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The ongoing transition toward electric vehicles is a major factor in the exponential rise in demand for lithium-ion batteries (LIBs). There is a significant effort to recycle battery materials to support the mining industry in ensuring enough raw materials and avoiding supply disruptions, so that there will be enough raw materials to produce LIBs. Nevertheless, LIBs that have reached the end of their useful lives and are sent for recycling may still have some energy left in them, which could be dangerous during handling and processing. Therefore, it is important to conduct discharge pretreatment of LIBs before dismantling and crushing them, especially in cases where pyrometallurgical recycling is not used. Electrochemical discharge in conducting solutions has been commonly studied and implemented for this purpose, but its effectiveness has yet to be fully validated. Non-electrochemical discharge has also been researched as a potentially cleaner and more efficient discharge technology at the same time. This article presents a non-electrochemical discharge process by completely draining the energy from used batteries before recycling. A comprehensive investigation of the behavior of LIBs during discharge and the amount of energy remaining after fully discharging the battery at different temperatures is analyzed in this work. According to the experimental findings, completely discharging the battery at higher temperatures results in a reduced amount of residual energy in the battery. This outcome holds great importance in terms of safe and environmentally friendly recycling of used LIBs, emphasizing that safety and environmentally friendly recycling must go hand in hand with a cost-effective and sustainable solution. [ABSTRACT FROM AUTHOR]

This paper discusses the short-time-scale transient processes in an isolated bidirectional dc-dc converter with phase-shift control. The deadband effect on the steady-state and transient commutating process are analyzed. The current variations caused by phase-shift errors at the boundary conditions are simulated and validated through experiments. The concept of 'energy deadband' is introduced to describe those specific transients where no energy flows from source to load or load to source. A set of strategies are proposed to increase the system robustness. Simulation and experiments on a 200-V/400-V, 6-kW dc-dc converter prototype validated these strategies. Index Terms--DC-DC converter, deadband effect, high-frequency transformer, phase shift, short-time-scale, transient process.

We propose new concepts for the design, optimization, and control of a doubly salient permanent-magnet machine (DSPM). We employ a uniform pole width so that the width of the rotor pole is the same as that of the stator salient pole. This design aims to minimize the cogging torque. Second, we used a skewed rotor with one-half the pole width to improve the commutation. Finally, based on the flux linkage of the skewed rotor, we used a six-state commutating mode to control the motor. We validated the feasibility of these new design concepts by simulations, field analysis, and experimental measurements of the prototype. Index Terms--Cogging torque, commutating mode, doubly salient permanent-magnet machine (DSPM), pole width, skewed rotor.

This paper presents an analytical method for the design of permanent-magnet (PM) traction-drive motors with emphasis on calculation of the magnet's volume and size. The method uses a set of formulas to properly size the magnets without the high effort of finite-element analysis (FEA). The formulas not only give optimized magnet sizes, but also provide quick solutions for the preliminary designs. The method can be used in the initial design stage to set up the base for FEA and optimization, as well as throughout the entire design and optimization process to validate a PM motor design. Numerical methods and experiments confirm the accuracy of the proposed method. Index Terms--FEA, magnet, optimization, permanent magnets (PMs), PM motors, sizing, traction drives, volume.

In permanent magnet (PM) synchronous machines, iron losses form a larger portion of the total losses than in induction machines. This is partly due to the elimination of significant rotor loss in PM machines and partly due to the nonsinusoidal flux density waveforms in the stator core of PM machines. Therefore, minimization of iron losses is of particular importance in PM motor design. This paper considers the minimizing of iron losses of PM synchronous machines through the proper design of magnets and slots, and through the choice of the number of poles. Both time-stepped finite element method (FEM) and the iron loss model from a previous study are used in this paper to draw the conclusions. Index Terms--Eddy currents, hysteresis, magnetic losses, permanent magnet machines, synchronous machines.

The battery thermal management (BTM) system plays an increasingly important role today in the safety of electric vehicles (EVs) and hybrid electric vehicles (HEVs) as the battery capacity and power ratings keep growing. The BTM system is commonly coupled with the vehicle passenger cabin HVAC system. This integrated thermal system is a major onboard energy consumer, and its complexity brings challenges to its control. With the planned-ahead speed profile and the corresponding power trajectory obtained from the connected and automated vehicle (CAV) technology, predictive control makes a desirable option for the integrated system to maintain battery safety and passenger comfort while lowering energy consumption. However, in order to achieve both high accuracy and low cost in a wide control range, a very long prediction horizon and high sampling rate are both necessary. This will overwhelm the processing capacity of the onboard electronic control unit (ECU) if using conventional predictive control. In this paper, a two-stage predictive control strategy for the BTM and HVAC coupled system is proposed to solve this problem. In stage 1, based on the integrated cooling system efficiency features, a hierarchical and iterative dynamic programming (HIDP) scheme is designed to derive the optimal battery temperature trajectory to reach the set point at the end of the horizon with a modest computation burden. In stage 2, a control-oriented model is constructed for the cooling system and a model predictive controller (MPC) is accordingly built to track the trajectory from Stage 1 while enforcing the energy saving. A high set-point-tracking performance and as high as 10.61% energy saving for the cooling system in the UDDS cycle are verified by simulation results. The real-time implementation capability of the proposed strategy is demonstrated by the vehicle emulator experiments based on hardware in the loop (HIL) and a rapid control prototyping (RCP) platform. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) technology has become a popular research direction in the field of industrial applications, with the advantages of contactless operation, high degree of freedom, and great controllability. However, there are still some challenging issues that need to be resolved. First of all, more advanced circuit topologies and magnetic coupling structures need to be designed to achieve the power conversion goals of diversified applications. Second, novel control methods, optimization algorithms, and modeling methods enable systems to be better controlled and designed. Finally, potential application scenarios need to be discovered so that this novel power transfer method can be applied in more suitable applications. Therefore, this topic is organized by the responsible editor to gather the power of more scholars. With reviewers' hard work and considerations, 32 papers were finally accepted for publication in this Special Issue. [ABSTRACT FROM AUTHOR]

