Low Switching Research Articles

A Modulation Strategy for Suppressing Current Ripple in H7 Current Source Inverters Through Coordinated Switching Operations

The DC bus current ripple is a critical performance parameter affecting the operation of current source inverters (CSIs). In high-power applications, CSIs often operate at lower switching frequencies to minimize losses. However, maintaining low levels of DC bus current ripple necessitates the use of large inductors on the DC side, which increases the size, weight, and cost of the system. This paper first explores the inherent limitations of conventional CSI designs. Subsequently, it proposes a hierarchical coordinated switching modulation strategy based on the H7 current source inverter (H7-CSI) to address the issue of DC bus current ripple. By segmenting the zero-vector states, the proposed method fully utilizes the modulation freedom of the H7-CSI, achieving high-frequency chopping effects on the DC-side current. Experimental results show that the new modulation strategy reduces the amplitude of DC bus current ripple to 43% of that achieved by conventional CSIs under similar switching loss conditions. Furthermore, the dynamic performance of the proposed scheme remains consistent with conventional CSIs. Spectrally, this method exhibits improved performance in the low-frequency range and slightly degraded performance in the high-frequency range, although the latter remains within acceptable limits.

Combined feature of enhanced stability and multi-level switching observed in TiN/Ta2O5/Ag-NPs/ITO/PET structure.

Both stability and multi-level switching are crucial performance aspects for resistive random-access memory (RRAM), each playing a significant role in improving overall device performance. In this study, we successfully integrate these two features into a single RRAM configuration by embedding Ag-nanoparticles (Ag-NPs) into the TiN/Ta2O5/ITO structure. The device exhibits substantially lower switching voltages, a larger switching ratio, and multi-level switching phenomena compared to many other nanoparticle-embedded devices. We attribute it to the embedded Ag-NPs effectively switching the mechanism of conductive filaments and the controlled distribution of Ag-NPs facilitates the occurrence of multi-level switching. Additionally, the fabricated structure demonstrated an impressive optical transmittance of nearly 85%. Undoubtedly, this combined feature of RRAM not only enhances stability but also enables multi-level switching, thereby demonstrating an approach to fabricating versatile and practical electronic devices aimed at boosting storage capacity and speed.&#xD.

Synchronization resilience of coupled fluctuating-damping oscillators in small-world weighted complex networks

The mechanisms of synergy in complex networks have garnered significant attention across scientific disciplines. In this paper, we present a model of coupled oscillators with damping fluctuations within a small-world weighted complex network. We analyze the system’s asymptotic synchronization to derive conditions for asymptotic stability and evaluate the steady-state response. Our numerical simulations highlight the substantial impact of network weight heterogeneity and scale on asymptotic synchronization. We also examine asymptotic synchronization resilience under various removal strategies, revealing that increased noise intensity and lower switching rates reduce resilience. Notably, the removal of strong links poses the greatest vulnerability, while weak links have minimal impact. Interestingly, enhancing weight heterogeneity and scale can improve resilience in certain cases. Our results further show that heterogeneity accelerates synchronization speed, indicating a non-monotonic relationship with network scale. Ultimately, we confirm our theoretical findings and reveal intriguing generalized stochastic resonance (GSR) phenomena.

Enhancing Rashba Spin-Splitting Strength by Orbital Hybridization.

