Low Voltage Steps Research Articles

High-voltage portable pulsed power supply fed by low voltage source

ABSTRACTThis article proposes a new structure of voltage multiplier for portable pulsed power applications. In this configuration, which is based on capacitor-diode voltage multiplier, the capacitors are charged by low AC input voltage and discharge through the load in series during pulse generation mode. The proposed topology is achieved by integrating of solid-state switches with conventional voltage multiplier, which can increase the low input voltage step by step and generate high-voltage high-frequency pulsed power across the load. After some discussion, simulations and experimental results are provided to verify the effectiveness of the proposed topology.

A Grid-Level High-Power BTB (Back-To-Back) System Using Modular Multilevel Cascade Converters WithoutCommon DC-Link Capacitor

This paper provides an intensive discussion on analysis, simulation, and experiment of a back-to-back (BTB) system unifying two modular multilevel cascade converters based on double-star chopper cells (MMCCs-DSCCs). Each of the two DSCCs connected back-to-back consists of multiple cascaded chopper cells and a center-tapped inductor per leg. Low voltage steps bring significant reductions in harmonic voltage and current to the BTB system. Neither dc-link capacitor nor voltage sensor is required for regulating the dc-link voltage and controlling the dc-link current. A three-phase 200-V, 10-kW, 50-Hz downscaled BTB system with phase-shifted PWM is designed, constructed, and tested to verify its operating principles and performance. Analytical, simulated, and experimental results agree well with each other in steady and transient states. Experimental waveforms confirm the effectiveness of a self-starting/restarting procedure.

Discussion on Triangular-Carrier Frequencies of a Modular Multilevel Cascade Converter Based on Double-Star Chopper Cells (MMCC-DSCC) with Phase-Shifted PWM

This paper presents a theoretical discussion on triangular-carrier frequencies of a modular multilevel cascade converter based on double-star chopper cells (MMCC-DSCC, hereafter referred to as the DSCC) with phase-shifted PWM. The DSCC consists of multiple cascaded chopper cells and a center-tapped inductor per leg. Low voltage steps bring significant reductions in harmonic voltage and current to BTB (back-to-back) or HVDC (high-voltage direct-current) systems using two DSCCs. When the DSCC adopts the 6-kV GCTs (gate-commutated thyristors) that are commercially available in the market, the switching frequency should be less than 200Hz to improve conversion efficiency. Theoretical analysis developed in this paper reveals that the most suitable triangular-carrier frequency is 125Hz or 175Hz. Simulated waveforms obtained from a three-phase 66-kV, 200-MW DSCC are included to verify this analysis. The analytical and simulated results agree well with each other.

Label-Free Detection of Alanine Aminotransferase Using a Low Operation Voltage and Single Reaction Step of Graphene Field-Effect Biosensor

not Available.

Application of a modular multilevel cascade converter (MMCC‐SDBC) to a STATCOM. Control of active power and negative‐sequence reactive power

AbstractThis paper presents the application of a modular multilevel cascade converter based on single‐delta bridge‐cells (MMCC‐SDBC) to a STATic synchronous COMpensator (STATCOM), particularly for negative‐sequence reactive‐power control. The SDBC is characterized by cascade connection of multiple single‐phase H‐bridge (or full‐bridge) converter cells per leg, which facilitates flexible circuit design, low voltage steps, and low electromagnetic interference (EMI) emissions. However, there is no published report on such a STATCOM with experimental verification or a control strategy. This paper designs, constructs, and tests a 100‐V 5‐kVA PWM STATCOM based on the SDBC with focus on the operating principle and performance. Experimental results confirm that this converter can control not only the positive‐sequence reactive power but also the negative‐sequence reactive power and low‐frequency active power intended for the flicker compensation of arc furnaces. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(4): 33–44, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22365

Local Anesthetics on Kv Channels - Closed State Binding of Bupivacaine?