The successful commercialization of wireless power transfer (WPT) technology in mobile phones, laptops, and electric vehicles requires a safe, reliable, and efficient charging infrastructure. A metal object, such as a coin, a key, or a nail, however, may be inadvertently exposed, by close proximity, to the magnetic fields generated by the WPT coupler, creating a potential safety hazard and affecting the electrical characteristics of the WPT system. In addition, the magnetic fields may produce adverse symptoms, such as dizziness and breathlessness, in living objects near the charging systems. This article provides a current state of the art review of all available designs for detecting metal and living objects in WPT systems. Working principles and qualitative comparisons in terms of sensitivity, accuracy, and cost of major detection methods are presented to reveal their inherent limitations and available applications. Finally, a number of research topics on foreign object detection are suggested to encourage more researchers to make contributions to the development and commercial application of wireless charging systems. [ABSTRACT FROM AUTHOR]

This article presents the state-of-the-art electric vehicle (EV) charging technologies that benefit from the wide bandgap (WBG) devices, which is regarded as the most significant revolution in the power electronics industry in the past few decades. First, the recent WBG device technology evolution, performance comparison, and reliability issues are introduced. Then, topology development, efficiency and power density boost, and cost reduction brought by the WBG devices for EV charging equipment, such as onboard chargers, fast-charging stations, and wireless chargers, are discussed. A figure of merit (FOM) for evaluating the performance of wireless chargers is also proposed. Finally, the EV charging technology roadmap forecast is presented based on the WBG devices’ evolutionary trends. [ABSTRACT FROM AUTHOR]

In this article, we propose a power relay system to power multiple loads wirelessly via magnetic coupling. Multiple power relays are placed in a line and the power can be transferred between these relays. Each power relay consists of two relay coils, which function as the receiver and transmitter, respectively. In order to suppress the magnetic coupling between the two relay coils in the same power relay, bipolar coils are adopted and placed perpendicularly. A compensation capacitor is connected in series with each transmitting coil, while another one is connected in parallel with each receiving coil. It is derived that the constant voltage characteristics can be obtained for each load, which means the load power is decoupled from each other. The two coils in the same power relay have different inductance values, which form an asymmetrical structure to achieve equal load voltage distribution. Moreover, zero phase angle can be obtained for the input impedance. The proposed system is suitable to power the gate drivers of series-connected insulated gate bipolar transistors, where multiple isolated power supplies are needed. An experimental prototype with six loads has been constructed to validate the proposed system. The maximum efficiency can reach 94.0% at a power level of 12.6 W. [ABSTRACT FROM AUTHOR]

In both normal and fast wireless electric vehicle charging systems, constant current/constant voltage (CC/CV) charging profile, regardless of the variation of the battery state of charge, is one of the most essential characteristics to ensure the battery performance and reliability. The input zero phase angle (ZPA) is able to minimize the system volt-ampere rating, enhance the power transfer capability, and make it easy to achieve soft-switching operation over the full range of battery charging profile. Therefore, the load-independent CC and CV output characteristics with ZPA conditions are necessary for wireless charging systems. However, the existing methods that can achieve these functions either add power switches or need a large number of compensation components, which make the system inefficient, uneconomical, and bulky. In this paper, a unified resonant tuning configuration with minimum passive component counts is proposed to achieve CC and CV outputs at two ZPA operating frequencies. According to the proposed configuration, all the possible inductive power transfer (IPT) and capacitive power transfer (CPT) topologies are analogized. With these topologies, both CC and CV outputs with ZPA are achieved using a minimum number of compensation components and no additional power switches. Among all the simplest IPT topologies, a primary Series-secondary Series and Parallel (S-SP) compensation topology is illustrated to demonstrate the analysis. [ABSTRACT FROM AUTHOR]

