for the characterization of inductive charging stations for electric vehicles. This article particularly focuses on static charging (stationary vehicle), while dynamic charging (charging while driving) requires a significantly different system. The measurement system is able to measure on-site performance and efficiency of the charging station and converters. The relative uncertainty is ≤10−3. The measurement system aims at accurately measure the power at the batteries and the power transferred from the ground to the onboard resonant circuit and makes possible a benchmarking between station measuring systems. Finally, this measurement system allows the characterization of the magnetic emissions by correlating them with the electric current in the coils. This system improves the ease and ability to characterize wireless charging stations both in field and laboratory environments. This article describes in detail the hardware, the software, the GPS synchronization, and, in summary, the system architecture. [ABSTRACT FROM AUTHOR]

In this paper, a distributed planning method for EV dynamic wireless charging system (DWCS) is proposed, which determines the locations and the scales of DWCS to maximize the economic effects of wireless charging while meeting EV charging demands. The Nesterov’s model with multiple traffic patterns is adopted in the traffic network (TN) to solve the traffic assignment problem and the traffic wave theory is used to analyze the distribution of road traffic density. In power distribution network (PN), the effect of EV connection modes on the expansion cost of power lines is considered. A mixed-integer linear programming (MILP) model for the proposed planning problem of DWCS in coupled power-traffic networks (PTN) with PN and TN constraints is formulated and solved with MATLAB/CPLEX. The DWCS case studies are carried out to verify the effectiveness of the proposed distributed planning method in PTN. [ABSTRACT FROM AUTHOR]

Coils misalignments restrain the wider implementation of inductive powering of implantable medical devices. The misalignment problem can be overcome with the help of the coils geometry optimization. Coil couple design implies simultaneous adjustment of the several parameters (coils radii, turns numbers, and pitch). Thus, it is desirable to have the means for computer-aided design of the system. An algorithm for the coil couple design is devised. The key feature of the algorithm is the use of predefined maximum and minimum acceptable values of the load power as a performance metric. The algorithm gives the geometry of the coil which ensures that the inductive powering unit provides the given range of the load power for the given range of the misalignments. A formal method is proposed for the calculation of the initial coils characteristics and consequent adjustment of the transmitting coil external radius, transmitting coil turns number, coils internal radii (simultaneously), and receiving coil turns number. The software implementing the proposed algorithm was developed. Eight design runs were performed in order to evaluate the algorithm performance in various conditions, including different power ranges (10 W, 100 mW, and $300~\mu \text{W}$ ), operating frequencies (0.2 MHz, 1 MHz, 6.78 MHz, and 13.56 MHz), and possible implementations (ventricular assist devices, cochlear implants, and spinal cord stimulators). It was proved that the power drop as low as 10% of the mean load power can be ensured for the lateral misalignments up to the receiving coil external radius. The low-power inductive powering unit was constructed and tested. The experimental results confirm the numerical modeling.

Inductively coupled resonant circuits are affected by the so-called frequency splitting phenomenon at short distances. In the area of power electronics, tracking one of the peak frequencies is state-of-the-art. In the data transmission community, however, the frequency splitting effect is often ignored. Particularly, modulation schemes have not yet been adapted to the bifurcation phenomenon. We argue that binary frequency shift keying (2-ary FSK) is a low-cost modulation scheme which well matches the double-peak voltage transfer function H(s), particularly when the quality factor Q is large, whereas most other modulation schemes suffer from the small bandwidths of the peaks. Additionally, we show that a rectified version of 2-ary FSK coined rectified FSK (RFSK), is even more attractive from output power and implementation points of view. The analytical and numerical contributions include the efficiency factor, the impulse response, and the bit error performance. A low-cost noncoherent receiver is proposed. The theoretical examinations are supported by an experimental prototype.

The operational flexibility of unmanned aerial vehicles (UAVs) can be considerably improved by wireless charging without manual intervention in battery charging. To ensure the stability of power receipt, the free-position wireless charging system of UAVs should be designed with urgency. In this article, a numerical definition of a uniform magnetic field and its criteria are presented. Furthermore, two methods, the valley-filling method (VFM) and peak-clipping method (PCM), are introduced to modulate the magnetic flux based on a uniform magnetic field. The correctness of the structures proposed to promote misalignment tolerance has been confirmed by simulations and experiments. The results show that the misalignment tolerance achieved with the employment of the PCM is better than that of other methods, which could keep the transmission efficiency stable when the UAV is horizontally offset. [ABSTRACT FROM AUTHOR]

