Reverse Current Research Articles

PV module single–diode model, parameter extraction of polycrystalline and amorphous solar panel

Solar energy is a good option to replace the fossil driven energy market. Research is still ongoing to make solar technologies more efficient and affordable. Modeling is key in this area. Parameter extraction of PV modules enables easier simulation and accurate modeling of various PV cells/modules. The parameters are namely: (I) the photo generated current, ????????ℎ, (II) the reverse saturation current, ????????, (III) ideality factor, n, (IV) the series resistance, ???????? and (V) the shunt resistance, ????????ℎ. This research work extracted the equivalent circuit parameters of polycrystalline and amorphous solar panels. An 11 V polycrystalline and 6 V amorphous solar panels were illuminated with a 500 W halogen lamp to generate I-V characteristics with the aid of a data capture device. A Matlab/Simulink model was modified using the single diode equation to model the two test solar panels. The Orthogonal Distance Regression (ODR) method from the origin lab was adopted to solve the nonlinear/transcendental equation of the solar cell/module with the single diode model to determine the parameters of a polycrystalline and amorphous solar panel. The results show a variation in the parameters of the two test solar panels. The polycrystalline indicates a higher ????????ℎ and ????????ℎ with low ???????? and n values, which result to high efficiency. The amorphous panel shows higher n and ???????? values, which makes it have low efficiency. The polycrystalline solar panel has smaller residual sum of square (RSS) which makes it a better retrieval while the amorphous solar panel has a higher residual sum of square (RSS), the ODR method for polycrystalline was more accurate than the amorphous solar panel as observed from the validation results of the two test panels.

Large-Scale β-Ga2O3 Trench MOS-Type Schottky Barrier Diodes with 1.02 Ideality Factor and 0.72 V Turn-On Voltage

β-Ga2O3 Schottky barrier diodes (SBDs) suffer from the electric field crowding and barrier height lowering effect, resulting in a low breakdown voltage (BV) and high reverse leakage current. Here, we developed β-Ga2O3 trench MOS-type Schottky barrier diodes (TMSBDs) on β-Ga2O3 single-crystal substrates with halide vapor phase epitaxial layers based on ultraviolet lithography and dry etching. The 1/C2−V plots are deflected at 2.24 V, which is caused by the complete depletion in the mesa region of the TMSBDs. A close-to-unity ideality factor of 1.02 and a low turn-on voltage of 0.72 V are obtained. This is due to the low interface trap density in the metal/semiconductor interface of TMSBDs, as confirmed by the current–voltage (I–V) hysteresis measurements. The specific on-resistance calculated with the actual Schottky contact area increases as the area ratio (AR) increases because of the current spreading phenomenon. Furthermore, the reverse leakage current of the TMSBDs is smaller and the BV is increased by 120 V compared with the regular SBD. This work paves the way for further improving the overall performance of β-Ga2O3 TMSBDs.

Analysis of reverse fault current regarding the impact of transformer core types on the two most common winding connections of distributed energy resources in distribution systems

As many DERs with solid grounding are connected to the distribution system, unwanted reverse fault current is generated during a single-line-to-ground fault. Therefore, it often causes protection problems such as protection blinding and sympathetic tripping. To ensure reliable protection coordination between protective devices, fault current should be calculated accurately. Although three-limb core transformers are utilized for DERs for economic and spatial reasons, the conventional method that assumes five-limb core transformers for DERs is still used to calculate fault current. The zero-sequence impedance of a three-limb core transformer is often unknown. For this, a methodology for evaluating the zero-sequence impedance according to the core-type of transformer is presented with IEC 60076-8 standard. Then, a methodology for evaluating fault current is proposed considering the impact of DERs, loads, and transformer core types. The proposed methodologies are used for a comprehensive analysis of fault current discrepancies according to the core-type of transformers. The results indicate that significant discrepancies exist in fault current evaluated with five- and three-limb core transformers. Therefore, to accurately calculate the fault current, utility engineers should use the proper zero-sequence impedance of three-limb core transformers instead of five-limb core transformers.

