High Current Power Research Articles

Effect of peak current on the microstructure, mechanical properties and tribological behavior of MoxN coatings deposited by high power impulse magnetron sputtering

The MoxN coatings are deposited by direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS). It is found that the MoxN coatings prepared by HiPIMS has a denser microstructure, higher hardness and wear resistance. Besides, the effect of peak current is investigated with respect to the microstructure, mechanical properties and tribological behavior of the coatings. As the peak current increases, the cross-sectional morphology of the coating transforms from featureless to columnar morphology, and the preferred orientation of the coating gradually transfers from (111) to (200). However, the hardness of the coating is not significantly influenced by the peak current. The MoxN coating with a peak current of 260 A owns a low friction coefficient of 0.28, which is better than that of the MoxN coating prepared by DCMS. The MoxN coating with a peak current of 300 A provides excellent wear resistance with the lowest wear rate of 5 × 10−8 mm3/(Nm).

F-Type Single Phase Five Level Inverter

In modern industrial and power electronics applications, high-voltage and high-current integrated modular power transistors (IGBTs) are increasingly being utilized. The F-type inverter, which is a modified version of the T-type inverter, has emerged as a promising option. This configuration separates the common point of the bidirectional power switch, reducing voltage stress and resulting in lower inverter costs and losses. The F-type inverter has a simplified design and lower conduction losses, making it a viable choice for medium-voltage applications compared to the clamp diode NPC inverter configuration. Detailed analysis of losses and efficiency has been conducted, and a simulation and experimental prototype have been built to validate the theoretical basis. In addition, the voltage rating of the power switches in the T-type three-level inverter is a limiting factor, as it is only 50% of the input DC voltage for each inverter phase leg.

Oxidation and wear behavior of CrAlMoN with varied Mo-content for cutting Ti6Al4V

The cutting of difficult to machine materials such as titanium alloys is challenging for the machining industry. In case of the titanium alloy Ti6Al4V, the properties of the material cause high temperatures, mechanical loads as well as high frequency vibrations at the cutting edge, leading to premature tool failure. The use of uncoated carbide tools is very common for machining of Ti based alloys. However, temperature active, self-lubricating physical vapor deposition (PVD) coatings like CrAlMoN showed promising results to reduce friction and wear during turning of Ti6Al4V. In the present study, self-lubricating (Cr34Al41Mo25)N, (Cr29Al36Mo35)N and (Cr25Al31Mo44)N coatings were investigated on cemented carbide tools. These were deposited by a hybrid process combining direct current Magnetron Sputtering and High Power Pulsed Magnetron Sputtering. Coating morphology, thickness, chemical composition, indentation hardness and modulus at ϑ = 20 °C, ϑ = 200 °C, ϑ = 400 °C and ϑ = 600 °C as well as the oxidation behavior were analyzed. Moreover, wear development after cutting tests using a CNC-lathe was investigated. Independent of Mo-content, all coating variants possessed a dense morphology and a smooth surface topography, as well as a coating adhesion class of HF1 to the cemented carbide substrate in Rockwell indentation tests according to DIN 4856. With an increasing amount of Mo, heat treatment temperature and time, more self-lubricating molybdenum oxides such as MoO3 and Mo4O11 were detected by Raman spectroscopy. Therefore, the coating with the highest amount of Mo possessed the highest amount of molybdenum oxides. After cutting tests, molybdenum oxides were also found on the tool flank face by Raman spectroscopy. The level of flank wear land width decreased with increasing amount of Mo.

A Region-Folding Electromagnetic Transient Simulation Approach for Large-Scale Power Electronics System

This paper proposes a region-folding electromagnetic transient simulation approach for large-scale power electronics systems to boost simulation speed. In the region-folding approach, the loop tear method is proposed to decouple the connections among power electronics blocks, the grouping and pre-calculating method of identical structural blocks is proposed to avoid computing the inverse of matrices repeatedly, and the global simultaneous response procedure is proposed to handle the simultaneous and multiple switching events. The implementation of the proposed approach is combined with high-performance parallelization technology to shorten the simulation time. The Modular Multilevel Converter (MMC)-based High Voltage Direct Current (HVDC) model and DC photovoltaic power station model are simulated respectively to validate the accuracy and efficiency. Simulation results indicate that the proposed approach has the same accuracy as other Electromagnetic Transients (EMT) commercial software with better efficiency.

