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Coil alignment plays a vital role in wireless charging systems which affects the transmission power and resonance coupling efficiency in electric vehicle (EV) charging. Also, the cutting-edge controlling model is used to improve the converter operations in the wireless inductive power transfer (IPT) system for EV charging. This work proposes a deer hunting optimized converter control (DHOCC) algorithm for buck dc–dc converter to effectively step down the desired voltage and reduce the system complexity such as misalignments and air gap. The coil’s misalignment and air gaps are changed through the buck dc–dc converter output. This algorithm aligns the coil by changing the ranges of misalignment and air gap to improve coupling efficiency. The EV is placed on its surface to charge the battery. The proposed work is designed in the MATLAB/Simulink platform and the experimental setup validation has been carried out through the laboratory test setup. The simulation output shows the high effective coupling between two coils for an 8 cm air gap with 89.7% power transfer efficiency (PTE) and the experimental output shows an 8 cm air gap with 84.77% of PTE. The obtained result demonstrates the performance of the DHOCC based on a wireless IPT system under less complexity. [ABSTRACT FROM AUTHOR]

Electrified pavements with inductive charging systems provide an innovative way of providing continuous wireless power transfer to electric vehicles (EVs). Electrified pavements have unique construction methods, resulting in different mechanical and thermodynamic characteristics from traditional pavements. This study aimed to investigate the mechanistic design of electrified pavements to mitigate thermal-induced reflective cracking due to the inclusion of concrete slabs with inductive charging units (CUs) under an asphalt surface layer. Finite element (FE) models were developed to analyze the temperature profiles, pavement responses, and crack potential in electrified pavements. The fatigue model and Paris' law were utilized to evaluate crack initiation and propagation for different pavement designs. Within the allowable range for sufficient wireless charging efficiency, increasing the surface layer thickness had a noticeable benefit on mitigating crack initiation and propagation. The results indicate that increasing the asphalt surface layer thickness by 20 mm can delay crack initiation and propagation, resulting in a two to threefold increase in the number of cycles needed to reach the same crack length. Reflective cracking can also be retarded by the optimized design of the charging unit. Increasing the concrete slab thickness from 100 mm to 180 mm resulted in an approximately 20% increase in the number of cycles to reach the same crack length. Reducing the slab width and length (shortening joint spacing) could also effectively reduce the reflective cracking potential, with the slab length having a more significant influence. These findings highlight the importance of balancing charging efficiency and structural durability in the design of electrified pavements. [ABSTRACT FROM AUTHOR]

A novel control scheme applicable to in-road inductive wireless charging pads in a dynamic system is presented. Primary inverter current sensing allows the primary pad to detect an approaching secondary pad. Zero-crossing detection of the same current allows the primary to synchronize to the secondary, functioning as a synchronous inverter with dual-active switching. Such primary synchronous inverters allow for independent primary pads. Necessary measures to ensure stable operation of the design are discussed. The control scheme only adds an analog filter to the bare-bones open-loop design. The design is validated through simulation and hardware experimentation, with a strong demonstration of robustness.

Utilizing agricultural UAVs for pesticide and insecticide spraying is an effective measure for plant protection. However, achieving effective coverage on the back side of target is often challenging. To address this issue, this study combined a contact-charging spraying system with a UAV to develop an electrostatic plant protection UAV system. Upon activating the electrostatic component, strong electrostatic effects were observed at the nozzle, altering the distribution of the liquid flow; the distribution within the liquid flow became more homogeneous, while the edge regions experienced electrostatic repulsion, leading to changes in droplet size and an increase in droplet density. In the central area, droplet size reduced from 159 μm to 135 μm, while in the edge area, it changed from no value to 120 μm. During field tests using the UAV, the results showed an increase of 1.0 m in effective spray width (at a flight height of 4.0 m), indicating that the charges and propellor wind field contributed to the diffusion of droplets towards the edges. Additionally, the droplet density increased by an average of 19.7 droplets/cm2, and the overall deposition increased by 0.12 μL/cm2, resulting in an approximate three-fold increase compared to conventional spray, which aids in insect control and reduces pesticide usage. [ABSTRACT FROM AUTHOR]

Abstract This paper proposes a three‐layer framework for energy efficiency evaluation of Shore‐to‐Ship Charging (S2SC) systems using load‐dependent loss models of the components. The considered S2SC system is supplied by the grid but is also supported by On‐Shore Batteries (OSB). The presented approach is then used to investigate the impact of the specific design and operational parameters on energy efficiency. Power system architectures for three general S2SC solutions for ac, dc, and inductive charging are defined and compared in terms of energy efficiency. Operational parameters are also considered in the analysis, namely, the grid power ratio, determining the load sharing between the grid and the OSB, as well as the OSB charging profile. A case study is performed with peak charging power of 1 MW, and the most efficient S2SC solutions are identified for both ac‐ and dc‐based onboard power systems. Moreover, it is shown that charging OSB with the highest available power from the grid between the charging breaks would often lead to higher energy efficiency than the maximum utilization of the available charging time. Field data from a real S2SC system is used to verify the estimated energy efficiency by the proposed framework. The analysis of the real case S2SC is then extended to include and verify a projected OSB.