A metal-rim-connected inductive coupler with series-none compensation topology is proposed for smartwatch applications. By cross-connecting the receiving coil to the metal rim with a 1 mm slot, the direction of the induced current on the metal rim is transformed to be the same as the current flowing on the receiving coil, leading to a strong magnetic coupling between the transmitting coil and receiving coil. Considering the space limitation in the smartwatch, non-compensation components are needed inside the smartwatch and only a series capacitance is integrated on the transmitter side. A prototype of the proposed inductive coupler has been built and the wireless power transfer through metal rim has been validated via experiment. The experimental results show that the prototype achieves 5 W output power with 87.4% coil-to-coil efficiency. [ABSTRACT FROM AUTHOR]

It is challenging to power a large number of gate drivers of the series-connected insulated gate bipolar transistors (IGBTs) in a high-voltage application because multiple isolated power supplies are needed. In this study, a novel wireless power transfer (WPT) system using repeater coils is designed to solve this problem. Every two repeater coils form a repeater unit, which transfers power to one load. With multiple repeater units in the system, multiple loads can obtain power simultaneously. To eliminate undesirable magnetic couplings between these coils, bipolar coils are used and the two bipolar coils in the same repeater unit are placed perpendicularly. It is derived that constant voltage can be obtained for all the loads, which is especially suitable for powering the IGBT's gate driver. Moreover, the variation of one load power will not affect others. The receiving circuit is designed to transform the received power to the DC voltage compatible with the driving circuits. An experimental setup with six loads has been constructed to validate the proposed WPT system. [ABSTRACT FROM AUTHOR]

This paper proposes a long-distance multi-load wireless power transfer (WPT) system with a constant voltage (CV) output for each load. A repeater unit consisting of two bipolar repeater coils is designed to power the load. Multiple repeater units are placed in a line and the power can be transferred from one unit to the next. Each repeater unit corresponds to one load and multiple loads can be powered simultaneously. The two repeater coils in the same repeater unit are placed perpendicularly to eliminate the magnetic coupling between them. In each repeater unit, a compensation capacitor is placed in series with the transmitting coil while two extra compensation capacitors form a series-parallel (SP) structure for the receiving coil. When neglecting the coil's parasitic resistance, the CV characteristics can be obtained, which enables the independent and flexible power control of each load. Moreover, the influence of the parasitic resistances on the system performance is analysed. Such a system is especially suitable for powering the gate drivers in a high-voltage converter where multiple insulated gate bipolar transistors (IGBTs) are connected in series. An experimental setup with six loads is constructed to validate the proposed system. The maximum system efficiency can reach 88.1%. [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]

In this paper, a battery balancing circuit is proposed for the series-connected lithium-ion battery cells based on the principle of synchronous rectification. The proposed balancing circuit, also referred to as an equalizer, mainly includes a buck–boost converter (BBC), a multiport half-bridge converter (MHBC), and a driving circuit. The MHBC is coupled with a multiwinding transformer. Compared with the conventional congeneric methods, the number of transformer windings is almost reduced by half, leading to a more compact size and lower cost. Moreover, the secondary mosfets of the MHBC are synchronously driven by the primary half-bridge converter (HBC) without the need of additional isolated mosfet gate drivers and power supplies, dramatically reducing the circuit cost and complexity. In addition, the proposed equalizer can realize the module-to-multi-cell (M2MC) equalization under severe imbalance conditions to improve the balancing speed, and work at the any-cell-to-any-cell (AC2AC) self-balancing mode under slight imbalance conditions to improve the balancing efficiency and effectiveness, which achieves a good trade-off between balancing speed and effectiveness. The expressions of the equalization current and efficiency are derived and verified by experimental results. The proposed equalizer is experimentally evaluated for a string with 12 series-connected lithium-ion cells. [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]

A dual-coupled inductor-capacitor-capacitor and series (LCC-S) compensated wireless power transfer (WPT) system with a compact receiver size is proposed in this paper to improve the misalignment performance and achieve fault tolerant operation as well as a stable output power. The compensation coil and the main coil are integrated as two decoupled unipolar coils on the transmitter side, while they are both coupled with the receiver coil. The two mutual inductances among the two decoupled coils and the receiver coil have opposite impacts on the output power when they both increase or decrease. Therefore, the output power can remain stable when the misalignment increases. The short- and open-circuit characteristics are analyzed, which demonstrates that the proposed topology can achieve both short- and open-circuit protection. A prototype was built and the experimental results verified the theoretical analysis and simulations. The system can deliver from 297 W to 321 W when the x-misalignment increases from 0 mm to 90 mm, with a dc-dc efficiency of 92.78% to 93.56%. The proposed WPT system can be used for the wireless charging of e-mobility scooters and autonomous underwater vehicles. The system can provide a stable output and can tolerate both short- and open-circuit faults at the output. [ABSTRACT FROM AUTHOR]