A Rashba spin-splitting state with spin-momentum locking enables the charge-spin interconversion known as the Rashba effect, induced by the interplay of inversion symmetry breaking (ISB) and spin-orbit coupling (SOC). Enhancing spin-splitting strength is promising to achieve high spin-orbit torque (SOT) efficiency for low-power-consumption spintronic devices. However, the energy scale of natural ISB at the interface is relatively small, leading to the weak Rashba effect. In this work, we report that orbital hybridization inducing additional asymmetry potential at the interface observably enhances spin-splitting strength, verified in the hexagonal boron nitride (h-BN)/Co3Pt heterostructures. First-principles calculations suggest the sizable Rashba spin-splitting derived from the out-of-plane p-d hybridization combined with SOC at the h-BN/Co3Pt interface. Then, the SOT efficiency is observably enhanced via the Rashba effect at the h-BN/Co3Pt interface and exhibits unusual temperature dependence, in which the large-area h-BN is in situ grown on the Co3Pt layer with perpendicular magnetic anisotropy by magnetron sputtering. Especially, the dominant damping-like torque is observed, resulting in the lower threshold switching current density and the enhanced switching ratio. Our results provide opportunities for interfacial control to enhance the Rashba effect and the SOT efficiency in heterostructures. It is expected to contribute to the design of energy-efficient spintronic devices.

Modelling Analysis and Characteristics of Multi-Level Inverter for Integrating Solar PV System to Grid

This paper investigates the implementation of a cascaded H-bridge multi-level inverter in a single-phase grid-connected solar photovoltaic (PV) system to address harmonic distortion challenges in DC-to-AC power conversion. The primary objective is to enhance power quality and system efficiency by leveraging the inverter's ability to reduce harmonics through power sharing and a lower switching frequency. A Simulink model is developed to evaluate the proposed system's performance, incorporating a unipolar Pulse Width Modulation (PWM) control strategy and an LCL filter for effective harmonic mitigation. The system employs Maximum Power Point Tracking (MPPT) based on the Perturb and Observe (P&O) algorithm, combined with Synchronous Reference Frame Theory-Phase Disposition PWM (SRFT-PDPWM) for optimal control. The proposed inverter ensures precise synchronization between the grid and inverter frequencies, achieving a Total Harmonic Distortion (THD) below 5%. Simulation results demonstrate the system's robust responsiveness to variations in solar irradiance, with increased irradiance leading to further reductions in THD and improved power quality. These findings validate the proposed inverter's capability to deliver high-quality, efficient power under varying environmental conditions, aligning with global objectives for integrating clean and sustainable energy into utility networks.

Efficient Charge‐to‐Orbit Current Conversion for Orbital Torque Based Artificial Neurons and Synapses

AbstractOrbital Hall effect (OHE) in light metal materials has attracted significant attention due to its potential applications in innovative orbitronic devices. Here, the OHE in titanium film is investigated and the orbital torque efficiency in Pt/[Co/Ni]3/Ti multilayers is characterized. A notable effective field per unit current density of orbital torque is achieved, nearing 560 Oe per 107 A cm−2 in a sample featuring 25 nm Ti layer. The corresponding orbital torque efficiency is ≈0.25. The resulting orbital torque effectively switches the perpendicularly magnetized moments in Co/Ni multilayers. In contrast, a reference sample of Pt/[Co/Ni]3/Pt demonstrates significantly lower switching efficiency. Furthermore, it is demonstrated that the multi‐states switching driven by orbital torque in Pt/[Co/Ni]3/Ti structure can mimic the behaviors of artificial neurons and synapses. This work not only enhances the understanding of the orbital torque but also offers the development of novel orbitronic devices based on OHE.

Reduction of torque ripples using the DTC-SVM method in PMSM with extended Kalman filter

A detailed analysis has been conducted on two motor control algorithms: direct torque control (DTC) and field-oriented control (FOC). There are two ways that a voltage source inverter (VSI) can regulate a permanent magnet synchronous motor (PMSM). When using the PMSM and voltage source inverter (VSI), dead time is employed to turn off both the upper and lower switches to prevent short circuits. However, by supplying the PMSM with unexpected polarity voltages at the VSI output voltage, this switching technique reduces distortion. It is challenging to utilize the sensor to directly detect the fault voltage that results in an open circuit. This work examines the nonlinearity of the electric power controller during dead time during PMSM operation using the DTC algorithm to increase control stability. The stress distribution is estimated using an extended Kalman filter (EKF). Ultimately, the model presented in this study verified the increase in stator current and torque output through simulations and testing.

