Total Output Current Research Articles

Energy-efficient power summator of hydrogen fuel cell

The most important task after the end of the COVID-18 pandemic is to solve the problem of preserving the planet's climate and improving the environment in populated areas (metropolises, cities, towns). The most important principles contributing to the solution of this problem were set out in the Centenary Memorandum (A.L. Gusev, T.N. Veziroglu, J. Sheffield and other scientists, 2006). The most important element of hydrogen energy is the fuel cell. Fuel cells are produced in different modifications, they can be different in principle of operation, and different in size and DC generation power. Large consumers, both stationary and autonomous, at different times consume different amounts of power from the minimum value to the average and maximum. Obviously, if an object consumes minimal power over a given period of time, then there is no point in generating maximum power. Typically, fuel cells are designed for a specific power range. In connection with the above, in practice situations arise when it is necessary, depending on energy consumption, to connect hydrogen fuel cells of various powers.A new principle for constructing energy-efficient and small-sized summing step-up capacitor DC-DC converters (SSCC) capable of not only converting the level of output voltages, but also summing the powers of several sources in a common load is proposed. The sources are hydrogen fuel cells converted into constant voltage sources, different in output parameters and having a common grounded bus. The principle of multi-cycle construction of SSСС is proposed, which provides additional improvement of their weight and size characteristics under conditions of increased source power. It is shown that the effect is achieved by a multiple increase in the conversion frequency of individual SSСС modules and the practical elimination of a bulky output capacitor due to a sharp decrease and multiple increase in the frequency of the first harmonic of the total output current. Analytical expressions have been obtained that make it possible to calculate the parameters of the reactive elements of the SSСС, to analyze and quantify their efficiency.

Current Tracking and Circulating Current Suppression Super-Twisting Sliding Mode Control for Parallel Operation of EAST Fast Control Power Supply

To quickly output sufficient current for plasma excitation control, parallel operation of a structure of multiple branches is adopted in the Experimental Advanced Superconducting Tokamak (EAST) fast control power supply. During the process of parallel operation of multiple branches in engineering, a larger inductance current sharing reactor is used to suppress the circulating current for the branches, which reduces the dynamic response speed of the output current and increases economic costs. In order to achieve cost savings and improve the dynamic response speed of the output current, the parallel branch current model of the EAST fast control power supply is analyzed, and the current of each branch is reconstructed into two parts: the current flowing to the load end and the circulating current flowing to other branches. Without changing the circuit structure and increasing the additional complex communication system for each branch, observation of the current flowing to the load end from each branch is achieved. Based on the observed current, a super-twisting sliding mode controller (STSMC) is designed to suppress the circulating current flowing through branches. To realize fast output of the branch current and circulating current suppression for the branches, a new STSMC with a linear term and parameter adaptive structure is designed, speeding up the convergence rate of the whole control system. The linear term and designed parameter adaptive structure based on the sliding mode system status ensure fast convergence speed and excellent control performance of the system. Simulation and experiments show that the designed control method can achieve fast output current control for each branch and that the tracking performance of the total output current is good. While reducing the inductance of the current sharing reactor, the circulating current for the branches is effectively suppressed compared with traditional control methods. The proposed method has great significance in cost savings and performance improvement in engineering practice applications.

A Carrier-Based Low Total Current Ripple Modulation Strategy for Parallel Converters With Leakage Current Attenuation

In order to meet the high performance and low leakage current requirements in high power rating photovoltaic applications, an improved carrier-based modulation (ICBM) for parallel converters is presented in this paper. Different from existing methods which are based on PS-PWM, a proper zero-sequence modulation wave is injected into the three-phase modulation waves to achieve low total current ripple based on the root mean square value analysis of output current ripple. Aside from this, the initial phase shift angles for the carriers in each converter are modified to minimize the excitation source of leakage current, while the quality of total output current is not affected. Furthermore, the proposed ICBM is extended to parallel multilevel converters according to the vector shift principle. By using the proposed ICBM, total current ripple reduction and leakage current attenuation in parallel converters can be achieved simultaneously. Experimental results validated the correctness and effectiveness of the proposed method.

