Branch Currents Research Articles

Устройства экспрессдиагностирования силовых полупроводниковых приборов и полупроводниковых преобразователей

The increase in the power of power semiconductor converters operated in the railway industry is associated with the use of group connections of power semiconductor devices in them, the variation in the parameters of which, and, therefore, their unequal load, causes a decrease in the reliability of the power semiconductor converters as a whole. In this regard, it becomes necessary to develop and implement innovative methods and devices for express diagnostics in order to identify potentially unreliable semiconductor devices, and the implementation of technical diagnostics should not be associated with dismantling the electrical circuits of the converters. The method is proposed for determining potentially unreliable power semiconductor devices in group connections based on the results of analyzing the distribution of reverse currents in parallel branches, which made it possible to create a series of devices for diagnosing power semiconductor devices in converters, both with and without communication resistors. The methodological error of measurements made using the developed express diagnostics devices of the transducers do not exceed the standard value equal to 10 %.

Adjacent Bi-Hierarchical Network for Scene Parsing of Remote Sensing Images

Driven by the rapid development and application of earth observation sensors, the scene parsing of remote sensing images (RSIs) has attracted extensive research attention in recent years. Restricted by the limited local receptive field of successive convolution layers, traditional models of scene parsing cannot effectively and interactively utilize the local-global information and digital surface model (DSM) of RSIs. Comparatively, accurate scene parsing faces more challenges because of unbalanced categories, small targets, and more complex scenes. To address these challenges, herein, we propose a novel adjacent bi-hierarchical network (ABHNet). Specifically, we introduce a DSM-enhanced (DSE) module to excavate characteristic DSM information from DSM images and enhance the red, green, and blue (RGB) features by exploiting informative cues between RGB and DSM modalities. In addition, an adjacent context exploration (ACE) module is proposed, which contains current and adjacent branches. The branches first exploit multiscale complementary characteristics of multilevel features and then integrate these features by applying adjacent exploration. Our model includes five ACE modules—three are deployed to activate detailed features and two obtain deep-guided features. The mutual collaboration of deep and detailed features is more beneficial to the segmentation of small objects. Extensive experiments on two remote sensing benchmark datasets (ISPRS Potsdam and Vaihingen) showed that the proposed ABHNet qualitatively and quantitatively outperformed other methods.

Position Sensorless Control for PMSM Drives With Single Current Sensor

The aim of this article is an attempt to provide a more credible control mode or a fault-tolerant control strategy for permanent magnet synchronous motor (PMSM) drives when an unexpected failure occurs to the current or position sensor. Considering that, a position sensorless control method that uses only one current sensor is proposed. Different from a traditional position sensorless control scheme that utilizes additional current sensors to obtain information of multiple phase currents, only a single current sensor (SCS) arranged on one of the current branches is included among the whole control circuit. Three-phase currents are reconstructed by sequentially sampling the SCS under specific voltage vectors, and directly employed for motor position estimation. A nonlinear position observer established according to the gradient descent is adopted. Focusing on the special current-acquisition pattern in this article, a step-size optimization method based on golden section search is proposed to minimize position estimation error. The experimental results reveal that the method in this article is comparable to the traditional full-current-sensor method in terms of position estimation, which confirms the fault-tolerant capability as one certain sensor of the control structure malfunctions.

0.5 V Universal Filter and Quadrature Oscillator Based on Multiple-Input DDTA

This paper presents a universal voltage-mode filter and quadrature oscillator based on low-voltage multiple-input differential difference transconductance amplifier (MI-DDTA). Unlike the previous published DDTAs, that utilize the bulk-driven (BD) multiple-input MOS transistor technique (MI-MOST) in the differential pair of the first stage only, the proposed DDTA, for the first time, utilize the BD MI-MOST in the second stage of the DDTA. This results in capability of providing more arithmetic operations without additional current branches or power dissipation. Hence, simplify the topology of the filter and oscillator applications, by decreasing the count of active blocks. The voltage-mode filter offers high-input and low-output impedances, and both non-inverting and inverting versions of five types of transfer functions, namely low-pass, high-pass, band-pass, band-stop, and all-pass characteristics. The oscillator offers three-phase of quadrature signals, and orthogonal control of the condition and frequency of oscillations. The circuit was designed in Cadence environment using 180 nm CMOS TSMC technology. The voltage supply is 0.5 V and the power consumption of the filter is 472 nW. The simulation results are in accordance with theory and confirm the performance of the proposed circuit.

