Constant Current Source Research Articles

An AI-Based Newly Developed Analytical Formulation for Discharging Behavior of Supercapacitors with the Integration of a Review of Supercapacitor Challenges and Advancement Using Quantum Dots

A supercapacitor is a type of electrical component that has larger capacitance, due to asymmetric behavior with better power density, and lower ESR (effective series resistance) than conventional energy-storage components. Supercapacitors can be used with battery technology to create an effective energy storage system due to their qualities and precise characterization. Studies have shown that the use of quantum dots as electrodes in supercapacitors can significantly increase their effectiveness. In this research article, we have used a Drude model based on free electrons (asymmetric nature) to describe the supercapacitor’s discharging characteristics. Commercially available Nippon DLA and Green-cap supercapacitors were used to verify the Drude model by discharging them through a constant current source using a simple current mirror circuit. The parameters of both the fractional-order models and our suggested method were estimated using the least-squares regression fitting approach. An intriguing finding from the Drude model is the current-dependent behavior of the leakage-parallel resistance in the constant current discharge process. Instead of using the traditional exponential rule, supercapacitors discharge according to a power law. This work reflects the strong symmetry of different aspects of designing a hybrid supercapacitor with high efficiency and reliability.

Research on portable constant pulse current source device

A set of portable constant pulse current sources with STM32 as the control core is developed, which mainly involves the SCM control module, operational amplifier circuit module, pulse output module, power module, key module, and display module. Based on the traditional constant-current source circuit design, the real-time display control system is constructed by software programming optimization, which has the characteristics of portable and strong stability. By connecting the field effect tube and operational amplifier in series to form a feedback loop, the current output accuracy is improved and the stability of the current output is ensured. The experimental results show that after the op-amp circuit is introduced into the series feedback system, the front and rear order circuit can be more stable, and ensure the reference voltage is stable at the same time, through the duty cycle of PWM wave to adjust the current output, so that the constant current source output 0~2mA adjustable low-frequency stable current. At the same time, in terms of human-computer interaction, in addition to the use of buttons to adjust the current at both ends of the load, a small OLED display screen is used to display the current, voltage, and pulse frequency in real time. The experiment shows that the instrument has high stability and load adaptability, and has high practical value.

Theoretical considerations and supporting evidence for the primary role of source geometry on field potential amplitude and spatial extent.

Field potential (FP) recording is an accessible means to capture the shifts in the activity of neuron populations. However, the spatial and composite nature of these signals has largely been ignored, at least until it became technically possible to separate activities from co-activated sources in different structures or those that overlap in a volume. The pathway-specificity of mesoscopic sources has provided an anatomical reference that facilitates transcending from theoretical analysis to the exploration of real brain structures. We review computational and experimental findings that indicate how prioritizing the spatial geometry and density of sources, as opposed to the distance to the recording site, better defines the amplitudes and spatial reach of FPs. The role of geometry is enhanced by considering that zones of the active populations that act as sources or sinks of current may arrange differently with respect to each other, and have different geometry and densities. Thus, observations that seem counterintuitive in the scheme of distance-based logic alone can now be explained. For example, geometric factors explain why some structures produce FPs and others do not, why different FP motifs generated in the same structure extend far while others remain local, why factors like the size of an active population or the strong synchronicity of its neurons may fail to affect FPs, or why the rate of FP decay varies in different directions. These considerations are exemplified in large structures like the cortex and hippocampus, in which the role of geometrical elements and regional activation in shaping well-known FP oscillations generally go unnoticed. Discovering the geometry of the sources in play will decrease the risk of population or pathway misassignments based solely on the FP amplitude or temporal pattern.

