Large Current Applications Research Articles

A Novel LQI Control Technique for Interleaved-Boost Converters

Hybrid electric vehicles (HEVs) and fuel cell electric vehicles (FCEVs) utilize boost converters to gain a higher voltage than the battery. Interleaved boost converters are suitable for low input voltage, large input current, miniaturization, and high-efficiency applications. This paper proposes a novel linear quadratic integral (LQI) control for the interleaved boost converters. First, the small-signal model of the interleaved-boost converter is derived. In the proposed method, an output voltage and a current signal error between two-phase input currents are selected to control not only the output voltage but also a balance between two-phase input currents. Furthermore, steady-state characteristics in terms of the output voltage and the input current are demonstrated by experiments and simulations using an experimental apparatus with a rated power of 700 W. The validity of the proposed method’s tracking performance and load response is demonstrated by comparing it with that of the conventional PI control. The tracking performance of the LQI control for the 40 V step response has a ten times faster response than that of the PI control. Also, the experimental results demonstrate that the proposed method maintains a constant output voltage for a 300 W load step while the PI control varies by 10 V during 70 ms. Additionally, the proposed method has an excellent disturbance rejection.

A Novel Current Self-Balancing Method for High-Gain and High-Frequency Converter

Matrix transformer is deemed the most widely used structure for large current application due to its natural current sharing. However, multiple transformers suffer from large core volume and core loss, especially with high frequency operation. In this paper, a novel current self-balancing method for high-gain and high-frequency converter is proposed. Only one magnetic core is employed and all secondary windings for large current are wrapped parallelly around the core. The H-bridges with two filtering inductors on the DC positive and negative bus are cascaded by these secondary windings to form a proposed cascaded H-bridge structure. Due to the large impedance in filter inductor loop in high frequency, the differential-mode current between different windings is largely suppressed and the current sharing of secondary windings and SR MOSFETs is achieved naturally. The filtering inductor can be easily implemented by using PCB-routed inductance without iron core, which means that the power density and efficiency will not be impaired. A 750V/48V-2kW unregulated LLC converter prototype is built and achieves the power density of 7 kW/L with maximum efficiency of 96.5%. With the proposed cascaded H-bridge structure, current self-balancing is achieved perfectly and the efficiency improvement reaches to 0.8% at full loading condition.

Highly extendable passive current balancing interleaved high step‐up boost converter using voltage multipliers

AbstractHigh step‐up boost converters with large input current capacity are necessary for low‐voltage renewable energy sources, such as photovoltaic panels and fuel cells. Interleaved converters are a suitable topology for low‐voltage, large input current applications. Conventional interleaved converters, however, face a variety of challenges, such as the necessity of additional current control loops for active current balancing, increased voltage stress of semiconductors, and poor extendibility. In this paper, highly extendable interleaved high step‐up boost converters with a passive current balancing and reduced semiconductor voltage stresses are proposed. Current capacities and step‐up conversion ratios of the proposed converters can be arbitrarily enhanced by extending the number of phases and voltage multiplier (VM) stages, respectively. The experimental results of 500‐W prototypes demonstrated passive current balancing, reduced semiconductor voltage stresses, and enhanced step‐up conversion ratios.

High-loading Pt-alloy catalysts for boosted oxygen reduction reaction performance

To improve performance of membrane electrode assembly (MEA) at large current density region, efficient mass transfer at the cathode is desired, for which a feasible strategy is to lower catalyst layer thickness by constructing high loading Pt-alloy catalysts on carbon. But the high loading may induce unwanted particle aggregation. In this work, H-PtNi/C with 33% (mass) Pt loading on carbon and monodisperse distribution of 3.55 nm PtNi nanoparticles, was prepared by a bimodal-pore route. In electrocatalytic oxygen reduction reaction (ORR), H-PtNi/C displays an activity inferior to the low Pt loading catalyst L-PtNi/C (13.3% (mass)) in the half-cell. While in H2-O2 MEA, H-PtNi/C delivers the peak power density of 1.51 W·cm−2 and the mass transfer limiting current density of 4.4 A·cm−2, being 21% and 16% higher than those of L-PtNi/C (1.25 W·cm−2, 3.8 A·cm−2) respectively, which can be ascribed to enhanced mass transfer brought by the thinner catalyst layer in the former. In addition, the same method can be used to prepare PtFe alloy catalyst with a high-Pt loading of 36% (mass). This work may lead to a range of catalyst materials for the large current density applications, such as fuel cell vehicles.