High Performance SiC Power Module Based on Repackaging of Discrete SiC Devices

Increased adoption of electric vehicles (EV), photovoltaic (PV), and battery energy storage systems (BESS) is driving the need for high-current SiC power modules. The state-of-the-art multichip module is substantially more expensive than the IGBT module. This paper proposes a cost-effective packaging methodology for high-power SiC intelligent power modules (IPMs) with discrete SiC devices. The proposed IPM integrates the gate drivers, decoupling capacitors, snubbers, discrete SiC devices, direct bond copper (DBC), base plate, temperature sensors, and overcurrent protection circuits, achieving very low loop inductance and thermal resistance, and more than 50% cost reduction. A 1200V/480A/2.15mΩ half-bridge IPM is presented for comparison with commercial counterparts. A 1200V/240A/4.3mΩ six-phase IPM is developed, and its performance is experimentally verified.

Dynamic Perovskite Homojunction Based Light‐Assisted, Direct Current Tribovoltaic Nanogenerators

AbstractTribovoltaic nanogenerators (TVNG) are an emerging energy technology featuring high direct current density and continuous power output. Recently, a new kind of perovskite/metal Schottky‐based TVNG has attracted increasing attention, which can co‐harvest mechanical and solar energy to dramatically improve the DC output performance. However, the instability of the perovskite‐metal interface and unnecessary carrier recombination loss limit its practicability. Here, a novel light‐assisted TVNG based on a dynamic N‐type perovskite/P‐type perovskite homojunction is developed. The homojunction design can ensure stable interface contact, and contributes to forming a strong built‐in electric field to promote efficient carrier separation/extraction and decrease interfacial charge recombination loss. In addition, the innovative design of the dual perovskite functional electrode maximizes its photovoltaic characteristics and further facilitates the excitation of more charges based on tribo‐photovoltaic coupling effects. Eventually, the output voltage and current of dynamic perovskite homojunction can boost up to ≈8.72 V and ≈30.84 µA under illumination, showing outstanding performance among the state‐of‐the‐art perovskite‐based TVNGs. These findings demonstrate the great potential of perovskite materials in generating DC power and present a feasible strategy to construct efficient, multifunctional TVNGs.

Development of Exciter System for Power Supply driven HTS-MRI

Exciter systems is examined for helium free high-temperature superconducting (HTS)-MRI magnet. We have developed an active magnetic field stability control by use of a highly stabilized power supply instead of the persistent current operation. The magnetic field stability was measured and evaluated using a HTS-MRI test magnet under the power supply driving mode of a dropper-type and of a switching-type direct-current exciter system. A high stable direct current power supply is normally designed using the dropper-type power supply which is suitable for constant current operation of less current ripple. However, it is of large power loss and is not suitable for charging/discharging operation. On the other hand, the switching-type power supply is suitable for variable current control operation and of less power loss. However, it is of large current ripple in the constant current operation which would degrade the magnetic field stability in HTS-MRI imaging operation. The availability of the power supply system was discussed in MRI imaging of a mouse using an experimental HTS-MRI system. HTS-MRI imaging of mouse (~50 mm).

선박용 연료전지 시스템을 위한 대전류 전력변환기 개발

Several basic components of the fuel cell system for ships include a fuel cell stack, a power conversion system, a battery, and a control device. Polymer electrolyte membrane fuel cell(PEMFC) is considered the most important component in this system as it has a variety of advantages such as high-power density, fast response speed, and low operating temperature. However, a stable, high-efficiency boost converter must be manufactured to utilize it as a power source for ships due to several drawbacks like low voltage and a wide range of fluctuation and high currents. This paper aims to study the design and implementation of a high-current power conversion system utilizing an insulated resonance converter for the fuel cell system for ships. The proposed power converter in this study consists of a two-stage conversion structure, which incorporates a two-phase interleaved boost converter and a series resonance converter(SRC). The performance of the structure is verified by testing a 30 kW class unit module manufactured.