Design of a wireless charging system in DC microgrids with accurate output regulation and optimal efficiency

This paper presents a general circuit and control design method for wireless power transfer (WPT) systems in DC microgrids to achieve optimal power transfer efficiency, while maintain accurate output voltage regulation. An auxiliary inductor is added at the transmitter resonator to form a current sink to ensure zero voltage switching (ZVS) of the primary-side full-bridge inverter with even extreme-light load conditions. Besides, an adaptive proportional-integral (PI) controller is adopted to track the output voltage references by regulating the phase shift angle of the phase shift control for the full-bridge inverter. The coefficients of the adaptive proportional-integral controller are determined by the inductor of the auxiliary inductor. Both simulation and experimental results have validated the effectiveness of the proposed circuit and control design in achieving optimal efficiency and output voltage regulation for wireless power transfer systems in DC microgrids with source and load variations.

Integration of Stand-Alone Controlled Active Power Filters in Harmonic Power Flow of Radial Distribution Networks

Utilization of active power filters (APFs) is the most efficient method to reduce harmonic pollution in distribution networks. Previous approaches utilized APFs in integrated control schemes based on broad data-gathering systems. Since a broad data-gathering system is not available in most practical distribution networks, previously proposed approaches may not readily be implemented. This paper presents the utilization of stand-alone controlled APFs (SACAPFs) in radial distribution networks. Utilizing APFs with a stand-alone control system decreases implementation costs and complexity by making them autonomous and independent of integrated control systems, which are complicated and expensive in practical applications. In this paper, a single SACAPF is modeled as a dependent current source where its injection current is equal in amplitude but opposite in phase compared to the harmonic content of the current passing through the point of common coupling (reference current). Due to the presence of both linear and nonlinear loads in the distribution network, the reference current changes after injection by SACAPF, so it is necessary to modify the injection current until reaching a constant value in the reference current. This is considered via an iterative procedure in the modeling scheme. Operation of multiple SACAPFs is handled using a backward procedure based on a priority list. Simulation results on an IEEE 18-bus test system show the proper operation of the stand-alone control systems for both single and multiple SACAPF implementation. Furthermore, optimal allocation of the proposed SACAPFs is performed in an IEEE 33-bus test network and a 9-bus test network, and the results are discussed and compared with the allocation of integrated control system APFs.

LFP polarity changes across cortical and eccentricity in primary visual cortex.

Local field potentials (LFPs) can evaluate neural population activity in the cortex and their interaction with other cortical areas. Analyzing current source density (CSD) rather than LFPs is very significant due to the reduction of volume conduction effects. Current sinks are construed as net inward transmembrane currents, while current sources are net outward ones. Despite extensive studies of LFPs and CSDs, their morphology in different cortical layers and eccentricities are still largely unknown. Because LFP polarity changes provide a measure of neural activity, they can be useful in implanting brain-computer interface (BCI) chips and effectively communicating the BCI devices to the brain. We hypothesize that sinks and sources analyses could be a way to quantitatively achieve their characteristics in response to changes in stimulus size and layer-dependent differences with increasing eccentricities. In this study, we show that stimulus properties play a crucial role in determining the flow. The present work focusses on the primary visual cortex (V1). In this study, we investigate a map of the LFP-CSD in V1 area by presenting different stimulus properties (e.g., size and type) in the visual field area of Macaque monkeys. Our aim is to use the morphology of sinks and sources to measure the input and output information in different layers as well as different eccentricities. According to the value of CSDs, the results show that the stimuli smaller than RF's size had lower strength than the others and the larger RF's stimulus size showed smaller strength than the optimized stimulus size, which indicated the suppression phenomenon. Additionally, with the increased eccentricity, CSD's strengths were increased across cortical layers.

3.6 mW Active-Electrode ECG/ETI Sensor System Using Wideband Low-Noise Instrumentation Amplifier and High Impedance Balanced Current Driver.