An innovative vigorous outlier recognition placed on LROAD for fix-amplitude impulsive noise

Due to large current applications on digital images in these recent years, outlier suppression is one of the primary stages for modern computer vision implementations thereupon there are tremendously invented for creating an efficient and practical outlier suppression, which ordinarily are composed of outlier recognition stage and outlier rebuilt stage. The localised rank ordered difference (LROAD) approach, which is progressed from rank-ordered absolute differences (ROAD), has been invented since 2016. Later, the LROAD approach evolved to be one of the efficient outlier recognition stages from its eminent effectiveness. The paper focus to propose the innovative vigorous outlier recognition placed on localised rank-ordered logarithmic differences (LROLD) approach, which is progressed from LROAD and rank-ordered logarithmic differences (ROLD), which is higher effectiveness than the ordinary LROAD, for applying on FAIN. From the computer experiments, which are examined on many depictions such as Girl, Pepper F16 and Lena, the innovative vigorous outlier recognition placed on LROLD approach has higher eminent effectiveness then the stage-of-art approach such as LROAD and ROAD approaches at numerous consistencies of FAIN.

Simplified cascade multiphase DC-DC buck power converter for low voltage large current applications: part II --- output current controller

<span lang="EN-US">This paper proposes a control method for new simplified cascade multiphase direct current-direct current (DC-DC) buck power converters used for low-voltage large-current applications such as cathodic protection. To control the proposed converter, a proportional-integral (PI) controller is used to regulate the output current of the converter. The control scheme analysis is carried out by linearizing the small-signal model of the proposed converter to form the output current transfer functions. This transfer function will be analyzed by using phase and gain margin approach to obtain the control parameters (Kp, Ki, and Ti). Simulation and experiment results are included to show the validity of the proposed concept.</span>

Huge Baltic project adds PE, later PP

To improve performance of membrane electrode assembly (MEA) at large current density region, efficient mass transfer at the cathode is desired, for which a feasible strategy is to lower catalyst layer thickness by constructing high loading Pt-alloy catalysts on carbon. But the high loading may induce unwanted particle aggregation. In this work, H-PtNi/C with 33% (mass) Pt loading on carbon and monodisperse distribution of 3.55 nm PtNi nanoparticles, was prepared by a bimodal-pore route. In electrocatalytic oxygen reduction reaction (ORR), H-PtNi/C displays an activity inferior to the low Pt loading catalyst L-PtNi/C (13.3% (mass)) in the half-cell. While in H2-O2 MEA, H-PtNi/C delivers the peak power density of 1.51 W·cm−2 and the mass transfer limiting current density of 4.4 A·cm−2, being 21% and 16% higher than those of L-PtNi/C (1.25 W·cm−2, 3.8 A·cm−2) respectively, which can be ascribed to enhanced mass transfer brought by the thinner catalyst layer in the former. In addition, the same method can be used to prepare PtFe alloy catalyst with a high-Pt loading of 36% (mass). This work may lead to a range of catalyst materials for the large current density applications, such as fuel cell vehicles.

Simplified cascade multiphase DC-DC buck power converter for low voltage large current applications: part I --- steady-state analysis

This paper presents a new simplified cascade multiphase DC-DC buck power converter suitable for low voltage and large current applications. Cascade connection enables very low voltage ratio without using very small duty cycles nor transformers. Large current with very low ripple content is achieved by using the multiphase technique. The proposed converter needs smaller number of components compared to conventional cascade multiphase DC-DC buck power converters. This paper also presents useful analysis of the proposed DC-DC buck power converter with a method to optimize the phase and cascade number. Simulation and experimental results are included to verify the basic performance of the proposed DC-DC buck power converter.