Research and design of high gain DC-DC converter based on coupled inductor

Abstract A high-gain DC-DC converter with soft-switching characteristics is proposed to meet the application requirements of new energy transportation and power systems. By using a coupled inductor boost structure and adding a voltage doubling unit, the boost capability of the converter is further enhanced. By constructing a resonant cavity, the switching transistor can operate in ZVS (Zero Voltage Switching), and all diodes can operate in ZCS (Zero Current Switching), significantly reducing device losses. The coupled inductor boost structure can achieve a higher voltage output at a lower switching transistor voltage stress and only requires control by a single switching transistor. The article analyzes a 300W experimental prototype of the converter, which can achieve an efficiency of 90% at a 10-fold voltage gain, verifying the feasibility and superiority of the converter.

Probability Modeling of Customer Switching Behavior and Voice Tariff Disparities in Tanzanian Telecom Markets

The telecommunications sector has experienced significant growth, driven by technological advances, improved internet access, investment from both the private and public sectors, and competitive pricing. Therefore, it is crucial to understand the factors that influence customer switching. This study examines voice tariff disparities between telecommunications operators in Tanzania and determines the probability of customer switching behavior. This was achieved by analyzing the relationship between tariff differences and the likelihood of customers switching service providers. A quantitative research approach was used using secondary data from the Tanzania Communications Regulatory Authority (TCRA), covering the period from the quarter ending March 2023 to the quarter ending June 2024. Descriptive statistics and logistic regression were used to model the effects of tariffs on switching behavior. Findings indicated that higher local SMS and on-net voice tariffs significantly increase the probability of customers switching providers, while higher international voice tariffs surprisingly reduce the likelihood of customer switching behavior. The study concluded that competitive pricing, particularly in SMS and local voice services, is essential for customer retention. It recommends that telecom operators focus on cost-effective service offerings and improve network quality to minimize churn. Future research should explore the dynamics behind the lower switching tendency for international services to enhance retention strategies for premium service users.

Mobile use in an age of interruption: Implications of capacity and structural interference for mobile users

We investigate the performance consequences of on-screen interruptions in mobile use. Drawing on capacity theory of attention, we conjecture that attention capacity may be lower in mobile use relative to PC use. A self-report instrument provides preliminary support for this conjecture. An online experiment provides additional support by showing that mobile users benefit from lower switching costs when they turn their attention to an interrupting task, while they suffer higher resumption costs when they resume a task that already demanded their attention. This study advances the understanding of mobile behavior while contributing to the broader literature on attention and interference.

Effect of annealing conditions on resistive switching in hafnium oxide-based MIM devices for low-power RRAM

Abstract This work presents resistive switching (RS) behaviour in HfO2-based low-power resistive random-access memory (RRAM) devices. A metal-insulator-metal (MIM) structure (Au/HfO2/Pt) was fabricated by sandwiching a thin insulating layer of HfO2 between Pt and Au electrodes. HfO2 films deposited by RF sputtering at room temperature were rapid thermally annealed in N2 ambient at 400 °C and 500 °C. Grazing angle x-ray diffraction (GIXRD), Field emission gun-scanning electron microscopy (FEG-SEM), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS) were employed to analyse the phase, crystal structure, morphology, surface roughness and chemical composition of the HfO2 films. The bipolar RS could be observed in both as-deposited and annealed HfO2 film-based devices from I–V characteristics measured using a source meter. We have investigated the effect of annealing temperature and annealing ambient on the phase formation of HfO2 as well as the RS characteristics and compared with as-deposited film-based device. Annealed HfO2 film-based devices exhibited improved electrical characteristics, including stable and repeatable RS at significantly lower switching voltages (<1 V) which indicates low power consumption in these devices. The relatively lower processing temperature of the HfO2 films and that too in the films deposited by physical vapor deposition (PVD) technique-RF magnetron sputtering makes this study significantly useful for resistive switching based non-volatile memories.

