High Current Power Supply Research Articles

Review of Cockcroft-Walton High Voltage Low Current DC Power Supplies

High-voltage power supplies are key for developing particle accelerators, neutron generators, x-ray systems, ion implantation, etc. This paper reviews various developed voltage low current power supplies based on Cockcroft-Walton voltage multiplier circuits for accelerator-based neutron sources and other industrial and medical applications. The paper presents a detailed review of the topology of the power supply used for the high voltage generation, the key design parameters, key active and passive components used in the High Voltage (HV) system, key experimental results, protection and measurement circuit used in the power supply and about the system performance. The improvement that occurred in the size and performance of the power supplies due to the development in the technology of the magnetic components, semiconductors and energy storage devices in successive years is apparent in the discussion. Finally challenges and possible solutions for the compact design and system performance are concluded for the development of high voltage low current power supplies.

A wearable DC tribovoltaic power textile woven by P/N-type organic semiconductor fibers

A high-performance, wearable tribovoltaic DC power supply textile was prepared using a traditional weaving process. The WDPs have high flexibility, excellent environmental robustness, lower internal resistance, and washability.

Short time resistance spot welding of 1.2Gpa ultra-high strength steel using high frequency power supply

The task of 1.2 GPa ultra-high strength steel sheet in short time’s high current spot welding has been clarified. High current and short time spot welding system and high frequency power supply has been developed. In order to prevent spatter, new dual-pulse welding method in which primary energization, cooling and secondary energization has been proposed. By using this novel welding method, nugget diameter and tensile shear strength satisfied the target and spatter did not occur. New method of 1.2 GPa ultra-high strength steel sheet in short time and high current spot welding has been established.

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).

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.

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.

A Novel Heat-Assisted Three-Roll Incremental Rolling System for Flexible Rolling

Abstract The increasing demand for customized products and rapid prototyping triggers the development of dieless forming process where the need of part-specific dies is eliminated compared to conventional forming processes. This paper presents a heat-assisted three-roll incremental rolling system capable of producing rods and tubes of various diameters without the need for die/tool replacement. The system incorporates two possible heating mechanisms, namely, an induction heater and a high-current power supply for electrically assisted forming. Due to its high flexibility and hot forming ability, this rolling system is ideal for low volume production or scientific research. The newly fabricated rolling machine was initially evaluated using low carbon steel rods. The experiments have shown that the machine can produce metallic rods down to 6 mm in diameter without apparent spiral marks on the outer surface of the rolled product using multiple passes. The finite element method (FEM) was used to analyze the reaction moment, depth of the spiral marks, and the effect of axial feeding speed on the spiral marks. The simulation model predicted the results of the experiments with less than a 10% error. The work established a flexible rolling platform for possible future research, which can include the study of interface behavior in the thermo-mechanical rolling processes, and the study of material behavior in this multi-axial multi-physics environment.

Two-Stage Factorized Power Architecture DC–DC Converter for Spacecraft Secondary Power Supply System

In this article, we propose a two-stage factorized power architecture (FPA) dc–dc converter, which caters to applications that require high efficiency, high power density, low ripple, and high dynamic response of space-borne low-voltage and high-current power supply. The first-stage 48 V intermediate bus converter (IBC) adopts the six-phase interleaving magnetic integration buck converter (IMIBC). A new array high symmetry multi-phase coupled inductor (CI) is constructed, and a general zero-voltage switching (ZVS) control strategy is proposed. The designed IBC provides 2.4 kW power with a density of up to 1400 W/in3 and efficiency up to 97.15%. The second-stage point of load converter (POLC) adopts the four-phase interleaving magnetic integration LLC dc/dc transformer (DCX). A new method of current sharing, which is based on the inverse coupling resonant inductor, is proposed. This method yields good current sharing under a 15% mismatch of resonance parameters. A highly symmetrical four-phase resonant CI and a four-phase magnetic integration transformer are developed; the design of magnetic components is optimized by constructing a high-precision magnetic circuit mode. The designed POLC has a power density of up to 700 W/in3 and an efficiency of up to 97.1%. Finally, the experimental prototype is fully tested against a similar type of Vicor’s products. According to the results, the power supply designed in this article has several benefits with regard to efficiency, power density, transient response speed, and ripple.