Correlations between reverse bias leakage current, cathodoluminescence intensity and carbon vacancy observed in 4H-SiC junction barrier Schottky diode

Reverse bias currents of ten commercial junction barrier Schottky diodes were measured, and the dies were studied by scanning electron microscope (SEM) and cathodoluminescence (CL) after the de-capsulation of the diodes. Defect emissions (DEs) of 2.62 eV were observed in all the CL spectra. By comparing the SEM images, the integral CL intensity spatial mappings and the reverse bias leakage currents, correlations between the leakage current, the integral CL intensity and the Al-implantation process were established. The data of reverse bias leakage current against the reverse bias voltage taken at room temperature followed the Poole Frenkel emission from the Z 1/Z 2 carbon vacancy states to the conduction band. The DE at 2.62 eV is associated with the electronic transition from Z 1/Z 2 to the valence band. The current observation also opens up the feasibility of screening off SiC diodes with large leakage current during production by inspecting the CL intensity before the device fabrication is complete.

Ultraviolet Photodetector Based on a Beta-Gallium Oxide/Nickel Oxide/Beta-Gallium Oxide Heterojunction Structure.

In this paper, an n-p-n structure based on a β-Ga2O3/NiO/β-Ga2O3 junction was fabricated. The device based on the β-Ga2O3/NiO/β-Ga2O3 structure, as an ultraviolet (UV) photodetector, was compared with a p-n diode based on a NiO/β-Ga2O3 structure, where it showed rectification and 10 times greater responsivity and amplified the photocurrent. The reverse current increased in proportion to the 1.5 power of UV light intensity. The photocurrent amplification was related to the accumulation of holes in the NiO layer given by the heterobarrier for holes from the NiO layer to the β-Ga2O3 layer. Moreover, the device could respond to an optical pulse of less than a few microseconds.

Junction temperature monitoring for cascode GaN devices using the Si MOSFET's body diode voltage drop

In this paper, a new online junction temperature monitoring method is proposed for cascode GaN devices using the body diode of Si MOSFET. The reverse current during soft-switching mode is utilized to extract the voltage drop of the Si MOSFET's body diode. It is pointed out that, to accurately obtain the voltage drop of Si MOSFET's body diode, the VDS voltage of cascode GaN device should be measured when the reverse current is small during the dead-time period. An experimental platform has been designed to validate the proposed method. The proposed method exhibits an accuracy within 0.6 °C and a R2 = 0.99 goodness of linear fit on a test Buck converter, showing that this method is practical for real applications.

Design, preparation, and characterization of a novel ZnO/CuO/Al energetic diode with dual functionality: Logic and destruction

Self-destructing chips have promising applications for securing data. This paper proposes a new concept of energetic diodes for the first time, which can be used for self-destructive chips. A simple two-step electrochemical deposition method is used to prepare ZnO/CuO/Al energetic diode, in which N-type ZnO and P-type CuO are constricted to a PN junction. This paper comprehensively discusses the material properties, morphology, semiconductor characteristics, and exploding performances of the energetic diode. Experimental results show that the energetic diode has typical rectification with a turn-on voltage of about 1.78 V and a reverse leakage current of about 3 × 10−4 A. When a constant voltage of 70 V loads to the energetic diode in the forward direction for about 0.14 s or 55 V loads in the reverse direction for about 0.17 s, the loaded power can excite the energetic diode exploding and the current rises to about 100 A. Due to the unique performance of the energetic diode, it has a double function of rectification and explosion. The energetic diode can be used as a logic element in the normal chip to complete the regular operation, and it can release energy to destroy the chip accurately.