In a wireless charging system, non-alignment has been a big problem that affects the transmission efficiency. The uniform magnetic field can ensure the charging power stability and extension of battery life in a multi-load wireless charging system, which also expands the free charging area of the loads. In this article, the array circular coils of wireless power transfer (WPT) with a compensation structure have been proposed, which can be obtained by analyzing the magnetic field trajectory of the elementary unit of the array coils. Larger scale of the uniform magnetic field could be expended by the joint of several elementary units. The correctness and validity of the structure are verified by theoretical derivation and finite element simulation. Besides, the compensation method could be used for any forms of array coils. [ABSTRACT FROM AUTHOR]

Dynamic wireless charging (DWC) is an attractive technology which can significantly extend the mileage of electric vehicles. However, experimental evaluation on a DWC system is often implemented at high costs due to the requirement on a movable platform. To address this problem, this article proposes a receiver-side-oriented DWC simulator characterized with wide speed range, compact size, flexible configurations, and controllable testing conditions. First, the emulated I-type multiphase receiver system and its basic operating characteristics are introduced. Then, the fundamental principle employing receiver-induced voltage equivalence and an implementation for a DQ-phase receiver DWC system are demonstrated. Further, movable platform experiments and circuit simulations are conducted to verify the accuracy of the simulator at full-range driving speeds. Finally, application demonstrations for operating the simulator are presented to show the feasibility and flexibility. [ABSTRACT FROM AUTHOR]

This article proposes a multiobjective optimization method of a primary double-D pad for inductive power transfer systems. First, a parametric sweep analysis is conducted to choose the crucial design parameters. Then, using the nondominated sorting genetic algorithm II, the structure of the double-D pad can be optimized based on two key objectives; ensuring a good coupling coefficient while minimizing the worst-case stray leakage magnetic fields. Several useful design guidelines are found from the optimization results, including how the dimensions of both the coil and layers affect the coupling coefficient and stray leakage magnetic fields around the pad. A practical coil suitable for wireless charging of electric vehicles at level 2, similar to that recommended in SAE J2954, is used as the reference and also as the starting point for the optimization. Two of the coil structures resulting from the optimization are chosen and investigated further to assess their performance with different secondary pad misalignments using finite element methods. Finally, an experimental setup is built to validate the optimal pad structures. [ABSTRACT FROM AUTHOR]

Wireless charging technology greatly improves the flexibility and convenience of electric vehicles (EVs) charging. The alignment of coils directly affects the performance of the wireless charging system. The shift of the secondary coil leads to the decrease in transmission power and efficiency. Aiming to solve the abovementioned problems, in this article a mesh-based accurate positioning strategy for the EV wireless charging coils has been proposed. The strategy takes the center of the primary coil as the origin and divides the meshed reference points in the plane of the secondary coil. It is based on the voltage principle induced by the detection coils installed on the secondary coil. The coordinate calculation formula is derived by fitting the curve of the induction voltage with distance. The centimeter-level positioning of the secondary coil is realized in the X and Y directions of the horizontal plane. The proposed strategy is verified by simulations and experiments. The effectiveness and stability of the proposed method are verified by many simulations and experiments. Without considering the rotation of the coil, the maximum error is within 3 cm in a 5 cm mesh width. The positioning strategy helps to align the coils and improves the electrical transmission performance. It is also helpful for automatic parking, unmanned vehicle, and other industrial applications. [ABSTRACT FROM AUTHOR]

The voltage stress of compensation capacitors in the wireless charging system could be up to several kilovolts. Things get worse for the dynamic operating condition because the resonant current gets fluctuating with the rigid variations of the coupling condition. In this article, a constant resistance (CR) control scheme on a boost converter is proposed to mitigate receiver current stress, i.e., the peak currents in the resonant tank and the boost chopper inductor. The receiver-side dynamic wireless charging (DWC) system with a postregulated boost converter is introduced by the static operating waveforms. To investigate how speed affects current stress, a receiver-side current analytical model is established based on the closed-loop input admittance of boost and the dc circuit model of resonant tanks. The modeling results illustrate that the overstress problem is prone to occur at high-speed condition under constant current charging control. CR control, which shapes boost input current and voltage in phase, is adopted to address this problem. Comparative studies for full-range speeds and nonideal coupling conditions, conducted by the DWC simulator, show that uniform low-stress performance is obtained under CR control with the same amount of energy transferred. Maximum stress improvement on the receiver resonant current is 29% for ideal condition and 44% for a nonsinusoidal condition when driving at 80 km/h. [ABSTRACT FROM AUTHOR]