Influence of various parameters on the current distribution and protection degree of impressed current cathodic protection for reinforced concrete with TiMMO mesh anodes

Impressed current cathodic protection (ICCP) is an effective technique to control reinforcement corrosion in concrete structures. The efficiency and design of an ICCP system with titanium mixed metal oxide (TiMMO) anodes in a mortar overlay is strongly influenced by the current distribution to the different reinforcement layers of a reinforced concrete element. An in-depth experimental study is performed to investigate the effect of various parameters on the current distribution and degree of corrosion protection: (i) chloride content, (ii) cement type, and (iii) reinforcement configuration. 24-hour depolarization measurements (EN ISO 12696:2022) indicate that an increase in chloride concentration in the concrete, related to an increase in the rate of reinforcement corrosion, leads to a general decrease in the degree of protection. The use of a CEM III/A cement leads to a large increase in concrete electrical resistivity compared to concrete with an ordinary Portland cement (CEM I). This causes a lower total current output to the reinforcement and a less uniform distribution of current. Finally, a lower steel reinforcement density resulted in a larger current density, as the total current is distributed over a smaller steel surface area, causing higher depolarization values.

Optimization of application Impressed Current Cathodic Protection design on the jetty steel structure to corrosion control

This paper discusses the case study of the impressed current cathodic protection (ICCP) system for jetty of barge loading conveyor (BLC). This impressed current cathodic protection system is corrosion mitigation using an inert anode and an electrical device: rectifier, voltmeter, DC source on the BLC structure, and jetty pile to provide accelerated corrosion protection to parts of the pipe submerged in seawater. In this study, a mapping of the service distribution of inert anode carried out so that it can protect the BLC structure and the pile. The results of the measurement of the structure potential and impressed current cathodic protection (ICCP) at BLC jetty considered to meet the protection criteria according to ISO 15589-2: 2012 standards. The obtained measurement results are in the range between -842 mV to -1197 mV (Ag/AgCl). The results of inspections and measurement of the output of the transformer rectifier show the total output current is safe.

High Transconductance Gain Current Differencing Transconductance Amplifiers Using a New Approach of gm Boosting

Two new structures of current differencing transconductance amplifier (CDTA) for high transconductance gains are proposed. Usually, the transconductance gain of conventional CDTA is controlled by varying the bias current which limits the transconductance gain up to a certain extent and increases the power dissipation. These problems have been eliminated by introducing a technique in which common source amplifiers are connected between gate and source terminals of the differential pair metal oxide semiconductor field effect transistors (MOSFETs) of conventional CDTA. The common source amplifiers are used to increase the gate-to-source voltages of differential pair MOSFETs which increase the transconductance gain of the proposed CDTA-I. To further increase the transconductance gain of the proposed CDTA-I, another structure namely, CDTA-II is also proposed which uses an ‘N’ number of n-type MOSFETs connected in parallel instead of a single n-type MOSFET in each side of the differential pair. The gate-to-source voltages of all ‘N’ parallel MOSFETs remain the same as in the proposed CDTA-I and the total output current of operational transconductance amplifier is increased and therefore, transconductance gain is further increased. The proposed CDTA-I and CDTA-II have been designed using Mentor Graphics Eldo tool. The simulation results have been obtained using 0.18 µm complementary metal oxide semiconductor technology parameters. The simulation results demonstrate that the transconductance gains of proposed structures have been increased significantly while power dissipations are the same as that of the conventional CDTA. The high-frequency Kerwin–Huelsman–Newcomb filters using both the proposed structures have also been presented to show the effectiveness of the proposed CDTAs.

(Invited) Demystifying the Electrode/Electrolyte Interface in Carbon-Based Electrochemical Capacitors with Specs Technique and Electrochemical Dilatometry

It is often said that the highly developed surface area of electrode materials ensures high capacitance, power and energy in electrochemical capacitors. However, the real ‘efficiency’ of the surface exploited in charge storage remains unknown. Recently, it turned out that the Step Potential Electrochemical Spectroscopy (SPECS) technique can be a useful tool for determining it.The SPECS technique allows for the comprehensive analysis of the total current output and evaluation of the capacitive, redox and other components. Together with the physicochemical data from nitrogen and CO2 adsorption techniques, we aim at the determination of the real electrode/electrolyte interface surface.Based on the knowledge gained to date, we assume that the efficiency of the interface ‘exploitation’ depends on many factors: pore size distribution, wettability of the electrode material by electrolyte, as well as the size of the ions. Thus, inappropriate selection of one of these parameters can aggravate the device performance, even if the excellent carbon material is applied as electrode component.The paper will provide the results from SPECS correlated with the physicochemical properties of carbon materials. It appears that the electrochemically accessible surface does not exceed 30% of the values estimated by N2 or CO2adsorption. The results will be supported by the recent findings from electrochemical dilatometry experiments.