Higher-voltage asymmetric-electrolyte metal-air batteries

Higher-voltage asymmetric-electrolyte metal-air batteries

A Novel Method for Wide Range Electric Current Measurement in Gas-Insulated Switchgears With Shielded Magnetic Measurements

Magnetic field (MF) sensing and interpretation remains an active area of research for source current reconstruction and measurement applications. One such area is large current measurement for power system components with contact less MF sensing. The output of recently made available magnetic sensors is favorable for large current measurement applications. This stimulates development of a noncontact magnetic sensor-based large electric current measurement system for fixed conductors to be employed in power systems. However, the presence of strong magnetic noise from near equipment imposes restriction on the use of sensitive magnetic sensor in open air where magnetic noise sources operating at the same frequency may distort the sensor output. The novelty of this paper is the application of MF sensor inside magnetic shielding layers for large current measurement. High-permeability Mu-metal is employed and arranged in three arc-shaped layers for designing a semicircular special shielding arrangement. The application of the method and design is demonstrated for large current carrying conductor arranged inside a gas-insulated switchgear. The measurement system is first validated by the finite-element analysis method and then tested with a comprehensive experimental setup in the presence of strong magnetic noise stimulus of 0.28 T generated by a strong neodymium magnet. The resultant apparatus is tested for current of up to 1000 A with a resolution of 0.01% and error less than 3% in the worst case scenario. The prototype demonstrated excellent linearity during experimental validation of current measurement of 100–1000 A in the presence of magnetic noise stimuli at different positions where the standard deviation between slopes value for sensor response to input current (100–1000 A) curve for six different test cases remains only 0.83%.

Purinergic receptor expression and function in rat vagal sensory neurons innervating the stomach

The nodose ganglion (NG) is the main parasympathetic ganglion conveying sensory signals to the CNS from numerous visceral organs including digestive signals such as gastric distension or the release the gastrointestinal peptides. The response characteristics of NG neurons to ATP and ADP and pharmacological interrogation of purinergic receptor subtypes have been previously investigated but often in NG cells of undetermined visceral origin. In this study, we confirmed the presence of P2X3 and P2Y1 receptors and characterized P2X and P2Y responses in gastric-innervating NG neurons. Application of ATP-evoked large inward currents and cytosolic Ca2+ increases in gastric-innervating NG neurons. Despite the expression of P2Y1 receptors, ADP elicited only minor modulation of voltage-gated Ca2+ channels. Considering the sensitivity of NG neurons to comorbidities associated with disease or neural injury, purinergic modulation of gastric NG neurons in disease- or injury-states is worthy of further investigation.

Optimum Design of 48-Pulse Rectifier Using Unconventional Interphase Reactor

In order to simultaneously reduce the harmonics of input line current and ripple of load voltage in multipulse rectifier, this paper proposes a 48-pulse rectifier using the unconventional interphase reactor (IPR) with an auxiliary single-phase diode-bridge rectifier at the dc link. The primary winding of the unconventional IPR is triple-tapped, and the secondary winding is connected with a single-phase diode-bridge rectifier. The operation mode of the unconventional IPR is analyzed, and the optimal tap ratio and turn ratio are designed. With the optimal parameters of the IPR and the optimal conduction time sequence of power devices, the proposed rectifier extends the conventional 36-pulse rectifier operation to a 48-pulse operation and draws near sinusoidal input line currents, the total harmonic distortion (THD) of which is about 3.81%. The proposed 48-pulse rectifier is easy and simple to implement, and it is more suitable for high-voltage and large-current application. Some simulation and experiments are provided to validate the theoretical analysis.