Performance Analysis of JL-FinFET with Varied Non-Uniform Doping Concentrations, Fin Height and Fin Width using Device Simulator

With the growth of the MOSFET technology, the size of the transistor becomes smaller which can lead to Short-Channel Effects (SCEs). In order to address the SCEs, multi-gate transistor such as Fin Field-Effect Transistor (FinFET) has been invented. Meanwhile, it is found that the conventional transistor with junctions also has its drawbacks and limitations due to the decrease in the gate length. The SCEs can occur and affect the overall performance of the device with lower switching times and lower current density . In order to address these limitations, new structure of transistor without junction known as a junctionless (JL) transistor has been proposed. In this work, the impact of uniform versus non-uniform doping concentrations, fin height (Hfin) and fin width (Wfin) in JL-FinFET were investigated by using Technology Computer Aided Design (TCAD) Tools. It was found that non-uniform doping concentration of 4 x1018 cm-3 for the source/drain and of 4 x1017 cm-3 for the channel, together with Hfin of 20 nm and Wfin of 4 nm provide the best electrical performance of Ioff = 6.45 x10-17 A, Ion = 6.14 x10-6 A, Ion/Ioff = 9.52 x1010 and DIBL = 11 mV/V. The outcome of this research work can be used as a basis to understand JL-FinFET biosensors for medical applications and more complex JL structures.

Synergetic engineering of oxidizable, redox, and inert metal decorated copper oxide for non-volatile memory and neuromorphic computing applications

Abstract In the quest for efficient resistive switching (RS) materials for both non-volatile memory and neuromorphic computing applications, a variety of functional materials have been researched in the last few years. Herein, we systematically synthesized Ni, Ag, and Au decorated copper oxide (CuxO) by using an electrochemical approach and investigated their RS performance for both non-volatile memory storage and neuromorphic computing applications. By tuning various electrochemical parameters, we optimized Ni, Ag, and Au decoration over the CuxO switching layers to understand the effect of oxidizable, redox, and inert metal decoration, respectively. Fabricated Ni-CuxO/FTO, Ag-CuxO/FTO, and Au-CuxO/FTO devices show forming-free bipolar and analog properties of RS behavior. The electrical measurements asserted that the electrodeposited Ni-CuxO/FTO RS device shows excellent RS, non-volatile memory, and synaptic learning properties compared to the Ag-CuxO/FTO, and Au-CuxO/FTO devices. Moreover, the statistical and Weibull distribution parameters suggested that the Ni-CuxO/FTO RS device has lower switching variation than the other two devices. The conduction mechanisms of all devices are investigated by fitting the appropriate physics-oriented models. It was found that Ohmic and Child's square law were dominated during the charge transport and the RS process occurred due to the filamentary switching effect. Results suggested the electro-decorated/-deposited Ni-CuxO is a suitable switching layer for memory as well as neuromorphic computing applications.

A Critical Analysis and Comparison of the Effect of Source Inductance on 3- and 4-Lead SuperJunction MOSFETs Turn-Off

This paper critically compares the turn-off performance of two package solutions, 3-lead (3L) vs. 4-lead (4L), in SuperJunction MOSFETs. It is commonly assumed that the better performance (lower switching losses) of the 4L MOSFET is obtained thanks to the decoupling of the power and driving loops. On the contrary, in this work, the experimental results, circuit models and Kirchhoff laws show that the turn-off improvement (lower turn-off losses) obtained by adopting the Kelvin source is due to the lower inductance of the driver loop of the 4L MOSFET, instead of the decoupling between the driver and power loops. In detail, an inductor is added to the gate path of the 4L MOSFET to obtain a total inductance in the driver loop equal to the 3L counterpart. The experimental results show that the 4L MOSFET presents the same drain current slew rate under this condition, although the driver and power loops are still decoupled.