An active electrode (AE) and back-end (BE) integrated system for enhanced electrocardiogram (ECG)/electrode-tissue impedance (ETI) measurement is proposed. The AE consists of a balanced current driver and a preamplifier. To increase the output impedance, the current driver uses a matched current source and sink, which operates under negative feedback. To increase the linear input range, a new source degeneration method is proposed. The preamplifier is realized using a capacitively-coupled instrumentation amplifier (CCIA) with a ripple-reduction loop (RRL). Compared to the traditional Miller compensation, active frequency feedback compensation (AFFC) achieves bandwidth extension using the reduced size of the compensation capacitor. The BE performs three types of signal sensing: ECG, band power (BP), and impedance (IMP) data. The BP channel is used to detect the Q-, R-, and S-wave (QRS) complex in the ECG signal. The IMP channel measures the resistance and reactance of the electrode-tissue. The integrated circuits for the ECG/ETI system are realized in the 180 nm CMOS process and occupy a 1.26 mm2 area. The measured results show that the current driver supplies a relatively high current (>600 μApp) and achieves a high output impedance (1 MΩ at 500 kHz). The ETI system can detect resistance and capacitance in the ranges of 10 mΩ-3 kΩ and 100 nF-100 μF, respectively. The ECG/ETI system consumes 3.6 mW using a single 1.8 V supply.

Radiation dosimeter and charge detector onboard BeiDou navigation satellites in MEO

Abstract The orbit of BeiDou satellite system is a very ideal space environment monitoring area. The radiation dosimeters are present on this series of navigation satellites, and they are respectively installed in the x, y and z positions. A charge detector installed in the satellite cabin is used for monitoring satellite deep charging potential. Radiation dosimeters select the 100 nm P-channel metal oxide semiconductor (PMOS) sensors, whose monitoring range can reach 2 × 106 rad (Si). In the circuit design part, the “zero temperature coefficient” current of the PMOS is used as the constant current source for measuring, which effectively reduces the influence of temperature effect. Three radiation dosimeters realize the daily dose change monitoring during the satellite’s operation, and the detection accuracy is high. The deep charging potential sensor adopts the equivalent capacitor design which is composed of the outer optical quartz glass and the inner circular gold-plate. The two kinds of detection instruments have the characteristics of small volume, low power consumption and high detection accuracy. The detection results show that they have important application value for space environment prediction and guarantee.

Low ozone dry deposition rates to sea ice during the MOSAiC field campaign: Implications for the Arctic boundary layer ozone budget

Dry deposition to the surface is one of the main removal pathways of tropospheric ozone (O3). We quantified for the first time the impact of O3 deposition to the Arctic sea ice on the planetary boundary layer (PBL) O3 concentration and budget using year-round flux and concentration observations from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) campaign and simulations with a single-column atmospheric chemistry and meteorological model (SCM). Based on eddy-covariance O3 surface flux observations, we find a median surface resistance on the order of 20,000 s m−1, resulting in a dry deposition velocity of approximately 0.005 cm s−1. This surface resistance is up to an order of magnitude larger than traditionally used values in many atmospheric chemistry and transport models. The SCM is able to accurately represent the yearly cycle, with maxima above 40 ppb in the winter and minima around 15 ppb at the end of summer. However, the observed springtime ozone depletion events are not captured by the SCM. In winter, the modelled PBL O3 budget is governed by dry deposition at the surface mostly compensated by downward turbulent transport of O3 towards the surface. Advection, which is accounted for implicitly by nudging to reanalysis data, poses a substantial, mostly negative, contribution to the simulated PBL O3 budget in summer. During episodes with low wind speed (<5 m s−1) and shallow PBL (<50 m), the 7-day mean dry deposition removal rate can reach up to 1.0 ppb h−1. Our study highlights the importance of an accurate description of dry deposition to Arctic sea ice in models to quantify the current and future O3 sink in the Arctic, impacting the tropospheric O3 budget, which has been modified in the last century largely due to anthropogenic activities.