Hybrid full‐bridge converter for DC microgrids: analysis and implementation

This study presents a soft-switching converter for direct current microgrid applications. The studied converter includes n cells of the hybrid full-bridge converter with primary-series–secondary-parallel connection for high-voltage input and large current output applications. Thus, the voltage stress of power switches and the current stress of rectifier diodes are decreased. Therefore, the low-voltage stress and low conduction resistance of power metal–oxide–semiconductor field-effect transistors are utilised in the studied converter to reduce conduction losses on power switches. The flying capacitors are connected between each circuit cell to prevent voltage unbalance on input split capacitors. On each circuit cell, a full-bridge converter with an additional half-bridge circuit is employed to achieve low circulating current losses, less output inductance and a wide range of zero-voltage switching. Finally, the studied converter with 1800 W rated power is constructed and tested to verify the theoretical analysis.

Comparison of Lithium-Ion Anode Materials Using an Experimentally Verified Physics-Based Electrochemical Model

Researchers are in search of parameters inside Li-ion batteries that can be utilized to control their external behavior. Physics-based electrochemical model could bridge the gap between Li+ transportation and distribution inside battery and battery performance outside. In this paper, two commercially available Li-ion anode materials: graphite and Lithium titanate (Li4Ti5O12 or LTO) were selected and a physics-based electrochemical model was developed based on half-cell assembly and testing. It is found that LTO has a smaller diffusion coefficient (Ds) than graphite, which causes a larger overpotential, leading to a smaller capacity utilization and, correspondingly, a shorter duration of constant current charge or discharge. However, in large current applications, LTO performs better than graphite because its effective particle radius decreases with increasing current, leading to enhanced diffusion. In addition, LTO has a higher activation overpotential in its side reactions; its degradation rate is expected to be much smaller than graphite, indicating a longer life span.

Ignitron-Based Switching Scheme for Multiple Ignitron Triggering in Pulsed Power Applications

This paper describes a low-cost ignitron-based switching scheme for transferring energy from capacitor bank to various loads, used in plasma physics and other pulsed power applications. Battery-operated driver modules have been designed to simultaneously trigger two ignitrons in parallel by using either transistor–transistor logic pulses or optical pulses using a fiber-optic interface with optical fibers of length up to 50 m, for applications prone to generate electromagnetic interferences. These driver modules are designed using insulated gate bipolar transistors as switches to deliver a pulse of amplitude of ~500 A and rise time of $\sim 1.2~\mu \text{s}$ to the ignitor–cathode junction of their respective ignitrons. The modules are designed to facilitate triggering of multiple ignitrons required for large current applications. The feasibility of this scheme and the performance of designed circuit are characterized using a test setup. Statistical variation of triggering delay for single ignitrons is studied extensively, and the effect of trigger energy on statistical parameters is reported. Jitters of 63.5 and 85 ns, respectively, have been observed for triggering of each ignitron used in this scheme. Difference in triggering of two ignitrons connected in parallel is also studied, and a jitter of 150 ns is observed in the onset of current discharges through individual ignitrons.

Improved State of Charge Estimation for High Power Lithium Ion Batteries Considering Current Dependence of Internal Resistance

For high power Li-ion batteries, an important approach to improve the accuracy of modeling and algorithm development is to consider the current dependence of internal resistance, especially for large current applications in mild/median hybrid electric vehicles (MHEV). For the first time, the work has experimentally captured the decrease of internal resistance at an increasing current of up to the C-rate of 25 and developed an equivalent circuit model (ECM) with current dependent parameters. The model is integrated to extended Kalman filter (EKF) to improve SOC estimation, which is validated by experimental data collected in dynamic stress testing (DST). Results show that EKF with current dependent parameters is capable of estimating SOC with a higher accuracy when it is compared to EKF without current dependent parameters.

