Transient Current Characteristics Research Articles

Capacitive and Inductive Characteristics of Volatile Perovskite Resistive Switching Devices with Analog Memory.

With the increasing demands and complexity of the neuromorphic computing schemes utilizing highly efficient analog resistive switching devices, understanding the apparent capacitive and inductive effects in device operation is of paramount importance. Here, we present a systematic array of characterization methods that unravel two distinct voltage-dependent regimes demonstrating the complex interplay between the dynamic capacitive and inductive effects in volatile perovskite-based memristors: (1) a low voltage capacitance-dominant and (2) an inductance-dominant regime evidenced by the highly correlated hysteresis type with nonzero crossing, the impedance responses, and the transient current characteristics. These dynamic capacitance- and inductance-dominant regimes provide fundamental insight into the resistive switching of memristors governing the synaptic depression and potentiation functions, respectively. More importantly, the pulse width-dependent and long-term transient current measurements further demonstrate a dynamic transition from a fast capacitive to a slow inductive response, allowing for the tailored stimulus programming of memristor devices to mimic synaptic functionality.

Influence of RF power in the sputter deposition of amorphous InGaZnO film on the transient drain current of amorphous InGaZnO thin-film transistors

The device electrical and transient current characteristics of the amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) are comprehensively investigated according to the radio-frequency (RF) power during the sputter-deposition of IGZO active film. The RF power dependencies of the oxygen vacancy (VO) concentration in IGZO and the surface morphology of IGZO film are analyzed through X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). According to the RF power change in the range of 100 ∼ 250 W, the optimal point in terms of threshold voltage (VT), ON current (Ion), field-effect mobility in the linear region (μFE_lin), hysteresis voltage (VHys), and the VT shift under current stress (ΔVT) is found to be 200 W. The existence of the optimal power condition originates from the RF-power dependencies of the electron carrier concentration, the density of electron traps in gate insulator (GI), and the interface trap density related to surface roughness.Furthermore, compared to the direct current (DC) current stress (CS) condition, it is found that when VGS rises rapidly, a total transient current ΔID can be decomposed into three components, i.e., ΔIOS, ΔIBOOST, ΔIDEG. While ΔIOS is attributed to the non-quasi static Fermi-level rising, ΔIBOOST and ΔIDEG result from the donor creation in IGZO and the electron trapping into GI and interface. Noticeably, the occurrence level of each component changes sensitively according to RF power.Our result suggests that the 200 W device has the least overshoot of transient current and shows the best reliability in terms of deterioration due to transient current characteristics.

New energy transmission line fault location method based on Pearson correlation coefficient

The access of new energy power source makes the traditional transmission line structure become complex, and due to the influence of power electronic device control strategy, the fault characteristics have been fundamentally changed, resulting in the traditional transmission line fault localization method can not be applied to the new energy sending line. To address the above problems, this paper analyzes the transient current characteristics of different power supply faults, and learns that there are obvious differences in the transient currents on both sides of the fault point inside and outside the transmission line area, and then proposes a new energy transmission line fault localization method based on the Pearson correlation coefficient, which determines the fault location by calculating the correlation coefficients of the fault waveforms of the neighboring monitoring points. Finally, comparative experiments are carried out under different fault types and fault locations to further verify the applicability of the proposed method.

Residual flux density estimation of the three-phase transformer using BP neural network

When the off-line transformer is re-energized, the phase-controlled switching strategy can avoid the generation of inrush current by controlling the phase. To determine the closing phase, the residual flux density (Br) in the transformer core needs to be accurately measured. This paper proposes a Br estimation method for three-phase transformers based on the finite element method and BP neural network. Firstly, the direction of Br in each phase core is determined based on the transient current characteristics. Then, the three-phase transformer is simulated and the BP neural network is trained to estimate the Br based on the simulation results. The experimental results on a three-phase transformer show that the proposed method can accurately determine the direction and amplitude of Br in each phase of the three-phase transformer.

Micro-Grid Line Protection Method Based on Current Frequency Variability

Due to the access of multiple distributed power sources (DG) in the Micro-Grid, the original radiation topology is changed, making the traditional distribution network line protection methods no longer applicable; and most of the existing Micro-Grid line protection methods discuss their grid-connected and Islanded operation separately, resulting in a complex and variable line protection configuration. By analysing the transient current characteristics provided by the DG side and the network side of the Micro-Grid during grid-connected operation and the transient current characteristics provided by different types and numbers of DG on both sides during Islanded operation, it is concluded that there are significant differences in the frequency characteristics of the first-mode components of the current provided on both sides of the protected section of the Micro-Grid line during a fault. As a result, a Micro-Grid line longitudinal differential protection method based on the frequency similarity of the current first-mode quantities is proposed to achieve the identification and removal of faults inside and outside the protected section. A 380 V Micro-Grid simulation model is set up in MATLAB software and the proposed method is tested in a large number of experiments to enable it to operate correctly under different operating modes, different fault locations, and different transition resistances of the Micro-Grid, and to adapt to different operating conditions.

