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This article proposes a holistic and improved methodology for the inductors' design in power electronic circuits operating at high frequencies. This methodology includes an analytical design, a finite element modeling of the electromagnetic behavior with JMAG software, a simulation analysis in a Simulink environment, and experimental verification of the effectiveness of inductor design in a laboratory‐scale step‐up boost power converter prototype. The holistic approach allowed us to achieve all target specifications such as maximum power (300 W), minimum voltage (60 V), inductance (1.77 mH), and maximum current ripple (1 A). It guarantees the losses' minimization in core and copper (21.47 W), and marginal errors below 4% between the analytical, simulated, and experimental values. [ABSTRACT FROM AUTHOR]

Titanium tetrachloride (TiCl4) is a well-known source of titanium (Ti) for the formation of titanium nitride (TiN) barrier material in the semiconductor interconnection process; however, the reaction of by-products with airborne molecules can cause unexpected pump trips and equipment breakdown from the by-product powder build-up. Plasma scrubbers are used to decompose by-products, but hydrogen chloride (HCl) and nitrogen oxides are produced during and after the process. The process mechanisms change when the temperature and applied power of the heat source change. In this paper, we study the influence of the reactor temperature and applied power to the heat source on the decomposition capacity of TiCl4 in a plasma pretreatment system (PPS). We examine the effect of the temperature and heat source power to understand the reaction mechanisms for the composition and decomposition of gaseous species with chemical reactions through simultaneous methods. We analyzed the system with computational fluid dynamics (CFD) and chemical kinetic simulation to investigate the changes of the system mechanism. Subsequently, we achieved results for the correlation between the temperature of the reactor, power applied to the heat source, composition and decomposition of species, and chemical reaction mechanisms. [ABSTRACT FROM AUTHOR]

Mechanically flexible and stretchable inductive coils are critical for enabling communication, sensing, and wireless power transfer capabilities in wearable electronics that conform to the body for healthcare and Internet of Things (IoT) applications. Leading stretchable conductors such as liquid metals (LMs) offer conformability but sacrifice electromagnetic performance compared with Cu wires, leading to lossy radio‐frequency (RF) characteristics. Here, a strategy leveraging multistranded 3D woven 'litz' transmission lines is presented to amplify the resonant RF performance of LM inductors. Through comprehensive simulations and experiments, it is discovered that interwoven LM litz wires boost the Quality Factor (Q) by 80% compared to standard liquid metal wires. A fabrication methodology is also demonstrated for stretchable coils that retain high Q (>30), outperforming the previously reported LM coils and maintaining 98% of their wireless transmission efficiency under up to 30% biaxial strain. Moreover, the versatility of this approach is showcased by 3D printing four‐terminal 'choke' inductors optimized for RF filtering and inductance tunability, overcoming the fabrication limitations of traditional planar printed electronics. These results offer valuable insights into the design and implementation of 3D‐printed inductors for a diverse suite of electromagnetic device applications. [ABSTRACT FROM AUTHOR]

The issues of selecting the frequency and power of high-frequency heating in soldering electronic modules and device enclosures are thoroughly examined. High-frequency electromagnetic energy is explored for its efficient non-contact heating capabilities, enabling rapid heating to soldering temperatures through the induction of eddy currents in the metal components and solder. Compared to convective heat sources, high-frequency heating can achieve heating rates up to 10 times faster, with the heating zone precisely localized within the area defined by the inductor design. Methods and device schematics for high-frequency soldering processes are provided, alongside descriptions of the technological equipment and fixtures utilized in these processes. Transistor generators operating at medium (66 kHz) and high frequencies (440 and 1760 kHz) have gained widespread adoption for high-frequency heating applications. To enhance the quality of solder joints and increase product yield, computer-controlled thermal profiles are essential for high-frequency soldering processes. The advantages of high-frequency heating, including locality, simplicity of design, high environmental cleanliness, and the ability to leverage electromagnetic forces for improving solder flow, make it an optimal choice for surface mounting of electronic modules. Induction devices constructed on magnetic cores are also viable for soldering power contacts, connectors, and wires to printed circuit boards, coaxial cables, and sealing metal-glass housings of integrated circuits. These applications highlight the versatility and efficacy of high-frequency heating techniques in modern electronic assembly processes. [ABSTRACT FROM AUTHOR]

Abstract One of the early design decisions for DC‐DC converters is the choice of an appropriate magnetic core material. Powder cores in particular are suitable due to their saturation flux density of up to 1.5 T. However, high DC currents constitutes a significant problem since the winding cross‐section rises with the current, which consequently increases AC losses due to skin effects. Another challenge is the reduction of winding layers to decrease proximity losses. This paper presents an improved single‐layer winding design procedure for DC‐DC converter powder cores. The procedure determines the optimum number of parallel cores and stacks. This way, the procedure enables a predefined maximum wire cross‐section for copper loss optimisation and single‐layer winding. The introduced approach defines the optimum switching frequency as a trade‐off between core loss and core volume. Finally, experimental tests with two setups validate 27 kW DC‐DC converters and hence the design procedure using Si‐IGBTs and SiC‐MOSFETs. The results demonstrate that SiC‐MOSFETs reduce core volume by a factor of 3 compared to Si‐IGBTs. Further, the SiC setup reaches high efficiencies of up to 98.53% compared to 98.17% for the Si‐based converter.