ISOS-SAB DC/DC Converter for Large-Capacity Offshore Wind Turbine

This study offers a modular isolated grid-connected DC/DC medium-voltage DC aggregation converter to support offshore full DC wind farms’ need for lightweight and highly efficient power aggregation and transmission. The converter can simultaneously have a smaller transformer size and lower switching frequency during operation through the dual-voltage stabilization three-loop control strategy and phase-shift modulation strategy, which greatly reduces the space occupied by the converter and lowers the switching loss, Additionally, the use of a two-level structure at a lower switching frequency has lower loss, which effectively reduces the cost of the power device compared with the commonly used three-level converter. The input series output series connection between the converter sub-modules effectively lowers the voltage stress on each power switching device and facilitates expansion into a multi-module structure, expanding its application in high-voltage and large-capacity environments. This study analyzes the two working modes of the DC/DC converter and its control approach, in addition to providing a detailed introduction to the application scenarios of this converter. Ultimately, the efficacy and practicability of the suggested topology and control scheme are confirmed by simulations and experiments.

A review on modulation techniques of Quasi-Z-source inverter for grid-connected photovoltaic systems

Photovoltaic (PV) is a promising way to meet the increasing global energy demand due to its sustainability, efficiency, and cost-effectiveness. For the wide-scale adoption of PV systems, converters with reliable input sources, stable control strategies and appropriate modulation techniques must be designed. In the literature, various modulation techniques have been developed that help to boost the voltage of the PV modules by implementing shoot-through (ST) in which the upper and lower switches of an inverter conduct simultaneously and short-circuit occurs. Various optimised modulation techniques have been implemented to enhance its performance. Among those, the quasi-Z-source inverter (qZSI) has attracted much attention due to its ability to achieve higher conversion ratios for grid-connected PV applications. In this paper, a detailed comparison of the modulation schemes for the qZSI PV systems has been done to understand the trade-off and select the most suitable approach. Upon the selection of the space vector modulation with unique switching sequences and rearranging upper ST and lower ST states, the inverter can achieve ST with reduced switching losses. Furthermore, a 600 VA three-phase grid-connected system utilizing a three-level neutral-point-clamped qZSI topology is modulated and simulated. It has been demonstrated that the constant boost control offers good performance in terms of reduced voltage stresses on switches, lower total harmonic distortion, and hence, higher efficiency.

An adaptive architecture for strategic Enhancement of energy yield in shading sensitive Building-Applied Photovoltaic systems under Real-Time environments

Building Applied Photovoltaic (BAPV) systems play a crucial role in developing renewable energy-generating architecture, particularly in urban settings. The BAPV arrays are designed considering the roof area and other installation factors to meet the building’s energy demand or contribute to the grid. However, the BAPV array encounters a significant challenge of partial shading by nearby trees or buildings that substantially reduce the generation efficiency. This paper proposes an energy yield enhancement solution for the BAPV system, focusing on the electrical reconfiguration of the arrays during partial shading. The solution, which employs a streamlined architecture with lower switches integrated with the dingo algorithm, ensures fast and reliable operation during dynamic shading scenarios. The solution’s efficiency is demonstrated in simulation using a BAPV system, considering real-time partial shading caused by neighbouring objects at different times of the day, considering the sun’s movement, and comparing it with existing techniques. The results show that the solution can yield 28.79 % and 15.53 % higher power than the conventional and existing techniques, with an average convergence rate and voltage standard deviation of 0.057 s and 1.26 %, respectively, thereby proving its superiority.