Experimental Study on the Transient Electric Shock Characteristics Between Metal Sheds and the Human Body Near Ultrahigh Voltage Alternating Current Transmission Lines

With the development of ultrahigh voltage (UHV) transmission lines in China, line corridors are becoming increasingly limited, and the lines pass closer to inhabited areas and the occurrence probability of induced electric shocks are increased. The research on transient electric shock and human sensory is essential due to the displeasure and complaints of people on electric shock. In this article, a real-size metal shed was established near a 1000-kV UHV alternating current (ac) transmission line, and the induced voltage and transient current characteristics were studied when the human body was in contact with the shed. Then, the amplitude and pulsewidth of the transient electric shock current were investigated, and the associations between discharge energy and sensation were established. The research found that transient electric shock is the most serious when the grounded human body contacts the insulated shed, and the imparted electric shock energy reaches 25 mJ. When the body and the shed are grounded, there is no electric shock sensation. When the insulated human body is in contact with the insulated shed, the electric shock sensation is intermediate, and women's perceptions of pain are more intense. The results provide references to transient electric shock protection for power transmission lines.

Analytical characterization of DFIG response to asymmetrical voltage dips for efficient design

The fault current characteristics of Doubly Fed Induction Generator (DFIG) based wind turbine generator (WTGs) differ from those of traditional generators. Although asymmetrical faults are far more frequent, the studies on transient current characteristics of DFIG-based WTGs are mainly focused on symmetrical faults and consider the variations in voltage magnitude only. This paper presents highly accurate and concise analytical expressions for the stator and rotor currents of DFIG-based WTGs under crowbar protection considering the variations in magnitude and phase angle of both the positive- and negative-sequence voltages during asymmetrical faults. The proposed expressions are validated using a detailed simulation model of a 1.5 MW DFIG-based WTG. The expressions can be directly integrated into protection tools for the evaluation of dynamic performance of relays and design of fault ride through (FRT) solutions.

High Voltage and Low Leakage GaN-on-SiC MISHEMTs on a “Buffer-Free” Heterostructure

The performance of a novel ‘buffer-free’ AlGaN/GaN-on-SiC MISHEMTs for power switching applications is demonstrated in this letter. High voltage operation with exceptionally low gate and drain leakage currents is shown. A specific on-resistance of 3.61 m <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol {\Omega } \cdot $ </tex-math></inline-formula> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and an abrupt breakdown voltage of 1622 V at a drain current of 22 nA/mm is achieved. Using two-terminal breakdown measurements, nitrogen-implanted GaN display breakdown fields of 0.96 MV/cm. The semi-insulating SiC substrate is capable of suppressing vertical leakage currents, ensuring that off-state operation is limited by lateral breakdown. The impact of electron trapping effects on dynamic on-resistance is small up to a drain quiescent voltage of at least 240 V. Drain current transient characteristics display a 14% increase in dynamic on-resistance with respect to quiescent drain bias, and a negligible change in resistance up to 100 ms. These types of ‘buffer-free’ heterostructures are of interest for power electronic applications above 1000 V and with potential for co-integration of power and RF-electronics.

A Protection Method for DC Distribution Network with Single Pole Grounding Based on Integrative Two-terminal MMC

Based on the analysis model of unipolar grounding fault occurred in two-terminal MMC DC distribution network, the characteristics of unipolar grounding fault are studied. The similarity characteristics of transient currents between the fault line and the non-fault line are analyzed when the fault is located in the feeder, tie line and bus respectively. According to the characteristics of single-pole grounding fault and the similarity principle, a new single-pole grounding protection method for DC distribution network based on two-terminal MMC is proposed. The simulation results show that the proposed single-pole grounding protection method can accurately determine the single-pole grounding fault at any position of the DC distribution network. The research results can effectively solve the problem of single-pole grounding protection in DC distribution network, and effectively improve the security and reliability of DC distribution network.