The scarce availability of non-renewable sources and the staggering amount of pollution have inevitably provoked many countries to opt for renewable sources. Thence, invariably, more renewable energy-based applications are hoarded by market stakeholders. Compared to all spheres of renewable energy applications, a considerable part of the energy is pulled into transportation. Wireless power transfer techniques play a significant role in charging infrastructure, considering the current development and advancement in the automotive industry. It will promise to overcome the widely known drawbacks of wired charging in electric vehicles. The effectiveness of wireless charging depends on coil design, compensation techniques, and the airgap between the coils. However, coil misalignment, improper compensation topologies, and magnetic materials reduce the efficacy. We can improve efficacy by overcoming the problems mentioned above and optimizing charging distance, time, and battery size. This paper comprehensively discussed the various electric vehicle charging technologies in conjunction with common charging standards, a list of factors affecting the charging environment, and the significance of misalignment problems. Furthermore, this review paper has explored the suitable coil design structure and different compensation techniques for an efficient wireless charging network. [ABSTRACT FROM AUTHOR]

In this article, a switching frequency-modulation-based inductive power transfer system that provides wireless charging of the scooters by magnetic in-band communication is newly proposed. Although the transmitter (Tx) and receiver (Rx) coils are misaligned, the scooters can be freely charged in the charging station by the proposed frequency modulation method without additional power converters in the Tx and Rx sides. In order to implement frequency modulation control, the Rx side can transmit the required information to the Tx side through the magnetic coupling between Tx and Rx coils, i.e., magnetic in-band communication, in the suggested approach. By virtue of the proposed magnetic in-band communication method, the switching frequency can be modulated so that the load power for charging the battery in the Rx side is appropriately controlled, considering the battery charging profile. Contrary to the Qi standard technology using both amplitude shift keying (ASK) and frequency shift keying, the proposed magnetic communication protocol is optimally and simply designed for targeting scooter wireless charging applications. Because the proposed communication method is based on only ASK technique for unidirectional information delivery, the coil misalignment sensitivity and the complexity of the communication process can be reduced, which guarantees the robust frequency modulation control for load power regulation. A 100 W power level prototype for the charging station and the scooters was fabricated and verified by simulations and experiments. The 97.3% of the coil-to-coil efficiency and 90.6% of the dc-to-dc efficiency were obtained at a nominal operating point of k = knom and PL = 100.8 W. As a result, the battery having 44.0–53.0 V and 13 Ah in the Rx side was charged under a wide range of battery charging conditions and coil misalignments. [ABSTRACT FROM AUTHOR]

With the recently published standard, wireless charging systems for electric vehicles (EVs) are at the stage of preparing for mass market production. In order to have success, safe, and efficient wireless power transfer (WPT) public charging needs to be ensured and therefore interoperability is a key element in the design of such systems. In this article, a design methodology based on impedance planes is presented, which enables consideration of many interoperability aspects at an early stage in the design and has a high degree of flexibility. Four impedance interfaces are presented and operational boundaries and system requirements are added at each interface to establish capability ranges, which can be transferred to any other interface and used to define and assess the design space. Furthermore, this article shows how magnetic field leakage limitations can be considered in the design process. Experimental verification of the simulations is then undertaken and an example presented of how the primary electronics for a public charging use case scenario could be assessed or designed. [ABSTRACT FROM AUTHOR]

Unwanted cross-couplings greatly hinder the development of double-receiver wireless power transfer (WPT) systems. Whenever the air gap changes or misalignment occurs, cross couplings disrupt the system stability. This article investigates a magnetic coupler for a double-receiver WPT system, which dramatically suppresses the unwanted cross-couplings. Two types of undesirable couplings are significantly reduced by using orthometric DD coils and Q-shaped coils. First, the unwanted couplings between receivers can be eliminated, validated by the measured coupling coefficient kAB = 0.003. Therefore, two receivers can work independently. Second, the unwanted couplings among the source coil and receivers can be eliminated (k1A = 0.003 and k1B = 0.003), resulting in load-independent constant voltage output. Compensation networks can also be designed straightforwardly. In addition, the inverter can achieve zero phase angle, alleviating volt-ampere rating and increasing efficiency. Thanks to the presented structure, this coupler design process is efficient because the decoupling is from the shape rather than turns. Also, it can be easily generalizable to other output voltage or power levels since turns can be changed to meet different charging demands. Validated by a laboratory prototype, experimental results successfully show remarkable agreement with the theoretical analysis, ensuring 72 V load-independent constant output voltages. It also realizes a 90.16% maximum measured overall dc–dc power transfer efficiency with 12 cm air gaps when delivering 518.4 W to two 20 Ω loads. [ABSTRACT FROM AUTHOR]

This letter proposes a novel capacitive power transfer system for the unmanned aerial vehicles (UAVs) with lightweight in receivers and robust misalignment tolerance characteristics. The design and analysis of a reconfigurable capacitive coupler are presented at first. The transmitter adopts four rectangular copper plates, which can be reconfigured according to the landing positions and directions. The receiver includes two hollow cylindrical copper-foil sleeves wrapped at the bottom of UAV landing gears, thereby leading to the adaption of the UAV's structure and the tolerance to lateral-, longitudinal-, and angular misalignment. Then, simulation and prototype experiments are carried out to verify the proposal. The results show that the prototype has low leakage electric flux at the UAV fuselage and can deliver 212.1 W with a dc-to-dc efficiency of 82.5%. Especially the proposal allows UAV to be powered within ±0.76 A of output current variation for different landing positions and directions, and the system dc-to-dc efficiency variation is within ±1%. [ABSTRACT FROM AUTHOR]