Design for the reconfigurable polarization rotator by inhibiting Fano resonance with graphene-metal grating structures

In this paper, the Fano resonance associated with the integrated grating-enhanced transmissive cross-polarization rotator (TCPR) superimposed via two polarization plates operating in disparate frequency bands is observed. The metal resonance frequency dramatically impacts the Fano effect, which triggers alterations in polarization conversion ratio (PCR). Through the analysis for the surface current distributions, the spring vibrator model driven by external forces in two orthogonal directions is employed to figure out the internal mechanism of the Fano line shape in the PCR curve. Subsequently, the symmetrical lateral current branches on the two gold polarization sheets are accessible. The relative bandwidth (RBW) value and the operating region of the ultimate optimized TCPR are 84.6% and 0.563 THz–1.388 THz, respectively. In other words, the PCR band is expanded successfully. Intended to obtain the fabulous polarization switching behavior to enhance the reconfigurability, the gated voltagedriven graphene is doped in grating gaps with the chemical potential fluctuating uniformly between 0.01 and 0.50 eV. The proposed optimizations with the PCR and the final TCPR are distinguished from precedented instances in the RBW and tunability, which is universally applicable in multitudinous terahertz-controlled scenarios.

An on-chip integrated current sensor with high precision and large current range for smart power ICs

This work presents a precision current sensor with a high gain amplifier. Three aspects are improved. Firstly, the gain boosting is achieved by adding nested-amplifiers, namely AMPH and AMPL. Secondly, the DC error is eliminated by implementing a cascode current mirror branch with bias current compensation. Thirdly, the damage of large negative overshoot voltage to the operational amplifier is avoided because of the inserted switch transistors disconnecting the amplifier from load. For the ratio of main-FET to sense-FET, a factor of M = 5000 is chosen to keep the power consumption low. Measurement results show that this current sensor can operate from −60 °C to 120 °C with supply voltage from 10 V to 30 V. The measured absolute error between the sensed signal and the load current is less than 3% in range of 20 mA to 3.6 A at 27 °C. This current sensor has been fabricated in a 0.5 μ m SOI BCD process, which can be applied in smart power ICs.

The Modified MPPT for PV System with Interleaved Hybrid DC-to-DC Boost Converter

A modified maximum power point tracking control technic for an off-grid photovoltaic system which include the interleaved hybrid DC-to-DC boost converter was presented in this paper. The input voltage was predicted by measured one branch current of the proposed hybrid DC-to-DC boost converter. The proposed control technic consists of maximum power point tracking with the predicted input voltage and PI controller. Thanks to the proposed control technic, the photovoltaic panel was forced to operate at maximum power point and the output voltage of the proposed converter ensured the desired value despite the varying input power. In addition, the interleaved hybrid DC-to-DC boost converter was increased the low output DC voltage of photovoltaic panel to the desired high voltage value and the stresses on the circuit elements was decreased by reducing the input current ripples. As a conclusion, the total cost of the proposed system is reduced by eliminating the sensing of the input voltage and the service lifespan of the proposed system is extended by using the interleave hybrid DC-to-DC boost converter. The simulation and experimental results of the proposed system were obtained by using MATLAB/Simulink and 400 W DSP TMS320F28379D based porotype, respectively.

A CMOS Relaxation Oscillator with Process and Temperature Variation Compensation

In this paper, a CMOS relaxation oscillator with trimming and temperature compensation is presented for the on-chip multi-sensor systems which need MHz level frequency source. The proposed scheme uses a single current branch to charge the capacitor to generate the oscillation with voltage average feedback (VAF) circuit. Binary-weight current trimming array is adopted to reduce the frequency variation caused by the process variation under different process corners. A compensation calibration resistor array with Kelvin connection is utilized to improve the frequency variation with temperature. With the help of VAF, the frequency spread caused by the comparator delay is suppressed. This relaxation oscillator with a typical frequency of 13.4 MHz is implemented in a standard 180 nm CMOS process. Simulation results show that it achieves a frequency temperature coefficient of 28.3 ppm/∘C from [Formula: see text]C to 125∘C and a 0.074%/0.1 V frequency variation when supply voltage changes from 2.9 to 3.7 V.