In this paper, a novel long-distance wireless power transfer (WPT) system using repeater coils is proposed to provide power supplies for the driver circuits in high-voltage applications, such as flexible alternative current transmission systems. Different from most of the existing wireless repeater systems where the load is only connected to the last coil and the repeater coils function solely as power relays, in the proposed system, multiple loads are powered by the repeaters. The repeater coils transfer power not only to the subsequent coils but also to the loads connected to them. Dual coil design is proposed for the repeaters with which load-independent characteristics are obtained with a suitable design of coupling coefficients. As a result, the load power can be easily adjusted without affecting each other. Load current characteristics and system efficiency have been analyzed in detail. The power transfer capability of the proposed system is illustrated for different coil quality factors and coupling coefficients. An experimental setup with 10 loads has been built to validate the effectiveness of the proposed long-distance WPT system. The maximum reachable system efficiency is about 84%. [ABSTRACT FROM AUTHOR]

This letter proposes a novel wireless power transfer (WPT) system with repeater coils for multiple loads. Every two repeater coils form a repeater unit where one is used to receive power from its preceding unit and the other transmits power to the subsequent unit. Each load is connected to a repeater unit and multiple loads can be powered with several repeater units. The two coils in the same repeater unit are both bipolar ones, which are placed perpendicularly so that the magnetic coupling between them can be eliminated. In order to obtain independent power control of all the loads, the series-parallel-series compensation method is adopted for each repeater unit. With a proper resonant condition proposed in this letter, the constant load current can be obtained for all the loads when neglecting the coils’ parasitic resistances. An experimental setup has been constructed and the effectiveness of the proposed multi-load WPT system is validated by the experimental. [ABSTRACT FROM AUTHOR]

This letter proposes a novel capacitive coupler array with free-positioning feature for mobile tablet applications. The capacitive coupler consists of three printed circuit boards, two of which constitute the transmitter and the third one is the receiver. The coupler is vertically arranged to make the charging system compact and feasible for mobile tablet applications. By applying a repetitive structure on the transmitter side and properly designing the receiver, free-positioning capacitive charging is realized and the coil-to-coil charging efficiency is not affected by the variation of the receiver position. Only two series inductances are utilized for compensation purposes, which makes the system more compact and easy to be fabricated. This proposed capacitive coupler is studied via finite-element analysis and verified by the experimental results at 1, 2.17, and 3.45 MHz. [ABSTRACT FROM AUTHOR]

In this paper, an automotive onboard heater equalizer is proposed to heat low-temperature batteries and balance cell voltages without the requirement of external power supplies. The proposed integrated topology only needs one MOSFET for one cell, resulting in a compact size and low cost, which can be easily applied to electric vehicles. In particular, all MOSFETs are driven by one high-frequency pulsewidth modulation signal and the batteries can be heated internally by the ohmic and electrochemical losses and warmed externally by the switching and conduction losses of MOSFETs, leading to a high heating speed and efficiency. Further, a thermoelectric model for the internal and external combined heating is developed to provide guidance for the optimized design of the proposed heater. In addition, the proposed topology can realize passive balancing of series-connected battery strings at a higher switching frequency and a smaller duty cycle. Experimental results show that the proposed heater, by generating a periodic ramped discharge current with an rms value of 1.8 C at a switching frequency of 150 kHz, can heat the lithium-ion batteries from −20 to 0 °C within 1.9 min, consuming about 5% of the cell energy. [ABSTRACT FROM AUTHOR]

The output characteristics and the transfer efficiencies of inductive power transfer (IPT) systems are affected by (but not limited to) the variation of parameters such as, variable load, misalignment between the primary and secondary coils, and resonance frequency detuning. This paper first analyzes the resonant conditions of all voltage-fed compensation topologies in IPT systems to achieve the load-independent voltage transfer characteristic at load-independent zero phase angle frequency. With these conditions, the parameters sensitivity to the key performance factors of the S-SP, LCC-S, LCC-P, and double-sided LCC compensated IPT systems are systematically investigated when considering the losses in coils and compensation networks. Comparisons of the quantitative sensitivity analysis and experimental results for all IPT systems are made in terms of the voltage transfer ratio and efficiency. These analyses can provide guidance for the selection of superior compensation networks to minimize the additional converter effort and simplify the control algorithm of closed-loop IPT systems. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) has attracted much attention in recent years. In an underwater WPT system, the eddy current loss tends to be non-negligible as the frequency or the coil current increases. Thus, it is crucial to analyze the eddy current loss in an underwater WPT system. The analytical model of the eddy current loss of a coreless WPT system in the seawater is established with Maxwell's equations. The expressions of the electric field intensity and the eddy current loss are derived. The eddy current loss is analyzed in different circumstances to illustrate the impacts of related factors. For a WPT system in the air, there is an optimum resonant frequency, for a higher frequency leads to a larger induced voltage, but will result in larger coil losses simultaneously. However, the optimum resonant frequency will be shifted because of the eddy current loss in the seawater. Then, the optimum operating frequency is obtained based on the analytical model. It is found that the optimum operating frequency is supposed to be larger than the resonant frequency to achieve the maximum dc–dc efficiency in the seawater. An underwater WPT prototype was built and the experimental results verified the theoretical analysis. [ABSTRACT FROM AUTHOR]