Green electricity and green transportation are the primary requirements for smart cities. Maximizing EV utilization is the key requirement in the development of green transportation. However, EV technology faces challenges due to the long battery recharging time and heavy batteries to achieve extended driving ranges. Different approaches are investigated to charge the EV by battery swapping, plugin, or wireless. Recently the wireless charging approach is gaining popularity because of safety, extended driving range, dynamic charging, and human intervention-free recharging. However, multiple factors need to be considered in the design of the WPT system and require expertise in different domains. This paper discusses a systematic approach on the various parameters involved in a dynamic wireless charging system design. The major functional units in WPT such as charging couplers, compensation network, and power inverters topologies are addressed. Additionally, this paper discusses the issues involved in grid-tied and renewable integrated dynamic charging systems. Moreover, the step-by-step procedure is described to understand the process involved in the dynamic charging system design. Finally, various case studies at different power levels are presented to get more insights into practical design.

Electric Vehicles are a realistic and sustainable alternative to traditional vehicles. However, their autonomy is still perceived as a strong limitation. To overcome it, new and simpler methods for charging must be provided. Wireless charging is a feasible solution for this issue. In particular, the charge based on induction methods is the most mature wireless charging technology but it is still under study to improve its efficiency under any condition. To enhace this metric, a deep study about the losses of the charger must be performed. This paper presents a theoretical model for the losses in EV wireless charger so it can help to estimate the efficiency of this system before it is implemented. The main advantage of the proposed model relies on the fact that it can be used without relying on the voltage and current waveforms. Instead, datasheet parameters are used for this computation. The model, which is valid for multiple operational conditions, has been tested in a 1.8-kW prototype. The evaluation is completed with an exhaustive study of the efficiency when the chargers are not operating with nominal conditions, in which critical operating points are detected.

This paper proposes a three‐layer framework for energy efficiency evaluation of Shore‐to‐Ship Charging (S2SC) systems using load‐dependent loss models of the components. The considered S2SC system is supplied by the grid but is also supported by On‐Shore Batteries (OSB). The presented approach is then used to investigate the impact of the specific design and operational parameters on energy efficiency. Power system architectures for three general S2SC solutions for ac, dc, and inductive charging are defined and compared in terms of energy efficiency. Operational parameters are also considered in the analysis, namely, the grid power ratio, determining the load sharing between the grid and the OSB, as well as the OSB charging profile. A case study is performed with peak charging power of 1 MW, and the most efficient S2SC solutions are identified for both ac‐ and dc‐based onboard power systems. Moreover, it is shown that charging OSB with the highest available power from the grid between the charging breaks would often lead to higher energy efficiency than the maximum utilization of the available charging time. Field data from a real S2SC system is used to verify the estimated energy efficiency by the proposed framework. The analysis of the real case S2SC is then extended to include and verify a projected OSB. [ABSTRACT FROM AUTHOR]

In this study, magnetic field emission (MFE) of the high-power double-D (DD) coil-based wireless charging system is investigated and a shielding technique is proposed. The MFE pattern produced by the DD coils is significantly different from the MFE of the unipolar (e.g., circular, square, or rectangular) coils, and the traditional aluminum shield does not suppress the MFE from the DD coils. This study shows that a conventional aluminum shield increases the MFE, and a magnetic shield effectively suppresses the MFE of the DD coils. Therefore, a magnetic shield consisting of high-permeability magnetic material, such as ferrites, nanocrystalline, etc., is proposed for the DD pads. The shielding effectiveness of the proposed shield is evaluated through finite-element analysis and verified through experiments. An 11-kW DD coil-based wireless charging system was used to test the proposed shielding technique. The experimental results show that a traditional aluminum shield increased the MFE by 29.8%, and the proposed magnetic shield suppressed the MFE by 50.5%. [ABSTRACT FROM AUTHOR]

An ideal transformer-like (IT-like) magnetic coupling wireless power transfer system is proposed in this article, which can achieve a large constant power and efficiency output over a wide transfer range. First, the general circuit model is presented along with the analysis of fundamental and harmonic current characteristics. Then, the IT-like operation mechanism with a fixed desired secondary-primary current amplitude ratio independent of mutual inductance is proposed, based on which the transfer range capable of both power and efficiency is greatly improved. The corresponding parameter criteria and implementation methods, including the zero-phase-angle mode and the zero-voltage-switching mode are derived and verified in a practical prototype. The experimental results show that the proposed system can take the output power, transfer efficiency, transfer range, and current characteristic into account at the same time, with strong position robustness and high tolerance to variable couplings. [ABSTRACT FROM AUTHOR]

Energy harvesting techniques have been increasingly employed in both consumer and industrial applications to provide clean energy supply. Among the many available energy harvesting techniques, ambient energy harvesting (AEH) is a promising one as it harvests free energy from the environment and, thus, is economically efficient. AEH techniques, however, heavily depend on the dynamic environment and are thus uncontrollable and unstable. More recently, the wireless power transfer (WPT) technique has attracted significant attentions due to its highly controllable feature when powering low-cost devices. Unfortunately, WPT faces strict regulatory limitations to provide high power density and requires charging infrastructures installed to perform effective wireless energy transfer. The pros and cons of the two techniques motivate this work to design a hybrid energy harvesting method by charging a device using a combination of AEH and WPT to maximize the throughput of a wireless system. Specifically, this work first proposes an optimal offline charging scheme to maximize the point-to-point data throughput of a wireless system by fully utilizing the ambient energy and providing extra power supply through WPT to determine the transmission rates. An online heuristic algorithm is further proposed to improve the computational efficiency for practical scenarios when the system has the estimation of future AEH patterns. Our experimental results show that the proposed approaches are effective in maximizing the data throughput when compared to the state of the art. [ABSTRACT FROM AUTHOR]