Simple but effective output voltage/current control schemes are essential for electric vehicle wireless charging systems (EVWCSs). This article proposes an EVWCS using interleaved boost converter (IBC) and flat solenoid coupler (FSC). The closed-loop control between the primary and secondary is realized by adjusting the duty cycle of the IBC. The currents and losses in the primary are reduced in the proposed system because the dc bus voltage in the primary is increased by using the IBC. The input current ripple is diminished owing to the interleaved structure. This article also proposes a parameter optimization method to obtain the optimal FSC. Without loss of generality, the total area of the transmitter (Tx) and receiver (Rx) is assumed to be constant, and the Tx is assumed to be larger than the Rx. A scale-down prototype whose output power is 500 W was built in the laboratory to verify the theoretical analysis. The output voltage of the prototype kept constant when the misalignment was 200 mm in the winding direction or 100 mm in the magnetic direction. A highest system efficiency, from dc input to dc output, of 90.1% was achieved when the power transfer distance was 170 mm. [ABSTRACT FROM AUTHOR]

Extensible magnetic resonance coupling-based wireless power transfer (WPT) systems are presented in this article. A transmitter (Tx) containing an 8-shape loop and two resonators is proposed to construct a bipolar Tx array. A unipolar receiver (Rx) is placed above the Tx perpendicularly to overcome the power null phenomenon. The proposed structure ensures that magnetic flux lines are confined in the vicinity of the Rx, leading to a high power transfer efficiency (PTE) over a wide range of lateral misalignment distances. Experiments demonstrated that the proposed WPT system can achieve an efficiency of 87% under perfectly aligned operating conditions, and maintain over 70% efficiency from 0 to 30 mm lateral misalignment distances. Based on the proposed Tx module, a single-feed Tx array is constructed to further increase the charging area. The PTE of a $1 \times 2$ array system is between 57.5% and 71.6% without the power null phenomenon. Meanwhile, the concern of heating due to magnetic field leakage can be significantly mitigated. These designs are proved to be very good candidates for dynamic WPT (DWPT) applications. [ABSTRACT FROM AUTHOR]

Megahertz-frequency inductive wireless power transfer holds the promise of compact and efficient wireless power transfer. Unfortunately, due to high-frequency losses in wide-bandgap semiconductors and low-Q high-frequency coil designs, these systems are universally less efficient, on a dc–dc basis, than wireless power systems operating at conventional frequency regimes. This letter describes the design considerations for inductive wireless power transfer systems operating at 6.78 MHz. With a novel high-frequency resonant amplifier topology, a high-Q self-resonant coil structure, and a better understanding of Coss losses in wide-bandgap power semiconductors, we demonstrate 6.78- MHz wireless power transfer systems that achieve 95% dc–dc efficiency at power levels up to and beyond 1 kW. [ABSTRACT FROM AUTHOR]

The development of Electric Vehicle (EV) helps to ease energy crises and deduce vehicle exhaust emissions. However, it also brings a great impact on both transportation networks and power grids. There are some serious impediments in terms of energy charging to the popularization of EV, such as high deployment cost of charging stations, low charging efficiency, and voltage deviation of power grid. To address these issues, we design a new EV charging system, which levers the bus network in urban areas through the integration of OnLine Electric Vehicle (OLEV) system and Microwave Power Transfer (MPT) system. We formulate the EV route scheduling problem based on this new charging system to maximize the total residual energy subject to all EVs can arrive to their destinations before deadlines. Then, we propose an approximation algorithm, RSA, to solve the route scheduling problem. To relieve the traffic congestion, we further formulate the conflict-free EV route scheduling problem, and use the matching based algorithm, FRSA, to find the EV route schedules with the maximal residual energy. Through the extensive simulations, we demonstrate that RSA and FRSA can increase the average residual energy by 67.66% and 50.36% compared with the solution without the designed wireless charging system, respectively. Moreover, RSA reduces 22.22% of travel time and outputs 77.23% of residual energy, and FRSA can obtain 83.51% residual energy with 3.62% of extra travel time of the corresponding optimal solutions on average, respectively. [ABSTRACT FROM AUTHOR]

The convenience and energy efficiency of electric trams have resulted in their rapid adoption in many areas of the world. Despite trams’ many advantages, overhead lines installed along the track cause severe problems, such as safety issues, maintenance problems, and difficulty in renovating the urban road system. To solve these problems, a wireless charging electric tram system has been developed to replace the overhead lines, catenary, and pantograph. With wireless charging segments installed underground, a tram can operate freely without any support from overhead lines. In order to successfully commercialize a wireless charging tram system, it is essential to minimize the energy cost of the wireless charging tram system. In this article, a model of a wireless charging electric tram system and an energy cost minimization algorithm are proposed. The Manchester Metrolink tram network is modeled using the Google Maps API, the Google Transit API, and the Metrolink API to simulate the wireless charging system under massive public transportation network. To determine the minimum energy cost, an energy cost minimization algorithm for the wireless charging tram system is proposed based on decentralized multiagent reinforcement learning with feedback. The numerical results show that the proposed algorithm can reduce costs while ensuring stable operation. [ABSTRACT FROM AUTHOR]

