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A nondestructive, simple detecting method of internal Li-metal plating in the Lithium-ion battery (LiB) is essential for diagnosing the safety of battery systems for realising the long-life use of the LiB. We show a direct Li-metal detection technology that is dependent on the electromagnetic response of the battery at a high-frequency (MHz). By the unique response of the high-frequency electromagnetics based on the Maxwell’s law, a negative correlation is observed between the real-part impedance and the internal Li-metal plating deposited on the anode surface by the partial electrochemical potential overstress. This finding makes the diagnostic process much simpler than conventional methods such as data-driven analytical approach, because this finding measures a direct response from the electronic behaves to the metal deposition, rather than symptoms from the ionic behaves. The sufficient decrease in the real-part impedance was confirmed only in the Li-metal plated commercial batteries (LFP-18650, 1500 mAh, representatively) that are degraded by repeated rapid charging. Notably, this finding can be assembled as a battery monitoring sensor that diagnoses the growth of Li-metal plating during real-field operation. This finding is expected to contribute to the solutions for the new global environmental challenges by supporting the safe and long-term use of LiBs both in the classification process and its reuse.

This article presents a multiport, bidirectional, contactless connector based on the inductive power-transfer technology. The unique structure of the axially gapped cylindrical core facilitates the proposed contactless connector to control the output of multiple low-voltage batteries in parallel, thereby balancing the state of charge. Axial gaps in the proposed transformer facilitate realization of accurate power distribution via multiple-input/output phase-shift control. Investigation performed on a prototype of the proposed connector revealed realization of 95% efficiency at $\mathrm{\pm }$ 1 kW, 3 mm contactless power transfer along with a power-balancing function between a 300 V output and six of 50 V inputs. The proposed technology is expected to enhance the safety and reliability of large capacity, high-power batteries employed in electrical-mobility and renewable-energy systems.

This article aims to realize an isolated dc–dc converter with high power density, high power efficiency, and low noise performance. Although a dual-active-half-bridge (DAHB) converter can achieve high efficiency, it requires input and output low-pass filters to suppress the operational ripple current and switching noise. Owing to the volume of the filters, a DAHB converter cannot be implemented with high power density. This article presents a design theory for a novel isolated bidirectional dc–dc converter with built-in filters. The proposed converter is derived from a DAHB converter and can eliminate the input and output filters via split windings and tank capacitors; the principle of elimination is based on $LC$ low-pass filter function and zero-ripple-current operation. As the number of transistors, capacitors, and magnetic cores of the proposed converter are equal to those of the DAHB converter, the application of the proposed converter allows volume reduction by eliminating the filter components at the input and output ports. Theoretical equations are derived to design a power flow control function and a filter function simultaneously. Finally, prototypes of a DAHB converter and the proposed converter are constructed for comparison. The results demonstrate that the input port noise of the proposed prototype is lower than that of the DAHB prototype by 10 dB (peak) over 1 MHz, and the proposed approach can achieve a significant improvement in efficiency.

A MagCap DC–DC converter using GaN semiconductor devices is presented to improve the efficiency and modularity of the vehicular power system. While the topology is as simple as the flyback converter, all the semiconductor switches turn on and off with soft switching. A design guideline to transformer and capacitor is suggested considering the conduction loss and voltage stress of the switches. A quasi-resonant (QR) operation for low output-power condition is also explained. The switches turn on at the valley of the drain-source waveform to secure soft switching and maximize the efficiency. A 180-W prototype hardware was populated on 63 mm × 31 mm printed circuit board using 200-V GaN FET devices. Peak efficiency was 97.1% at 155-W output power and 1.2-MHz switching frequency. Another prototype was built for the QR operation and demonstrated 91.6% peak efficiency by maintaining the soft switching and avoiding excessive switching frequency.

The major challenges for electric vehicle deployment include the prohibitive battery cost and a large amount of time required for energy refueling. Although the concept of battery swapping can solve the latter problem, it is difficult to overcome the former problem while ensuring a long-range drive. Thus, this paper reports upon a conceptual electric vehicle (BaaS-EV) that shares a part of the battery and presents an optimization model for its service infrastructure, battery as a service (BaaS). The BaaS-EV has two different batteries and operation modes. For short-range drive, the BaaS-EV can be driven using only one of the batteries, and to operate in a long range, an additional shared battery can be employed. Such shareability can increase the utilization rate of the battery and reduce the battery cost. The BaaS infrastructure provides BaaS-EV users with recharged batteries on demand. A cost-efficient operation of BaaS requires simultaneous optimization of the number of batteries, charging techniques, and transportation costs. To realize this aspect, an optimization model is established based on the minimum cost flow problem. Results of numerical simulations and case studies based on the model highlight the possibility of cost-benefit pertaining to the battery, user opportunity, battery charging, and transportation costs.