Intrinsically Stable Charged Domain Walls in Molecular Ferroelectric Thin Films

AbstractCharged domain walls in ferroelectrics hold great promise for applications in ferroelectric random‐access memory (FeRAM), with advantages such as low energy consumption, high density, and non‐destructive operation. Due to the mechanical compatibility condition, the neutral domain walls are dominant in traditional ferroelectric thin films. Herein, using phase‐field simulations, the formation of intrinsically stable charged domain walls (CDWs) in the molecular ferroelectric films is demonstrated, which can be mainly attributed to the small mechanical stiffness. The switching kinetics are further investigated for the CDWs, showing a lower switching barrier as compared to the neutral counterparts. Moreover, it is indicated that increasing the compressive misfit strain can lead to prolonged switching time, with a significantly increased switching energy barrier. These findings pave the way for the potential applications of metal‐free organic ferroelectric materials in FeRAM devices.

Slow-Scale Bifurcation Analysis of a Single-Phase Voltage Source Full-Bridge Inverter with an LCL Filter

In high-power photovoltaic systems, the inverter with an LCL filter is widely used to reduce the value of output inductance at which a lower switching frequency is required. However, the effect on the stability of the system caused by an LCL filter due to its resonance characteristic cannot be ignored. This paper studies the stability of a single-phase voltage source full-bridge inverter with an LCL filter through the bifurcation theory as it is a nonlinear system. The simulation results show that low-frequency oscillation appears when the proportional coefficient of the system controller increases or the damping resistance decreases to a certain extent. The average model is derived to analyze the low-frequency oscillation; the theoretical analysis demonstrates that low-frequency oscillation is essentially a period in which doubling bifurcation occurs, which indicates the intrinsic mechanism of the instability of the full-bridge inverter with an LCL filter. Additionally, the limitation of the existing damping resistor design standards, which only considers the main circuit parameters but ignores the influence of the controller on system stability, is identified. To solve this problem, the analytical expression of the system stability boundary is provided, which can not only provide convenience for engineering design to protect the system from low-frequency oscillation but also expand the selection range of damping resistance in practice. The experiments are performed to verify the results of the simulation and theoretical analysis, demonstrating that the analysis method can facilitate the design of the inverter with an LCL filter.

Ni3C nanosheets and PVA nanocomposite based memristor for low-cost and flexible non-volatile memory devices

Two-dimensional (2D) MXenes have gained extensive attention in the field of memristors due to their high ion mobility, chemical stability and tunable electrical and surface properties. Moreover, MXenes have tunable interlayer bonding which enables enhancement in memristor performance. In this work, we synthesize a novel nanocomposite of Ni3C nanosheets and polyvinyl alcohol (PVA) and fabricate a flexible memristor with Ag/Ni3C-PVA/ITO/PET configuration for non-volatile memory applications. Ni3C nanosheets were synthesized from Ni-MAX (Ni3AlC2) through a solvothermal etching and exfoliation process. The nanosheet like structure of Ni3C is confirmed through Scanning Electron Microscopy (SEM) and Transmission Electron microscopy (TEM). Characterization techniques like X-ray diffraction (XRD), Raman spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR) reveal the crystalline phases, surface functional groups and chemical bonds present in Ni3C nanosheets and Ni3C-PVA nanocomposite. The memristor was fabricated through a facile low cost solution processed based fabrication technique. The Ag/Ni3C-PVA/ITO/PET memristor exhibits bipolar non-volatile switching characteristics. The device with optimised mass ratio of 4:3 (Ni3C: PVA) shows a decent off/on ratio of 2.09 × 102, long retention time of 104 s, and an endurance of 102 DC cycles. The SET voltage of the as-fabricated device is 2.8 V and the RESET voltage is −5.33 V. The flexible memristor exhibits outstanding mechanical robustness over 500 bending cycles. The high charge carrier mobility of Ni3C results in lower switching voltage and the dielectric property of PVA improves data retention and off/on ratio of the memristor. The resistive switching behaviour is explained through conductive metallic bridge mechanism. The conduction mechanism follows Ohmic conduction in ON state and trap controlled space charge limited current (TCSCLC) mechanism in OFF state. The results demonstrate that the nanocomposite with its superior resistive switching effects is suitable for cost-effective, high-performance, flexible non-volatile memory devices.