Internet‐of‐Things and Cyber‐Physical‐System applications demand compact power converters, which require inductors to have small footprints but considerable power handling abilities. 3D air‐core tubular inductors fabricated using the self‐rolled‐up membrane (S‐RuM) technology have demonstrated significantly higher inductance density compared to conventional planar structures. However, previous design options and associated performance are constrained by the resistive loss due to the thickness of the metal and magnetic coupling limited by the air core. Here, the study reports a post‐rolling electroplating scheme aimed at enhancing the metal conductivity and core magnetic permeability in S‐RuM inductors, all while maintaining their compact footprint. A DC resistance improvement of over 10X and an inductance enhancement of over 30X are achieved by the 3D S‐RuM inductors, via parallel‐processed Cu‐electroplated strips on the cylindrical shells and partially permalloy‐electroplated core. The improvement is projected to continue to improve as the entire core is filled. This advancement paves the way for scalable applications of this technology in ultra‐compact, low‐loss passive power electronics, such as converters and filters. [ABSTRACT FROM AUTHOR]

One of the early design decisions for DC‐DC converters is the choice of an appropriate magnetic core material. Powder cores in particular are suitable due to their saturation flux density of up to 1.5 T. However, high DC currents constitutes a significant problem since the winding cross‐section rises with the current, which consequently increases AC losses due to skin effects. Another challenge is the reduction of winding layers to decrease proximity losses. This paper presents an improved single‐layer winding design procedure for DC‐DC converter powder cores. The procedure determines the optimum number of parallel cores and stacks. This way, the procedure enables a predefined maximum wire cross‐section for copper loss optimisation and single‐layer winding. The introduced approach defines the optimum switching frequency as a trade‐off between core loss and core volume. Finally, experimental tests with two setups validate 27 kW DC‐DC converters and hence the design procedure using Si‐IGBTs and SiC‐MOSFETs. The results demonstrate that SiC‐MOSFETs reduce core volume by a factor of 3 compared to Si‐IGBTs. Further, the SiC setup reaches high efficiencies of up to 98.53% compared to 98.17% for the Si‐based converter. [ABSTRACT FROM AUTHOR]

According to the structural characteristics of the spiral inductor wound by rectangular cross-section wire, a calculation model of pulse spiral inductor was established. A design method of pulse spiral inductor was presented, which takes inductance value, spatial size, and temperature rise as constraints, takes the volume, resistance and external magnetic flux density of the pulse spiral inductor as optimization objectives, adopted hierarchical screening method and weighted summation method to obtain the optimal number of spiral inductor turns. A $16~\mu $ H pulse spiral inductor for a pulsed power supply (PPS) was designed. Finally, the pulsed spiral inductor was manufactured according to the design size and the discharge test was carried out for several times, the structure of the pulse inductor was complete after the tests, and the experimental pulse current was consistent with the simulation current. The experiment shows the effectiveness of the pulse spiral inductor design method and has a strong practical significance.

In this study, the origin of growth pits on the surface of 4H-silicon carbide epitaxial films grown using a chemical vapor deposition reactor was clarified by evaluating the surface morphology of substrates immediately before the epitaxial growth and of epitaxial films. When the film was grown under non-optimized conditions, we found that numerous Si particles were formed on the surface of the substrate before the epitaxial growth and that the numerous growth pits on the subsequently grown epitaxial film were originated from Si particles. We observed that, by increasing the HCl flow rate through the outer nozzles in the gas inlet, which has a double-pipe structure consisting of inner and outer nozzles, the growth pit density was successfully decreased. [ABSTRACT FROM AUTHOR]

This paper presents a control technique for flying capacitor multi-level (FCML) converters to achieve zero-voltage switching (ZVS) across the full range of duty cycles, with application in high power density and high efficiency power converters. Previous works have used variable frequency control to enable ZVS at specific duty cycles in FCML converters, but have not been able to use these methods to enable ZVS across the full range. This work uses dynamic level selection and variable frequency control to increase inductor current ripple at duty cycle ranges for which ZVS was previously unattainable. An experimental 5-level FCML prototype has been built using GaN devices on a single-sided PCB to demonstrate this control technique. We demonstrate 4-level and 5-level operation with ZVS at duty cycles that are not possible with 5-level operation alone, as well as a dynamic level transition with active capacitor voltage balancing.

Along with the commercialization of SiC‐MOSFETs and progress in the development of GaN power devices, high‐speed, high‐frequency switching and reduction in conduction loss of power devices are expected. Hence reduction of the size and increase of conversion efficiency of power electronics equipment is greatly expected. On the other hand, even if power devices are switched at high speed and high frequency, the loss of passive devices such as transformers, inductors, and capacitors used in power converters increases, making it difficult to make the power converters smaller than expected. In other words, there is a demand for performance improvements of passive devices from various viewpoints, including miniaturization and low loss, which are compatible with high‐speed, high‐frequency switching operations of power devices. This paper introduces recent research results on loss evaluation methods considering the operating state of passive devices used in small‐to‐medium‐capacity power converters those perform high‐frequency switching operations. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This article analyzes the problem of modeling the properties of such magnetic elements as inductors, coupled inductors, and transformers using the SPICE software (version 17.2). Both the classical models of magnetic elements, built in this software, and the models implemented in the form of subcircuits are described. In particular, attention was paid to the possibility of taking into account the non-linearity of the characteristics of the considered elements and mutual couplings between electrical, magnetic, and thermal quantities. Using the results of thermographic measurements, the need to take into account the differences in temperature values between the individual windings and the core of inductors and transformers was justified. Selected models of the considered elements given in the literature are briefly characterized. The network structures of the electrothermal models of the considered elements elaborated at Gdynia Maritime University are presented. The results of calculations and measurements illustrating the correctness of the described models and their prac-tical usefulness for the elements of different structures are presented and discussed. [ABSTRACT FROM AUTHOR]