Inductive-power-transfer (IPT) converters should desirably achieve nearly zero reactive circulating power, soft switching of power devices and load-independent constant output voltage or current with optimized transfer efficiency, and lowest component ratings. However, the load-independent output characteristic is dependent on IPT transformer parameters and their compensation. The space-constrained IPT transformer restricts the design of the low-order resonant circuit compensated IPT converter, making the IPT converter hard to optimize. This paper will analyze conditions under which any extra design freedom can be allowed for a double-sided LC compensation circuit in order to achieve load-independent output and zero reactive power input. A detailed analysis is given for the double-sided LC compensation achieving zero reactive power input and constant current output, without being constrained by the transformer parameters. Design conditions of the compensation circuit parameters for achieving these two properties are derived. A complementary LC-CC compensated IPT converter is further proposed to extend the output current amplitude limitation of the double-sided LC compensated IPT converter. Finally, the prototypes of the IPT converters are constructed to verify the design flexibility of the proposed double-sided LC compensation circuit for achieving the multiple objectives. [ABSTRACT FROM AUTHOR]

In some applications of wireless power transfer, such as wireless charging of consumer electronics and electric buses, the coupling between the transmitter and the receiver is strong in order to improve efficiency. With a strong coupling, the compensation on the receiver side can be eliminated to achieve a high-level integration of the receiver device and a smaller receiver-side loss, forming a series-none (SN) topology, which has not been fully investigated before. The commonly used first harmonic approximation method for the SN topology has discrepancies with a low-power output and cannot fully reveal the characteristics of the SN topology. Therefore, this paper establishes a model of the SN topology and derives the analytical expressions of the transmitter and receiver currents based on differential equations. The distortion of the receiver current is studied. The coil-to-coil efficiency is obtained and its maximum condition is investigated. The SN topology offers approximately the same efficiency as the SS topology when the coupling is strong and the coil quality factors are large. Theoretical calculations and experimental results confirm the analysis. [ABSTRACT FROM AUTHOR]

Electric vehicles (EVs) are becoming increasingly popular as a mean of mitigating issues associated with fossil fuel consumption in transportation systems. A wireless inductive power transfer (IPT) interface between EV and the utility grid has several key advantages, such as safety, convenience, and isolation. However, physical misalignments between the pads of IPT charging systems used in EVs are unavoidable and cause variations in key system parameters, significantly increasing losses and affecting power throughput. This paper presents a novel series-hybrid topology in which the series inductors of the primary and pick-up inductor–capacitor–inductor (LCL) networks are integrated into polarized magnetic couplers to improve the system performance under pad misalignment. A mathematical model is developed to investigate the behavior of the proposed system under misalignment. To demonstrate the viability of the proposed method, the results of a 3.3-kW prototype series-hybrid IPT system are presented, benchmarked against a conventional IPT system. Experimental results clearly indicate that the proposed system maintains the output power within ±5% of its rated power despite the pad misalignment. The proposed system is efficient, reliable, and cost effective in comparison to conventional LCL- and CL-compensated IPT systems. [ABSTRACT FROM AUTHOR]

Wireless power transfer systems in seawater inevitably suffer some energy loss as a consequence of eddy current loss. Here, we present a coil structure utilizing two transmitter coils placed symmetrically adjacent to each side of the receiver coil. This coil arrangement, termed a 1 × 1 × 1 structure, yields improved power transfer efficiency. The eddy current loss caused by the transmitter coils in a 1 × 1 × 1 system can be reduced to roughly half of that in a 1 × 1 system, with one transmitter coil and one receiver coil. The experimental results show that the power transfer efficiency from the transmitter to the receiver is improved by nearly 10%. After the introduction of equivalent eddy current loss impedance into the circuit, two arrangements of the 1 × 1 × 1 circuit topology are investigated. They consist of a shared or separately compensated capacitance topology. It is found that the shared-compensated capacitance topology is more robust to the change of mutual inductance than the separately compensated capacitance topology. This kind of structure is very useful in underwater vehicle applications. [ABSTRACT FROM AUTHOR]

The classical switched-capacitor (SC) equalizer is widely used in battery management systems because of the accurate balancing and ease of implementation. However, it only achieves the adjacent cell-to-cell equalization, and its balancing speed and efficiency become extremely low for multicell series-connected battery strings. Therefore, a delta-structured switched-capacitor equalizer is introduced to achieve a high-speed and high-efficiency any-cells-to-any-cells (AC2AC) equalization at arbitrary imbalanced status for any number of cells. The slow switching limit and fast switching limit impedances of the proposed equalizer are developed to provide a theoretical guidance for the optimized design of the SC equalizers. A prototype for four battery cells was built, and a comparison with existing equalizers was presented. Experimental and comparative results show that the proposed solution exhibits an automatic AC2AC balancing with high reliability and strong robustness. The measured balancing efficiency is up to 94.5%. [ABSTRACT FROM AUTHOR]