Wafer-Scale Fabrication of Solid-State on-Chip Microsupercapacitors Based on Silicon-Processing Techniques

Conventional silicon-based fabrication techniques, ranging from photolithography to various etching processes, are well-established approaches for achieving high-resolution patterns for microelectronics in the semiconductor industry. Although the use of microfabrication methods in the production of electrochemical energy storage (EES) devices has not really been considered, the adaption of these silicon processing techniques can open up new fabrication routes especially for integrated on-chip energy storage devices. One important consideration for the development of on-chip EES devices is to fabricate a mechanically rigid solid electrolyte with spatial and thickness control, which can be achieved using photopatterning functionality.1 This presentation will review our results on the synthesis and characterization of a photopatternable, ionically conducting solid electrolyte for on-chip micro-supercapacitors (MSC). Our approach was to create ‘quasi-solid’ electrolytes in which the photopatternable epoxy-based polymer matrix (SU-8) confines charge-carrying ions to provide measurable ionic conductivity. The resulting ion modified electrolyte is a promising gel polymer electrolyte with excellent thermal and physical properties and a room temperature ionic conductivity of 10-4 S cm-1. In addition, we demonstrate wafer-scale fabrication of all-photopatterned solid-state MSC devices. Electrochemical testing of tandem MSC devices validated that the potential range and total current output of MSC devices can easily be tailored through modifying the device arrangements in series or parallel configurations. The proposed fabrication strategy, based on magnetron sputtering of electrode materials in conjunction with a photopatternable solid electrolyte, provides a unique opportunity for the development of robust solid-state MSC that can be integrated with microelectronics in a single chip.Reference 1. Choi, J. Lau, J. Hur, L. Smith, C. Wang, B. Dunn, Advanced Materials. 30 (2017) 1703772.

A Family of Hybrid IPT Topologies With Near Load-Independent Output and High Tolerance to Pad Misalignment

Inductive power transfer (IPT) systems have many unique benefits compared to conventional plugged-in systems. The coupling pads in IPT systems are inevitably misaligned in many practical applications, thus leading to variations of the transferred power and efficiency that necessitate the use of complicated control for output regulation. A common solution is to use two IPT converters with opposite trends of output to pad misalignment, so that the total output voltage or current could be kept near constant for large coupling variations. However, methods for deriving effective configurations for such hybrid IPT converters and their achievable tolerance to the misalignment are still missing. This article constructs a family of hybrid IPT topologies, including input-parallel-output-parallel, input-parallel-output-series, input-series-output-parallel (ISOP), and input-series-output-series for delivering a constant current (CC) or a constant voltage (CV). Design principles and characteristics for all the hybrid systems with near load-independent output and high tolerance to pad misalignment are derived and discussed in detail. Based on this family of configurations, this article also combines some existing IPT topologies and derives multiple hybrid converters for CC or CV output by using a simple duty cycle control. Finally, a 3.5-kW hybrid IPT prototype converter based on the ISOP structure is built to verify the theoretical analysis.

Comprehensive sharing control strategy for input‐series output‐parallel connected modular DC–DC converters

The systems consisting of multiple DC–DC converters with input-series output-parallel (ISOP) connection are widely used in high-power applications. In the ISOP connection, the total input voltage and output current should be divided equally between the converters. However, in order to achieve this purpose, a proper control scheme should be used. This study proposes two control schemes: (i) output current feedback (OCF) and (ii) input voltage feedback (IVF). Based on the power balance, in the IVF scheme, the total output current, and in the OCF scheme, the total input voltage are divided automatically between the converters, and there is no need to use an extra control loop. The IVF and the OCF control schemes consist of two control loops: a common output voltage regulator (OVR) loop and individual input voltage sharing loops in the IVF scheme or individual output current sharing loops in the OCF scheme. The proposed control scheme can effectively improve the stability and dynamic characteristics of system. Finally, both the results of the simulation and laboratory prototype of an ISOP system consisting two forward converters have verified the performance of the IVF and OCF control schemes.