Interventional magnetic resonance imaging (MRI) could allow for diagnosis and immediate treatment of ischemic stroke; however, such endovascular catheter-based procedures under MRI guidance are inherently difficult. One major challenge is tracking the tip of the catheter, as standard fabrication methods for building inductively coupled coil markers are rigid and bulky. Here, we report a new approach that uses aerosol jet deposition to three-dimensional (3-D) print an inductively coupled RF coil marker on a polymer catheter. Our approach enables lightweight conforming markers on polymer catheters and these low-profile markers allow the catheter to be more safely navigated in small caliber vessels. Prototype markers with an inductor with the geometry of a double helix are incorporated on catheters for in vitro studies, and we show that these markers exhibit good signal amplification. We report temperature measurements and, finally, demonstrate feasibility in a preliminary in vivo experiment. We provide material properties and electromagnetic simulation performance analysis. This paper presents fully aerosol jet-deposited and functional wireless resonant markers on polymer catheters for use in 3T clinical scanners.

In the traction system of rolling stock, the common-mode (CM) voltage is over 500 V, so the inductors that suppress the CM current are prone to saturation. To prevent saturation, the traction inverter needs many numbers of cores inside CM inductors, but the required number of cores has been determined empirically. This paper proposes a method calculate the approximate number of nanocrystalline cores to avoid saturation of CM inductors in railway traction inverters without circuit simulation. Using the only the CM capacitance of traction motor and the core characteristics on the datasheet, the maximum flux density of the inductor is calculated. Comparing calculated results of the maximum flux density with the results measured with a 1500 V DC inverter indicates that the proposed method can better identify the occurrence of saturation than the methods based on CM current presented in the literature. Furthermore, for the entire CM voltage range from 500 V to 3000 V, the minimum number of cores which saturation is prevented by the proposed calculation method is shown to be in reasonable agreement with the simulation results.

In this paper, the application of regression-based supervised machine learning (ML) methods to the modeling of integrated inductors and transformers is examined. Different ML techniques are used and compared to improve accuracy. However, it is demonstrated that none of the ML techniques considered provided good results unless a smart modeling strategy, tailored to the specific design problem, is used. Taking advantage of these modeling strategies, high accuracy can be obtained when compared to full-wave electromagnetic (EM) simulations (less than 2% error) and experimental measurements (less than 5% error). The most accurate model, obtained by the appropriate combination of an ML technique and modeling strategy, has been integrated into a tool called PACOSYT. The tool uses optimization algorithms to allow the designer to obtain an inductor/transformer with optimal performances in just seconds while keeping the accuracy of EM simulations. Furthermore, the tool provides the passive component S parameter description file for seamless use in circuit simulations. The tool can be used standalone or integrated with design frameworks, like Cadence Virtuoso or AIDASoft, a framework for circuit optimization. To illustrate the different usages of the tool, several passive devices are synthesized, and hundreds of millimeter-wave power amplifiers are synthesized using AIDASoft together with PACOSYT. The tool has been developed using open-source Python frameworks and does not use any closed-source licenses. PACOSYT, which also allows other designers to create their models for different technologies, is made publicly available.

This study focuses on the loss of inductors in a multiphase bidirectional chopper, which is a DC-DC conversion system. The current at the inductors in a multiphase bidirectional chopper consists of a DC current equivalent to the load current and an AC current called ripple current. The discussion regarding the effect of the increased number of phases should include the loss due to the ripple current, which is caused by semiconductor switching. Therefore, this study clarifies the loss due to the ripple current from an experiment with an increase in temperature. From the extraction of AC loss from the total loss, it is demonstrated that the loss due to the ripple current is equivalent to the no-load loss in the multiphase bidirectional chopper. When the number of phases increases, the load loss decreases whereas the no-load loss increases. This relationship indicates that an optimal number of phases exist according to the load current. This study deduces an analytical solution for the optimal number of phases and applies the methodology for determining the optimal number of phases to an actual onboard bidirectional chopper for an onboard energy storage system and traction system as an example. The optimal number of phases differs depending on the application.

Inductor designs with large dc current relative to ac ripple are often constrained by saturation, which limits their size, loss, and current-carrying capability. Typical saturation-limited designs, though, further handicap their performance by substantially underutilizing their core material's flux carrying capabilities. Instead of operating the core across its full flux swing range from reverse saturation to forward saturation, these designs only use half the range. To use the full range, we propose a permanent magnet (PM) hybrid core in which a PM provides a dc flux offset in the core, boosting its effective saturation capability. In the proposed core, the PM is placed outside of the main winding flux path to reduce losses and risk for PM demagnetization. In this work, we derive first-order theory for analyzing and designing the PM hybrid core. We then provide some example PM hybrid core implementations. Finally, we demonstrate a working proof-of-concept prototype using off-the-shelf parts that outperforms two comparable ferrite inductor designs. This PM hybrid core prototype achieves half the dc resistance of a ferrite inductor with the same energy storage, and it achieves 70% more energy storage than a ferrite inductor with the same dc resistance. The prototype's improved performance thus demonstrates the potential advantages of the PM hybrid core.