Investigation of the current density’s non-uniform distribution in dead-end PEMFC with multi-zone measurement methods

Uneven current density distribution in a proton exchange membrane fuel cell (PEMFC) can decrease the reactant and catalyst utilization, reduce the energy conversion efficiency of the whole fuel cell, and even lead to a shortened cell life. Therefore, studying current density distribution has a critical role in the research and development of PEMFC. To investigate the distribution of the proton exchange membrane fuel cells' local current density under different operating conditions, a single cell using the segmented cell technique consisting of 36 zones was designed. The results show that the maximum current density first appears at the outlet and then moves to the inlet. In addition, when the cell output is stable, the most negligible current density appears in the cell's middle area. The current density distribution was improved when the cell temperature was 50 °C. Compared with other operation temperatures (without cooling, 40 °C, 60 °C), the current density is decreased by 14.0 %, 9.8 %, and 40.6 %, respectively. At the same time, the cell voltage is increased by 10 %, 6.45 % and 22.22 %, respectively. Higher gas pressure is more favourable to improving cell performance and the uniformity of current density distribution. However, when the cathode gas pressure exceeds that of the anode, the reverse inverse current is pronounced in the middle of the cell at the starting process. The reverse duration of the 50 °C cell is reduced by 30 s (25.4 %) compared to the cell without cooling.

Design of an efficient convolutional buck-boost converter for hybrid bioinspired parameter tuning

Power-electronic systems with voltage boosts use buck-boost converters. These converters suppress current and invert voltage to improve voltage swing. Power-electronic systems with voltage boosts use buck-boost converters that suppress current and invert voltage to improve voltage swings. Researchers propose many converter models, but their total harmonic distortion (THD) limits their scalability. Harmonics from additional current components increase THD. The model filters excessive currents using inductor-based storage, capacitive filters, and resistive circuits. However, these models are unstable, reducing their performance in large converter circuits. This text proposes a novel convolutional neural network (CNN) with a hybrid bioinspired model based on genetic algorithm (GA) and particle swarm optimization (PSO) to overcome this limitation. Estimating internal buck and boost parameters efficiently reduces reverse currents. These parameters include inductor current ripple, recommended inductance, internal switch current limit, and switching frequency. The model finds low-power, high-efficiency buck-boost configurations based on these values. Incremental learning operations tuned the GA model, which was applied to many buck-boost configurations. The proposed model had a 5.9% lower delay, 16.2% lower harmonics, and 4.6% better power efficiency than state-of-the-art buck-boost models.

Numerical simulation of the distribution of reverse currents in a practical alkaline water electrolysis stack immediately after electrolysis

In alkaline water electrolysis, reverse currents are reported to occur after rapid cell voltage change due to the electrodes oxidation state difference and such currents lead to electrodes degradation. The reverse current problems can be more severe in practical applications with larger electrode sizes and larger numbers of cells. In this study, reverse current with changes in the oxidation state of electrodes and potential distribution after sudden shutdown were analyzed based on a multi-physical simulation considering an electronic and ionic conduction in practical-scale. The effects of stack height, number of cells, and ionic resistance through the manifold on the reverse current distribution were investigated. The numerical results reveal that, especially under the condition of low manifold resistance and higher stack height, the discharge current extremely concentrated near the bottom of the edge electrode. This information is important for future stack development because this current concentration can cause severe stack degradation.

A Novel Broadband ± 45° Dual-Polarized Cross-Dipole Antenna with Multimode Resonance

A novel broadband ± 45 ° dual-polarized cross-dipole antenna is presented for application in 2G, 3G, 4G, and sub-6 GHz 5G base station. A bent structure with a coplanar transmission line is used in the antenna design, which achieves multimode resonance, broadening the impedance bandwidth tremendously. Especially, it can work at 3 λ / 2 and 2 λ resonant modes without the impact of reverse current. The antenna covers the frequency spectra from 1.7 GHz to 3.8 GHz with an enhanced impedance bandwidth of roughly 76.4% and VSWRs < 1.65 at two ports. A gain of 8.3 ± 1.9 dBi and port-to-port isolation > 22.5 dB are attained in the operating frequency range. Additionally, the presented antenna has a very simple configuration and is easy to construct. A mechanical prototype of the antenna has been manufactured and measured. The experimental findings and the computational results are in good agreement.