A Design and Validation of 400 W PV Emulator Using Simple Equivalent Circuit for PV Power System Test

In this paper, we propose a photovoltaic emulator (PVE) composed of a series of connected power diodes with a single constant current source, rather than a power converter-based PVE. Accordingly, this enables readily verifying the operation because a the simple hardware structure and lack of a complex control algorithm. The proposed PVE can be intuitively implemented using the proposed selection criteria for the power diode and equivalent resistances. Since there is no feedback control based on complex analog/digital controls and sensors, the control response can be very fast. In addition, the proposed PVE can be easily integrated with a PV power system such as a power optimizer, to allow testing in a simple and flexible manner. Spice simulation was performed based on the electrical characteristics provided by the solar panel manufacturer, and this was utilized to validate the applied emulator circuit model, the Norton Equivalent Circuit. During the design process, the simulation helped to manufacture the PVE within error ranges satisfying the desired I–V and P–V curves, as well as the maximum power point (MPP). Partial shading could be easily implemented through use of the multiple series connection of individual PVEs, demonstrating local MPP and global MPP. A 400 W class PVE was built through appropriate power diode selection, with a thermal design to increase the output power. Moreover, its performance and feasibility were verified through intensive experiments. The measured efficiency, transient response time, and maximum transient error of the partial shading tests were 91%, 22 μs, and 5.8%, respectively.

Comparative Study on Numerical Simulation of Wave-Current Nonlinear Interaction Based on Improved Mass Source Function

In coastal waters, wave propagation is often affected by rivers and tides. The wave current interaction increases the complexity of the wave propagation. In this study, we consider the Boussinesq type equation with an improved dispersion term as the governing equation and establish a numerical model of wave propagation in the coexistence of wave current environment. Firstly, we use the MIKE 21 BW model to simulate the propagation of dual-frequency waves. The Navier–Stokes equation wave model is used to verify the results and the Fourier transform is used to analyze and discuss the dual-frequency waves. Our findings show that the numerical model established by the Boussinesq equation can better describe the nonlinear interaction between waves more accurately at a much higher computational efficiency compared with the Navier–Stokes equation wave model. In addition, we set the constant current source point in the wave numerical model and conduct the numerical simulation of waves in the current environment, by improving the mass source wave generation method. The numerical simulation of wave-current interactions between uniform and variable water depths is performed, thus demonstrating its capability to describe accurately the influence of water flow on wave propagation.

An Auxiliary Passive Circuit and Control Design for Wireless Power Transfer Systems in DC Microgrids with Zero Voltage Switching and Accurate Output Regulations

This paper presents an auxiliary passive circuit and control design for wireless power transfer (WPT) systems in DC microgrids to achieve optimal power transfer efficiency while maintain accurate output voltage regulation. An auxiliary inductance is added at the transmitter resonator to form a current sink to ensure zero voltage switching (ZVS) of the primary-side full-bridge inverter with even extremely light load conditions. Moreover, an adaptive proportional–integral (PI) controller is adopted to track the output voltage references by regulating the phase shift angle of the phase shift control for the full-bridge inverter. The coefficients of the adaptive PI controller are determined by the inductance of the auxiliary inductance. Both simulation and experimental results validated the effectiveness of the proposed circuit and control design in achieving optimal efficiency and output voltage regulation for WPT systems in DC microgrids with source and load variations.

Time-Domain Battery Impedance Identification Under Piecewise Constant Current Excitation

This paper shows how to model the voltage response of a battery excited by a piecewise constant current source. Modeling is done both by using a mathematical approach based on an orthonormal basis of functions and a fractional-order model, both identified in the time domain. The equivalent circuit model is based on the usage of the Mittag-Leffler function and on the proposal of a technique to ease the computational burden. The developed methods allow reduction of the estimation times without approximating the exact solutions of the equivalent circuit model. Experimental results are aimed at validating both models. Outcomes obtained in the time-domain are compared with corresponding results obtained through electrochemical impedance spectroscopy in the frequency-domain. Additional experimental results validate the approach using a standardized profile of discharge currents applied to an initially charged battery.