In this letter, a novel magnetic coupler with high rotational misalignment tolerance is proposed for unmanned aerial vehicles (UAVs) wireless charging. The transmitting coil consists of an inner coil and an outer circular coil connected in series, which generates a horizontal magnetic field from the center to all periphery directions within the charging range. Then, to receive the flux effectively and to adapt to UAV's structure, a vertical square air-core coil is designed and attached to the landing gear. The proposed magnetic coupler can reduce significantly the magnetic fluxes penetrating through the body of the UAV, therefore mitigating electromagnetic interference with onboard devices. Simulation based on ANSYS Maxwell and experiments based on a laboratory prototype are carried out to validate the proposal. The results show that, the proposed magnetic coupler can transmit power in all 360° of rotational misalignments, and the output voltage of the wireless charging system fluctuates only 2% around the 48 V reference. [ABSTRACT FROM AUTHOR]

Electric Vehicles are increasingly common, with inductive chargepads being considered a convenient and efficient means of charging electric vehicles. However, drivers are typically poor at aligning the vehicle to the necessary accuracy for efficient inductive charging, making the automated alignment of the two charging plates desirable. In parallel to the electrification of the vehicular fleet, automated parking systems that make use of surround-view camera systems are becoming increasingly popular. In this work, we propose a system based on the surround-view camera architecture to detect, localize, and automatically align the vehicle with the inductive chargepad. The visual design of the chargepads is not standardized and not necessarily known beforehand. Therefore, a system that relies on offline training will fail in some situations. Thus, we propose a self-supervised online learning method that leverages the driver’s actions when manually aligning the vehicle with the chargepad and combine it with weak supervision from semantic segmentation and depth to learn a classifier to auto-annotate the chargepad in the video for further training. In this way, when faced with a previously unseen chargepad, the driver needs only manually align the vehicle a single time. As the chargepad is flat on the ground, it is not easy to detect it from a distance. Thus, we propose using a Visual SLAM pipeline to learn landmarks relative to the chargepad to enable alignment from a greater range. We demonstrate the working system on an automated vehicle as illustrated in the video https://youtu.be/%5fcLCmkW4UYo. To encourage further research, we will share a chargepad dataset used in this work (an initial version of the dataset is shared https://drive.google.com/drive/folders/1KeLFIqOnhU2CGsD0vbiN9UqKmBSyHERd here). [ABSTRACT FROM AUTHOR]

This article proposes an intermediate coil-aided wireless charging systems via interactive power transmitting mechanism. The study is motivated because the occurrence of coil misalignment is known to affect the transfer efficiency and may destabilize the output voltage. The article is, hence, devoted to designing auxiliary repeater-aided coil module along with interoperable power adjustment, anticipating enhancing the tolerating capability of misalignment during the wireless charging. The design of this system includes two half-bridge inverters deployed to drive main transmitting coil and repeater coil. Circuit operations consist of repeater-aided mode and power-interactive mode. An interoperable power-transmitting strategy is applied to regulate the gain following the movement of receiving coils, by which a higher efficiency is ensured while a constant voltage is better maintained. To confirm the effectiveness of this design approach, both circuit simulation and hardware realization are accomplished under different test scenarios. Experimental outcome support the practicality of the approach, serving as beneficial references for wireless charging applications. [ABSTRACT FROM AUTHOR]

In this letter, wireless charging chests suitable for smart garments are analyzed and optimized. The coil structure is optimized to generate a uniform magnetic field in a variety of drawer sizes. With the hybrid Helmholtz–solenoid coil structure, the variation of coupling factor is reduced from 78.2% to 26.4% as compared with solenoidal coil. Two design approaches for multidrawer chest are examined. In the first approach, the coils are optimized for individual drawers. In the second approach, the coils are optimized by considering the entire drawer chest. The measurement results show that the second approach further reduces the variation of charging current of receiver coils placed at different locations. [ABSTRACT FROM AUTHOR]

Electromagnetic compatibility testing plays an important role in the type testing of radiation protection dosemeters in view of technical developments and the associated increase in electromagnetic fields. Lately, the use of inductive charging devices has grown as a user-friendly type of charging mobile-phones. In this article, we investigate their impact on active personal dosemeters (APD). The measurements show a substantial additional dose reading of up to several tens of mSv when exposed to the field of an inductive charger for 20 s. According to the widely used Qi standard, the charging devices operate at frequencies of between 87 kHz and 205 kHz for power transfers between 5 W and 30 W. These parameters fall outside the scope of type-testing standards for APD. An update of the standards might therefore be necessary., (Creative Commons Attribution license.)