A Bidirectional Grid-Tied ZVS Three-Phase Converter Based on DPWM and Digital Control

In this paper, a bidirectional grid-tied ZVS three-phase converter is proposed. The circuit operation principle in both the rectifier and inverter modes was analyzed. The proposed topology could achieve zero-voltage switching in the six main switches and the auxiliary switch both in the rectifier mode and inverter mode. In addition, the reverse recovery current of body diodes in the main switches was also suppressed. Furthermore, in order to realize the ZVS control scheme under the grid-tied bidirectional power flow condition and reduce the number of switchings, a modified carrier-based discontinuous PWM was proposed to fit the bidirectional switching sequence. Finally, a 3 kW prototype was constructed. Some simulation and experimental results are presented to verify the validity of the proposed circuit topology and PWM control scheme.

Performance improvement of reconfiguration strategies in photovoltaic array by replacement of blocking diodes with MOSFETs

ABSTRACT The power from photovoltaic array (PVA) is affected by temperature, solar irradiation, dust concentration, wind velocity, photovoltaic array configuration (PVAC) and shading pattern. The problem of partial shading (PS) is recognized as a major concern which decreases the PVA output power and represents multiple peak power points in the PV characteristic. Different PVACs respond differently with regard to their mismatch power loss (MPL) and fill factor (FF) under partial shaded condition (PSC). The conventional PVACs, such as SP-diode (Series-Parallel), TCT-diode (Total-Cross-Tied), BL-diode (Bridge-Link) and HC-diode (Honey-Comb), use blocking diodes (B-diodes) to block the reverse current. On the other hand, the proposed PVACs, including SP-MOSFET, TCT-MOSFET, BL-MOSFET and HC-MOSFET, replace the B-diodes with Blocking P-MOSFETs (BP-MOSFETs). The improvement in power output of the PVA is examined for four different configurations with B-diode and BP-MOSFET under changing illumination conditions. It is observed that TCT-MOSFET configuration shows better performance with least power losses and maximum efficiency under PSCs.

Gate-assisted MoSe2 transistor to detect the streptavidin via supporter molecule engineering

Atomically thin two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductor materials have garnered significant attention due to their remarkable properties surpassing conventional metal-oxide semiconductors. These properties include high carrier mobility, adjustable bandgaps, and exceptional sensitivity, providing them with tremendous potential for various applications. The remarkable characteristics of these 2D semiconductor materials led to fabricating of atomically thin electronic devices including diodes, photodetectors, memristors, and biosensors. Here, we present an atomically thin transistor composed of n-type molybdenum di-selenide (n-MoSe2), exhibiting a large reverse current. The charge transport through the MoSe2 transistor is modulated via back gate voltage, studied at various basing and gate voltages. Finally, the MoSe2 transistor device is utilized as a biosensor to detect the protein (streptavidin) as target analyte at fixed biasing and gate voltages. Using our designed pyrene-based supporter molecule, which is stacked over the MoSe2 surface via π-π stacking, the target protein is identified while avoiding any screening effects like Debye screening. Additionally, the real-time response of the biosensing device is recorded while maintaining a constant biasing voltage of 0.5 V, covering a range of streptavidin concentrations down to the lowest detectable concentration of 1 pM. Such utilization of the MoSe2 device as a biosensor could pave the way for manufacturing cutting-edge electrical devices which can detect a broad range of biomolecules, such as DNA (like ct-DNA) and the COVID-19 spike protein.