This paper proposes an on-board charger circuit which integrates an interleaved totem-pole PFC and a Dual Active Bridge (DAB) converter. The proposed on-board charger features single-stage conversion and a high level of components integration. In the course of an analytical investigation, the operation principle of the proposed charger is described. With this analytical expression, the pareto-front with regard to efficiency and volume for the proposed charger was calculated. The optimal design parameters were extracted, and 3.0 kW, 100 kHz prototype was constructed. Experimental results verify the working principle and the power density of 3.2 kW/L and the efficiency of 95.4% was achieved at rated power of 2.9 kW.

Electrothermal design of a synchronous buck converter with heat flow control is presented. A commercial reference circuit design for a synchronous buck converter is selected for the study. A functional printed circuit board (PCB) of the converter is fabricated and tested to establish baseline performance. The baseline PCB layout is modified by incorporating a design of electrothermal traces from a heat flow control optimization study. Electrical plus thermal characteristics of each design are experimentally evaluated. It is found that the modified design manipulates the heat flow across the PCB. At low output current (

This paper proposes a new bidirectional dc–dc converter capable of improving the convenience and modularity of the dc power grid system. By the unique operation of the $LC$ resonant transformer, the proposed converter achieves bidirectional power control with only two switches. Also, the resonant transformer drives the soft switching turn-on and turn-off over a wide power range. Hence, the circuit has high potential to downsize the converter by exploiting high frequency and simplicity. This paper provides the operating principle and the experimental verification of the proposed circuit. A prototype was fabricated by using a simple and high-density printed circuit board ( $\geq$ 10 W/cc). It is verified that the circuit resonant operation successfully drives bidirectional power control with high efficiency ( $\geq$ 92%). An application example is also provided for dc grid system integration.

This paper proposes time synchronization and an encoding technology for controlling the gate signals of a contactless power transfer system. Contactless bi-directional power transfer is controlled using 50-Mbps near field electromagnetic coupling communication that has low jitter and a phase-shift power transfer circuit. A prototype is tested to validate the performance of the proposed control operation. Relatively low jitter is detected, and efficiencies of 93.6% at ±3.3kW, 94.8% at ±1.8kW, 92.3% at ±4.0kW are achieved between 300-V systems with a 2-mm gapped .

This paper proposes a multi-port, bidirectional contactless connector based on the inductive power transfer technology. Owing to the unique structure of the axial gapped cylindrical core, the proposed contactless connector can control the output of multiple low-voltage batteries in parallel to balance those State of Charge. The axial gaps of the proposed transformer enables precise power distribution in multi-input/output phase-shift control. The prototype of the proposed connector verified ±1 kW, 95%, 3 mm contactless power transfer and the power balancing function between 300 V output and 6 of 50 V inputs experimentally. The proposed technology will contribute the growing of use of large capacity, high power battery for mobility system and renewable energy systems with safety and reliability.

A novel filter built-in converter with split windings is presented. Because of its extreme simplicity, flexibility, and efficiency, it has the potential to replace some of the conventional electric power conversion methods used today. The background, design, and operation of the proposed filter built-in converter are discussed in this paper. The proposed converter is derived from a dual active half bridge (DAHB) converter, and it can achieve zero-ripple-current operation and LC low-pass filter function by the split windings and tank capacitors. Due to the zero-ripple-current operation and the LC low-pass filter function, the proposed converter can eliminate or decrease the input and output filters, and with a phase-shift control strategy, all the switches are operated under zero-voltage switching (ZVS) condition. In order to design a power flow control function and a filter function simultaneously, theoretical equations for these functions are derived. Finally, the DAHB and the proposed converter prototypes are constructed for comparison. The results show that the noise in the input port of the proposed prototype is smaller than that of the DAHB prototype by 16 dB (peak), and the proposed approach can achieve a significant improvement in efficiency.