Summary: High‐frequency characteristics of passive components are crucial to the electromagnetic compatibility (EMC) of an electronic system, and modeling of passive components is of significance for EMC analysis. However, challenges remain in the modeling of passive components with multiple resonant frequencies. In this paper, a method for establishing equivalent models of multi‐resonant frequency passive components, including capacitors, inductors, and resistors, is proposed. Firstly, high‐frequency equivalent circuit topologies of the multi‐resonant frequency passive components, which are simple, easy to understand, and can be applied to the modeling of passive components with various impedance characteristics, are developed. Secondly, a calculation method of equivalent circuit parameters based on least squares and particle swarm optimization (PSO) is presented, which is not sensitive to the initial value, only needs the estimated range of the equivalent circuit parameters, and very suitable for getting the parameters of equivalent circuit models accurately and efficiently. Finally, to validate the method, some SPICE models of single components are established, and a PCB‐level EMC analysis is implemented. The comparisons of the simulated and experimental results show the validity and accuracy of the method. The method is very useful for future components modeling when doing EMC design or other high‐frequency designs. [ABSTRACT FROM AUTHOR]

This article proposes a novel control for the multiple-input, single-inductor, multiple-output dc–dc converters. It is digitally and discretely implemented, which can have an outstanding performance in low-power applications so that at the power of 10 mW, it has an efficiency of 92.5%. Conventionally, in this power range, an attempt is made to take advantage of an analog design that is flexible. Thus, a fully programmable (software designed) converter with digital design using a microcontroller is in great demand. This converter design basis is to deploy the microcontroller's central processing unit (CPU) as little as possible. Also, it only turns on the CPU when necessary to be employed in low-power, portable systems, e.g., energy-harvesting technologies. Therefore, construction costs are significantly reduced. Depending on the energy level of the inputs, they can simultaneously be utilized to charge the outputs. This article uses stability analysis, time-multiplexing control method, and variable-frequency pulsewidth modulation in the proposed control design. Each output can be charged with different frequencies according to its load, and the maximum switching frequency is equal to 10 kHz. Also, the proposed technique for zero-current switching has been digitally implemented; it can be utilized to determine the optimal value of the inductor discharge duty cycle based on the inductor's left-side voltage. Comparative simulations and experimental results reveal the superiority and practicality of the proposed approach. [ABSTRACT FROM AUTHOR]

Zero voltage switching (ZVS) of power semiconductor devices is an effective way to improve the efficiency and power density of the power electronic converters with extremely high switching frequency. This article aims to analyze and realize the true full-range ZVS operation of a totem-pole power factor correction circuit. The available ZVS control strategies are investigated, and the conditions for the realization of full-range ZVS operation are analyzed. It is revealed that the existed control strategies did not consider the influence of the dead-time, resulting in the failure of ZVS operation in some input voltage ranges. To address this issue, two feasible retrofitted control strategies, namely the turn-off current optimization control and the adaptive dead-time control, are proposed. The merits and drawbacks of the two control strategies are carefully analyzed and compared. It is found that the adaptive dead-time control can not only achieve the true full range ZVS but also significantly reduce the loss of the freewheeling diodes. The design consideration of key parameters is discussed. Finally, the feasibility of the proposed control and the correctness of the theoretical analyses are verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

This article proposes a new voltage-balancing dual-active-bridge (VB-DAB) converter for the bipolar dc distribution system. The proposed converter comprises the same components as those of the conventional DAB converter, and it integrates functions of a VB without additional components. The proposed converter transmits power using the same principle and control as the conventional DAB converter. Furthermore, it regulates both output voltages equally and redistributes the unbalanced load current. Therefore, the proposed converter neither requires additional components nor results in losses by them. Consequently, it can achieve high efficiency and high power density. The effectiveness of the proposed converter is verified by 3-kW prototypes with a 380-V input and ±190-V outputs conditions. [ABSTRACT FROM AUTHOR]

In this article, a coupled-inductor (CI)-based bidirectional dc–dc converter with a high voltage conversion ratio (VCR) and low voltage stress is proposed. The topology can achieve high VCR by employing two CIs; moreover, the interleaved technique overcomes the defect of large current ripple in CI. A sensorless current balance between the two CIs is also realized without an auxiliary circuit and complex control method. The pulsewidth modulation plus phase-shift control is employed, where the duty cycle D is used to adjust the VCR, and the phase-shift angle ϕ is used to control the direction and amount of the transferred power. In addition, all switches can achieve soft-switching under a wide operation range. The steady-state analysis of the proposed converter is analyzed in detail, followed by comprehensive experimental verification under a 1-kW prototype. [ABSTRACT FROM AUTHOR]