Circulating Current Generating Mechanism and Suppression Control of HMMC

Hexagonal modular multilevel converter (HMMC) is a full-bridge ac/ac converter, and it can achieve the interconnection between the ac grid and the low frequency system. However, the coupling of input and output on the branches causes the large fluctuation both in dc voltage of submodules (SMs) and branch currents. Moreover, the internal circulating current in branch current comprises large dc component and ac components, which causes an increase in current stress. The traditional circulating current control of HMMC adopts circulating current injection for dc voltage stability, which cannot decrease the current stress. Therefore, basing on dc voltage fluctuation analysis, the circulating current generating mechanism is analyzed. According to the influence mechanism of circulating current, a circulating current suppression control (CCSC) is proposed to decrease the current stress. Eventually, the CCSC is verified in the real-time (RT)-lab platform.

Optimalno pozicioniranje sinhrofazorskih jedinica primenom genetičkog algoritma

Energy transition implies a larger share of the intermittent renewable energy sources connected to the power grid. These utilities can change their production within a short period of time, thus, significantly affecting the voltage conditions and load flows in the grid. This adds to the complexity in achieving required reliability and stability of the system. Proper and timely insight into the grid parameters plays an important role in regulation of such power system. Implementation of Phasor Measurement Units (PMUs) provides information about electrical parameters of the grid with as much as microsecond precision. Therefore, possible occurring dynamical processes could also be observed and regulated in a proper manner. Considering PMU can give information regarding voltage phasor as well as currents of adjacent branches, the observability of the system can be achieved even if some nodes are not equipped with their own PMU. Furthermore, installation of PMU in every node is not economical solution considering the size of the power grid and the number of PMUs accordingly. One should assess the sufficient number of PMUs cautiously and locate them carefully in order to maintain observability, but also to reduce expenses as much as possible. In the grid topology with a vast number of nodes and branches, the usage of metaheuristic optimization algorithms with adequate criteria function and limiting conditions could reduce the computing time compared to the linear and non-linear programming algorithms. In addition, the quality of such solution is also preserved. In this paper, the usage of genetic algorithm is proposed in order to determine the number and position of PMUs for several different grid samples.

Reducing Circling Currents in a VHF Class Φ2 Inverter Based on a Fully Analytical Loss Model

This paper proposes a fully analytical loss model to reduce circling currents and improve the power efficiency of a class Φ2 inverter. Firstly, analytical expression of the switching node voltage is derived by analyzing its harmonic components. Based on the result, the power switch is modeled as a voltage source, where the circuit is simplified to a linear network and analytical expressions of branch currents are solved. Secondly, root mean square (RMS) values of branch currents and component losses are calculated to form the analytical loss model for a Φ2 inverter. The influence of circuit parameters on the circling current and power efficiency are thoroughly analyzed, which derives optimal design constraints to reduce circling currents of a class Φ2 inverter. Furthermore, detailed design guidance and equations are provided to calculate circuit parameters of a class Φ2 inverter, which reduces its circling currents and improves overall power efficiency. Finally, a class Φ2 inverter prototype is built, and experimental results demonstrate a 7% efficiency improvement compared to conventional empirical design methods.

Fault current limitation control of multiple distributed renewable generations under unbalanced conditions

For multiple distributed generation units (DG unit) parallel system, excessive fault current has adverse effects on the safe and stable operation of the utility grid. As a result, a fault current limitation control of multiple DG units is developed in this paper to limit the fault current of related fault branch and ride through the associated fault conditions. The injection fault current amplitude and phase angle of each DG unit for grid-side converter are controlled through the point of common coupling (PCC) voltage support and fault current limitation to limit the total current amplitude at the corresponding fault location. The validity of the proposed control strategy has been verified by simulation and hardware-in-loop (HIL) experiment results.