Research on mechanical properties and impact resistance of origami-based metamaterial for GIL

Gas insulated metal enclosed transmission line (GIL) is a high voltage, high current power transmission equipment, widely used in large hydropower stations, large-scale energy hubs and other occasions. Aiming at the shock environment that GIL may face, such as earthquake shock and water flow shock, a mirror folded mechanical metamaterial based on the Miura-ori patterned is proposed in this paper, and its mechanical responses and shock resistance performance were studied through the numerical simulation and experiment. The results showed that compared with the single-layer folded structure, the mirror connection mode increased the plastic hinge in the deformation process of the structure, causing the better energy absorption. Moreover, the parameters research indicated that reducing the plane angle and increasing the dihedral angle can improve the energy absorption. Most importantly, the structure can achieve more than 60% energy absorption under the impact load, showing a good buffer energy absorption effect. This paper can provide some significant reference and guidance for the impact resistance of the GIL in the practical engineering.

Passivity-Based Control and Current Balance Control of a Current-Source Pulse-Width-Modulation Rectifier

To improve the static performance, dynamic performance, and current balance of a current-source PWM rectifier with multi-modules, a comprehensive control method with passivity-based control and current balance control is proposed in this paper. Current balance control, which is based on AC voltage sequencing, has the advantages of being easy to implement and not being limited by the number of modules. Mathematical modelling, controller design, and simulation verification were conducted successively, and the results show that the comprehensive control method has a low current impact and high power quality. At the same time, module currents are well balanced, even under external disturbance, when using current balance control.

Structural, electrical and electron emission property studies of high dielectric constant (Pb0.88La0.12)(Zr0.65Ti0.35)O3 ceramics for ferroelectric cathode applications

Ferroelectric materials with high dielectric constant produce high electron emission and the life span of ferroelectric cathodes might be potentially increased if their piezoelectric charge coefficient can be made negligible. For achieving these properties, two different methods were employed to synthesize (Pb0.88La0.12)(Zr0.65Ti0.35)O3 (PLZT12/65/35) ceramics viz., the conventional method (mortar and pestle) followed by uniaxial pressing and the high energy, mechanical activation method (abbreviated to MA, hereinafter). This was done using a high-energy ball mill to reduce particle size drastically. Cold isostatic pressing was used to compact the milled powder which resulted in a significant increase in the density. X-ray diffraction confirmed single phase with cubic perovskite structure. Particle size was measured from TEM images. Morphological studies were carried out by SEM analyses to observe the grain structure. Of these two syntheses methods, PLZT 12/65/35 ceramics prepared via high energy ball milling exhibited significantly higher dielectric constant, surpassing the previously reported values and also exhibited low remnant polarization value, negligible piezoelectric charge coefficient at room temperature. High temperature dielectric measurements at various frequencies confirm the relaxor behavior of PLZT 12/65/35 ceramics. Ferroelectric cathode configuration based on PLZT 12/65/35 ceramics with high relative permittivity allowed us to achieve exceptionally high current density and power obtained in Radio frequency range.

Grid-Side Current Harmonic Suppression and Power Factor Improvement Using q – Axis Damping Current Injection for PMSM Drives Without Electrolytic Capacitor

The dc-link film capacitor with low-capacitance in permanent magnet synchronous motor (PMSM) drives without electrolytic capacitor will not only reduce the system stability, but also generate LC resonance with the grid-side filter inductor, which is the important reason for high grid side harmonic current and low power factor. In this paper, a grid side current harmonic suppression strategy using q-axis damping current injection is proposed to address these issues of PMSM drives without electrolytic capacitor. The analysis of the transfer function based on the simplified circuit of the drive shows the instability and LC resonance of the system. The feedforward modification method based on the difference between the quasi-dc-link voltage and the dc-link voltage is applied to improve the system performance. Meanwhile, the specific implementation of the proposed method by injecting damping current into the q-axis is introduced. In addition, a phase disturbance angle is introduced in the proposed control strategy to adjust the phase of quasi-dc-link voltage. By properly adjusting the phase disturbance angle, the conduction angle of the single-phase uncontrolled rectifier bridge can be effectively expanded, and the grid side power factor can be further improved. Experiments on a PMSM drive with the low-capacitance of dc-link film capacitor are carried out to verify the effectiveness of the proposed method.