In a disaster struck area (DSA), macro base stations (MBSs) are usually damaged, and thus the wireless network becomes dysfunctional. To efficiently recover the communications, drone mounted base stations (DBSs) are deployed to relay data between the mobile users (MUs) in a DSA and working MBSs in the proximity of the DSA. However, a DBS may be deployed far away from a working MBS, thus limiting the backhaul link capacity between the DBS and the MBS. Also, the hovering time of current drones is limited, and thus caps the usage of DBSs. In order to increase the backhaul link capacity and prolong the hovering time of a DBS, we propose to apply free space optics to enable an MBS to simultaneously transmit data streams and energy to a DBS with high efficiency. The problem of jointly optimizing the DBS placement as well as the access link bandwidth allocation is formulated to maximize the hovering time of a DBS and guarantee the data rate requirements of the MUs. The joint bandwidth allocation DBS placement (TWIST) algorithm is proposed to solve the problem. The performance of TWIST is demonstrated through simulations. [ABSTRACT FROM AUTHOR]

This paper presents a framework to determine the strategic bidding of the wireless charging aggregators that operate wireless charging stations to provide in-motion charging services for the electric vehicles. The proposed framework captures the interactions between the electricity and transportation networks through competition among the wireless charging aggregators. Wireless charging aggregators participate in the wholesale electricity market to minimize the cost of gained energy from the bulk electricity network. In the retail wireless charging market, wireless charging aggregators compete to maximize their revenue by offering energy to the electric vehicles that are traveling on the transportation links. The strategic behavior of the wireless charging aggregators highlights the interdependence between the electricity and transportation infrastructure systems. In each system, the strategic behavior of the entities is determined by formulating a bi-level optimization problem which is further transformed into a mathematical problem with equilibrium constraints. The upper-level problem maximizes the profit of the entities while the lower level problem ensures the balance between the demand and supply in each infrastructure system. The demand and supply balance is guaranteed by the optimal power flow in the electricity network and the user equilibrium traffic assignment in the transportation network. [ABSTRACT FROM AUTHOR]

In this article, a new direct ac–ac active-clamped half-bridge converter feeding a series–series compensated inductive charging system is proposed. The proposed converter eliminates the rectification stage and bulky life-limited electrolytic dc-link capacitors, resulting in an actual single-stage (ac-to-ac) conversion with low component. The operation principles, steady-state analysis, and design considerations of the proposed converter are presented in detail. Moreover, a new predictive dead-beat technique for input current control and a linear average charging current controller are developed for the proposed converter, which enables the unity power factor and charging current regulation. The performance of the proposed battery charger is validated through experimental results on a 1-kW field programmable gate array (FPGA)-controlled silicon carbide based laboratory prototype. [ABSTRACT FROM AUTHOR]

Wireless Power Transfer has become a commercially viable technology to charge devices because of the convenience of no power wiring and the reliability of continuous power supply. This paper concerns the fundamental issue of wireless charger placement with electromagnetic radiation (EMR) safety. Although there are a few wireless charging schemes consider EMR safety, none of them addresses the charger placement issue. In this paper, we propose PESA, a wireless charger Placement scheme that guarantees EMR SAfety for every location on the plane. First, we discretize the whole charging area and formulate the problem into the Multidimensional 0/1 Knapsack (MDK) problem. Second, we propose a fast approximation algorithm to the MDK problem. Third, we propose a near optimal scheme to improve speed by double partitioning the area. We prove that the output of our algorithm is better than $(1-\epsilon)$ of the optimal solution to PESA with a smaller EMR threshold $(1-\epsilon /2)R_{t}$ and a larger EMR coverage radius $(1+\epsilon /2)D$. We conducted both simulations and field experiments to evaluate the performance of our scheme. Our experimental results show that in terms of charging utility, our algorithm outperforms the comparison algorithms. [ABSTRACT FROM AUTHOR]

In this article, we present a clothing-integrated wireless power transfer and harvesting system that uses a novel class of anchor-shaped antennas for wireless power transfer up to the 4-ft distance. Notably, the system allows wireless charging during daily life activities, such as sitting on a chair or while lying on a fabric surface. Owning to up to a 4-ft power transfer, a user may also walk around during the wireless charging. The proposed system features a novel anchor-shaped antenna, which is miniaturized than a loop antenna and extends the range of fringing fields. Furthermore, a textile-based rectifying circuit with RF-to-dc conversion efficiency of 77.23% at 22.5 dBm is proposed. The efficiency remains better than 60% for an input power from 2 dBm to 24 dBm. For garment integration, a system consisting of a rectifier and an antenna were prototyped by using embroidered conductive thread on denim fabric. To understand the effectiveness, wireless power transfer tests are conducted under mechanical deformations and misalignments. The resulting prototype was tested for power transfer of several mW power over an area of 4 ft $\times4$ ft and by using a 1-W transmitter. This textile power harvesting system can be used as an ergonomic charging platform to supply power to a wide range of wearable medical, Internet of Things, and portable devices. [ABSTRACT FROM AUTHOR]