The double-sided LCC topology provides a highly efficient compensation method for electric vehicle (EV) wireless charging systems. However, the two compensated coils occupy a large volume. In order to address the volume increase as well as to be compatible with unipolar coil structures, which are widely applied in EV wireless charging systems, an integration method is introduced in this paper. Aspect ratios of the compensated coils are studied to minimize the respective coupling effect. With the proposed integration method, the extra coupling coefficients are either eliminated or decreased to a negligible level. A wireless charging system with the proposed integration method is built and the experimental results show that the system resonates at 85 kHz and delivers 3.09 kW with a dc–dc efficiency of 95.49% at an air gap of 150 mm. Furthermore, a comparison with the integration method into bipolar coil structures is presented and the results demonstrate that the system with the proposed integration method is more immune to front-to-rear and vertical misalignments. [ABSTRACT FROM AUTHOR]

Connected and automated hybrid electric vehicles (CAHEVs) are a potential solution to the future transportation due to their improved fuel economy, reduced emissions, and capability to mitigate congestion and improve safety. The battery thermal management (BTM) in CAHEVs is one of the crucial problems, because the lithium-ion batteries are highly temperature sensitive. Therefore, a practical and energy-efficient BTM strategy is required for both improving the operating temperature of batteries and saving energy. In this study, the dynamic programming (DP) is implemented for a BTM system in CAHEVs for achieving the optimal cooling/heating energy savings for batteries. To enhance the real-time capability, an iterative approach is proposed to approximate the optimum control strategy iteratively in a multidimensional search space. The proposed iterative DP strategy can improve the system performance and energy-efficiency by fully exploiting the future road information in CAHEVs combined with a model predictive control method. The hardware-in-the-loop validation of the proposed strategy is conducted on the UDDS and the WLTC drive cycles based on a Toyota Prius PHEV model. The results demonstrate the feasibility and effectiveness of the proposed BTM strategy that leads to a considerable BTM energy reduction. [ABSTRACT FROM AUTHOR]

In cold climates, lithium-ion batteries suffer severe power/energy loss, bad performance, and reduced life cycle. Many internal ac heating strategies have been proposed to provide fast heating with a higher efficiency and better uniformity. However, the ac current is typically generated by an offboard equipment with grid power supply, which is a main bottleneck of the ac heating applied to electric vehicles. Therefore, an automotive onboard ac heater is proposed to heat lithium-ion batteries at low temperatures without the requirement of external power supplies. Only one pair of complementary pulse width modulation signals is employed to drive the proposed ac heater, and the heating speed can be online regulated by controlling the switching frequency. Particularly, the heating time can be reduced drastically by combining two heaters in interleaved parallel without causing harm to the batteries. In addition, the heating circuit can also realize the automatic balancing for battery cells if needed. Experimental results show that the proposed interleaved parallel heater, by circulating an ac current with the amplitude of 3.1 C and the frequency of 833 Hz, can heat lithium-ion batteries from −20 to 0 °C within 5.9 min, consuming about 5% of cell energy. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present the design and implementation of a hybrid energy storage system (HESS) with wireless power transfer (WPT). This study combines a battery bank and a supercapacitor bank to achieve high performance energy sources for electric scooters. The proposed system can be employed on commercial 48-V electric scooters for evaluation. The presented approach follows the WPT frequency standard of SAE J2954 to build the energy transmission. Based on the control of the state of charge on the battery bank, this paper proposes a three-mode strategy for hybrid energy management. The proposed HESS makes three compact and integrated contributions. First, it acts as the regulator to manage the input energy from WPT. Second, it manipulates the energy distributions to the battery and supercapacitor. Third, it provides a mechanism to initiate a short period of “negative current” to avoid excessive exploitation of the battery and facilitates palliation upon polarization. This function has the ability to extend battery life. The system performance of the electric scooter, as a result, can be improved. A double-sided LCC coil with a 15-cm air gap for wireless charging was built on a 0.8-kW electric scooter. In the wireless stage, the efficiency from the dc source to the dc output after the rectifier is 90.362%. The overall system efficiency from the dc source to the battery and supercapacitor is 86.4%. [ABSTRACT FROM AUTHOR]

This paper presents a rotation-resilient wireless charging system with a reversely wound receiver that supports efficient charging for lightweight autonomous underwater vehicles. By employing a two-part reversely wound receiver coil structure, the total mutual inductance of the proposed coil structure remains relatively constant when rotational misalignment between the transmitter and receiver coils occurs, thereby ensuring wireless charging power is nearly continuous during rotational misalignment. Finite element analysis was performed with ANSYS Maxwell to verify the proposed coil structure. Double-sided LCC compensation topology was applied and circuit analysis was conducted via a mesh current method. A prototype of the rotation-resilient wireless charging system with the proposed coil structure was built and tested. Experimental results are well-matched to simulations, demonstrating that the system can deliver 745 Watts at a dc-dc efficiency of 86.19% when the system is fully aligned, and efficient under worst-case rotational misalignment. [ABSTRACT FROM AUTHOR]