Electrolytic capacitors used in adjustable speed drives (ASDs) are affected more by low-frequency currents than high frequency. It is shown in this article that even-ordered harmonics in the supply voltage create a 150 Hz current component in the dc bus, and impact the heating in the capacitor. It is further shown that the total harmonic distortion of the current drawn by the ASD is adversely affected due to the even-ordered harmonics. This article discusses a cost-effective approach based on suitable triggering of the silicon controlled rectifiers (SCRs) in the bridge of ASD to suppress the effect of even-ordered harmonics on capacitor ripple current and source current. Using parameters taken from capacitor datasheets, and the supply voltage characteristics from field studies, exhaustive simulation studies are presented to identify an approach to the determination of various thresholds required. The applicability of the method to the ASDs of various power levels is also presented. The proposed strategy is analyzed by simulations under different grid impedance and harmonic combination cases and validated by a hardware test setup. [ABSTRACT FROM AUTHOR]

A conventional asymmetric half-bridge (AHB) conve rter with zero dc offset current of the transformer at any operating points was proposed. It has low-voltage stresses on the two diodes that are clamped to the output voltage. However, for a wide input voltage range, it can have a small nominal duty ratio that causes to large conduction loss at the maximum input voltage. Moreover, it has high-voltage stress on one of the secondary diodes that leads to high power loss. In order to improve these problems, in this article, an AHB converter with an integrated boost converter is proposed. The proposed converter has identical operation to the conventional one as well as boost operation for the wide input voltage range. Thus, it has a large nominal duty ratio and low-voltage stress on the secondary diode at the maximum input voltage. Moreover, it has zero dc offset current of transformer and higher efficiency over the entire input voltage range compared with the conventional converter. The proposed converter has been verified for a laboratory prototype with 200–400 V input and 50 V/300 W output. [ABSTRACT FROM AUTHOR]

This article proposes a unidirectional high step-up dc–dc converter. The study approaches principle of operation, analysis, guide design, and experimental validation. The high-voltage gain is reached using coupled inductors and voltage multiplier cells (VMC). An interleaved structure of two phases is employed to provide a low-current ripple in the input side. The current balance between the phases occurs due to the insertion of a built-in transformer, which also contributes to increasing the voltage gain. The energy from the leakage inductances is reused, reducing voltage spikes across the semiconductors. Additionally, the proposed converter provides an input–output common ground, which is a requirement for many applications. To verify the proposed converter, a 1-kW prototype, 48–800 V, and 16.67 of voltage gain, was designed and tested. The maximum peak efficiency reached was 94.89% and the rated power efficiency was 93.86%. [ABSTRACT FROM AUTHOR]

Applying the recycled power battery to automatic guided vehicles can greatly reduce system cost and prolong the life cycle of the battery. However, the consistency of recycled power batteries is poor, and the imbalance of battery voltage will occur during the charging or discharging process. Therefore, a double-switch single-transformer integrated equalizer is proposed to balance automatic guided vehicles in both charging and discharging operations. The equalizer's multiwinding transformer shares the dc–dc converter's inductor, and the secondary side generates current by utilizing the current ripple on the primary windings. The battery string is balanced by the multiwinding transformer, without extra switches, when the circuit works in charging and discharging mode. A prototype for four battery cells is built to verify the proposed equalizer and its dynamic balance conditions, and a comparison with existing equalizers is presented. The results show that the system in both modes can realize the automatic balance without affecting the function of the dc–dc converter. The proposed circuit requires fewer components than the existing bidirectional integrated equalizer. [ABSTRACT FROM AUTHOR]

A passive current sharing method for paralleled LLC resonant converters is proposed in this article, and the current sharing effect of paralleled common capacitor LLC resonant converter is analyzed. The passive current sharing method is achieved by adding coupled impedance between the LLC resonant converters, and the coupled impedance can be inductive, capacitive, infinitely small, and infinitely large. Among them, it is traditional paralleled LLC resonant converter without current sharing ability when the coupled impedance is infinitely large. First, the mathematical model of paralleled common capacitor LLC resonant converter with coupled impedance is built based on fundamental harmonic analysis. Second, according to the mathematic model, the current sharing effect of the paralleled common capacitor LLC resonant converter of different coupled impedance under different parameter difference is analyzed, it is easy to see the current sharing effect is improved after the couple impedance is added, and in general, inductive coupled impedance has a better current sharing effect for paralleled common capacitor LLC resonant converter. Last, the theoretical analysis results are verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

In a dc microgrid, a bidirectional dc–dc converter is an essential link between voltage bus and energy storage system (ESS). When galvanic isolation and high efficiency are required, dual active bridge (DAB) converter is preferred. Due to the instability of renewable energy sources, the DAB converter may transmit high or low power to ESS. To improve the efficiency across wide power range, this article proposes a reactive power minimization and soft switching optimization algorithm that combines the augmented Lagrangian method and triple-phase-shift (TPS) modulation. Unlike an offline algorithm with look-up table, the proposed algorithm can compute phase-shift-angle online, avoiding a large database for various working conditions. A prototype with an 800 W rated power is built, and the efficiency test results validate the efficiency improvement over other TPS-based algorithms. Furthermore, a current regulation experiment demonstrates that the proposed algorithm is suitable for ESS charging, which must deal with varying output voltage and power demand. [ABSTRACT FROM AUTHOR]