Control System of Multidirectional Bending Robotic Device Using SMA Wires for Laser Irradiation During Transurethral Lithotripsy

The difficulty of transurethral ureterolithotripsy while operating in a complex and elaborate structure of the urinary system hinders surgeons from using a ureteroscope with a fixed optical fiber to reach the targeted calculus. A continuum-robotic device is proposed to position laser irradiation independently in ureteroscopes actuated by three slackened shape memory alloy (SMA) wires. The deformation of SMA wires is driven by the joule heat generated by electrical current. An adjustable constant current source was fabricated to provide triple power outputs for SMA tendons.

Waveform Correlation Based Harmonic Voltage Contribution Determination of Iron and Steel Plants Supplied From PCC

This paper presents a new waveform correlation based method which determines the individual harmonic voltage contributions of Electric Arc Furnace (EAF) plants supplied from a point of common coupling (PCC). The method is based on the waveform correlation computations between the PCC voltage and the feeder current at the individual harmonic frequency. PCCs supplying multiple EAF plants usually suffer from high voltage harmonic components due to their operation principles. A relationship between the correlation coefficient of the PCC voltage and the feeder current waveforms, and the harmonic voltage contribution of each plant is derived and this relationship is used to derive the individual contributions to the PCC voltage. The main idea of the method is based on the fact that harmonic voltage at the PCC is a result of the additive effect of voltage drops on the source side impedance of the power system caused by the individual feeder currents. No real-time impedance measurements are required in the proposed method and no need for the measurements of the other feeders to compute the contribution of a specific feeder in contrast to some previously proposed methods for the same problem. The proposed method is further expanded in order to reveal the effects of the compensation systems of the EAF plants, which identifies the harmonic current sinking problem of a victim plant with a powerful compensation system using further correlation computations between the feeder currents and in-plant current measurements. The proposed method can be easily adapted as a real time harmonic contribution detection tool for the already-installed power quality analyzers, most of which employ synchronized voltage and feeder current waveform measurements.

How large is the mitigation potential of natural climate solutions in China?

China is facing a huge challenge in achieving its carbon neutrality goal by 2060 given that it is currently one of the world’s largest greenhouse gas (GHG) emitters and has set a very short timeline for going from peak emissions to carbon neutrality. Natural climate solutions (NCS) that protect, manage, and restore ecosystems have shown substantial potential for increasing carbon sinks or reducing GHG emissions to offset fossil fuel CO2 emissions. This study quantified the mitigation potential of 18 NCS pathways in China at 0.67–1.65 Gigatonne of CO2 equivalent (Gt CO2e) yr−1 averaged from 2020 to 2060, which is even larger than the size of the current national terrestrial carbon sink. Compared with a previous global estimate, our results show a lower mitigation potential in forest ecosystems but a much greater potential for cropland ecosystems in China. From 2020 to 2060, all 18 pathways combined can provide cost-effective mitigation compared to the global social cost of CO2 emission and carbon prices, and 98.6% and 83.3% mitigation potential are cost-effective, respectively. This study further showed that immediate action provides the greatest mitigation. Our estimates highlight the important role of NCS in achieving the national carbon neutrality goal because of their large mitigation potential and cost-effectiveness.

Research on control algorithm of strong magnetic interference compensation for MEMS electronic compass

In view of the complicated data acquisition process of traditional MEMS electronic compass compensation methods and the inability to achieve high-precision compensation under strong magnetic interference, this paper studies a compensation method with an external three-axis coil. Firstly, the error modeling of the magnetometer is carried out, and two methods of compensation without heading reference based on M−estimates and compensation with heading reference are introduced. We built a hardware circuit on the basis of a physical coil, used a PXI industrial computer as the data acquisition and processing center, provided current excitation for the coil through a voltage-controlled constant current source, and used LabVIEW to design a control program. Finally, we comprehensively evaluate and verify the feasibility and compensation accuracy of the proposed scheme through vehicle-mounted tests. The test results show that: a heading reference compensation algorithm has higher compensation accuracy, the compensated heading error is within ± 1.5°, and the standard deviation is below 0.8°, which meets the needs of car navigation.

A Hardware System for Synchronous Processing of Multiple Marine Dynamics MEMS Sensors.