As an emerging technology, wireless power transfer (WPT) can be applied in many fields such as consumer electronics. Due to the limited charging area, the user experience of wireless charging for consumer electronics needs to be enhanced. Based on the tilted long-track transmitting coil array, this brief proposes a high-degree-of-freedom WPT system to achieve free positioning wireless charging when the receiver is placed horizontally or with a tilted angle on the charging plane. Using long-track transmitting coils can enlarge the charging area along the track direction. Using the transmitting coil array and supplying power via two adjacent transmitting coils when the receiver is placed in between the transmitting coils can enhance the charging area along the direction perpendicular to the track direction. Using the tilted transmitting coils can enable wireless charging when the consumer electronics are in use, normally in a tilted angle. The adopted LCC-S (inductor-capacitor-capacitor-series) topology facilitates wireless charging with a weak coupling. The proposed system can achieve free positioning wireless charging horizontally, based on a limited number of transmitting coils and no selection switches. The experimental results have validated the proposed WPT system. [ABSTRACT FROM AUTHOR]

Wireless rechargeable sensor networks (WRSNs) employ wireless charging transfer technology to provide dynamic energy replenishment for sensors. Previous related research considers enhancing the flexibility of WRSNs with the use of wireless charging vehicles (WCVs). Although this research prolongs network lifetime to some extent, there still exist two essential drawbacks: off-road limitation and traveling speed limitation. Benefiting from the intrinsic flexibility, high flight speed, low cost and small size, wireless charging drones (drones) have great potentials to be used to charge sensors in WRSNs. However, suffering from limited battery capacities, it is impossible to use drones for charging sensors in large WRSNs independently. To conquer the drawbacks of WCVs and drones, we propose a novel WRSN model which integrates WCVs, WCV-carried drones and independent drones to construct an efficient novel charging system. The proposed system, which aims to extend network lifetime and to minimize the time of charging scheduling on premise of satisfying charging requests with the cooperation of WCVs and drones. Thus, we develop a novel charging scheduling scheme, which divides the sensing region into three circular sub-regions for scheduling the WCVs or drones collaboratively. Sensor nodes located in the inner ring are charged by independent drones directly from the base station. Nodes located in the middle ring are charged by WCVs, while the outer ring charged by WCV-carried drones. Simulation results show that our scheduling scheme outperforms multiple WCVs which either employ temporal or distantial priority scheme and earliest-deadline first scheme with respect to the lifetime and network charging efficiency. [ABSTRACT FROM AUTHOR]

Wireless charging vehicle to grid (V2G) system is not-so-futuristic. It can maintain the power supply balance and stabilize the grid through a wireless link between vehicles using batteries based on energy supply-demand statistics. Most of the existing privacy preservation methods are based on data tampering approaches (e.g., encryption, adding noise, aggregation), which are not practicable over V2G due to complexity in billing and inaccurate state estimation. In this paper, we develop a novel adaptive demand-side energy management framework by employing federated learning-based privacy preservation for the wireless charging V2G systems. Our framework learns the temporal evolution of energy consumption of dynamic charging electric vehicles in a distributed fashion and exploits the reinforcement learning model for cost-saving and reward maximization. The convergence and the privacy preservation properties of the framework are demonstrated with extensive evaluations. [ABSTRACT FROM AUTHOR]

Wirelesscharging for electric vehicles (EVs) enjoys many benefits, such as convenience, safety, and automation. One of the major issues concerning EV wireless charging is misalignment tolerance along the door-to-door direction of the EV. This letter proposes a misalignment-tolerant dual-transmitter EV wireless charging system with a reconfigurable topology. At central positions, the system can be reconfigured to the S-S (series-series) topology where the two transmitting coils are connected in series to feed the load. At boundary positions, the two transmitting coils form the LCCC-S (inductor-capacitor-capacitor-capacitor-series) topology to enhance power transfer capability and tolerate weak couplings. In this way, not only the output power can be smoothed with door-to-door misalignment, but also wireless charging is guaranteed at weak couplings. Experimental results reveal that within the cover area of the transmitting coils, high-efficiency stable output can be achieved. [ABSTRACT FROM AUTHOR]

This article proposes a free-positioning omnidirectional wireless power transfer (WPT) system with a reticulated planar transmitter, which enables multiple receivers to be powered simultaneously in arbitrary positions and orientations. The reticulated planar transmitter is equipped with four interleaved and overlapped meander coils, thus, a three-dimensional (3-D) rotating magnetic field is generated with the designed excitation current. Therefore, only a planar single-coil (such as a loop-type coil) is required to realize free-positioning omnidirectional WPT. According to the theoretical modeling of the magnetic field, the excitation current that can generate a 3-D rotating magnetic field is given. To obtain a uniform and strong magnetic field distribution, the transmitter grid width is optimized. Furthermore, an excitation current modulation strategy based on phase-shift control is presented to regulate the amplitude of the excitation current. The experimental results show that the output power is greater than 13.1 W no matter how the center of the receiver moves or rotates freely within 400 × 400 mm. When five receivers are powered simultaneously in different positions and orientations, 82.5 W total output power and 55.6% efficiency can be achieved. The experimental results demonstrate that free-positioning omnidirectional WPT can be realized with only planar single-coil receivers by using the proposed reticulated planar transmitter and its excitation current modulation strategy. [ABSTRACT FROM AUTHOR]