Wireless power transfer systems require compensators to improve efficiency by increasing transfer power between transmitter and receiver. The most commonly used compensators are series-series (SS), series–parallel, and double-sided LCC. This article analyzes the comparison between typical compensators focusing on transfer efficiency. Due to these characteristics of typical compensators, a hybrid compensation topology is designed based on two compensators. Hybrid compensation topology is capable of switching between SS and double-sided LCC topologies. Two ac switches are used on the transmitter and receiver for switching mode in hybrid compensation topology with wireless communication links, and its variation algorithm is clarified. A novel compensation topology guarantees system’s efficiency for a wide range of loads based on the maximum efficiency of two compensation topologies. The possibility of a proposed hybrid compensator is verified with an experimental prototype used for massive vehicles. [ABSTRACT FROM AUTHOR]

A linear-resonant hybrid bridge dc–dc converter is proposed in this article. The converter adds a set of linear-bridge-arm based on the traditional half-bridge LLC resonant converter. This converter can operate in a high-voltage-gain (HG) mode and a low-voltage-gain (LG) mode by adopting pulsewidth modulation strategy and pulse frequency modulation strategy respectively. In the HG mode, it can control the inductor current increasing linearly by the linear-bridge-arm to obtain higher voltage gain and wider output range than the traditional LLC resonant converter, and the voltage gain is less affected by the magnetizing inductor. In the LG mode, the voltage gain characteristics of the proposed converter are similar to that of the traditional LLC resonant converter. The proposed converter works with negligible feedback current. In addition, all power switches can realize soft-switching in a wide load range. The working principle, voltage gain, design approach, and topologies comparison are introduced in this article. Finally, an experimental prototype based on constant current and constant voltage charging was built, with 400 V input voltage, 180–310 V output voltage, and 0–4.5 A output current. The experimental results verified its feasibility. [ABSTRACT FROM AUTHOR]

In switched-capacitor (SC) based multilevel inverters (MLIs), capacitors are usually replenished by a dc voltage source or other capacitors, inrush charging current are found at switching instants. In order to solve this issue, this article presents a new type of step-up MLIs, which is implemented by using a front-side quasi-Z-source unit to feed SC-based multilevel circuits. As a result, the charging current variation of capacitors is effectively limited by the quasi-Z-source impedance. Moreover, the charging voltage can be regulated by controlling the duty ratio of shoot-through states of the quasi-Z-source unit, and the total voltage gain of the new MLI is enhanced as both SC and quasi-Z-source units have boost capability. Structurally, the two units share a common switch network so that the new MLI has simple structure. Topologies for single- and three-phase configurations, operation, and modulation, as well as the parameter design are analyzed in detail. Finally, the feasibility of the new MLI is verified experimentally by a downscale three-phase prototype. [ABSTRACT FROM AUTHOR]

This article presents a highly reliable push–pull resonant dc/dc converter for medium-power applications. At medium power, conventional push–pull resonant dc/dc converter experiences a very high current spike at the secondary-side switches, and this spike can destroy the active power components. We eliminate this current spike by connecting clamp diodes to the resonant capacitors. Moreover, the proposed converter achieves fully zero-voltage-switching (ZVS) turn-off at the secondary-side switches when the load exceeds the threshold. Furthermore, the proposed converter is invulnerable to the short-circuit problem at the output. Experimental results are presented to show the effectiveness of the proposed dc/dc converter at the medium power against a conventional solution. [ABSTRACT FROM AUTHOR]

This article introduces a new nonisolated soft-switching coupled-inductor (CI) step-up dc/dc converter. The presented topology utilizes a three-winding CI (TWCI) along with a voltage multiplier circuit to increase the voltage conversion ratio without needing a high duty cycle. Using this circuit, a high voltage gain can be achieved without requiring a large number of turns ratio in the CI. The input current ripple of the introduced converter is very low, which is very desirable for renewable energy sources applications. The TWCI also creates an additional design freedom to increase the voltage gain, which indicates more circuit flexibility. Additionally, the voltage stress across the single power switch is limited with the help of a regenerative clamp capacitor. The leakage inductor of the CI is used to create a resonant tank to reduce power losses further. The leakage inductances help provide the zero-current switching conditions for the single power switch and decrease the reverse-recovery issues for all diodes, leading to an efficiency improvement. The operation principle, steady-state analysis, and design considerations are discussed thoroughly. Finally, the theoretical analysis is validated through experimental results obtained from a 200 W prototype with 250 V output voltage. [ABSTRACT FROM AUTHOR]

Three-level boost dc–dc converters present several advantages in comparison with conventional boost converters, such as reduced switching losses, lower voltage ratings for the diodes and switches, and smaller size of reactive components. The topology requires three voltage levels at the output, therefore, replacing the output capacitor of the traditional boost converter with two capacitors and a midpoint. However, due to component tolerances and/or current flowing through the midpoint, output capacitors voltages become unbalanced, leading to converter malfunctioning or destruction. To overcome this issue, an exact feedback linearization control strategy is proposed, for which an implementation with minimum sensors is obtained. Analyses of its performance at different input voltages and of its robustness against component variations are included. Simulation results are provided, showing a comparison of the proposal with a conventional control strategy and its steady-state performance with nonlinear loads. The proposed control strategy was implemented in a low-cost microcontroller unit and, experimental verification is included. [ABSTRACT FROM AUTHOR]