Temperature, depth, conductivity, and turbulence are fundamental parameters of marine dynamics in the field of ocean science. These closely correlated parameters require time-synchronized observations to provide feedback on marine environmental problems, which requires using sensors with synchronized power supply, multi-path data solving, recording, and storage performances. To address this challenge, this work proposes a hardware system capable of synchronously processing temperature, depth, conductivity, and turbulence data on marine dynamics collected by sensors. The proposed system uses constant voltage sources to excite temperature and turbulence sensors, a constant current source to drive a depth sensor, and an alternating current (AC) constant voltage source to drive a conductivity sensor. In addition, the proposed system uses a high-precision analog-digital converter to acquire the direct current (DC) signals from temperature, depth, and turbulence sensors, as well as the AC signals from conductivity sensors. Since the sampling frequency of turbulence sensors is different from that of the other sensors, the proposed system stores the generated data at different storage rates as multiple-files. Further, the proposed hardware system manages these files through a file system (file allocation tab) to reduce the data parsing difficulty. The proposed sensing and hardware logic system is verified and compared with the standard conductivity-temperature-depth measurement system in the National Center of Ocean Standards and Metrology. The results indicate that the proposed system achieved National Verification Level II Standard. In addition, the proposed system has a temperature indication error smaller than 0.02 °C, a conductivity error less than 0.073 mS/cm, and a pressure error lower than 0.8‱ FS. The turbulence sensor shows good response and consistency. Therefore, for observation methods based on a single point, single line, and single profile, it is necessary to study multi-parameter data synchronous acquisition and processing in the time and spatial domains to collect fundamental physical quantities of temperature, salt, depth, and turbulence. The four basic physical parameters collected by the proposed system are beneficial to the in-depth research on physical ocean motion, heat transfer, energy transfer, mass transfer, and heat-energy-mass coupling and can help to realize accurate simulation, inversion, and prediction of ocean phenomena.

Bidirectional LCL-T Resonant DC–DC Converter for Priority Loads in Undersea Distribution Networks

In undersea long-distance dc power distribution networks, power converters are distributed over the length of the trunk cable carrying constant dc current. Under regular circumstances, these series-connected isolated dc–dc converters deliver power from the constant current feed to their respective loads while regulating their output voltage or current. However, in the event of a cable or other faults, the converters in the string lose power from the source, and hence bidirectional load(s) could be employed for continuing power delivery to the priority loads. In this article, it is shown how a dual active bridge (DAB) based <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> -T resonant converter can be designed to meet the requirements of driving such bidirectional loads to provide constant voltage to the load from a constant current source under regular operation and convert a voltage source to a constant current drive for the priority loads in the event of loss of power from the main feed. Steady-state modeling and analysis are furnished for the DAB <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> -T converter with three-angle modulation to derive all the dc and ac signals of the converter. Detailed design and modulation angle control are presented to minimize the overall VA rating of the resonant tank, transformer, and H-bridges. Experimental validation is provided for a prototype hardware system converting 1-A input current to 150-V output voltage in the forward direction and 1-A current drive from 150-V dc source in reverse power transfer, operating at 250-kHz switching frequency over a 50–500 W load range.

Quadratic Programming-Based Simultaneous Charging Strategy for Battery Packs of Electric Vehicles

An optimal strategy for simultaneous charging of electric vehicle battery packs is proposed as a multiobjective optimization problem in this article. The charger consists of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{n}$</tex-math></inline-formula> constant voltage current sources for charging <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{n}$</tex-math></inline-formula> batteries, respectively. Considering the energy loss and the charging criteria, a battery charging issue for the charging mode is formulated as a multiobjective optimization problem and the optimal solution is obtained with the application of quadratic programming. In addition, an adaptive momentum-based steepest descent algorithm is propounded to minimize the simultaneous charging time in the charging mode. Simulation and experimental results show that the actual state of charge converges to the same value within the theoretical shortest time for under the charging mode.