The Study of Usable Capacity Efficiency and Lifespan of Hybrid Energy Storage (Lead-Acid with Lithium-ion Battery) Under Office Building Load Pattern

One of the greatest practices in energy management is the Energy Storage System (ESS). ESS can be used for renewable energy control as well as peak shaving in the build-up of a Smart Grid. The cost of a lithium ion battery is more than 200 percent greater than that of a lead-acid battery, which is a significant barrier to project start-up. This paper focuses on the use of a hybrid energy storage system that includes a lithium-ion battery and a lead-acid battery. This work presents the hybrid energy storage using lithium-ion battery and lead-acid battery to reduce costs of the project. However, usability that requires high current power supply considerably affects the usable capacity of a lead-acid battery. Results showed that the ratio 68.63: 31.37 was the most suitable among 7 ratios, compared to the model building installed a 50kW solar power generator on the rooftop, in the worst case scenario when the batter have 85% DoD per cycle. The EOL for hybrid energy storage is about 4 years lifespan with the 0.5C and 0.2C for LFP and AGM respectively. In terms of economic evaluation, hybrid energy storage could initially reduce the project cost by 47.5%.

Power quality improvement for 20 MW PEM water electrolysis system

Hydrogen is an important alternative as a clean fuel for industry and power-to-gas energy storage. The water electrolysis process is a promising technology in green hydrogen production where proton exchange membrane (PEM) technology has been keenly interested. Industrial large-scale PEM electrolyzers need a high current power supply. When connected to an alternating current (AC) source, high current power rectifiers are used to convert AC to DC. Currently, the most commonly used topology in large-scale PEM electrolysis systems is the thyristor-based topology due to its technology maturity and low cost. However, this topology presents several drawbacks in terms of power quality and consequently leads to higher stack-specific energy consumption (SEC) and additional losses. In the present research, we demonstrate the potential power quality improvement for a 20 MW PEM water electrolysis system by rectifier topology upgrade. Rather than traditional thyristor-based topology, a 3-phase interleaved buck rectifier topology is proposed. The new topology presents advantages on both AC and DC sides via a validated simulation model, which is built using MATLAB/Simulink and then validated with experimental data from an industrial 20 MW PEM water electrolyzer at Air Liquide's Bécancour plant. Results show a great improvement in terms of power factor, Total Harmonic Distortion (THD), and DC-current ripple reducing the total losses and the SEC of the PEM stack, especially under partial load. Towards a higher power efficiency, the proposed rectifier topology may be considered in the construction of future large-scale PEM systems.

Electrospray characteristics and cooling performance of dielectric fluid HFE-7100

Electrospray (ES) cooling is a promising route of efficient heat removal for electronic components with powerful cooling capacity, a small liquid supply, and precise temperature control. In this study, we experimentally investigated the electrohydrodynamic (EHD) disintegration and ES cooling performance of the dielectric fluid HFE-7100. The stainless-steel capillary nozzle was connected to a high voltage direct current (DC) power supply, whereas the hot copper surface was grounded. A high-speed camera was used to capture the spray morphology of the coolant. The results indicated that a small amount of ethanol significantly improved the charging performance of HFE-7100 by increasing the liquid electrical conductivity. An uncharged column liquid jet was stretched into a thin liquid film by the EHD forces, generating numerous ultrafine droplets along the lower edge. The ES cooling heat flux was increased by about 2.2 times compared with the neutral condition. In addition, the influences of the applied voltage, flow rate, spray height, liquid subcooling, and ethanol concentration on the ES cooling capacity were discussed. Finally, correlations of the ES cooling heat transfer based on the Reynolds number, Weber number, Prandtl number, electric Weber number, Jacob number, and normalized surface temperature were established.

A Scalable High-Current High-Accuracy Dual-Loop Four-Phase Switching LDO for Microprocessors

High-performance microprocessors need high current (ampere-level), high accuracy, and fast-response power supplies. Comparing to analog and digital low-dropout (LDO) regulators, the switching LDO can be a better candidate for such requirements, as it can drive large power transistor(s) fast and accurately. However, conventional switching LDOs need large load capacitance to reduce the output ripple, which restricts their applications. This article presents a 1.5-A fully-integrated switching LDO for microprocessors, with an easily scalable load capability. Here, we introduce three techniques together to relief the output capacitance requirement: 1) four-phase 500-MHz pulsewidth modulation (PWM) with inherent current balancing; 2) current-limited power cells resisting processor voltage and temperature (PVT) variations; and 3) hybrid fast-slow power transistors. Therefore, we reduce significantly the load capacitance to maximum load current ratio <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C_{\mathrm {L}} / I_{\mathrm {MAX}}$ </tex-math></inline-formula> when compared with the prior switching LDOs. Also, the proposed dual-loop architecture not only achieves a fast transient response, but also provides high-accuracy regulation. In addition, we design the tunable active voltage positioning (AVP). Fabricated in 28-nm CMOS, the proposed switching LDO measures a maximum 70-mV undershoot with a 1-A load current step with 10-ns edge time. The measured load regulation is 1 mV/A and the line regulation is 1.5 mV/V. Also, we obtain a good power supply rejection (PSR) of −63 dB at 10 kHz and −20 dB at 1 MHz. The PWM automatically moves to a pulse-skipping mode at light load, reducing the quiescent current to 1.8 mA, while the peak current efficiency is 99.27%.