Dead-Time Optimization and Magnetizing Current Design for a Current-Fed Dual Active Bridge DC–DC Converter to Secure Full Load Range ZVS in Wide Voltage Range

Current-fed dual active bridge (CF-DAB) converters are widely used because of the small input current ripple and high power density. This paper proposes the dead-time optimization methods and the magnetizing current design for a CF-DAB converter under the pulse-width plus phase-shift (PPS) control to achieve full load range zero-voltage-switching (ZVS) in a wide voltage range. In the ZVS analysis, the influence of junction capacitance and dead time is considered, including the dead-time effect on leakage inductance current, which can effectively explain that the CF-DAB converter under PPS control is difficult to achieve ZVS at light load in practice. Based on the analysis, it is first revealed that the CF-DAB converter under PPS control is not sufficient to achieve ZVS only by adjusting the dead time. Based on the new ZVS model and analysis of the dead-time effect, the magnetizing inductance design and dead-time optimization without adding extra control degrees of freedom and auxiliary components are proposed to achieve the full load range ZVS and improve the overall efficiency of the converter in a wide voltage range. Besides, to obtain the low root-mean-square (RMS) current, the design of DC inductance and leakage inductance are also investigated. Finally, a 1 kW prototype is built to verify the effectiveness of the proposed solution.

AlGaN/GaN superlattice-based multichannel RF transistors for high linearity and reliability: a simplified simulation approach

Multichannel RF power amplifiers offer high frequency operation, high current and RF power, combined with excellent linearity. 3D and 2D simulation is used to investigate how changes in device architecture impact both the linearity and off-state reliability, allowing an improved linear design which does not compromise reliability. Linearity is assessed by extraction of , and third order intercept (TOI) as a function of gate bias, using a straightforward 2D approximation which is computation time and resource efficient compared to the full 3D simulation normally used for these devices. Off-state reliability is assumed to be linked to dielectric failure, and hence peak electric field as a measure of reliability is evaluated at gate corners and edges using a full 3D simulation. It is found that introducing a channel number-dependent doping in the AlGaN/GaN-based superlattice structure can be used to enable an improved transconductance–linearity. It is also found that there is a strong increase in TOI as gate dielectric thickness or fin width is increased. On the other hand, in order to maintain reliability, increased fin height is found to be essential in order to reduce electric field as dielectric thickness is increased. Finally, a device architecture for improving linearity, power and reduced OFF-state field is suggested.

Machine learning based model for plasma prediction in high power pulsed magnetron sputtering processes

The coating development using physical vapor deposition (PVD) is time intensive and expensive. The coating processes are usually developed and improved based on the operator's experience. In order to improve the understanding of the processes during coating deposition, methods of plasma diagnostics can be used. However, this is time intensive and requires the installation of special diagnostics. The aim of the current study is to build a machine learning based model of PVD processes to predict the ionized to excited intensity ratio of the plasma species during the coating process. This enables a knowledge-based, cost-reduced process improvement. Based on measured data of different coating processes, the models were trained and tested in the current study. Therefore, a database was established by measuring process and plasma properties in hybrid processes of direct current magnetron sputtering and high power pulsed magnetron sputtering using an industrial coating unit. Different processes with variations of cathode powers and gas flows of the reactive gases oxygen and nitrogen were processed. The intensities of the ionized and excited species were measured using optical emission spectroscopy with six substrate side positioned collimators for spatial resolution to calculate the intensity ratios. The data was measured time resolved during the coating process. Compared to the measured data, the predictions show similar trends and values for the species within the coating chamber. The model was used to predict the influence of oxygen gas flow for CrAlON coating development. Furthermore, the models can be used for a more targeted process development. This can contribute to the application oriented adjustment of the coating processes and the coating properties.

Development of a Scalable MMC Pulsed Power Supply through HIL Methodology

Nuclear fusion experiments are becoming one of the most interesting focuses of research, given the hope of generating programmable, safe, and green energy. Among them, ASDEX (axially symmetric divertor experiment) upgrade has been operating at the Max Planck Institute for Plasma Physics (IPP) research center since 1991. To ignite and confine the plasma, several coils must be supplied through controllable high-current pulsed power supplies. The toroidal field magnets are here considered and a modular multilevel converter (MMC)-like system was designed and tested thanks to a small-scale prototype in previous works. The MMC-like topology, consisting of full-bridge submodules (SMs) with IGBTs and supercapacitor and exploitable also for other industrial applications, was chosen because of its modularity, redundancy, fault tolerance, and large amount of stored energy. The prototype, made of four SMs, was necessary to highlight critical key points in the design process. However, its scalability must be further tested before building a full-scale power supply, meant to reach almost 2400 SMs to guarantee the energy required by the load. This paper aims at validating hardware-in-the-loop (a powerful, safe, and relatively inexpensive real-time simulation environment that enables testing with real control boards) as a useful technology for power supply scalability studies and not only for control strategy tests. The results obtained previously from the prototype will allow us to finally increase the number of SMs and test the MMC-like scalability.