A dual-transformer-based hybrid dual active bridge (DAB) converter for plug-in electric vehicle charging to cope with wide load voltages is introduced in this article. The control degrees of freedom are extended by splitting the leg and transformer of the conventional DAB converter (CDABC) in two parts. Based on the numerical analysis, the full-domain four-variable closed-form optimal trajectories targeting at the minimum root mean square value of the leakage inductor current is attainted, and the unified-segmental control strategy is proposed to handle the working modes shifting without the current inrush. As a result, the conduction losses and switching losses can be significantly reduced in boost mode compared to CDABC. The discussed converter and control strategy are verified by a 1.0-kW prototype. [ABSTRACT FROM AUTHOR]

Bidirectional dc–dc converter (BDC) is an integral part of energy storage interface, where high efficiency, high voltage transfer ratio and small input ripple current are essential for application, such as dc microgrid and electric vehicle. In this article, a new approach is proposed to achieve reduced input ripple current at the low voltage side, which potentially replaces the necessity of using interleaved circuit structure. Parallel coupled inductor and capacitor circuit are utilized for charging and discharging the two parallel paths in a complementary fashion using a mosfet. The proposed solution helps to increase the voltage conversion ratio unlike interleaved structure. Additionally, in proposed BDC, zero voltage switching turn on operation of all active switches are possible utilizing synchronous rectification principle in both the operating modes. Parallel path structure not only reduce the input current ripple, but also helps to share the input current, thereby reducing the coil size and associated losses. A 250 W BDC is designed to validate performance in 1kW dc microgrid system [ABSTRACT FROM AUTHOR]

Slow load transient performance, potential cross-regulation, and low efficiency are the major drawbacks for pseudocontinuous conduction mode single-inductor dual-output (SIDO) dc–dc converters. To overcome these drawbacks, this article proposes a voltage-ripple (VR)-based dynamic freewheeling (DF) control technique for hybrid conduction mode (HCM) SIDO buck converter. With the employment of VR controller, the proposed control technique improves the load transient performance significantly. As the fast recovery during load transition, the cross-regulation is minimized. Additionally, due to the DF controller, the freewheel current value automatically updates in each switching period, which can improve the efficiency of the HCM SIDO buck converter, especially under the light load conditions. Finally, the proposed converter has been verified through experimental results. The transient response time on 0.5 A load change takes only 1–2 switching periods. No observable cross- regulation is found and maximum efficiency of 92.03% is achieved. Finally, the experimental waveforms are presented to verify the theoretical research. [ABSTRACT FROM AUTHOR]

In this article, a new efficient soft-switching synchronous rectification (SR) buck converter is proposed, which is without voltage stress increment for all switches and diodes. By introducing an auxiliary circuit to the SR buck converter,the soft-switching condition is achieved within the wide range of load power for the power semiconductor devices. The auxiliary network, which consists of capacitor, inductor, switch, and three diodes, provides a zero-voltage condition for main switch and SR switch at both the turn-on and the turn-off instant. Besides, the auxiliary inductor creates a zero-current turn-on and a zero-voltage turn-off condition for the auxiliary switch. Considering the resonance between the parasitic capacitors of the semiconductor components and the auxiliary inductor, two diodes are designed to avoid the additional voltage stress on power devices. The operating principle of this proposed converter is analyzed. A 600 W prototype is implemented to test the soft-switching operation. The advantage of the proposed converter is demonstrated by the efficiency curve over a wide range of load power against the conventional SR buck converter. [ABSTRACT FROM AUTHOR]

A flexible dc grid is important for supporting large-scale new energy integrations. To ensure the stable operation of the dc grid, a dc circuit breaker (DCCB) is needed for fault isolation. At present, the cost of DCCBs is high, and the breaking capacity is limited. This limitation can be effectively solved through the coordination of fault current limiters (FCLs) and DCCBs. In this article, a coordinated interruption topology of an magnetic coupling FCL (MCFCL) and hybrid DCCB is proposed. A coordinated interruption strategy based on magnetic coupling current-limiting and energy dissipation is proposed to improve the dynamic performance of the FCL and reduce the energy dissipation and breaking time of the DCCB. A two-stage mathematical model of coordinated interruption is established, and its control principle is analyzed. Furthermore, the influence of the inductance and resistance of the MCFCL secondary side, coupling coefficient and rated voltage of the arrester on the coordinated interrupting process is researched. On this basis, parameter optimization and economic analysis are carried out. Finally, a scaled test for the coordinated interruption of the DCCB and MCFCL was carried out, which verifies the feasibility of the coordinated interruption strategy based on magnetic coupling current-limiting and energy dissipation. [ABSTRACT FROM AUTHOR]