Autonomous underwater vehicles (AUVs) are increasingly used for undersea exploration. The endurance of AUVs is limited by the onboard energy storage among which the battery systems dominate. Various underwater recharging methods are employed to increase the AUV range and autonomy. Currently, contact-based underwater recharging utilizes the wet-mate connector technology that requires a high-precision AUV docking, and is prone to electrical safety issues. To overcome these limitations, underwater wireless recharging techniques for AUVs have been explored in recent years. Wireless charging offers a safe and reliable method for autonomous power transfer between a charging station and a vehicle. This article reviews the state-of-the-art inductive wireless power transfer (IWPT) solutions for underwater applications and discusses the engineering challenges of the IWPT system design. Underwater environmental factors, such as seawater conductivity, temperature, pressure, water currents, and biofouling phenomenon, impose constraints on IWPT systems. A comprehensive review of AUV energy storage systems, docking methods, IWPT system control methods, and compensation networks is presented in this article. Based on the main operational and constructional principles, the AUV IWPT systems are categorized as loosely coupled transformers and resonant IWPT systems. Each of the categories is illustrated through their main design principles and implementations reported in the literature so far. Technical challenges, such as integration of IWPT system into an AUV hull, interoperability, alignment and retention issues, docking station sinking and stability, the design of pressure-tolerant charging electronics, data transfer, and the battery operation in the underwater environment are discussed in this article too. The article is concluded with the best practice overview of designing an IWPT system for AUVs. [ABSTRACT FROM AUTHOR]

Recently available high-frequency power converter topologies for inductive power transfer (IPT) system utilize either zero voltage switching (ZVS) or zero current switching (ZCS) based power electronic converters while maintaining a near sinusoidal current for limited power transfer range. However, achieving ZVS or ZCS for all power switches simultaneously is still a challenging task in IPT systems. In this article, an improved zero-voltage zero-current switching (ZVZCS) IPT topology and its switching pattern are proposed. ZVS is achieved by optimizing the classical series compensation and additionally, an auxiliary network is employed to achieve ZCS. The proposed concept is verified by using MATLAB/Simulink based simulations for resistive and battery load. Finally, the practical viability of the proposed topology is validated by the results obtained using a laboratory prototype rated for 1.1 kW, 85 kHz. An efficiency of 91.26% is achieved with ZVZCS for a full dynamic power transfer range of 20 W–1.1 kW. [ABSTRACT FROM AUTHOR]

Wireless charging has become increasingly popular for electric vehicles (EVs) in recent years. However, possible device damage may happen because of the sharp variations of inverter output current and the ZVS angle due to the alignment variation between resonant coils especially while charging. To design a protection strategy, the characters of the inverter output current and phase angle are analyzed when the wireless charging EV leaves. The protection strategy is composed of the insufficient angle protection, overcurrent protection, and the excessive angle protection. A detection circuit is designed to measure the variation of inverter output current and phase angle. A wireless charging EV prototype is established to validate the proposed methods. The experimental results show that the designed detection circuit and protection strategy can catch the abnormal working state of the system when the wireless charged EV leaves and take measures immediately to protect the main circuit of the system from device damages. [ABSTRACT FROM AUTHOR]

In this article, we discuss numerical aspects related to the accuracy and the computational efficiency of numerical dosimetric simulations, performed in the context of human exposure to static inductive charging systems of electric vehicles. Two alternative numerical methods based on electric vector potential and electric scalar potential formulations, respectively, are here considered for the electric field computation in highly detailed anatomical human models. The results obtained by the numerical implementation of both approaches are discussed in terms of compliance assessment with ICNIRP guidelines limits for human exposure to electromagnetic fields. In particular, different strategies for smoothing localized unphysical outliers are compared, including novel techniques based on statistical considerations. The outlier removal is particularly relevant when comparison with basic restrictions is required to define the safety of electromagnetic fields exposure. The analysis demonstrates that it is not possible to derive general conclusions about the most robust method for dosimetric solutions. Nevertheless, the combined use of both formulations, together with the use of an algorithm for outliers removal based on a statistical approach, allows to determine final results to be compared with reference limits with a significant level of reliability. [ABSTRACT FROM AUTHOR]