Local anaesthetics (LAs) are generally assumed to block action potentials by binding to Nav channels, preferentially when in inactivated and/or open state. Recently, it has been suggested that they, in addition or preferentially, bind to Nav channels when in intermediate closed states. This is based on the finding that LAs reduce the peak current more at low voltage steps than at high in voltage clamp experiments.In previous studies we have concluded that LAs preferentially block Kv channels by binding to exclusively open channels. In the present study we have reanalysed the effect, with special reference to the new findings of closed state binding. We analysed the effects of bupivacaine on Kv3.1 channels expressed in Xenopus oocytes. In contrast to the results from the Na studies, bupivacaine reduced the early current more at higher voltages than at lower. Nevertheless, analysing kinetic models we found that the results are explained by binding preferentially to open channels.We thus conclude that bupivacaine block K channels mainly in the open state. We also conclude that a time and voltage-dependent block, similar to that reported for Na channels, does not necessarily imply binding of channels in different closed states. Furthermore, the results stress the general fact that a block of the early current in voltage clamp experiments does not necessarily imply that LAs bind to the channel when in closed state, contrary to a widely held view.

A Phase-Shifted PWM STATCOM Using the Modular Multilevel Cascade Converter (MMCC-SSBC)

This paper presents a transformerless phase-shifted PWM STATCOM intended for installation on the 6.6-kV power distribution system. The power circuit of this STATCOM is characterized by using the modular multilevel cascade converter based on single-star bridge-cells (MMCC-SSBC). This paper designs, constructs, and tests the 140-V, 10-kVA downscaled STATCOM with a per-cluster cascade count of N=6, to verify operating performance in both steady and transient states. The 13-level (line-to-neutral) voltage waveform with low voltage steps yields a nearly sinusoidal current with a current THD (total harmonic distortion) of 1.7%. Modeling and analysis of the phase-shifted PWM STATCOM are carried out, leading to the design of current control gains.

Facile Synthesis and Morphology Control of Bamboo-Type TiO2 Nanotube Arrays for High-Efficiency Dye-Sensitized Solar Cells

We report fast synthesis of bamboo-type TiO2 nanotube arrays via anodization of Ti in nonhazardous electrolyte under alternating voltage condition for applications as photoanodes in high-efficiency dye-sensitized solar cells (DSSCs). Formation mechanism of bamboo-type nanotubes is also explored. The low-voltage step reduces pH and ion-diffusion gradient inside TiO2 nanotubes and induces formation of bamboo ridges on outer tube walls when a second high-voltage step is conducted. Ridge spacing and length of bamboo-type nanotubes can be facilely tuned by adjusting time of high-voltage step and electrolyte composition. All DSSCs based on bamboo-type TiO2 nanotube arrays show higher efficiencies than those based on smooth-walled nanotubes with the same tube length due to enhanced surface area of bamboo-type nanotubes for dye loading. It is also noted that DSSC efficiency increases with the ridge density of bamboo-type nanotubes of the same length. For example, DSSC based on bamboo-type nanotubes (8 μm long) wi...

Negative-Sequence Reactive-Power Control by a PWM STATCOM Based on a Modular Multilevel Cascade Converter (MMCC-SDBC)

This paper presents the application of a modular multilevel cascade converter based on single-delta bridge cells (SDBCs) to a STATic synchronous COMpensator (STATCOM), particularly for negative-sequence reactive-power control. The SDBC is characterized by cascade connection of multiple single-phase H-bridge (or full bridge) converter cells per leg, thus facilitating flexible circuit design, low-voltage steps, and low-electromagnetic-interference emissions. This paper designs, constructs, and tests a 100-V 5-kVA pulsewidth-modulated STATCOM based on the SDBC, with focus on the operating principle and performance. Experimental results verify that it can control not only positive-sequence reactive power but also negative-sequence reactive power and low-frequency active power intended for flicker compensation of arc furnaces.

Control and Design of a Modular Multilevel Cascade BTB System Using Bidirectional Isolated DC/DC Converters

This paper discusses the control and design of the 6.6-kV back-to-back (BTB) system combining bidirectional isolated dc/dc converters and modular multilevel cascade pulsewidth modulation (PWM) converters. The system consists of multiple converter cells connected in cascade per phase at both front ends. Each converter cell consists of a bidirectional isolated medium-frequency dc/dc converter and two voltage-source H-bridge (single-phase full-bridge) PWM converters. Extremely low-voltage steps bring a significant reduction in harmonics and electromagnetic interference emissions to the BTB system. This paper designs, constructs, and tests a single-phase downscaled BTB system rated at 120 V and 3.3 kW to verify the viability and effectiveness, leading to the actual system.