As an intelligent collection of power electronics, automated guided vehicles (AGVs) tend to involve more and more devices. Thus, it is necessary to develop a versatile charger with different double outputs for AGVs. This article investigates a dual-receiver inductive charging system. Through a well-organized magnetic coupling structure, relatively load-independent outputs can be realized simultaneously by these two receivers. Specifically, the first receiver ($R_{\mathrm {X}}$ #1) can realize constant current (CC) output, whereas the second one ($R_{\mathrm {X}}$ #2) can achieve constant voltage (CV) output. By utilizing such a passive coupling structure, complex control methods and additional decoupling circuits can be avoided, facilitating a compact and light on-board part. Moreover, this system can realize zero phase angle (ZPA) to lower the volt-ampere rating and improve the overall efficiency. Overall, a scaled-down experimental prototype with 2 A charging current and 12 V charging voltage is constructed to validate the feasibility of such a system. Experimental results demonstrate that the voltage and current deviation, compared to the reference, is as small as 3.33% and 4%, respectively, when the load at the first receiver side ($R_{L1}$) varies from 5 to $10~\Omega $. Moreover, the voltage and current deviation is as small as 3.33% and 1.5%, respectively, when the load at the second receiver side ($R_{L2}$) varies from 10 to $20~\Omega $. [ABSTRACT FROM AUTHOR]

Accurate estimation of mutual inductance in wireless power transfer (WPT) system is a prerequisite for accurate identification of load parameters, which is critical in system constant output and efficiency tracking control. In this article, a general load decoupling method for WPT system considering soft-start process and battery initial voltage is proposed. Moreover, a double-sided LCC topology is used to explain how to calculate the boundary conditions of load decoupling. Based on the proposed load decoupling method, a mutual inductance identification method is proposed for WPT system with double-sided LCC topology. Within the frequency range recommended, the unique solution of mutual inductance can be obtained by solving high-ordered equivalent impedance equation. In this case, there is no need to discuss the situation for multiple solutions. Based on the WPT prototype, the effectiveness of the proposed load decoupling method is verified, and parameter sensitivity of the identification method is analyzed in detail. Finally, the proposed method is experimentally verified. Results show that high identification accuracy can be achieved even when the coils are misaligned. Compared with the existing identification methods, the proposed method does not need any additional switches and auxiliary circuits, which reduces the complexity and system cost effectively. [ABSTRACT FROM AUTHOR]

This article proposes a reconfigurable single-stage regulating asymmetrical full-wave step-down rectifier (SDR) for fast wireless charging. The SDR is reconfigurable into a step-up power amplifier (SUPA) for device-to-device (D2D) wireless charging. The SDR and SUPA can have a direct connection with the battery without an additional voltage regulator module (VRM). With the single-stage structure, the transmitting (TX) and receiving (RX) ac voltages across the resonant coil can be boosted, which greatly reduces the coil currents and losses, improving the D2D charging power. A reconfigurable controller for the TX/RX mode selection, as well as the switching timing control, is designed. The chip is fabricated in 0.35- $\mu \text{m}$ CMOS that contains 20-V devices. For the asymmetrical operation, one GaN device is used for the high current path. Also, zero-voltage switching (ZVS) is realized for all the power transistors with one small (180 nH in the 4015 package) power inductor. The bidirectional D2D WPT system achieves a maximum charging power of 5.1 W with a D2D total efficiency of 46.3% and a charging distance of 1.6 cm. Finally, the peak total efficiency is 51.4% with a charging power of 3.4 W and a charging distance of 1 cm. [ABSTRACT FROM AUTHOR]

Wireless charging devices for implantable cardiac pacemakers have not been clinically applied. For actual applications, safety assessments of a wireless charging system must be conducted. For systems with a certain power, frequency is one of the important factors that directly affect safety. This paper aims to study the safety evaluation method and optimal operation frequency of a cardiac pacemaker wireless charging system. The wireless power transfer (WPT) model considering the coils’ AC resistance is established, which is more in line with the actual situation. The analytical solution to the current in coupling coils is derived, which reveals the effect of the frequency. The currents used in electromagnetic and thermal simulations are calculated or measured for different charging prototypes. A safety evaluation method that comprehensively considers specific absorption rate (SAR), electric field, efficiency, temperature rise and electromagnetic interference (EMI) is proposed. In particular, the temperature rise is an innovative perspective as it has rarely been studied in previous literatures. The optimal frequency of a 3 W wireless charging system for cardiac pacemaker is determined based on the results of safety evaluation. The theoretical temperature rise reaches the minimum at 203 kHz, and the theoretical energy loss reaches the minimum at 260 kHz. The comfort and safe frequency band is approximately from 150 kHz to 370 kHz based on theoretical and experimental results, and the optimal frequency band from 200 kHz to 300 kHz is recommended. [ABSTRACT FROM AUTHOR]

Tunable Self-Oscillating Switching (TSOS) methods are a robust solution for tuning of Inductive Power Transfer (IPT) systems. However, they require deep analysis to be an appropriate choice for Dynamic Wireless Charging (DWC) systems. In this paper, the optimal operation point of TSOS in the maximum power transfer, efficiency, and Zero Voltage Switching (ZVS) realization perspectives are determined based on sensitivity analysis for DWC of Electric Vehicles (EVs). In the sensitivity analysis, all the possible states of the coupling factor and state of charge (SOC) are considered as system variables. Moreover, a new phasor modeling for constant voltage (battery) loads is proposed. The performance of this model is quite different from the conventional static model for the loads. Moreover, to limit the current of the charger under light couplings, a simple hysteresis controller is employed. A setpoint is proposed based on the sensitivity analysis method to transfer maximum energy in misaligned conditions. The proposed setpoint increases transferred energy and energy efficiency while limits the current of the charger. To analyze this method, simulation is done in the Simulink/MATLAB, and to verify the results, a laboratory prototype is implemented.