High Bandwidth Active Gate Driver for Simultaneous Reduction of Switching Surge and Switching Loss of SiC-MOSFET

This study investigates an active gate driver (AGD) for an SiC-MOSFET. The source current feedback type AGD utilizes the induced voltage of the source wire inductance as a negative feedback signal to regulate the source current di/dt. Recent improvements in the switching performance of the AGD is limited due to the feedback system bandwidth. In this paper, a high bandwidth current feedback type power operational amplifier is applied as the gate drive circuit. Switching characteristics of the conventional resistive gate driver and AGD are experimentally investigated via a double pulse test setup. The switching setup condition is 700 V / 80 A. This paper describes the development of the AGD circuit and experimental results. The over-shoot and ringing of the Vds and Is are reduced using the AGD. Moreover, the switching loss is simultaneously reduced.

Cladding-pumped Raman laser with M2 of 1.3 and 400 µJ first Stokes energy

Cladding-pumped Raman lasers have often been cited for their potential for brightness enhancement, but so far have never achieved high power and beam quality simultaneously. By utilizing a fiber geometry with a larger cladding to core ratio than current high power Raman fiber lasers for brightness enhancement (BE-RFLs), a noise-seeded Raman fiber laser pumped by a 100 ns pulsed laser with record beam quality is achieved with M2=1.3 and 0.4 mJ first Stokes output, with an instantaneous brightness enhancement of 60. The results here support the hypothesis that the limiting factor to high beam quality in BE-RFLs is Raman conversion in the pump cladding, rather than higher order core modes as in most conventional fiber lasers.

Feedback-controlled flux modulation for high-temperature superconducting magnets in persistent current mode

High-temperature superconducting (HTS) magnets have found wide applications in high-field settings owing to their high current capabilities. Typically, these magnets are powered by high-current power supplies via current leads, which can complicate insulation between cryogenic and room temperature environments. However, new developments in flux pumps for HTS magnets have enabled charging of kA levels of current without power supplies. By combining flux pumps with HTS persistent current operation, it is possible to achieve accurate flux modulation and eliminate the need for power supplies and current leads. In this study, we report on a novel feedback-controlled flux modulation for HTS magnets in persistent current operations. This flux modulation is based on a flux pump mechanism that generates a DC voltage across the charging superconductor by applying a current higher than its critical current. With closed-loop feedback control, our flux modulation can achieve precise injection and reduction of HTS magnet current in increments of 0.5 A. This technology can lead to stable magnetic fields in HTS magnet designs. We anticipate that this work will enable future magnets to operate in a stable persistent current mode within a closed cryogenic chamber, significantly reducing the footprint and power demand of HTS magnets and opening up new opportunities for their applications.

Compact size buck converter using small output capacitance with pole-tuning technique

This paper presents a compact buck converter using a pole-tuning technique in a 180-nm bulk CMOS process. The proposed pole-tuning technique enables the miniaturization of the output capacitor by reducing the required capacitance and improves the regulation characteristics by optimizing the inductor.The designed converter uses a high-speed switching frequency to reduce the inductor size, and by tuning the poles, the unity-gain bandwidth of the circuit is maintained. The ripple size owing to the reduced size of the capacitor showed a negligible change owing to the equivalent series resistance of the LCR filter.The designed buck converter uses an inductor of 0.1 μH and a capacitor of 0.1 μF. To apply a wide current range and high power efficiency, the converter has a load current range of 50–1000 mA and generates a voltage of 0.6–1.5 V with a source of 1.6–2.4 V. The designed buck converter was fabricated using a 0.18 μm CMOS. It operates at a switching frequency of 30 MHz, and the current ripple is within 15% under full load conditions. The converter exhibited a peak efficiency of 92.2% at 800 mA and conversion efficiency of over 76% over a load range of 50–1000 mA.