To optimize the voltage regulation performance and enhance the robustness, an adaptive model predictive controller is proposed in this article for an interleaved dc–dc boost converter. The predictive model is constructed by linearizing the nonlinear equations of the converter at the current operating point. A novel parameter update mechanism is developed based on the static model, which enables fast and accurate identification of the model parameters, thus the control law can guarantee the desired control performance in the wide operating range. Based on the adaptive model, a disturbance observer is constructed to correct the model predictions and mitigate parameter uncertainties. Then an explicit control law is derived by solving the optimization problem offline, and the stability analysis is carried out using the linear control theory. Finally, the effectiveness of the proposed method is verified by both simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this article, a single-switch continuous input current (CIC) buck–boost converter with noninverted output voltage is proposed. The proposed converter utilizes capacitor and inductor along with three diodes in conjunction with a quadratic boost converter to adopt its CIC feature. The features of high voltage gain, single active power switch, less ripple CIC, and noninverted output voltage make the proposed converter suitable for renewable and industrial applications. In addition, it provides a wide operating voltage gain with optimum component count, which is higher than the conventional buck–boost converter. Furthermore, it has low voltage stress across the power switch with comparable converters. To elevate the importance of the proposed converter, a detailed comparison analysis has been carried out considering voltage stress, voltage gain, effectiveness index, and component count. The operating principle and steady-state analysis in continuous conduction mode and discontinuous conduction mode of the proposed converter are discussed in detail. To validate the theoretical analysis and performance of the proposed converter, a prototype has been developed and tested in laboratory. [ABSTRACT FROM AUTHOR]

DC–DC converters with a wide input voltage range have earned numerous daily applications in the industry. An example is power systems for electric vehicles, where $LLC$ converters with remarkable features have also been deployed to provide isolation. It is, therefore, common to find a front buck converter cascaded to a back $LLC$ converter, where their intermediate bus voltage is set low to accommodate the lowest input voltage to the buck converter. Unfortunately, this causes efficiency to drop at a high input voltage. To avoid the drop, a reconfiguring strategy has been proposed to convert the front buck converter from full bridge to half bridge, as its input voltage rises above a specified threshold. Furthermore, to ensure a smooth and fast reconfiguration, a dynamic control method has been proposed to direct the intermediate bus voltage to track a reference trajectory with a lower current surge. Besides, the method employs pulse-shift modulation to keep a stable output voltage and proper control initialization to prevent oscillation during the transition. These favorable features and an overall higher efficiency have subsequently been verified through experimental testing with a wide input voltage range. [ABSTRACT FROM AUTHOR]

Hybrid ac/dc off-grid topologies offer the combined advantage of higher energy efficient dc loads, and existing low-cost ac loads. Such budding topologies tender a promising solution for rural electrification when supplied from solar power along with battery backup. The desirable features of such a scheme for catering household appliances are: low semiconductor count, continuous current ports for PV, battery and dc load, low-voltage levels for PV and battery, dc and ac load voltage regulation, maximum power point tracking, battery overcharge and deep-discharge protection, high-voltage boosting sans low-frequency transformer, and reduced power converter stages. The schemes reported in the literature lack one or more of these features. To address this concern, a hybrid ac/dc scheme is proffered. The first stage is formed by a novel three-switch four-port converter, which facilitates most of the aforesaid features required in a hybrid system. The remaining features are obtained using a conventional dc–ac converter, which forms the second stage of the proposed solution. The overall solution is substantiated through comprehensive analysis and experimental demonstrations using a 400 W experimental prototype. [ABSTRACT FROM AUTHOR]

In this article, a power-split-based wireless charging system (WCS) with communication-free coordination control is proposed to combat wide load and coupling variations. By using a magnetic integrated inductor, two power delivery channels are created from a single receiver coil. Large portion of received energy is directly delivered to the load. Small amount of energy is converted by using a low-voltage low-power dc–dc converter to regulate the output voltage or current achieving constant voltage (CV) or constant current (CC) charging operation. This proposal achieves higher power conversion efficiency than the traditional two-stage cascaded converter WCS. Since the dc–dc converter only processes partial power of the WCS system, this proposal reduces the voltage stress of the devices and design difficulty. A communication-free coordination control is applied, which is established by sensing the input current drop caused by the burst operation of the partial-power dc–dc converter. Thus, the CC-CV charging is realized by PWM control at the receiver (Rx) side, and the inverter is regulated with subharmonics control scheme to maintain nearly constant Rx coil current. Simulation results for both high-voltage high-power scenarios and low-voltage low-power (LVLP) scenarios are provided to investigate the operation of the proposed WCS. Finally, experimental results are captured from a 250 W/60–84 V LVLP prototype to validate the feasibility and practicability of proposed concept. [ABSTRACT FROM AUTHOR]

An isolated dc–dc converter with dedicated 3-level modulation is proposed to achieve a 4:1 output voltage range, and complete zero-voltage-switching (ZVS) of all active switches using the magnetizing inductors. The single input 3-level modulation scheme coordinates the phase-shift, duty cycle, and switching frequency to ensure 1) the magnetizing currents are independent of load voltage and current; 2) the output voltage is proportional to the modulation input. As a result, the dual half- and full-bridge modes of the switching network are unified and modeled as a voltage-controlled voltage source, with the same control parameters for both modes of operation. In addition, the magnetizing-to-series inductance ratios of the leading and lagging transformers are increased to 100 and 25 times, respectively. Therefore, the circulating current is low, and the series inductors can be integrated into the transformers. The proposed topology is intended for high-power applications with a wide output voltage range but less input voltage variation. A $\text{30}\,\text{kW}$ prototype with a power density of $\text{7.2}\,\text{kW}/\text{L}$ and an output voltage of $\text{165}\,\text{V}$ - $\text{680}\,\text{V}$ was built and tested to verify the characteristics and feasibility of the proposed H8 topology plus modulation scheme. [ABSTRACT FROM AUTHOR]