Lightweight autonomous underwater vehicles (AUVs), powered by rechargeable batteries, are widely deployed in inshore surveying, environmental monitoring, and mine countermeasures. While providing valuable information in locations humans have difficulty accessing, limited battery capacity of such systems prevents extended mission times. In order to extend mission times, this paper proposes a three-phase wireless charging system that could be used in a field-deployable charging station capable of rapid, efficient, and convenient AUV recharging. Wireless charging should not, however, affect instrumentation located inside the AUV. Thus, a three-dimensional finite element analysis tool is employed to study the characteristics of magnetic fields inside the AUV during three-phase charging. Simulation results reveal that the magnetic field generated by the proposed three-phase coil structure is concentrated away from the center of the AUV, where instrumentation would nominally be located. Detailed circuit analysis and compensation method to achieve resonance on both transmitter's and receiver's sides are also given. To validate the proposed concept, a three-phase wireless charging system is developed. Experimental results demonstrate that the system is able to transfer 1.0 kW with a dc–dc efficiency of 92.41% at 465 kHz. [ABSTRACT FROM AUTHOR]

This paper proposes a dual-coupled LCC-compen-sated inductive power transfer system with a compact magnetic coupler to improve misalignment performance. In the magnetic coupler, the main coils form the first coupling, and compensation inductors are integrated with the main coils to form a second coupling. In the design presented in this paper, the main coils are unipolar and the compensation inductors are in a Double D structure. The fundamental harmonics approximation method is used to analyze the circuit, and the couplings between the main coils and compensation inductors are considered to determine the net power flow. In misalignment cases, it is shown that the coupling between the compensation inductors, and the cross couplings between the compensation inductors and main coils, contribute to increasing the system power. A 3.5 kW prototype is designed and implemented to validate the proposed dual-coupled system. The primary coil size is \text450 mm\times \text450 mm, and the secondary coil size is \text300 mm\times \text300 mm. Experimental results show that the proposed dual-coupled system can significantly improve the misalignment performance, and retains at least 56.8% and 82.6% of the well-aligned power at 150 mm misalignment in the x- and y-directions, respectively. [ABSTRACT FROM PUBLISHER]

To improve a vehicle’s fuel efficiency when operating on roadways, this study develops an ecological driving system under the connected and automated vehicle (CAV) environment. The system includes three critical functions, including traffic state prediction, eco-driving speed control, and powertrain control implementation. According to the real-time traffic information obtained from vehicle-to-infrastructure and vehicle-to-vehicle communications, the embedded traffic state prediction model will estimate and predict the average speeds and densities of freeway subsections. With an objective of minimizing the fuel consumption, the eco-driving speed control function follows a two-stage hierarchical framework. The first stage, which is executed at the global level, aims to optimize the travel speed profile of the CAV over a certain time period. The second stage, local speed adaption, is designed to dynamically adjust the CAV’s speed and make lane-changing decisions based on the local driving condition. The resulting control parameters will then be forwarded to the powertrain control system for implementations. To evaluate the proposed system, this study performs comprehensive numerical tests by using simulation models. This results confirm the effectiveness of the proposed system in reducing fuel consumption. Further comparisons with different models highlights the need to consider traffic state information in the first-stage optimization and lane-changing decision module in the local adaption function. [ABSTRACT FROM AUTHOR]

This paper proposes the use of an adaptive control of a hybrid electric vehicle with dual clutch transmission (HDCT). First, this paper shows mathematical equations for the nonlinear system. Then it presents the linearized model for the proposed system. The control objective of the model reference adaptive controller (MRAC) considered in this paper is to minimize fuel consumption and reduce torque interruption in a hybrid electric vehicle. The MRAC can be used to control the electric motor during changes in speed and gear, and the system can adapt to a model that simulates different driver patterns. The effects of using different model responses as input combinations are analyzed in an effort to exploit the over-actuation feature of the system, as is the sensitivity of the performance to various design factors. The simulation results for an HDCT demonstrate that the MRAC achieves reduced torque interruption and less vehicle jerk compared to the conventional method of operation. [ABSTRACT FROM AUTHOR]

This paper proposes a double-sided LC-compensation circuit for a loosely coupled, long-distance capacitive power transfer (CPT) system. A CPT system usually contains two pairs of metal plates as the capacitive coupler. An LC-compensation circuit resonates with the coupler to generate high voltages, and corresponding electric fields, to transfer power. When the compensation circuit is used on both the primary and secondary sides, it results in a double-sided LC-compensated CPT system. The working principle and frequency properties of the CPT system are analyzed. The results show a similarity with the series–series-compensated inductive power transfer system, which has both constant-voltage (CV) and constant-current (CC) working modes. LC-compensation is also compared with LCLC -compensation in terms of power, frequency properties, and output efficiency. A 150-W double-sided LC -compensated CPT prototype is designed and implemented to demonstrate a loosely coupled CPT system with 2.16% coupling coefficient. For both CC and CV working modes, the experimental results achieve dc–dc efficiencies higher than 70% across an air-gap distance of 180 mm with a switching frequency of 1.5 MHz. [ABSTRACT FROM AUTHOR]