Due to various advantages, wireless charging as well as wired charging for electrical vehicles (EV) will co-exist for some time to come. A hybrid system that provides either wired or wireless charging mode is proposed in the paper. The hybrid system shares the workplaces and the power devices to save costs significantly. The cost of DC power module accounts for a large proportion of the total cost of the wired or wireless charging system and is directly related to its rated power. To reduce the rated power requirement of the DC module of the hybrid charging system, an optimized parameter design method regarding the coupling inductance of the wireless charging is presented for the hybrid system. Under the optimized coupling inductance, the minimum rated DC power requirement is achieved while meeting the battery charging profile of both the wired and wireless charging application. An EV hybrid charging system prototype is designed, built, and tested. Experiments showed that the proposed hybrid charging system has good adaptability for either charging method. Moreover, the proposed parameter design procedure can minimize the rated power requirement of the DC power module. [ABSTRACT FROM AUTHOR]

Power fluctuation caused by the coupling variation is frequently observed in a dynamic wireless charging (DWC) system. To solve this problem, a uniform power solution based on the I-type power supply rail and DQ-phase-receiver is proposed employing receiver-side control. The outputs of DQ-phase voltages are series connected after rectifications to get a higher but less-fluctuated voltage. For further eliminating the fluctuation, the dual-input buck converter with constant resistance control is utilized. The uniform power characteristic, benefiting from the individual control on DQ-phase voltages, is demonstrated under the proposed solution. The uniform power performance is verified on a 1.5-kW prototype with wide-range driving speeds and various practical nonideal conditions. Experimental results, obtained by the DWC simulator, indicate that the output fluctuation factors under the ideal condition are 1.37%, 3.19%, and 4.69% at the driving speeds of 10, 40, and 100 km/h, respectively. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) is an enabling technology for electric vehicles (EV), as it eliminates driver intervention during charging. Major challenges to the adoption of WPT systems include coil misalignment and large air-gap WPT, both of which degrade the transfer efficiency. To address these issues, this article presents a compact WPT charger for the rear of an EV, capable of correcting lateral misalignment $\Delta$ x using two integrated electromagnetic coils. The air-gap $\Delta$ y is reduced due to the rear placement of the charging pads. The variation in $\Delta$ y, however, increases due to vehicle parking accuracy, which impacts the operation of the electromagnetic coils. This article proposes a closed-loop three-stage position-correcting control algorithm capable of detecting the impedance and resonant frequency of the system, which, in conjunction with the electromagnetic coils, results in improved vehicle alignment. The experimental prototype achieves a peak dc–dc efficiency of 90.1% at 5 kW WPT. With $\Delta$ y = 50 mm, the electromagnetic coils laterally align the pads within 1.75 s and correct $\Delta$ x as large as 240 mm. The position-correcting control was successfully demonstrated in four parking scenarios with the charging pads being corrected to within a 10-mm radius of perfect alignment. [ABSTRACT FROM AUTHOR]

In this paper, a method to generate the downward image of current vehicle location using a commercial around view monitor (AVM) is proposed. The proposed system consists of three stages, namely feature tracking, obstacle filtering, and downward view generation. In the feature tracking stage, the Shi–Tomasi corner detection is used and feature tracking is performed with a Kanade–Lucas–Tomasi (KLT) tracker to determine the transformation between AVM images. In the obstacle filtering stage, features on obstacles are filtered by using the difference in a tracking distance between features detected on the ground and features detected on the obstacle. This is performed by using a histogram based on the tracking distance of features. Finally, in the downward view generation stage, transformation between the current AVM image and the previous AVM image is obtained by using the tracked feature pair refined via the aforementioned steps. Specifically, the random sample consensus (RANSAC) method is used to obtain transformations from which the influence of outliers is removed. The downward image of the current vehicle is generated by the obtained transformation and is synthesized to the existing AVM image. The results indicate that the proposed system synthesizes the existing AVM image and the generated downward image of a vehicle in a seamless way by determining the exact pair of matching points between current and the previous AVM images. We believe the proposed system can be utilized in efficient wireless charging system and safe driving system. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) has recently emerged as a prominent technology to liberate various applications with small devices from limited mobility and design constraints. Among various techniques, magnetic field focusing (MFF) with multiple transmit (Tx) coils have been known as a powerful solution to enhance the efficiency of power transfer to multiple receivers (Rxs) in midrange WPT. However, in such MFF techniques, even unintended Rx may suffer from unwanted power due to leakage, which may disrupt the operations of the devices. Motivated by this issue, in this article, we consider selective magnetic resonance coupling (MRC)-based WPT, which enables WPT systems to better shape power distribution only focusing on the intended Rxs while leakages to the unintended Rx are suppressed. To this end, we first formulate the selectivity requirement of WPT as an optimization problem. Then, we propose a method to obtain the optimal Tx voltage vector for simultaneous MFF and null-steering optimization. Simulation and experimental results validate the theoretical analysis and the proposed method in practical scenarios. [ABSTRACT FROM AUTHOR]