Multilevel programming at a low-voltage step using junction avalanche hot carrier injections

A highly efficient program method is proposed for multilevel programming with a low-voltage step in a conventional polycrystalline silicon-oxide-nitride-oxide-silicon structure. This method uses junction avalanche hot carriers for charge storage in the nitride layer. A multilevel storage is easily obtained by using a low-voltage step of 0.1 V at each level of the three programmed states along with a fast program time of 1 μs. In addition, a localized charge-injection near the junction edge is clearly observed with an acceptable read margin and threshold voltage difference between the forward and the reverse read at the three programmed states.

スマートグリッドに対応した次世代パワーエレクトロニクス技術

This paper presents an overview of the next-generation power electronics technology for the Japanese-version smart grid. It focuses on a grid-level battery energy storage system, a grid-level STATCOM (STATic synchronous COMpensator), and a 6.6-kV BTB (Back-To-Back) system for power flow control between two power distribution feeders. These power electronic devices play an important role in achieving load frequency control and voltage regulation. Their circuit configurations based on modular multilevel cascade PWM converters are characterized by flexible system design, low voltage steps, and low EMI (Electro-Magnetic Interference) emission. Their downscaled laboratory models are designed, constructed, and tested to verify the viability and effectiveness of the circuit configurations and control methods.

モジュラー・マルチレベル・カスケード変換器（MMCC-SDBC）のSTATCOMへの応用

This paper presents the application of a modular multilevel cascade converter based on single-delta bridge-cells (MMCC-SDBC) to a STATic synchronous COMpensator (STATCOM), particularly for negative-sequence reactive-power control. The SDBC is characterized by cascade connection of multiple single-phase H-bridge (or full-bridge) converter cells per leg, which facilitates flexible circuit design, low voltage steps, and low electro-magnetic interference (EMI) emissions. However, there is no published report on such a STATCOM with experimental verification or a control strategy. This paper designs, constructs, and tests a 100-V 5-kVA PWM STATCOM based on the SDBC with focus on the operating principle and performance. Experimental results confirm that this converter can control not only the positive-sequence reactive power but also the negative-sequence reactive power and low-frequency active power intended for the flicker compensation of arc furnaces.

モジュラー・マルチレベル・カスケード変換器を用いた電池電力貯蔵装置の電池電力個別制御

This paper focuses on a battery energy storage system that can be installed in a 6.6-kV power distribution system. This system comprises a combination of a modular multilevel cascade converter based on single-star bridge-cells (MMCC-SSBC) and multiple battery modules. Each battery module is connected to the dc side of each bridge-cell, where the battery modules are galvanically isolated from each other. Three-phase multilevel line-to-line voltages with extremely low voltage steps on the ac side of the converter help in solving problems related to line harmonic currents and electromagnetic interference (EMI) issues. This paper proposes a control method that allows each bridge-cell to independently adjust the battery power flowing into or out of each battery module. A three-phase energy storage system using nine nickel-metal-hydride (NiMH) battery modules, each rated at 72V and 5.5Ah, is designed, constructed, and tested to verify the viability and effectiveness of the proposed control method.

Kv Channel Modulation: Closed State Block of Benzocaine But Not of Bupivacaine

Local anaesthetics (LAs) block action potentials mainly by blocking Na channels. They are generally assumed to preferentially bind to channels in inactivated and/or open state. Recently it has been suggested that they mainly bind to channels in intermediate closed states. This is based on the finding that LAs affect the currents time and voltage-dependently in voltage clamped channels; that they reduce the peak current more at low voltage steps than at high.In previous studies on inactivating K channels we have concluded that LAs preferentially bind to channels in open state. In the present study we have reanalysed the effects of LAs on K channels with special reference to the new findings of closed state binding. We analysed the effects of bupivacaine and benzocaine on Kv3.1 and Shaker channels expressed in Xenopus oocytes. As shown previously bupivacaine induces a peaked current in both channel types. In accordance with the results on the Na currents bupivacaine reduced the peak less at +60 mV than at lower potentials. Nevertheless, a modelling analysis suggested that the results are explained by binding preferentially to open channels. In contrast, benzocaine did not induce a peak at any potential, but the early current was reduced more at low potentials than at high. The modelling analysis suggested that the effect is caused by binding to closed and open channels.We thus conclude that bupivacaine and benzocaine blocks K channels differently; bupivaciane open state-dependently and benzocaine both open and closed state-dependently. We also conclude that a time and voltage-dependent block, similar to that reported for Na channels, with less inhibition of the peak current at high potentials than at low potentials, does not necessarily imply binding of channels in a closed state.

