Search Results (184)

The resilience of Intelligent Transportation Systems (ITSs) heavily relies on distributed Battery Energy Storage Systems (BESSs) deployed in harsh, unattended highway environments. Traditional maintenance strategies often fail to account for the dynamic feedback between battery aging, environmental stress, and maintenance response latency. This study proposes a system dynamics (SD) framework to evaluate and optimize the resilience of these critical power infrastructures. By modeling the nonlinear interactions among sensor data, controller logic, and remote discharge terminals, we simulate the system’s dynamic behavior over a 36-month lifecycle. The results reveal a critical “scalability threshold”: when battery pack quantity exceeds 40 units, the system’s self-healing time increases disproportionately, degrading resilience. Furthermore, the study identifies 384 V as the optimal “Resilience Topology Voltage”, offering the fastest recovery speed by balancing thermal stability with consistency management efficiency. These findings provide theoretical guidelines for configuring BESS capacity and optimizing remote maintenance protocols to ensure uninterrupted highway operations. Full article

Voltage security assessment is increasingly challenged by stochastic demand growth and localized stress patterns that are not well represented by deterministic, single-snapshot analyses. This paper proposes a fully steady-state probabilistic stress-testing framework based on Monte Carlo simulation and Newton–Raphson AC power flow, jointly evaluating the minimum bus voltage magnitude $V_{min}$ (voltage-floor adequacy) and the scenario maximum Fast Voltage Stability Index $FVS{I}_{max}$ (worst-case line stress). Stress is injected selectively on screened weak buses by sampling a random stress footprint and intensity across three progressive levels (L1–L3), while preserving the local power factor. The approach is demonstrated on IEEE 14-, 30-, and 118-bus benchmark systems using $N=2000$ realizations per level, with 100% convergence across all cases. Across all systems, results show a consistent, monotone degradation of the voltage floor and a systematic increase in violation risk as stress intensifies. For the IEEE 14 system, the voltage-risk profile escalates rapidly, with $\mathbb{P}(V_{min}<0.90)$ rising from 0.16 (L1) to 0.54 (L3), while the worst-case FVSI tail strengthens markedly (p95 increasing from 0.1455 to 0.2081), indicating a growing likelihood of severe voltage-stress events. In contrast, the IEEE 30 and IEEE 118 systems exhibit milder shifts in central voltage levels but maintain substantial exposure relative to the 0.95 pu planning threshold, with $\mathbb{P}(V_{min}<0.95)$ reaching 0.79 and 0.74 at L3, respectively. Beyond risk magnitudes, the framework reveals a nontrivial structural phenomenon in worst-case line stress: as system size increases, stochastic stress outcomes become increasingly concentrated into a small number of dominant transmission corridors. Recurrence analysis at the highest stress level shows fragmented criticality in IEEE 14 (Top-3 lines sharing criticality), near-total dominance by a single corridor in IEEE 30 (>92% of cases), and complete dominance collapse in IEEE 118 (one corridor governing 100% of $FVS{I}_{max}$ events). These results demonstrate that probabilistic stress-testing can simultaneously quantify voltage-risk escalation and expose hidden structural bottlenecks that remain invisible under deterministic screening, providing a scalable diagnostic tool for planning-stage monitoring and reinforcement prioritization. Full article

With the active modernization of power facilities and the increasing deployment of maneuverable combined-cycle gas turbines (CCGTs), the selection of rational start-up strategies becomes increasingly important from the perspective of power quality. Excessive acceleration of power ramp-up may lead to undesirable voltage deviations, particularly in transmission networks with limited grid stiffness. This study investigates the impact of CCGT start-up ramp rate on voltage dynamics and power quality indicators at a 110/220 kV grid node. A detailed model of the Almaty power hub was developed in MATLAB/Simulink, taking into account the network structure, generating units, transformers, and aggregated loads. Three start-up scenarios were analyzed: an existing combined heat and power plant, a 504 MW combined-cycle gas turbine unit, and a 560 MW combined-cycle gas turbine unit with fuel afterburning. Voltage dynamics were evaluated using RMS-based indicators and a stabilization criterion incorporating a 5 s sliding time window and an 80% admissibility threshold. The simulation results reveal a nonlinear relationship between the start-up ramp rate and voltage quality. Increasing the ramp rate reduces the voltage stabilization time; however, beyond approximately 0.05 MW/s, further acceleration does not lead to additional improvement in power quality. The results indicate the existence of an optimal range of start-up ramp rates that provides a compromise between start-up speed and voltage quality requirements. The proposed approach can be used in the development of start-up algorithms for modern combined-cycle power plants connected to 110/220 kV transmission networks. Full article