Photonic power converters (PPCs) are a class of photovoltaic devices designed for efficient conversion of monochromatic (laser or LED) light to electricity. These devices are composed of multiple p-n junction diodes arranged in a tandem configuration and connected in series. They have reached high energy conversion efficiencies (70%) and areal power densities of 100 W/cm $^2$ . When these devices are illuminated with a high-efficiency diode laser, they can provide isolated dc–dc conversion from the laser voltage ( $^{3}$ , compared with 1.5 W/cm $^{3}$ for the reference. Relative to switch-mode power conversion, the photonic technology has lower efficiency and lower power density, but superior isolation and rejection of ripple and EMI. Both technologies are highly scalable. For the second application, the same unit is applied to power a 650-V SiC mosfet gate driver requiring high galvanic isolation, demonstrating a 20 dB reduction in conducted-current EMI from the power circuit into the low-voltage control systems.

This paper presents a new architecture for the next-generation reconfigurable power management control (PMC) system for all-electric vehicles, which can handle the personalization and evolution of vehicle architectures in a plug-and-play (PnP) fashion. The proposed control system utilizes multi-agent system (MAS) for reconfigurability and integrates on-line model learning with Gaussian process. In the two case studies of PnP scenarios, one with limited power supply and another with excessive power supply, the simulation results suggest that the proposed PMC system is capable of stabilizing the system and performs better than the baseline controller. The improvement in performance over the baseline voltage-power droop controller can be up to 59% when parameters are optimized using on-line learning.

The design of anisotropic thermal conductivity in multilayer printed circuit boards (PCB) is studied, where the flow of heat is manipulated through the informed layout of circuit board electrothermal traces. Three representative circuit board configurations are considered to illustrate the basic method. A baseline circuit board (Configuration 1) comprising a heat-generating device in thermal communication with a heat sensitive device by the way of a standard electrical trace connection is studied first to characterize heat flow due to conduction and convection. Building off of this baseline structure, the thermal management advantages and disadvantages of a closed heat shield for anisotropic PCB thermal conductivity are explored using the second circuit board (Configuration 2). The design of the third multilayer circuit board (Configuration 3) with optimized anisotropic PCB thermal conductivity for enhanced heat flow control is simultaneously explored. It is experimentally shown that, for PCBs subject to free convection and power densities on the order of 1–10 W/cm2, the design technique allows for noticeable (−10 °C) reduction in the temperature of the heat sensitive device without a significant (

A novel multiport dc–dc converter with a coupling magnetic inductor is analyzed and designed. The proposed circuit integrates two multiphase converters and one isolated dc–dc converter. These converters can be controlled independently in one circuit by adjusting the duty ratio and phase angle difference. There are four dc ports in the circuit, and the dc power can be delivered multidirectionally among the four dc ports. In this paper, a 1.5-kW prototype of the multiport converter was constructed and successfully operated under full power. The experimental results confirm the theoretical analysis, and the conversion efficiency is above 90% over a wide range of output power. In addition, an example of a multifunctional power conversion system using the multiport converter is demonstrated.

This paper presents a magnetically integrated isolated bidirectional three-port DC-DC converter (TPC) that includes an integrated dual active bridge converter (DAB) and non-isolated bidirectional DC-DC converter (NBC), each of which can be independently controlled. The proposed TPC simultaneously uses large, small, and magnetizing inductances, of which the small and magnetizing inductances are used for the DAB function, while the large inductance is used for the TPC function. The proposed magnetic component can function as any of the three inductances in the TPC. We constructed a 750 W, 175 kHz prototype of the proposed TPC along with an example of a conventional TPC and measured their respective efficiencies. The results show the efficiencies of the integrated TPC were all above 90% across the entire range of output power and were nearly equal to those of the conventional device. However, compared to the conventional type, the magnetic components in the proposed converter were 10% smaller, and the overall size of the converter was 33% smaller.

Increasing demand for urban mobility has contributed to heavy traffic in metro areas, rising transportation costs and travel times. The concept of driverless centrally-controlled electric vehicles has been attracting attention for its potential of minimizing traffic congestion. This study is introducing the tools and methods needed for evaluating the benefits of the concept. An intelligent route planning algorithm, along with a traffic simulation environment, which is coupled to a vehicle performance model have been developed. An interactive graphical tool has been created to showcase the resulting benefits of the concept and to support the conceptual design of energy efficient electric vehicles for centralized large scale operations. The study has identified correlations between a driving environment's traffic density and the potential of relieving the effects of congestion, with considerable travel time, energy and vehicle wear savings attainable.