A quick fault location and isolation method for distribution network based on adaptive reclosing

Feeder automation is important to improve the reliability of power supply for distribution network. Existing voltage-time feeder automation scheme exists the problems of long fault processing time and the upstream switches of the fault point need to tolerate fault current twice and the upstream sections need to experience two short time power outage. In this paper, a quick fault location and isolation method for distribution network based on adaptive reclosing is proposed. Three key technologies of the strategy are introduced, including a phase segregated switch of the distribution network based on the permanent magnet operating structure, the phase selector based on transient current characteristics, and the temporary fault and permanent fault identification method based on the power frequency voltage characteristics. The proposed strategy can avoid the second impact on upstream switches and power-off of the upstream section in case of the permanent fault and can effectively shorten the fault processing time.

Investigation of current collapse and recovery time due to deep level defect traps in β-Ga2O3 HEMT

In this paper, drain current transient characteristics of β-Ga2O3 high electron mobility transistor (HEMT) are studied to access current collapse and recovery time due to dynamic population and de-population of deep level traps and interface traps. An approximately 10 min, and 1 h of recovery time to steady-state drain current value is measured under 1 ms of stress on the gate and drain electrodes due to iron (Fe)–doped β-Ga2O3 substrate and germanium (Ge)–doped β-Ga2O3 epitaxial layer respectively. On-state current lag is more severe due to widely reported defect trap EC – 0.82 eV over EC – 0.78 eV, −0.75 eV present in Iron (Fe)-doped β-Ga2O3 bulk crystals. A negligible amount of current degradation is observed in the latter case due to the trap level at EC – 0.98 eV. It is found that occupancy of ionized trap density varied mostly under the gate and gate–source area. This investigation of reversible current collapse phenomenon and assessment of recovery time in β-Ga2O3 HEMT is carried out through 2D device simulations using appropriate velocity and charge transport models. This work can further help in the proper characterization of β-Ga2O3 devices to understand temporary and permanent device degradation.

Studies of Current Modulation in the DC Voltage Link of the Frequency Converter during its Operation with Asynchronous Load

The paper discusses current issues on the inverters peculiarities in the frequency converter. Theoretical studies have been carried out to determine the influence of the induction motor mode on the current modulation in the DC link. The authors suggest a calculation technique to determine the form of transient current characteristics when exposed to a single pulse of the inverter. Model studies of the system, calculation and construction of current characteristics proved the correspondence of theoretical and practical results. The research results determined the relationship between the current modulation in the DC link and the induction motor mode of operation.

Experimental and simulation studies of single-event transient in partially depleted SOI MOSFET**Project supported by Funds of Key Laboratory, China (Grant No. y7ys011001) and Youth Innovation Promotion Association, Chinese Academy of Sciences (Grant No. y5yq01r002)

In this study, we investigate the single-event transient (SET) characteristics of a partially depleted silicon-on-insulator (PDSOI) metal-oxide-semiconductor (MOS) device induced by a pulsed laser.We measure and analyze the drain transient current at the wafer level. The results indicate that the body-drain junction and its vicinity are more SET sensitive than the other regions in PD-SOI devices. We use ISE 3D simulation tools to analyze the SET response when different regions of the device are hit. Then, we discuss in detail the characteristics of transient currents and the electrostatic potential distribution change in devices after irradiation. Finally, we analyze the parasitic bipolar junction transistor (p-BJT) effect by performing both a laser test and simulations.

Fabrication and Optimization of Vertically Aligned ZnO Nanorod Array-Based UV Photodetectors via Selective Hydrothermal Synthesis.

Vertically aligned ZnO nanorod array (NRA)-based ultraviolet (UV) photodetectors (PDs) were successfully fabricated and optimized via a facile hydrothermal process. Using a shadow mask technique, the thin ZnO seed layer was deposited between the patterned Au/Ti electrodes to bridge the electrodes. Thus, both the Au electrodes could be connected by the ZnO seed layer. As the sample was immersed into growth solution and heated at 90 °C, the ZnO NRAs were crystallized and vertically grown on the ZnO seed layer, thus creating a metal-semiconductor-metal PD structure. To investigate the size effect of ZnO NRAs on photocurrent, the PDs were readily prepared with different concentrations of growth solution. For the ZnO NRAs grown at 25 mM of concentration, the PD with 10 μm of channel width (i.e., gap distance between two electrodes) exhibited a high photocurrent of 1.91 × 10−4 A at an applied bias of 10 V under 365 nm of UV light illumination. The PD was optimized by adjusting the channel width. For 15 μm of channel width, a relatively high photocurrent on-off ratio of 37.4 and good current transient characteristics were observed at the same applied bias. These results are expected to be useful for cost-effective and practical UV PD applications.