Study on transient photocurrent induced by energy level defect of schottky diode irradiated by high power pulsed laser

The transient photocurrent is one of the key parameters of the spatial radiation effect of photoelectric devices, and the energy level defect affects the transient photocurrent. In this paper, by studying the deep level transient spectrum of a self-designed Schottky diode, the defect properties of the interface region of the anode metal AlCu and Si caused by high-temperature annealing at 150 ℃, 200 ℃ and 300 ℃ for 1200 h have been quantitatively analyzed. The study shows that the defect is located at the position of + 0.41 eV on the valence band, the concentration is 2.8 times 1013/cm2, and the capture cross section is sigma = 8.5 times 1017. The impurity energy level mainly comes from the diffusion of Al atom in anode metal. We found that the defect did not cause the electrical performance degradation and obvious morphology change of the device, but the transient photocurrent increased significantly. The reason is that the high temperature treatment results in a growth in the density of states at the interface between AlCu–Si. The more mismatched dislocations and recombination center increased the reverse current of the heterojunction. The above view is proved by the TCAD simulation test.

Investigation of the leakage mechanism in multi-channel GaN-on-Si SBDs

This work presented the reverse leakage current (I R) mechanisms in multi-channel GaN-on-Si Schottky barrier diodes (SBDs). The device showed excellent performances in both ON and OFF-states thanks to the advanced multi-channel tri-gate architecture. The I R is dominated by thermal field emission at 25 °C–75 °C before pinch-off of the 2-dimensional electron gas (2DEG) channel in the Schottky region, due to the thinned Schottky barrier, which turned to be thermal emission (TE)-dominated under further elevated temperatures resulted from the small Schottky barrier height. Once the 2DEG channel is pinched off by the tri-anode, the I R is firstly dominated by Poole–Frenkel emission and then is trap-assisted tunneling after the full depletion of the channels beneath the field plates. These results are supported by excellent consistency between experimental results and theoretical models, offering a key understanding of multi-channel SBDs and shedding lights on this promising multi-channel technology for future energy conversion.

On band-to-band tunneling and field management in NiOx/β-Ga2O3 PN junction and PiN diodes

Due to the non-availability of p-type β-Ga2O3 films, p-type NiO x is gaining attention as a promising alternative to complement the n-type β-Ga2O3 films. This work investigated the band-to-band tunneling (BTBT) related reverse leakage current in NiO x /β-Ga2O3 PN junction diodes. The analysis reveals that a low barrier between the valence band maxima of NiO x and conduction band minima of β-Ga2O3 may promote direct BTBT and trap-assisted BTBT currents during the reverse bias. On the contrary, NiO x /β-Ga2O3 diodes in PiN configuration offer a wider BTBT depletion width and lower peak electric field, lowering the reverse leakage current by orders of magnitude. Thus, we show that NiO x /β-Ga2O3 heterojunction diodes in PiN configuration offer better field management strategies and suppression of the reverse leakage. The analysis performed in this work is thought to be valuable in informing device-design of NiO x /β-Ga2O3 heterojunction diodes for future high-power applications.