Lateral misalignment along the driving direction may achieve half the length of a transmission coil in a dynamic wireless charging system for electric vehicles, which is called limit misalignment. This limit misalignment may cause the dynamic wireless charging system to malfunction because of the large fluctuation in mutual inductance. In this paper, an asymmetric and reverse series coil (ARSC) structure is proposed. In the ARSC structure, the transmission coil is smaller than the receiving coil in size to smoothen the fluctuation in mutual inductance. The receiving coil consists of a large coil ($\boldsymbol{R}_{\mathrm {x1}}$) and a small coil ($\boldsymbol{R}_{\mathrm {x2}}$) and $\boldsymbol{R}_{\mathrm {x1}}$ is reversely connected to $\boldsymbol{R}_{\mathrm {x2}}$ in series. The purpose of this design is to further reduce the fluctuation in mutual inductance. A calculation method of mutual inductance is then proposed based on the vector potential to calculate the mutual inductance of the ARSC structure. The law of mutual inductance is analyzed by the proposed calculation method for the ARSC structure. Moreover, an optimization method of coil parameters is proposed to obtain quasi-constant mutual inductance. The ARSC structure and optimization method are not only simple but can also make the mutual inductance nearly constant. Calculation, simulation, and experimental results validating the proposed method and structure are shown. [ABSTRACT FROM AUTHOR]

In this article, a metal resonator design of enabling wireless charging of a metal-encased device was demonstrated using a two-coil magnetic resonant system operating at 6.78 MHz. Despite high metal population on metal housing, the transmitting magnetic field was efficiently linked to the receiving resonator through segmenting the metal housing with a small gap. In addition to the initially transmitting magnetic fields passing through the gap, extra magnetic fields were generated by the eddy currents induced on the segmented metal housing. These two magnetic fields were added up in phase and used to couple to the power-receiving coil. The principle of operation was demonstrated with electromagnetic simulation and measurement. Furthermore, a prototype of metal housing, including the power-receiving coil and ferrite, was fabricated and integrated with a commercial smartphone. The measurement results showed 86% of resonator coupling efficiency (RCE) with an aluminum metal casing of the device when tested with a regular Class 3 AirFuel Alliance (AFA)-compatible transmitter. Actual measured power delivered to a smartphone battery was 8.7 W at maximum coupling position with 89% of the RCE. [ABSTRACT FROM AUTHOR]

This article proposes a tripolar plane-type (TPT) transmitter enabling three-dimensional (3-D) omnidirectional wireless power transfer (WPT) for consumer electronics, such as mobile phones and tablet computers. The proposed TPT transmitter is a 2-D plan-type structure, but it shows a 3-D omnidirectional power transmitting capability. This structure consists of two crossed bipolar coils and a unipolar circular coil, and the three coils are mutually decoupled naturally. By calculating the magnetic field distribution generated by the TPT transmitter, a 3-D omnidirectional magnetic field can be obtained. Then, a detailed circuit topology based on the inductor-capacitor-capacitor-series compensation networks and full-bridge inverters with phase-shift control is modeled and analyzed. On this base, an excitation current vector modulation strategy based on a targeting magnetic field is designed, which can improve and stabilize the system output power and efficiency. Finally, an experimental prototype is set up to verify the 3-D omnidirectional power transmitting capability of the proposed TPT transmitter and the effectiveness of the designed current vector modulation strategy. Besides, the superiority of the proposed 3-D omnidirectional WPT system is verified by comparison with other methodologies. The experimental results show that the system output power and efficiency are maintained at 61.4–80.6W and 80.7%–85.2% under arbitrary angular misalignment of the receiver. [ABSTRACT FROM AUTHOR]

The misalignment between the transmitting (Tx) coil and the receiving (Rx) coil is an urgent problem in the drone charging system using wireless power transfer technology. The coupling coefficient is so low when the resonance coils is not aligned, which degrades the drone wireless charging performance. In this article, the optimization processes of the coupling mechanism are presented in detail. First, we illustrate the great superiority of unequally spaced Tx coil, compared with traditional uniformly spaced one. Then, a genetic algorithm to optimize the side lengths of the Tx coils is highlighted by discussing the main design considerations and methods in a comprehensive manner. Furthermore, the Rx coil with varying radius size per turn is proposed in terms of the distribution of magnetic field generated by the optimized Tx coil. Experimental results show that the optimized coils have better coupling performance due to small mutual inductance change under the condition of misalignment. Power transfer efficiencies in different misalignment situations are measured and the best power transfer efficiency improvement achieved by the proposed system can reach 56.23% in contrast with traditional coils. This drone charging system can transfer a maximum power of 100 W with the remarkable transfer efficiency of 92.41%. [ABSTRACT FROM AUTHOR]

In this article, coupled electromagnetic-thermal simulations of inductive power transfer (IPT) pads using finite-element simulations are discussed. Derivation of each electrical and thermal parameters required for the modeling process is outlined. Simulation models are used to predict the power loss and the temperature rise of an IPT pad at different ambient temperatures at steady state. Using these simulation methods, the power loss within an IPT pad operating at 50 ${^\circ }$ C ambient temperature is predicted. A 10-KW IPT system is set up within an environmental chamber to validate the predicted losses within the system. [ABSTRACT FROM AUTHOR]