The conventional state-of-charge (SoC) estimation methods based on the equivalent circuit model (ECM) integrate all state variables into one augmented state vector. However, the correlations between RC voltages and SoC degrade the stability and accuracy of the estimates. To address this problem, this paper presents an adaptive SoC estimation method based on the split battery model, which divides the conventional augmented battery model into two submodels: the RC voltage submodel and the SoC submodel. Hence, the cross interference between RC voltages and SoC is reduced, which effectively reduces the oscillation in the estimation and improves the estimation accuracy. In addition, the adaptive algorithm is applied on the SoC submodel to improve the system robustness to noise disturbances. A case of a second-order ECM is analyzed and two types of Lithium-ion batteries are employed to verify the universality of the proposed method. Experimental results show that the undesired oscillation is eliminated during the convergence stage and the maximum SoC error is within 1% over a wide SoC range. [ABSTRACT FROM AUTHOR]

This paper proposes an LC-compensated electric field repeater to extend the transfer distance of a capacitive power transfer (CPT) system. The repeater contains two metal plates connected with an external capacitor and an external inductor. The plates are used to generate electric fields to transfer power. The external inductor and capacitor are used to resonate with the plates in order to increase the voltage levels. The repeater is placed between a transmitter and a receiver, which also contains metal plates compensated by an LC network. The repeater can increase the transfer distance of the CPT system without significantly influencing the system power and efficiency. In this paper, the capacitive coupler structure and dimensions are designed and simulated using Maxwell software. Considering all the capacitive coupling between plates, an equivalent circuit model is derived. The fundamental harmonics approximation method is used to analyze the working principle of the circuit. A 150 W input power CPT system is designed as an example to validate the proposed repeater structure and compensation circuit topology. The system can achieve an efficiency of 66.9% from dc source to dc load, when the transfer distance is 360 mm and the repeater is placed between the transmitter and the receiver. [ABSTRACT FROM AUTHOR]

This paper proposes a novel coupler structure for wireless power transfer, which takes advantage of both magnetic and electric fields. The coupler contains four metal structures, two each at the primary and secondary sides, which are capacitively coupled. Each structure consists of long strips of metal sheet to increase its self-inductance, which is then inductively coupled with the other three structures. The structures are vertically arranged and the outer structures are larger than the inner ones to maintain the capacitive couplings. An external LCL compensation network is proposed to resonate with the coupler. The resonance provides conduction currents flowing through each plate to establish magnetic fields and displacement currents flowing between different plates corresponding to electric fields. A 100-W output power prototype is designed and implemented to operate at 1.0 MHz, and it achieves 73.6% efficiency from dc source to dc load across an air-gap distance of 18 mm. The contribution of this paper is to propose a concept to transfer power using magnetic and electric fields simultaneously. [ABSTRACT FROM AUTHOR]

This paper proposes a distance-based two-stage ecological (eco-) driving scheme by using estimation of distribution algorithms (EDA) and model-based prediction of traffic conditions. Before departure, the optimal speed profile for an entire route is generated by an EDA in combination with speedup approaches for a faster computing time, which can optimize the complex cost function of ecodriving without simplification within a reasonably short computing time. This optimization is performed in a distance domain for localizing changes in the optimal speed profile due to traffic conditions while driving. After departure, by taking the optimal speed profile and actual traffic conditions into consideration, the speed profile for a short term—to only the next location—is adapted. In order to reliably react to actual traffic conditions, additional points are interpolated into the long-term distance step and fine control of speeds at the additional points is established, which is based on a predictive model for estimating the spacing to the preceding vehicle. The proposed ecodriving system is evaluated in two types of route conditions, and its results are compared with the optimization result by the quadratic programming method. This comparison shows that an EDA can generate a speed profile with better optimization results in terms of fuel efficiency and driving time within a shorter computing time. [ABSTRACT FROM AUTHOR]

This paper proposes an automatic any-cells-to-any-cells battery equalizer, which merges the forward and flyback converters through a common multiwinding transformer. The windings of the transformer are divided into two groups, which have opposite polarities. The principles of the proposed equalizer are that the equalization in one group is achieved based on forward conversion and the balancing between the two different groups is based on flyback conversion, by which the magnetic energy stored in the transformer can be automatically reset without using additional demagnetizing circuits. Moreover, only one MOSFET and one primary winding are required for each cell, resulting in smaller size and lower cost. One pair of complementary control signals is employed for all MOSFETs, and energy can be automatically and directly delivered from any high-voltage cells to any low-voltage cells without the requirement of cell monitoring circuits, thereby leading to a high balancing efficiency and speed. The proposed topology can achieve the global equalization for a long battery string through connecting the secondary sides of transformers without the need of additional components for the equalization among modules, which also overcomes the mismatching problem of multiple windings. The validity of the proposed equalizer is verified through experiments, and the balancing efficiency can reach up to 89.4% over a wide range of conditions. [ABSTRACT FROM PUBLISHER]