(Invited) Beyond Single Cell Characterization: Impacts of Module Configuration on Lithium-Ion Battery Performance and Degradation

Batteries are commonly connected in series and parallel to form modules that meet the power and energy requirements of specific applications. However, conclusions about battery performance and degradation under different conditions are often based on single cell cycling results. In this study, we evaluate the performance of lithium-ion eight-cell modules in six different series-parallel configurations over the course of hundreds of cycles. Each cell was individually instrumented for voltage, current, and temperature monitoring. Current data were collected using closed-loop Hall effect sensors to provide accurate measurements of parallel branch currents without the influence of in-circuit shunt sensing elements. This cell-level data collection enabled calculation of the underutilization of individual cells and assessment of differences in energy lost to cell balancing for different configurations. We also evaluated current redistribution in parallel cells, which in some cases yielded transients with peak magnitudes more than twice the average expected cell current value. The capacity and energy fade of the full modules was compared to that of individual cells cycled under the same conditions. This module cycling study, one of the broadest reported to date, allows us to systematically evaluate the performance trade-offs and safety implications of different module configurations.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2022-5209 A

Residual-based Short-Circuit fault detection and isolation in LVDC microgrid

Designing protection for a DC microgrid is challenging due to its DC nature and heavily capacitor-dominated DC bus that induces high amplitude current spike during short-circuit faults. Moreover, for small-scale applications such as residential DC microgrids, low line-resistance cables increase the fault detection time constraint. Thus, this paper proposes a fast short-circuit fault detection and isolation method based on current residual computation for a standalone residential DC microgrid. The proposed method continuously compares the computed residual from sensed branch currents to their respective defined thresholds. These thresholds are predetermined by analyzing the microgrid operation in healthy mode, considering both steady-state and transient operations. The protection device isolating the faulty branch is then activated once the corresponding residual exceeds its threshold. The protection scheme is validated through a processor-in-the-Loop simulation approach, during which the power stage of the system remains simulated on the host computer using PSIM software, while its control algorithm is executed from a Texas Instrument TMS320F28335 hardware target. The proposed protection algorithm is able to discriminate transient perturbations due to load connection from short-circuit faults. Furthermore, the algorithm implementation is not limited by the size of the DC microgrid nor by the type of the connected loads.

Discrete-Time Domain Modal Analysis of Oscillatory Stability of Renewables Integrated Power Systems

Modal analysis in the continuous-time state-space is a mature and effective method for analyzing the subsynchronous oscillation (SSO) problems of power systems. But it has limitations on oscillation traceability analysis due to the loss of system topology information. To address this issue, a discrete-time domain modal analysis method is developed in this paper. It represents the target system as a networked discrete-time equivalent circuit and uses the nodal method to generate the state matrix, from which the discrete-time eigenvalues in the z-plane can be solved. Based on the oscillation frequency and damping ratio defined in the discrete-time domain, the stability of the oscillatory mode can be quantitatively analyzed. Then, participation factors analysis is carried out similarly to the continuous-time method to locate the contributive components. Most importantly, the distribution coefficients of branch currents/ node voltages are finally defined and derived for in-depth analysis of the oscillatory mode. With this index, the propagation path of the oscillation in the mesh power system is expected to be identified.The proposed method has been applied in several case systems with wind farms integrated. Theoretical analysis results are highly consistent with the electromagnetic transient simulation results in PSCAD/ EMTDC, thus verifying its effectiveness.

Improvement and test of high-voltage pulsed power supply for HFRC

Field-reversed theta-pinch (FRTP) is commonly used to form high-performance field-reversed configuration (FRC) plasmas, and it is employed for the initial plasma formation in the HFRC device. The high-voltage pulsed power supply which is used to feed the θ-pinch coils in HFRC has already demonstrated its importance for initial plasma formation. This paper presents two attempts to improve the performance of the high-voltage pulsed power supply. To reduce the space occupation and increase the accuracy of the triggers of hydrogen thyratron, a newly designed high-voltage floating trigger is proposed in this paper. Experimental tests show that the optimized trigger can work stably under a floating voltage of 35 kV with a voltage rising rate of about 12 kV/μs and a total jitter time of less than 60 ns. Besides, a high-voltage laminated busbar is proposed to reduce the stray parameters. Experimental tests show that it can withstand a voltage of 34 kV. The peak current and frequency of each branch of the power supply are increased by at least 10%. Tests of the entire power supply show that the power supply can work stably under a voltage of 34 kV. The oscillation frequency of the Pre-Ionization (PI) branch can reach 152.0 kHz and the peak current of the Main branch can reach 78.3 kA. The results show the validity and reliability of the improvements.