Investigation of Deep Interface Traps in Very-Thin Oxide/Si Structures Prepared at Low Temperatures Using Chemical Solutions

An advanced equipment for the charge version of deep level transient spectroscopy (Q-DLTS) and C-V measurements with newly developed software on LabView platform is presented. The ability to record several Q-DLTS behaviors with different rate windows simultaneously is the most important property of the equipment. Q-DLTS with excitation of the MOS structures by low-voltage step and time domain C-V measurements were used to determine interface properties. The contribution presents mainly results obtained on very-thin oxide/n-type crystalline Si structures prepared by oxidation at very low temperatures in nitric acid solutions with various concentrations.

Pyrite as cathode insertion material in rechargeable lithium/composite polymer electrolyte batteries

The chemical and physical properties of pyrite have been reviewed with reference to cathode material in lithium/polymer electrolyte batteries. The analysis of d Q/d V curves showed that the charge–discharge process in Li/polymer electrolyte/pyrite battery is more complicated than in non-aqueous and molten media. At least seven domains are distinguished on the d Q/d V discharge curve. The low-voltage step on discharge may be associated with the formation of a new phase causing from the reaction of metallic iron with the electrolyte components. This would explain the capacity fading of the cell. The high-voltage 1.85–2.25 V charge region may be attributed to the insertion of lithium into Li 2− x FeS 2. However the de-intercalation of lithium from Li 2FeS 2 in a LiI-CPE cell operating at 130°C is not a pure topotactic one, but rather the Li 2− x FeS 2 undergoes some structural change on cycling. Iron oxides, hydroxides and sulfates contaminate the surface of pyrite from different sources. However the performance characteristics, such as reversible capacity and polarization of the Li/composite polymer electrolyte/FeS 2 cells were found to be independent of the amount of impurities. The thin-cathode cell design has a projected energy density of 130 W h/kg at C/3 rate and specific power of 300 W/kg (on the basis of 5 mA/cm 2 demonstrated in experimental cells). Over 500 100% DOD cycles with a capacity fading rate of less than 0.1%/cycle have been demonstrated in a small laboratory prototype 7 μm-thick modified cathode cell.

Ceramic superconducting materials as intercalation cathodes in secondary non-aqueous lithium batteries

Electrodes formed from PTFE bound (Ta 1/2Cu 1/2) Sr 2GdCu 2O 8 − d , were cycled in 1 M LiAsF 6/propylene carbonate electrolyte using cyclic voltammetry. It has been demonstrated that the cyclic voltammograms measured below 2.0 mV s −1 exhibit a well defined reversible multipeaked wave. Prototype cells incorporating both PTFE bound and thin highly porous films of (Ta 1/2Cu 1/2)Sr 2GdCu 2O 8 − d exhibited an initial discharge with two well defined voltage steps. Subsequent discharge cycles only retain characteristics of the higher voltage step suggesting that the process characterised by the low voltage step is irreversible.

Determination of the profile of the bulk generation lifetime from pulsed MOS-C transients

After a metal-oxide-semiconductor capacitor (MOS-C) is derived towards deep depletion by the application of a depletion voltage step on its gate, the transients relaxing to equilibrium can be used to investigate the generation characteristics of surface space-charge region of the semiconductor. It has been proved that not only may the average bulk generation lifetime be extracted, but also its profile can be determined. We have suggested two methods of determining the profile of the bulk generation lifetime in this paper. The surface generation and field-enhanced generation have been ignored in analysis, therefore, it is important that the samples have low interface-state density and undergo rather low voltage steps in experiments in order to achieve reasonable and reliable results.

Experimental evidence for supersoliton modes in a long modulated Josephson junction

We report experimental observation of steps in multi-fluxon current-voltage characteristics of a long overlap Josephson junction with a periodic modulation of the critical current density. For the period of the fluxon chain incommensurable with the spatial period of the modulation we observed a low-voltage step in the current-voltage characteristic with the voltage approximately proportional to the incommensurability parameter. This effect is explained in terms of so-called “supersoliton” excitations in spatially modulated Josephson junctions.