Efficiency Improvement of Dual-Receiver WPT Systems Based on Partial Power Processing Control

In wireless power transfer (WPT) system for light electric vehicles (LEVs), adopting dual receivers on the receiver side is an available way to offer a high-current power supply. In this article, the partial power processing (PPP) control method is proposed for optimizing the power loss of the dual-receiver WPT system. With the PPP control method, only one of the active rectifiers will be regulated by the variable angle phase-shift (VAPS) modulation to adjust the required power under different load power demands and misalignment situations. As a result, the switching loss of the two active rectifiers, which accounts for a considerable part of the overall power loss with a high operating frequency, can be dramatically reduced. At last, 24 V-50 A-1200 W LEV wireless charging experimental setup to verify the effectiveness of the proposed PPP control method. Compared with the conventional power distribution method based on impedance matching with VAPS, the proposed PPP control method can increase the efficiency by 6%–7% with misalignment situations, achieving the overall efficiency as high as >92% at the heavy load.

Suppression of damages on cathodes in the negative hydrogen ion source for the stable NBI system

A protection system of ion source components from local abnormal discharge has been developed with ITER-class filament-driven negative ion source for high power and stable long-term operation. Protection from unpredictable discharge is a common issue for filament and RF-driven ion sources. To understand how fast should be cut off the discharge, threshold energy not to cause critical damage on the filament was investigated. The experimental exploration concluded that the energy less than 1.87 J or fast cut-off faster than 343 μs is the threshold for the robust protection of the filaments. A developed system successfully detected and cut off the discharge at 100 μs under noisy environments with the high current power supply. Moreover, the detection system is remotely adjustable. Such versatile protection system can contribute to any abnormal discharges in high current system including various ion sources, gyrotron, and high voltage components.

Effect of ignition, initial pressure and temperature on the lower flammability limit of hydrogen/air mixture

In this research, the effect of ignition, initial pressure (50–250 kPa) and temperature (20–100 °C) on the lower flammability limit (LFL) of hydrogen/air mixture are investigated experimentally and numerically. The results show that with the ignition energy increases, the LFL of hydrogen decreases. When high voltage direct current power supply (HVDC) is used, the time for the flame to propagate to the edge of the window is much shorter than that of 15 kV high voltage transformer (15 kV HVT) ignition. As the initial pressure increases, the LFL of hydrogen increases. When HVDC is used, the time to reach the peak deflagration overpressure increases with the increase of initial pressure. However, when 15 kV HVT is used, the time to reach the peak deflagration overpressure is almost the same. As the initial temperature increases, the LFL of hydrogen decreases. The change of the LFL of hydrogen with 15 kV HVT ignition is greater than that of HVDC. Through the analysis of chemical kinetic factors, the effect of OH radical generation when the LFL of hydrogen increases with the increase of initial pressure is revealed.

A Repetitive Low Impedance High Power Microwave Driver

A low impedance high power microwave (HPM) driver is designed, which can be used in studying multi-gigawatt HPM devices such as the magnetically insulated transmission line oscillator (MILO), based on a helical pulse forming line (PFL) and the Tesla pulse transformer technology. The co-axial PFL is insulated by ethanol–water mixture, whose dielectric constant can be adjusted; and the helical line increases the output pulse width as well as the impedance to make a better match with the load. By the optimal combination of PFL charging voltage and output switch working voltage, the reliability of the PFL can be improved. The Tesla transformer has partial magnetic cores to increase the coupling coefficient and is connected like an autotransformer to increase the voltage step-up ratio. The primary capacitor of the transformer is charged by a high voltage constant current power supply and discharged by a triggered switch. A transmission line is installed between the PFL and the HPM load, to further increase the load voltage. A ceramic disk vacuum interface is used for improving the vacuum of the HPM tube. The experiments show that the driver can operate at 30 GW peak power, 75 ns pulse width and 5 Hz repetition rate.

Preliminary Design of a Superconducting LVDC Power Cable for Tokamak Application

Tokamak device requires a very high current power supply from the local power distribution sources to the targeted magnets such as toroidal field (TF) coils and poloidal field (PF) coils. This paper presents a preliminary design of a 30-m/1-kV/10-kA low voltage direct current (LVDC) superconducting cable for the potential in Tokamak applications. The outer diameter of the DC cable is 122.41 mm, and the pressure drop of liquid nitrogen (LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) in the inner and outer channels is about 6.59 kPa. The flow velocity of inner and outer LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> channels are 0.5 m/s and 0.25 m/s, respectively. The temperature rise of the entire cable was designed to be less than 5 K, which enhances the electricity supply safety and reliability. These preliminary design lays some technical bases for achieving high current and low loss power transmission. The designing results show that the LVDC superconducting cable has significant potentials for Tokamak applications compared with conventional copper cables.