A 0.000747 %/V, 64.59 dB PSRR CMOS-only voltage reference for ultra-low power WSN applications

An ultra-low power voltage reference with ultra-low line sensitivity (LS) and high power supply reject ratio (PSRR) for wireless sensor network (WSN) applications is proposed in this paper. Proposed voltage reference consists only of MOSFETs and the PSRR enhancement block provides a negative feedback loop to adjust the internal power supply voltage and suppress the power supply voltage ripple. By using the gate-to-bulk voltage multiplexing (GVM) current generator and subthreshold technology, the current branch and supply voltage are significantly reduced compared to the previous CMOS reference. The triple-process-trim circuit corrects the temperature coefficient (TC) and reference voltage under different corners, so that the reference has well PVT stability under the whole corners. In addition, a novel multi-start-up circuit is presented to reduce the start time. The simulation results show that, using standard 0.18 µm CMOS process design, the output reference voltage only changes by 1.09 µV in the range of 0.5 V to 1.8 V power supply voltage, and the LS is 0.000747 %/V. The TC is 44.54 ppm/°C across a range of −40 °C to 85 °C. Due to proposed PSRR enhancement structure, a PSRR over −64.59 dB can be obtained at 100 Hz with 35.57 nW power consumption. The simulation results match the theoretical analysis.

EXPERIMENTAL EVALUATION OF DISTRIBUTION OF 14C PHOTOASSIMILATED INTO CARBOHYDRATES IN DIFFERENT GROWTH STAGES OF FRUIT-BEARING APPLE SHOOTS USING A 13CO2 IN-SITU EXPOSURE SYSTEM.

In this study, we aimed to investigate the photoassimilation process of 14CO2 into agricultural plants through determining the photoassimilated carbohydrate-13C in each part (leaves, current branch and fruit) of the fruit-bearing apple shoots exposed to 13CO2 in different growth stages (early and late fruit development stages). The carbohydrate content was assessed as soluble (ethanol-extracted fraction) and other (HCl-extracted and residual fractions) components. The total (i.e. sum of the three fractions) bulk carbohydrate concentrations in all parts of the shoots were statistically similar between different growth stages. The changes in the concentration of 13C-labeled soluble carbohydrate (i.e. ethanol-extracted fraction) to the total content between different growth stages were statistically unclear among all parts of the shoot. These results suggest that the distribution ratio of photoassimilated 13C in soluble and other components in the apple shoot was thereabout constantly independent of the growth stages.

A branch current estimation and correction method for a parallel connected battery system based on dual BP neural networks

In the actual use of a parallel battery pack in electric vehicles (EVs), current distribution in each branch will be different due to inconsistence characteristics of each battery cell. If the branch current is approximately calculated by the total current of the battery pack divided by the number of the parallel branches, there will be a large error between the calculated branch current and the real branch current. Adding current sensors to measure each branch current is not practical because of the high cost. Accurate estimation of branch currents can give a safety warning in time when the parallel batteries of EVs are seriously inconsistent. This paper puts forward a method to estimate and correct branch currents based on dual back propagation (BP) neural networks. In the proposed method, one BP neural network is used to estimate branch currents, the other BP neural network is used to reduce the estimation error cause by current pulse excitations. Furthermore, this paper makes discussions on the selection of the best inputs for the dual BP neural networks and the adaptability of the method for different battery capacity and resistence differences. The effectiveness of the proposed method is verified by multiple dynamic conditions of two cells connected in parallel.

Resolving Kirchhoff’s Laws for Parallel Li-Ion Battery Pack State-Estimators

A state-space model for Li-ion battery packs with parallel-connected cells is introduced. The key feature of the model is an explicit solution to Kirchhoff’s laws for parallel-connected packs, which expresses the branch currents directly in terms of the model’s states, applied current, and cell resistances. This avoids the need to solve these equations numerically. To illustrate the potential of the proposed model for pack-level control and estimation, a method to bound the error of a state-estimator is introduced and the modeling framework is generalized to a class of electrochemical models. It is hoped that the insight brought by this model formulation will allow the wealth of results developed for series-connected packs to be applied to those with parallel connections.