Cellular automata simulation of interactions between metastable corrosion pits on stainless steel

The interactions between metastable corrosion pits on stainless steel are studied by a two-dimensional cellular automata model at a mesoscopic scale. The cellular automata model focuses on a metal/film/electrolyte system, including fifteen kinds of species. A series of local evolution rules for the growth of corrosion pits is performed to simulate the corrosion kinetics processes. The transient current characteristics of the interactions between metastable corrosion pits under different simulation factors including the breakdown time and extent of pit cover are analyzed. The analysis of the pit stability product shows that the simulation results are close to the experimental conclusions.

Heavy Ion SEU Cross Section Calculation Based on Proton Experimental Data, and Vice Versa

The aim of this work is to provide a method to calculate single event upset (SEU) cross sections by using experimental data. Valuable tools such as PROFIT and SIMPA already focus on the calculation of the proton cross section by using heavy ions cross-section experiments. However, there is no available tool that calculates heavy ion cross sections based on measured proton cross sections with no knowledge of the technology. We based our approach on the diffusion-collection model with the aim of analyzing the characteristics of transient currents that trigger SEUs. We show that experimental cross sections could be used to characterize the pulses that trigger an SEU. Experimental results allow yet defining an empirical rule to identify the transient current that are responsible for an SEU. Then, the SEU cross section can be calculated for any kind of particle and any energy with no need to know the Spice model of the cell. We applied our method to some technologies (250 nm, 90 nm and 65 nm bulk SRAMs) and we show that the proton (respectively heavy ions) cross-section curve can be obtained without any further parameter when the heavy ion (respectively protons) cross-section curve is known.

Application and modeling of single contact electron beam induced current technique on multicrystalline silicon solar cells

The first demonstration of single contact electron beam induced current (SCEBIC) technique on multicrystalline silicon (mc-Si) solar cells is reported. A lumped single-diode analytical model is also proposed to theoretically explain the SCEBIC phenomenon within solar cells as well as the current transient characteristics of the major model parameters, such as shunt resistance Rsh, junction capacitance Cj and parasitic capacitance Cs. The accuracy of the analytical model is then verified using PSPICE simulations, which show a close match with the experimental results. It is found that a large value of parasitic capacitance Cs is necessary to achieve good SCEBIC signal strength with a relatively low signal-to-noise ratio (SNR), and this is realized experimentally by adopting a metal enclosure in the measurement setup. In addition, an advantage of SCEBIC over the conventional double-contact method is also demonstrated by characterizing partially processed solar cells, which clearly illustrates the high degree of flexibility of SCEBIC in solar cell characterization.

A fault location criterion for MTDC transmission lines using transient current characteristics

Multi-terminal DC (MTDC) transmission system is applied in modern power systems due to its technical features. In an MTDC system, the converter stations are generally connected in parallel. To smooth the DC current output from the converter, the smoothing reactors are integrated in the converter outputs, instead of in the DC transmission line. When a fault occurs on the DC transmission line of the MTDC system, the fault current will flow along the whole DC line. As a result, the protection scheme may not locate the fault accurately. Based on the characteristics of DC filter, this paper analyzes the impedance characteristics of the combinational circuits, and proposes a method to identify the fault location by the characteristic harmonic. A protection criterion of the non-integer harmonics comparison is composed with phase-frequency characteristics curve derived from complex wavelet transform. The inevitable blind zone is analyzed in theory which exists on the terminal of transmission lines just like distance protection in AC systems. The algorithm is successfully tested and compared with other techniques.

Drift-diffusion and hydrodynamic modeling of current collapse in GaN HEMTs for RF power application

Current collapse due to the trapping/de-trapping of the carriers at the surface and in the bulk of a 0.25 µm gate length AlGaN/GaN high electron mobility transistor is investigated using 2d technology computer aided design transient simulations. Gate and drain pulse techniques are used to study the dynamic picture of trapping and de-trapping of carriers within drift-diffusion and hydrodynamic transport models. In addition, coupled electrical and thermal simulations are performed to model the energy exchange of the carriers with the lattice and to predict electron temperature in the channel. It is found that current degradation upon electrical stress is due to two different types of traps, donor-like traps and acceptor-like traps, respectively. The collapse next to 5% and 75% was observed for bulk and surface traps, respectively. The combined effect of surface and bulk traps on current transient characteristics has been investigated and simulations are in very good qualitative agreement with the experimental observations.

Effect of current filament characteristics on the output current of high-gain photoconductive semiconductor switch

The output current characteristics of a high-gain photoconductive semiconductor switch (PCSS) were analyzed under different bias voltages. The results indicate that the voltages on different discharge regions of current filament are dynamic, which determines the output current transient characteristics. The physical processes of anode region influenced by the bias voltage of PCSS dominate that the output current presents the characteristic of lock-on or overshoot. The quench of current filament is determined by the external circuit and the carrier recombination process, resulting in the turn-off of high-gain PCSS.