We present a new design for an isolated power converter using optical power transducer (OPT) technology. The converter transmits optical power from a laser diode (LD) to a phototransducer (PT) across an air gap. The PT device consists of 12 GaAs pn junctions, each current-matched to achieve a record optical-to-electrical power conversion efficiency of ≥ 66% with an open-circuit voltage of 14.5 V. Using a LD with 840 nm wavelength, the OPT can output more than 3.2 W of electrical power with 25% electrical-to-optical-to-electrical conversion efficiency, a value twice as efficient as a similar OPT built using previous generation PT technology. This new prototype successfully provides the driving power to the gate driver for 75 kV/μs fast switching of a SiC-MOSFET, made possible by a low stray input-to-output capacitance of ≤ 1 pF. We measure a 70% reduction in conducted electromagnetic interference (EMI) compared to a conventional transformer-based isolated power supply.

With the demand and supply for electric vehicles (EVs) in rapid growth at a global scale, due to factors such as environmental awareness, tax and monetary incentives, government regulations, and technological advances, a range of technical issues in efficient EV design has been gaining great attention. With consumer concerns around EV range and battery degradation, several initiatives have been investigating technologies which could further address the above issues. Recognizing the need for increasing the driving range and decreasing the impact of scenarios that negatively affect it as prime design issues, one of the resulting areas of interest is to explore options on better managing energy for heating, ventilation and the air conditioning (HVAC) system, which can decrease the range of EVs by as much as 30% when in use. With key driver for identifying the most promising ideas and technologies worth extensive investigations, the objective is to develop a methodology for managing the selection of technologies during conceptual design, through assessing HVAC power demand effects and employing advanced energy management techniques. A methodology for identifying emerging technology concepts has been outlined and demonstrated in the context of a virtual electric vehicle system. As a result, MOTEVETOR, a portable, interactive multi-criteria decision making tool has been created which allows for performing trades between vehicle configurations carrying different technology packages, as part of supporting EV conceptual design.

In this article we explore a coupled design strategy for the simultaneous optimization of lumped-parameter (electrical) and continuum parameter (thermal) systems. In terms of electrical circuit response, advances in the development of wide band-gap semiconductors and the high speed transient behavior of these devices leads to challenges associated with damping or over-shoot. To address such issues, traditional circuit design strategies should evolve to incorporate next generation electrical components effectively. Thus, we propose the incorporated design of circuit layout and routing in conjunction with heat spreader design as a more comprehensive means to optimize the layout of power-dense electronics. The effects of this multidisciplinary design are evaluated by analyzing the Pareto set, which was observed to shift towards the utopia point with each additional design consideration.

This extended digest is focused on design for additive manufacturing of next-generation wide band-gap power electronics components, where high operating frequencies, on the order of 100 kHz to 100 MHz, and high volumetric power densities are expected. Common components that enable future WBG power electronics systems, namely high frequency circuit-level magnetics and system-level high performance cold plates for thermal management, are discussed in the context of additive manufacturing. In both cases, three-dimensional printing enables performance enhancements that are explained in detail. Future opportunities for, and challenges in, the application of additive manufacturing to the realization of wide band-gap system components is additionally described.

GaAs phototransducers with 5 to 12 p/n junctions are shown to demonstrate breakthrough performance in optical conversion efficiency ranging from 65% to just under 70%. In particular, for a current-matched 12 junction device we have recorded an efficiency of 66.5% at V oc = 14.46V (open circuit voltage) with an approximately 650 suns / 841 nm monochromatic source. Our simulations reproduce the PV characteristics of the physical devices with good (∼ %) accuracy for V oc and I sc (short circuit current), which allows us to numerically study the influence of experimental conditions and design factors on device performance. Moreover, our simulations suggest that measured efficiencies are very close to the theoretical limits of the heterostructures under consideration. Our focus in these proceedings is twofold: a) to present an overview of the results of these experiments as well as b) study the factors which limit simulated device performance with the objective of attaining monochromatic conversions efficiencies exceeding 70%.