Evaluation of DC-Link Voltage Switching Ripple in Multiphase PWM Voltage Source Inverters

This article presents a generalized approach toward the dc-link voltage switching ripple analysis in the two-level multiphase pulsewidth modulation (PWM) voltage source inverters with a balanced load. Since the voltage ripple is one of the crucial sizing criteria for a dc-link capacitor, a simple and practical equation for designing the dc-link capacitor, based on the maximum (peak-to-peak) value of the dc-link voltage ripple, has been proposed for the multiphase inverters. The amplitude of the dc-link voltage switching ripple is analytically derived as a function of operating conditions. The effect of the number of phases on the dc-link capacitor size is investigated as well. It is found that considering the same total output current, the dc-link capacitor size is reduced by increasing the number of phases up to seven. However, from the point of view of the dc-link capacitor size, there are no benefits of further increasing the number of phases. Reference is made to two commonly used modulation strategies—sinusoidal PWM and continuous symmetric centered PWM (i.e., space vector). The mathematical models are derived with an aim to provide the precise dc-link capacitor sizing and hence improve the power density of the whole system. The comparison of different phase numbers has been made. Proposed theoretical developments are verified by the simulation and experimental tests.

Coordinated Elimination Strategy of Low Order Output Current Distortion for LC-Filtered DFIG System Based on Hybrid Virtual Impedance Method

This paper proposes a coordinated control strategy for the rotor-side converter (RSC) and the grid-side converter (GSC) of an LC-filtered doubly fed induction generator (DFIG) under distorted grid voltage condition, to eliminate the distortion of the total output current (including the stator current, the GSC current, and the filter capacitor current). For an LC-filtered DFIG connected to a distorted grid, the low-order current harmonics can freely flow into the filter capacitor thereby polluting the total output current, even when the stator current and the GSC current are both controlled as sinusoidal. Although this problem can be addressed by measuring the output current or the capacitor current, the extra current sensors are undesired in industrial applications. In this paper, a novel hybrid virtual impedance method is implemented in both the RSC and the GSC, to reshape the parallel impedance of the stator, the GSC and the filter capacitor to nearly infinite for low-order harmonics, thus, the freely flowing output current harmonics can be mitigated. Meanwhile, the low-order current harmonics required by the output current compensation can be flexibly distributed between the stator and the GSC according to their operating conditions, to disperse the side-effects on the drive train and the GSC, thereby better protecting the whole system. The effectiveness of the proposed strategy is theoretically analyzed and verified with both simulation and experiment.

Vertical geometry 33.2 A, 4.8 MW cm2 Ga2O3 field-plated Schottky rectifier arrays

The performance of arrays consisting of 21 β-Ga2O3 field-plated rectifiers fabricated on thick epitaxial layers (n-type carrier concentration ∼1.6 × 1016 cm−3) grown on conducting substrates (carrier concentration 3 × 1019 cm−3) is reported. We show that by interconnecting the output of 21 smaller (0.4 × 0.4 mm2 to 1 × 1 mm2, total area 0.09 cm2) individual rectifiers using e-beam deposited Au, we can achieve a high total forward output current of 33.2 A, at 4.25 V in the single-sweep voltage mode, and a low forward turn-on voltage of 2.9 V (defined at 100 A cm−2) and maintain a reverse breakdown voltage of 240 V (defined at 1 μA cm−2). The current density was 376 A cm−2, and the on-state resistance was 0.012 Ω cm2. The total forward current was 10 A at 1.9 V and 22 A at 3 V. The power figure-of-merit for the array, VB2/RON, was 4.8 MW cm−2, with a reverse recovery time of individual rectifiers of 32 ns. The on/off ratio of the rectifier array was in the range of 105–1010 for +1 V/−1 to −100 V.