High-efficiency CMOS rectifier with minimized leakage and threshold cancellation features for low power bio-implants

A high-efficiency architecture for full-wave CMOS rectifier is presented in this paper to solve the power supply issue of wirelessly-powered low-voltage biomedical implantable systems. It uses bootstrapped capacitors to reduce the effective threshold voltage and a CMOS inverter to minimize the reverse leakage. The designed architecture provides high Power Conversion Efficiency (PCE) at the cost of low dropout voltage. Therefore, this proposed architecture is a good candidate for low-voltage power supplies and large load current applications. The proposed rectifier is implemented in standard Samsung 0.18µm CMOS technology in cadence environment. Simulation results demonstrate an improved voltage and power conversion efficiency with a small layout area compared with the best recently published results of CMOS rectifiers.

Characterization of Critical Current Distribution in Roebel Cable Strands Based on Reel-to-Reel Scanning Hall-Probe Microscopy

We have characterized the local critical current distribution in 2-mm-wide Roebel cable strands using reel-to-reel scanning Hall-probe microscopy (RTR-SHPM). Roebel cable is an equally transposed cable formed from coated conductor architectures that is promising for large current applications. Local spatial critical-current uniformity becomes a crucial issue for the thermal stability of high-current windings. In general, the one-dimensional longitudinal critical-current distribution in coated conductors has been characterized by TAPESTAR as a de-facto standard method. However, it has proved to be difficult to use this method to achieve sufficient quality control of Roebel strands because of the unavailability of information on current flow across the width at a transposition. Furthermore, the lack of spatial resolution across the width becomes a problem for narrower strands. In this study, we applied RTR-SHPM for the characterization of Roebel strands. By scanning a Hall senor across the width of a conductor that was moving in a longitudinal direction, a high spatial-resolution two-dimensional distribution of magnetic field can be obtained for long-length conductors. This enabled us to estimate the local critical current, including the dependence on effective strand width, as a function of a longitudinal coordinate. This information is critical to the optimization of the fabrication processes and for nondestructive quality assurance of long-length Roebel strands.

A Novel 24-Pulse Diode Rectifier with an Auxiliary Single-Phase Full-Wave Rectifier at DC Side

A simple and robust 24-pulse diode rectifier for low-voltage and high-current applications is proposed in this paper. The proposed 24-pulse diode rectifier consists of a conventional four-star 12-pulse diode rectifier and an auxiliary single-phase full-wave rectifier (ASFR) installed at dc side. The low-power (3.4%Po) ASFR extracts two rectangular currents from the modified second-stage interphase transformer and injects a square current into the output of the rectifier system. This modification extends the conventional four-star 12-pulse operation to 24-pulse operation. The proposed 24-pulse rectifier draws near sinusoidal input line currents with the absence of 5th, 7th, 11th, 13th, 17th, and 19th harmonics. The average value of current through the ASFR has only 1.7% of load current, which means the current rating and conduction losses of ASFR are very small. The proposed scheme has low-diode conduction losses, and it is more suitable for low-voltage and large-current applications. Since only an additional ASFR is needed, the proposed scheme is low cost and simple to implement. The detailed analysis for the proposed rectifier is presented, and experimental results are provided to verify the proposed concept.

Distributed Control and Redundant Technique to Achieve Superior Reliability for Fully Modular Input-Series-Output-Parallel Inverter System

Input-series-output-parallel (ISOP) inverter system is very suitable for high input voltage and large output current power conversion applications. One of many merits of this assembly system lies in that its characteristic of multimodule series–parallel combination can significantly improve the reliability of the operation. To address this point, redundancy should be realized for the whole system. However, the existing methods for the ISOP inverter system all belong to centralized control, which restricts the modularity of the system. From the above perspective, this paper proposes a new scheme to achieve both power balance and distributed configuration according to the conception of compound control. Also, the relationship of control loops is analyzed and the design procedure of them is given. Based on the fully modular system actualized by the distributed control, the hot-swap technique is then raised to get a redundant system with superior reliability. Here, the way of bypassing other than cutting off is adopted to fulfill withdrawal of the faulty module from the system due to series connection at the input terminal. In addition, the detailed timing sequence of system operation is provided to ensure the smooth transition during the hot-plugging transient. Finally, a three-module prototype is built and the experimental results validate the effectiveness of the presented strategy.