(Invited) Challenges and Opportunities of Alkaline Water Electrolysis

Alkaline water electrolysis has been operated on 100+ MW scale in the 20th century powered by hydropower. Because of this history, the technology is often regarded as a mature technology with limited improvement potential that is less suitable for flexible operation. As a result most research efforts in the field of water electrolysis focus on other technologies such as PEM, solid oxide and AEM electrolysis. This is a pity, since alkaline electrolysis is very well positioned to be deployed on large-scale for the production of green hydrogen in the coming decades. Main reason is that in contrast to the other technologies, alkaline technology does not depend on scarce and/or expensive noble or rare earth metals. Also, the use of a diaphragm instead of a membrane makes the technology more robust.Yet, to enable the large-scale deployment of alkaline electrolysis for production of green hydrogen from renewable electricity certain technical challenges need to be overcome. These include safety challenges associated with rare scenarios where hydrogen and oxygen can mix, flexibility limitations associated with gas crossover limiting the minimum load of the plant, and durability challenges resulting from frequent shutdowns of electrolyzers. In principle all these challenges can be overcome by rigorous plant design and the selection of suitable diaphragm and electrode materials, but they do require research efforts.Next to that, there is room to significantly drive down the costs of green hydrogen produced by alkaline electrolyzers. Traditionally, alkaline electrolyzers have been operated at low current densities of 0.2-0.4 A cm-2. This was related to the high ohmic drop associated with the use of thick diaphragms and non-zero-gap cell designs. Presently, advanced alkaline electrolyzers are under development that can operate at significantly higher current densities (~1 A cm-2) through the use of thinner diaphragms, zero-gap cell designs and improved electrode materials. Operation at these increased current densities increases the output of alkaline electrolyzers and in this way can effectively reduce the costs and footprint of water electrolysis plants. Yet, the use of thinner diaphragms and advanced electrodes also creates new challenges, since they can lead to increased gas crossover and vulnerability to impurities and reverse currents that occur upon the shutdown of electrolyzers.In this presentation the fundamentals of alkaline water electrolysis will be discussed. These include overpotentials and durability of electrode coatings, the role of electrolyte impurities, ohmic resistance, gas crossover through the diaphragm, the influence of operating temperature and pressure, the effect of bubbles, and the influence stray currents resulting from the manifold design. These fundamentals will be translated into a potential design for the perfect alkaline electrolyzer.Figure:alkaline electrolyzers operational in Norway in 1931. Source: Norsk Industriarbeidermuseum Figure 1

A non-destructive method for detecting turn-to-turn resistivity distribution in NI REBCO coils

A non-destructive method is proposed for detecting the turn-to-turn resistivity distribution (TTRD) of non-insulation (NI) coils made of REBCO tapes. In conventional designs, TTRD is often estimated to be a constant, while it is actually non-uniform. It is crucial to detect the TTRD of NI coils more accurately as it determines the behaviour of NI coils and may lead to peculiar phenomena such as local reverse currents. The proposed approach involves acquiring the temporal change of voltage distribution during an excitation/demagnetization process, which is subsequently incorporated into a system of ordinary differential equations derived from an equivalent circuit model. A genetic algorithm (GA) is then employed to fit the collected time-varying voltage data and generate the results of the ‘measured’ TTRD. The system of equations can actually be numerically solved. The solved time-varying TTRD results are averaged over the measuring period, which serve as the initial value of GA fitting, and accelerates the fitting process. Virtual measurements were performed on an artificially established mock coil, demonstrating high accuracy in reproducing the predetermined TTRD. Furthermore, an actual measurement was also conducted on a single-pancake coil, however with unknown TTRD, using eight voltage measurement points during the demagnetization process. The measured TTRD was incorporated into the equivalent circuit model to predict the temporal changes in voltage and magnetic field of the coil under additional excitation/demagnetization conditions. By comparing the predicted results with the experimental data, a high level of agreement was observed, thus confirming the potential application of the proposed method.

15 MeV proton damage in NiO/β-Ga2O3 vertical rectifiers

15 MeV proton irradiation of vertical geometry NiO/β-Ga2O3 heterojunction rectifiers produced reductions in reverse breakdown voltage from 4.3 kV to 3.7 kV for a fluence of 1013ions·cm−2 and 1.93 kV for 1014 ions·cm−2. The forward current density was also decreased by 1–2 orders of magnitude under these conditions, with associated increase in on-state resistance R ON. These changes are due to a reduction in carrier density and mobility in the drift region. The reverse leakage current increased by a factor of ∼2 for the higher fluence. Subsequent annealing up to 400 °C further increased reverse leakage due to deterioration of the contacts, but the initial carrier density of 2.2 × 1016 cm−3 was almost fully restored by this annealing in the lower fluence samples and by more than 50% in the 1014 cm−2 irradiated devices. Carrier removal rates in the Ga2O3 were in the range 190–1200 for the fluence range employed, similar to Schottky rectifiers without the NiO.