Problems in the Classic Frequency Shift Islanding Detection Methods Applied to Energy Storage Converters and a Coping Strategy

This paper first derives a usable formula for frequency shift islanding detection methods on the basis of the parallel R , L , C load and the conclusions in current literature: the angle by which the total output current of the distributed resources (DR) units leads the point of common coupling (PCC) voltage must be conducted to have the same shifting direction as the load admittance angle during the variation of the frequency. According to the formula and multi-DR operation, the scenarios in which the classic frequency shift methods are applied to energy storage converters are analyzed. The results indicate that the setting of the angle by which the energy storage converter current leads the PCC voltage may need to be modified when running state changes. It results in the problems that the classic methods are not applicable for non-unity power factor (non-UPF) control and have to distinguish between generation mode and consumption mode for UPF control. On account of the problems, a coping strategy, i.e., an improved method, is proposed. The analyses indicate that the improved method is applicable in every state. The last simulations and experiments confirm the preceding conclusions.

A Dense Manganese Porphyrin-Nanobar Random Arrays: Direct and Electrocatalytic Oxidation of Ascorbic Acid in the Presence of Dopamine and Uric Acid

An array of micro/nanoelectrodes offers most of the advantages of single micro/nanoelectrodes, but with the added benefit of a higher total current output and increasing sensitivity. This work reports the analytical performance of a gold electrode modified with a Mn(III) porphyrin nanobar-film (NBMn-PPh) employed for the sensitive determination of Ascorbic Acid (AA) at pH = 7.4 in the presence of always coexistence interferences Dopamine (DA) and Uric Acid (UA).

Novel Power Allocation Method to Distribute the Working Current of Parallel-Connected Lithium-Ion Battery Packs

Owing to the growing environmental awareness, finding alternative energy sources of petroleum has become an important issue. Out of the total petroleum consumption, vehicle transportation accounts for up to half of it. Therefore, electric vehicles have swept the globe, and lithium-ion battery is among the best electric energy-storage candidates because of its high working voltage, high energy density, and long cycle life without memory effect. For high power equipment, a battery pack which is composed of large number of batteries in series and parallel is necessary. However, after cyclic charging and discharging loops, the uniformity in the parallel-connected battery pack is destroyed; consequently, electrical current appears in the pack between any two batteries with potential difference. Therefore, it can be easily expected that analysis of paralleled batteries becomes more and more complicated while the number of batteries increases. For example, in a set of 100 parallel-connected batteries, 4950 directional branch currents are needed to be manipulated to satisfy Kirchhoff Circuit Laws. Obviously, heavy computational load makes the analysis of mass batteries based on the electrochemical model impossible. In this study, we propose a novel solution in combination with the ESP (enhanced single particle) model as proposed in Ref. [1] to enable an electrochemical analysis even with a huge amount of batteries in the pack. The main idea of the novel solution originates from the “power allocation”, which means that when an electron leaving a certain battery owns a larger kinetic energy, the current dedicated by this battery accounts for a higher proportion of the total output current. Since the kinetic energy of an electron amounts to the electrical potential difference, the current distribution of a certain battery k in a parallel-connected battery pack with a total of n batteries can be assumed to be Eq.(1), where is the summation of equilibrium currents between the battery k and all the other batteries, and it can be obtained from the view of electrical work as Eq. (2), where is a weighting factor which is related to the convergence. Accordingly, the working current of the battery k at the next time interval () can be calculated from the current and voltage information at the time t, i.e., Eq. (3). From the simulated discharge-charge curve shown in Fig. 1, it can be seen that by employing this method, the working voltage of the parallel-connected battery pack with 100S120P reaches the same in a dozens of time steps. The corresponding discharge and charge current distributions within each parallel string are presented in Fig. 2 and 3, respectively. This method finds an approximate solution instead of the exact solution from KCL, however, the deviation of the result is only within 10-3~10-5 volt, which is a tolerable error range. REFERENCES [1] N. Baba, H. Yoshida, M. Nagaoka, C. Okuda, and S. Kawauchi, J. Power Sources, 252, 214 (2014). Figure 1

Self powered neutron detectors as in-core detectors for Sodium-cooled Fast Reactors