The mass and volume of wireless power transfer (WPT) systems for charging electric vehicles are directly related to the rated power of the system. The difficulties of high-power wireless charging are exacerbated by the need to meet the same practical constraints associated with vehicle integration as lower power systems. Therefore, more advanced techniques are necessary to improve power density and specific power of wireless charging systems for high-power applications. This article presents theory and analysis of three-phase inductive WPT systems with bipolar phase windings. Magnetic coupler topologies and the theoretical and practical aspects of series three-phase resonant compensation networks are discussed. The systems under consideration are designed to utilize rotating magnetic fields to achieve a power transfer characteristic that is temporally smoother than single-phase systems. Other benefits associated with rotating magnetic field based WPT, including reduced ferrite mass, filter component requirements, and electromagnetic field emissions, are discussed. Experimental results of a prototype system are presented in both aligned and misaligned configurations. The system is demonstrated transferring 50 kW with 95% dc-to-dc efficiency over a 150-mm airgap in the aligned case. On a per-pad basis, the magnetic couplers achieve a power density of 195 kW/m $^2$ and a specific power of 3.65 kW/kg. This article is accompanied by a video of the rotating magnetic field produced by a simulated three-phase WPT system. [ABSTRACT FROM AUTHOR]

A three-coil wireless charging system is proposed for full metal-cover smartphone applications. Considering the space limitation and other antennas in the smartphone, the receiver coil embedded in the smartphone is designed to be miniaturized as 16 mm × 65 mm. By integrating a series capacitance at the end of the 2-mm width narrow horizontal slot loading on the metal cover, the metal cover is converted to a relay coil of the three-coil system and wireless power transfer (WPT) through the metal cover is thus achieved. A prototype of the proposed three-coil system has been built and WPT through metal cover has been validated via experiment. The experimental results show that the prototype achieves 5 W output power with 71% coil-to-coil efficiency. [ABSTRACT FROM AUTHOR]

Expandable and flexible wireless power transfer (WPT) systems have been in demand in numerous industry applications, especially for dynamic chargers in electric vehicles. Those systems, however, bring about certain technical issues such as modulation technique and topology of the transmitter side, and transferred power profile of the transmitters. In this article, a new converter topology to drive closely spaced segmented dynamic wireless power transfer (DWPT) systems is proposed. The proposed converter can be expanded to cater for different number of transmitters, and it can provide a uniform transferred power profile throughout the path of transmitter coils, known as track. Furthermore, this article focuses on analyzing the operation of the converter and the effect of closely spaced transmitters over its operation. To show the effectiveness of the proposed topology and its modulation technique, the converter is simulated and experimentally tested using a laboratory prototype. The results are compared and analyzed, and their close agreement shows the validity of the proposed technique. [ABSTRACT FROM AUTHOR]

The study of extending navigation range of autonomous underwater vehicles (AUVs) is popular for ocean exploration. A common method is to use the underwater docking station to recover and recharge AUVs. This paper uses the simple but effective inductive power transmission (IPT) system to realize underwater wireless charging for an AUV docking system. A design procedure is provided to select the optimal underwater operating frequency of the IPT system in consideration of eddy-current loss in seawater. To solve the power failure problem of the control power system, an inrush current limiter (ICL) is proposed on the basis of the dynamic model of the IPT system. The test results in the laboratory experiment and sea trial both verify the advantages of the frequency design method and the effectiveness of the ICL. [ABSTRACT FROM AUTHOR]

Wireless charging technology presents an ideal fit for autonomous electric vehicles for realizing a fully automated system (vehicle and charger). This article presents a planning optimization analysis for a pilot project of in-route wireless charging infrastructure serving fixed-route on-demand shared automated electric shuttles (SAESs) at Greenville, SC, USA. A single-objective nonlinear mixed integer system planning optimization problem is formulated. A comprehensive cost model representing the overall inductively charged SAESs system is developed, considering road construction, power electronics and materials, traction battery, and installation costs. The optimization problem is solved to determine the best combination of the system key design parameters (number and allocations of wireless chargers, charging power level, track length, and on-board battery capacity) that show the most cost-effective solution and allow the SAESs to achieve charge-sustaining operation. The planning platform incorporates representative simulated traffic data (driving speed and routes) for four SAESs in the Greenville using the Simulation of Urban Mobility tool. These data are fed to a vehicle powertrain model and a wireless charger power model to predict the battery power, energy and state-of-charge profiles, which are provided to the search algorithm to assess the design objectives under specific constraints. The results indicate that implementing high-power (100 kW) wireless charger at a few designated stops for fixed-route SAESs with the proper track length allows the vehicles to realize charge-sustaining operation, infinite range, and zero recharge downtime, with a significant reduction in the on-board battery (36%) and road coverage (69%), at minimum cost. [ABSTRACT FROM AUTHOR]