Free positioning wireless charging for consumer electronics allows the devices to be charged at arbitrary positions and angles to improve user experience. However, a user-initiated sudden movement of the device during charging can cause hazards due to the abrupt variation of the coupling coefficient. To solve this issue, the coupling coefficient variation at different positions should be mitigated, which is also good for the design and high-efficiency operation of power electronics converters. This article proposes a design methodology to employ antiparallel windings to smooth the coupling coefficient variation over different positions by reducing the coupling coefficient at central positions and enhancing it at boundary positions. Two optimization methods are proposed: turn-by-turn optimization and winding-by-winding optimization. A design flow is offered. The hexagonal coil is compared with the square coil and proved to achieve better performance than the latter. An experimental prototype is implemented to validate the effectiveness of the proposed design methodology. [ABSTRACT FROM AUTHOR]

The wireless power supply solution has shown great advantages in rail transit applications, such as maglev trains and trams. However, research works on designing the magnetic coupler for wireless charging system in rail applications, which is a crucial problem, are not sufficient. Considering the high power and lightweight requirements, this article selects the coaxial M-shape magnetic coupler with LCL/S compensation for railway applications, which contains the transmitting rail and the receiving coil wound on an M-shape magnetic core. First, analysis was conducted on the requirements for inductance parameters of the magnetic coupler under the circuit constraints, including transmission power, input and output voltages, and component electrical stress, etc. Then, the influence of the geometric parameters of the coil structure and misalignment on its inductance parameters is analyzed. Based on these analysis results, the design method for the M-type magnetic coupler based on the lightweight principal is proposed. The geometric parameters are designed following a certain sequence to minimize the number of iterations and FEM simulation parameter sweeps, making the design procedure suitable for engineering practice. According to the proposed method, the magnetic coupler for a 360 kW wireless charging tram is designed and implemented. Through simulations and experiments, the magnetic coupler is verified to be feasible for the system with light weight. [ABSTRACT FROM AUTHOR]

This paper presents a transmitter side control scheme for a series-series compensated wireless power transfer (SS-WPT) system for electric vehicle (EV) charging applications. The proposed control scheme matches the reflected load impedance, by controlling accordingly the front-end dc-dc converter (FEC) of the SS-WPT system. The proposed control scheme drives the FEC, through an optimizer which takes into account the misalignment but also the operational conditions of the system to achieve high efficiency throughout the entire charging process - regardless the EV type, the misalignment conditions or the on-board charger. The novelty of the proposed optimizer lies upon its universal characteristic, which makes it compatible to various SS-WPT topologies. As such, the proposed charging concept is a universal solution, which optimizes the system efficiency regardless the receiver side on-board charger topology (single-stage or double-stage), technical characteristics or control scheme that implements the charging profile. Finally, for the necessary communication between the transmitter and the receiver sides, the Internet of Things (IoT) is employed, offering a low-cost and flexible solution that overcomes compatibility problems between wireless antennas. Simulation and experimental results validate the feasibility of the proposed control scheme, highlighting the efficacy of the proposed wireless charging process.

Electric vehicles (EVs) are gaining more and more user acceptances due to their clean, efficient, and environmentally friendly nature. Currently, most commercial EVs use conductive charging for their batteries. Inductive charging, which is an alternative charging technology, has recently received a great deal of attention because of its increased user convenience and safety. It is forecast that the two charging technologies will be implemented in future charging infrastructures globally. Consequently, future EVs need to be capable of dealing with both charging methods. So far, there have only been a very few charging topologies reported in the literature that describe both charging methods in the same vehicle. However, solutions that have been proposed do not show a significant component reduction. In this article, we propose a hybrid charger system where the high-frequency transformer of an onboard dc–dc converter becomes the coupling point between the conductive and inductive charging. Using this coupling point, the circuit utilizes the same components for conductive and for inductive charging. This results in the reduction of component count and, therefore, an improved integration. The proposed system is verified by both simulation and experiment. For the experiment, a 3-kW prototype has been built and tested. The maximum efficiency of 97.4% and 93.6% was achieved in the conductive and inductive mode, respectively. [ABSTRACT FROM AUTHOR]

In order to inductively charge electric vehicles, which are based on a low-voltage drive train, high currents have to be overcome. This work describes a simulative approach to charge 48 V-based electric vehicles wirelessly with high power. A system was designed on the basis of various boundary conditions and validated by simulation. In order to increase the transmittable power, the system was investigated for an extendable approach and was examined for modularity. In particular, the influences of the secondary coils on each other must be taken into account. Finally, the entire system was evaluated by physical and electrical simulation. [ABSTRACT FROM AUTHOR]

A three-phase dynamic wireless charging system with balanced primary currents can yield a constant induced voltage. Compared with a three-phase primary and three-phase secondary system, a three-phase primary and single-phase secondary (TS) system has a simpler coil structure and circuit topology on the secondary side but its reflected impedances are unbalanced among three phases and vary with the position. In order to obtain balanced primary currents, the suitable three-phase inverter and compensation topology need to be studied. This article accurately describes the unbalanced reflected impedances of the TS system and reveals its impedance characteristics varying with position. The three-phase LCC topology for the TS system is provided to solve the problems of unbalanced and varying reflected impedances and the resonance conditions are also given. In addition, the corresponding topology and adjustment method of the inverter are proposed to ensure its balanced primary currents and constant induced voltage. Furthermore, a prototype was implemented to verify the topology and control method. [ABSTRACT FROM AUTHOR]