Neutron flux monitoring system forms an integral part of the design of a Generation IV sodium cooled fast reactor. Diverse possibilities of detector system installation must be studied for various locations in the reactor vessel in order to detect any perturbations in the core. Results from a previous paper indicated that it is possible to detect changes in neutron source distribution initiated by an inadvertent withdrawal of outer control rod with in-vessel fission chambers located azimuthally around the core. It is, however, not possible to follow inner control rod withdrawal and precisely know the location of the perturbation in the core. Hence the use of complimentary in-core detectors coupled with the peripheral fission chambers is proposed to enable robust core monitoring across the radial direction.In this paper, we assess the feasibility of using self-powered neutron detectors (SPNDs) as in-core detectors in fast reactors for detecting local changes in the power distribution when the reactor is operated at nominal power. We study the neutron and gamma contributions to the total output current of the detector modelled with Platinum as the emitter material. It is shown that this SPND placed in an SFR-like environment would give a sufficiently measurable prompt neutron induced current of the order of 600nA/m. The corresponding induced current in the connecting cable is two orders of magnitude lower and can be neglected. This means that the SPND can follow in-core power fluctuations. This validates the operability of an SPND in an SFR-like environment.

Duty-Ratio-Control-Aided LLC Converter for Current Balancing of Two-Channel LED Driver

Duty-ratio-control-aided LLC converter for current balancing of two-channel light-emitting diode (LED) driver is proposed and analyzed. Conventional current-balancing methods have the limitation on the power density and losses from additional components. With the aid of duty ratio control of an LLC converter, the proposed driver does not require any additional component. The total output current is controlled with the frequency modulation, and the duty ratio control is added to obtain current balancing of each LED channel. The advantage of the proposed method is the high power density and high efficiency. Also, it does not affect design procedure of a conventional LLC converter. The prototype of two-channel LED driver with 400-V input and 150–100-V/0.3-A output for each channel verifies the effectiveness of the proposed driver.

Editors' Choice—Electrolyte Film Thickness Effects on the Cathodic Current Availability in a Galvanic Couple

A combined modeling and experimental study was performed to understand the dependence of the cathodic current delivery capacity on the electrolyte film thickness and cathode size in a galvanic couple. The appropriate cathodic kinetics for the modeling were generated by use of a rotating disk electrode to simulate the electrolyte film thickness. These results provided boundary conditions for a finite element model which calculated the potential distribution along a metallic surface and the associated cathodic current supplied for electrolyte layers of varying thickness. The total cathodic current was then calculated through integration of the current density across the surface. Electrolyte layer domains were delineated by three limits which described, in order of decreasing film thickness, i) transition in exposure condition from full immersion to thick film, ii) the hydrodynamic boundary layer due to natural convection which defined the upper limit of the thin film regime, and iii) the relative dominance of ohmic resistance over mass transport in determining the total current output. This study also showed that for sufficiently thin films, this total current was independent of the size of the cathode and the nature of kinetics at the electrochemical interface, being solely driven by the ohmic resistance in solution.

Design Considerations for a 11.3 Gbit/s SiGe Bipolar Driver Array With a <inline-formula> <tex-math notation="LaTeX">$5\times \text {6 V}_{\mathrm {pp}}$ </tex-math> </inline-formula> Chip-to-Chip Bondwire Output to an MZM PIC

This paper presents the design of a 5-channel driver array IC with a high total output current of $5\times \text {120 mA}$ and a $6~\mathrm {V}_{\mathrm {pp}}$ differential output voltage in SiGe bipolar technology. Special attention is given to design considerations for stable electrical and thermal operation and to the minimization of cross-coupling between the array channels. The related driver array is intended to realize a low-cost, small footprint $10\times \text {11.3 Gbit/s}$ dense wavelength division multiplexing transmitter assembly, consisting of a pair of two driver ICs with a chip-to-chip bondwire interface to a ten-channel Mach–Zehnder modulator (MZM) in a photonic integrated circuit (PIC). The driver IC contains all required components, including the far-end terminations of the MZMs as well as an energy-efficient concept for flexible MZM biasing. Current hogging in the transistors of the output stages is mitigated by a novel circuit concept that is introduced along with an electro-thermal model for dense multi-transistor arrangements, especially in driver output stages. The performance of the design is demonstrated by measurement results of the driver array IC in both standalone and integrated PIC assemblies.