Impact dynamics of a charged droplet onto different substrates

Impact behaviors of an electrically charged water droplet on different solid substrates and subsequent dynamic mechanisms were experimentally investigated in this study. Droplets were generated from a metal capillary by a syringe pump with a constant diameter of about 2.2 mm. The capillary was directly connected to a high voltage direct current power supply, while a lower counter ring electrode was grounded. A high-speed camera was utilized to visualize the droplet impact morphology. The influences of the droplet charge density, substrate wettability, and surface temperature were analyzed. The results showed that the impact on hydrophilic surfaces exhibited a greater spreading diameter but a smaller recoiling height than that on a hydrophobic surface, which was attributed to the increased viscous dissipation on the substrate. In addition, compared with a neutral droplet, the maximum spreading diameter of a charged droplet was found to be improved by about 8.4%, where the enhancing effects were proportional to the droplet charge ratio. This was due to the weakening effects of the Coulomb repulsion on the liquid surface tension. Moreover, the impact of charged droplets on a hot copper substrate in three different boiling regimes, called convection, nucleate and film boiling, was also discussed. Finally, a model of the maximum spreading ratio of a charged droplet based on the Weber number, charge ratio, and wettability was established. This study demonstrated that the free charges in a droplet was able to influence its impact behaviors, which would hold great promise for some related technologies.

Microcontroller Based High Voltage, High Speed Trigger Control Circuit for SMARTEX-C

Microcontroller based trigger control circuit for fast pulsing of electrode potentials on wide range of time scales has been designed, installed, and tested for electron plasma experiments which are carried out in partial toroidal trap SMall Aspect Ratio Toroidal Electron plasma EXperiment in C – shaped geometry (SMARTEX – C), a device to create and confine non-neutral plasma (electron plasma). The sequence of trap operation is inject-hold-dump for which electrodes need to be pulsed with applied voltages at a high switching speed of few nanoseconds. Also this sequence of operation needs to be controlled over a very wide range of time scales from few microseconds to few seconds. As the available COTS (Commercial-Off-The-Shelf) high voltage DC power supplies generally do not provide this feature of fast switching at nanosecond time scale, MOSFET based circuit is developed which provides fast switching in the range of 20 – 100 nanoseconds of high voltages (200Vdc - 500Vdc) of multiple electrodes. The timing pulse widths of these trigger pulses are controlled using a microcontroller-based circuit. This experimental set-up also requires the triggering of a high current dc power supply used for an Electro-magnet (Toroidal Field Coil) to generate a toroidal magnetic field, at the start of this experiment. For this purpose, a Silicon Controlled Rectifier (SCR) based circuit is used. The gate pulse to trigger the SCR circuit is also generated from this microcontroller-based circuit. National Instrument’s LabVIEW software based Graphical User Interface (GUI) is developed for triggering the SCR and electrodes with a programmable time period through the serial link.

An Electrohydraulic Direct Current Discharge for Inactivation of &lt;i&gt;Escherichia coli&lt;/i&gt; in High-Bacterial Density Wastewaters

The United Nations, through its Sustainable Development Goals, have identified access to clean water as one of the challenges facing society. With reported global deaths exceeding 1 million annually linked to untreated water consumption, which is usually contaminated by pathogenic micro-organisms, further research continues in water disinfection. The direct generation of non-thermal plasma in water is a promising method for the inactivation of disease-causing bacteria present in the wastewater. This study explored the efficacy of plasma in the inactivation of different bacterial densities (4.0×104, 1.5×105, and 2.5×107 CFU/mL) using a 500 mL plasma batch reactor operating at atmospheric pressure. The plasma discharge was generated in water by a Technix-SR-10R-5000 high voltage direct current power supply in negative polarity with a set current of 0.45 A and a maximum pre-set ignition voltage of 9 kV. The electrodes used in the discharge was a copper material. A bacterial culture of Escherichia coli ATCC® 25922TM (E.coli) was used as a model for the direct plasma discharge. The study further investigated the contribution of copper ions (0.4 and 0.7 mg/L) released into the water during treatment by having two control reactors that were not exposed to plasma. The results show a complete inactivation at 180 seconds for the bacterial densities from 4.0×104 to 2.5×107 CFU/mL. The results from this study indicated the potential of a direct electric discharge in handling water source with high-bacteria densities.