A twelve-junction monolithically-integrated GaAs phototransducer device with >60% power conversion efficiency and >14 V open-circuit voltage under monochromatic illumination is presented. Drift-diffusion based simulations including a luminescent coupled generation term are used to study photon recycling and luminescent coupling between each junction. We find that luminescent coupling effectively redistributes any excess generated photocurrent between all junctions leading to reduced wavelength sensitivity. This broadened response is consistent with experimental measurements of devices with high-quality materials exhibiting long carrier lifetimes. Photon recycling is also found to significantly improve the voltage of all junctions, in contrast to multi-junction solar cells which utilize junctions of differing bandgaps and where high-bandgap junctions benefit less from photon recycling.

The current filament movement within and between emitter pads of an IGBT under unclamped inductive switching conditions was measured. This measurement was achieved by using a test setup capable of measuring the emitter current distributions in nine independent points over the active area of the IGBT. The measured filament speed into the pads was between the range of 150–400 μm/μs, and the filament speed increases by increasing the collector current. Moreover, current hopping phenomenon was observed between non-neighbouring emitter pads as well.

This paper deals with a new resonant gate-drive circuit for power MOSFETs. The proposed gate-drive circuit is characterized by a resonant inductor connected in series to the gate terminal of the MOSFET. It is possible to charge or discharge the input capacitance of the MOSFET by using the resonance between the inductor and the input capacitance. Experimental results are shown to verify the viability of the resonant gate-drive circuit. As a result, the proposed resonant gate-drive circuit reduces its power consumption to one tenth, compared with a conventional one. It was experimentally clarified that the proposed circuit makes it possible to improve efficiency of a high-frequency inverter using MOSFETs.

A three-port DC/DC converter (TPC) having DC48V and DC12V ports, and an isolated DC port is designed and analyzed. The newly designed TPC integrates a non-isolated bi-directional DC-DC (NBC) converter and an isolated dual-active-bridge (DAB) converter using a coupling inductor technique, and DC power can be delivered multi-directionally among three DC ports. In the present study, a loss estimation method for the TPC is developed in order to analyze losses in all load conditions. A 750 W, 125 kHz prototype using a Si MOSFET is constructed in order to confirm the accuracy of the newly developed estimation method. The measured efficiency is over 90% for a wide range of load conditions, and the calculated efficiency curves correspond well with the measured efficiencies. In addition, the improvement in efficiency provided by using a GaN FET is also discussed. The efficiency is expected to increase 2% by replacing the Si MOSFET with a GaN FET. Finally, a prototype using a GaN FET is constructed in order to verify the above estimation.

In the present paper, a novel multi-port converter with coupled magnetic components is analyzed and designed. The proposed circuit integrates two multi-phase converters and one isolated dc-dc converter. These converters can be controlled independently and simultaneously by duty cycle and phase-shift modulation, because the impedance behavior of magnetic components is different for each converter. A 1.5-kW prototype of the multi-port converter has been constructed and successfully operated under full power at a switching frequency of 40 kHz. The experimental waveforms confirm the theoretical analysis, and the conversion efficiency is above 90% over a wide range of output power. In addition, loss analysis is carried out in order to define the critical parts of the proposed converter.

This paper proposes a new multi-port converter with interleaved magnetic coupling technologies. With the focus on the impedance behavior of coupled magnetic components and the control parameters, this multi-port converter integrates one isolated dc-dc converter and two multi-phase boost converters, and controls these topologies independently. The proposed converter has the capability to connect four dc applications or sources in total, and so brings significant cost reduction and improves the total loss consumption of power systems. In addition, magnetic isolation brings high reliability of complex power systems such as electric vehicles or grid-connected industries. In this paper, the basic circuit behavior is verified by theoretical considerations and experiments. An example of the proposed circuit as a multifunctional dc power system is demonstrated with the simulation results. Such an approach could bring about variable application fields to dc electric power systems.

This paper deals with a resonant gate-drive circuit for fast and high-voltage power semiconductor devices, which is equipped with optical fibers for both gate control signal and dc power supply. A resonant inductor connected with the gate terminal makes it possible to charge or discharge the gate-to-source voltage by using the parallel resonance between the inductor and the input capacitance of the device. The optical fibers can be used to deliver the driving power to the gate drive circuit, because the circuit theoretically causes no power consumption for driving the power device. Moreover, the proposed circuit makes it possible to suppress fluctuations in the gate voltage caused by a rapid change in the drain-to-source voltage. Experimental results are shown to verify the viability of the proposed circuit.