This work mainly deals with replacing the wired power transmission method for charging electric vehicle with the help of an efficient wireless power transmission method. For identifying an efficient wireless power transmission method, the inductive power transfer method and the laser optic method are taken into consideration to charge the electric vehicle battery. These methods are compared by hardware implementation for various conditions. Wireless power transmission is an emerging technology utilized to charge the electric vehicle battery through an air gap. The use of this new charging technique is due to its easy access from annoying charging cables, better efficiency, and smaller charging time. Also, it contributes to the remarkable reduction of pollutants and carbon dioxide (CO2) emissions into the atmosphere by the conventional vehicles. However, the implementation of inductive charging for electric vehicle still presents challenges in terms of power transfer efficiency, transmission distance, utilization of heavy batteries with ripple-free and charging time, and stress on compensation network to maintain resonant condition for maximum power transfer. This system will be verified through the simulation in MATLAB/Simulink environment. The simulation results of the inductive power transfer method and the comparison of hardware setup results with laser optic hardware setup have to be verified. [ABSTRACT FROM AUTHOR]

Electric vehicles (EVs) has tiny environmental impact and will constitute a major mean of urban transportation in the future. Shared EV is quickly becoming a new business model under the sharing economy initiatives, providing easy access for commuters who possess no private cars. In this paper, we consider a carsharing company that owns EVs and some parking lots. Passengers can hire an EV at one parking lot and drive it to another one and pay for the service at a certain price determined by the company. A dedicated EV mobility model is proposed to capture the spatial transportation of energy without tracking every single vehicle. Price elasticity is described by a linear demand-price function. The company schedules the aggregated charging of unoccupied EVs in each parking lot, aiming at maximizing the total profit. Parking lots possess relatively large capacity and have to participate in a distribution power market; energy consumption is paid at the locational marginal price. The decision-making problem of the company is formulated as a bilevel program. The lower level simulates the distribution market clearing, and the upper level represents the pricing and charging scheduling problem faced by the company. Starting from a global polyhedral approximation of the power flow model, we develop an equivalent mixed-integer program based on primal-dual optimality condition and integer algebra technique, together with a warm-start strategy which accelerates computation remarkably. Case studies demonstrate that the proposed business model can reshape the load profile by shaving the peaking and filling the valley without harming the profit of the company. [ABSTRACT FROM AUTHOR]

In high-power electric vehicle wireless charging systems, the charging distance is short, and the coupling is strong in order to increase the power density and reduce the coil size and the system cost. With a strong coupling, the receiver-side compensation can be eliminated, and a high efficiency can still be obtained. The inductor-capacitor-inductor-none (LCL-N) topology is formed with the LCL compensation on the primary side. The phase difference between the transmitter and receiver currents is larger than 90°, leading to the magnetic flux cancelation in the ferrites. Thus, the required ferrite thickness of the LCL-N topology is smaller than the fully-compensated topologies. Therefore, a compact, lightweight, and low-cost receiver structure is achieved with the omitted compensation and thinner ferrite. Moreover, the LCL-N topology can achieve zero voltage switching for all loading conditions, withstand open-circuit and short-circuit faults, and is suitable for constant-current and constant-voltage charging due to the fact that it has neither a CC nor a CV output characteristic. A 100-kW system is designed and simulated. A downscaled 1-kW system is implemented. The simulations and experimental results verify the effectiveness of the analysis. [ABSTRACT FROM AUTHOR]

Misalignment of wireless power transfer (WPT) system’s transmitting and receiving ends can cause severe efficiency degradation and electromagnetic radiation. In this paper, a novel parallel transmission (TX) coil matrix structure was proposed to improve the performance of the WPT in the misalignment condition. The receiving (RX) coil’s position measurement method was innovated by investigating the magnetic field and the mutual inductance change caused by the relative position change between RX and TX coils. Both theory and experiments confirmed that the phase difference between signal coil and detector coil can be featured as the parameter to represent the magnetic field’s change. Based on this principle, a $4\times 4$ TX coil matrix was made which verified the proposal and the sensitivity of the sensor. It was found that the position measurement result was sufficient to decide which TX coil to gate to facilitate the wireless charging in misalignment conditions. The structure and the size of the TX coil matrix could be further optimized to enhance the sensor’s reliability and sensitivity. [ABSTRACT FROM AUTHOR]