To address the malfunction and unreliable operation of traditional open discharge gaps in high-altitude environments (with sandstorms and low pressure), which are prone to interference from factors like electrode corrosion and contamination, this study proposes an intelligent sealed neutral point protection device for transformers. Its core is a sealed discharge gap filled with nitrogen gas, effectively isolating it from external conditions and significantly stabilizing the power frequency discharge voltage. Innovatively, an active breakdown technology is introduced. Overvoltage signals at the transformer neutral point are acquired in real time via a capacitive voltage divider. After processing by a microcontroller unit (MCU), if both the amplitude and duration meet the preset thresholds, the MCU triggers a pulse to actively induce a discharge at the gap’s low-voltage end, enabling controlled breakdown. This allows the transient discharge voltage to be raised to 3–4 times the steady-state value, avoiding overlap with the surge arrester’s residual voltage. Tests confirm that the gap breaks down stably only when both amplitude and duration conditions are met, remaining reliable otherwise. This design successfully resolves the critical issues of failure and maloperation under both steady-state and transient overvoltages in high-altitude settings, significantly improving protection selectivity and reliability, and offering a novel solution for transformer safety in such regions. Full article

Distinct from the traditional Modular Multilevel Converter (MMC) which focuses on fundamental frequency operation, the Static Var and Filter (SVF) within the Multi-Source Line-Commutated Converter (SLCC) system is tasked with the core function of high-frequency harmonic filtering. This paper reveals a unique engineering reliability issue stemming from this functional difference: to satisfy the Nyquist sampling theorem for precise tracking and elimination of high-frequency harmonics, the update frequency of the capacitor voltage balancing algorithm in the SLCC-SVF system is forced to increase significantly. Mathematical modeling and quantitative analysis demonstrate that this strong coupling between harmonic tracking demands and the voltage sorting strategy directly drives an abnormal surge in the average switching frequency (reaching over five times that of the fundamental condition), severely threatening device safety. To address this, an optimized adaptive hybrid modulation strategy is proposed. The system operates under Nearest Level Modulation (NLM) in normal conditions and automatically transitions to Carrier Phase-Shifted PWM (CPS-PWM)—leveraging its closed-loop balancing capability—when switching frequency or junction temperature exceeds safety thresholds. Furthermore, a non-integer frequency ratio optimization theory for low-modulation indices is constructed specifically for SVF conditions to prevent low-frequency oscillations. PLECS simulation results validate the theoretical analysis, showing that the proposed strategy effectively reduces the average switching frequency by approximately 20% under complex harmonic conditions, significantly enhancing thermal stability and operational reliability while guaranteeing filtering performance. Full article

Severe surface deformation induced by super-large mining height longwall extraction poses a significant threat to the safe operation of high-voltage transmission towers. In this study, a 330 kV straight-line transmission tower located above the 122104 working face of the Caojiatan Coal Mine was selected as a case study to investigate tower stability under mining-induced surface deformation and to develop corresponding protection technologies. An integrated monitoring system combining instantaneous and long-term measurements was established to characterize surface movement throughout the mining process. The results indicate that the maximum surface subsidence reached 7300 mm, while the maximum inclination and curvature attained 50 mm/m and 0.62 mm/m², respectively, reflecting intense deformation of the overlying ground. Numerical simulations based on ANSYS 2021R1 were conducted to systematically evaluate the effects of surface inclination, compressive deformation, and tensile deformation on the structural response of the transmission tower. The critical deformation thresholds leading to structural failure were identified as 30 mm/m for inclination, −7.2 mm/m for horizontal compression, and 7.7 mm/m for horizontal tension. Based on these findings, a comprehensive protection system was proposed, integrating tower body reinforcement, combined foundation reconstruction, surface subsidence monitoring, dynamic jacking-based rectification, and foundation grouting reinforcement. The proposed scheme was successfully implemented in field practice. Monitoring results demonstrate that, after reinforcement and rectification, differential settlement of the tower foundation was controlled within 20 mm, and tower inclination remained below 1‰. This ensured uninterrupted underground mining operations and continuous power transmission within the Caojiatan Coal Mine corridor. The outcomes of this study provide a practical reference for the protection of high-voltage transmission towers under similar mining conditions. Full article

Oxide transistors have attracted significant interest in the field of integrated circuits (ICs). Among various oxide semiconductors, InAlZnO (IAZO) stands out as a promising candidate due to its potential for high mobility and excellent stability. In this work, we fabricate high-performance IAZO transistors with a field-effect mobility of 56.60 cm²/V·s, a subthreshold swing of 82.59 mV/decade, an on-to-off current ratio over 10⁷, and a small threshold voltage shift of 0.09 V and −0.03 V under positive and negative bias stress, respectively. Based on these transistors, Pseudo-Enhancement-Load (PEL) inverters were constructed. An adjustable bias voltage (V_BIAS) was also introduced as an additional control parameter, which allows for flexible control of the trade-off between circuit performance and power consumption. The resulting inverters achieve a balance between static and dynamic performance, exhibiting a voltage gain of 1.83 V/V and a relatively low power consumption of 2.58 × 10⁻⁶ W (V_BIAS = 1.0 V). Our work demonstrates the potential of IAZO transistor-based PEL inverters for high-performance, low-power oxide IC applications. Full article

This paper presents a low-area, low-temperature coefficient (TC) CMOS voltage reference (CVR) circuit utilizing a compensation technique. Compared to traditional CVR circuits, this design does not rely on compensating the temperature characteristics of the threshold voltage. It lowers current demand, reducing resistor dependency and thus minimizing circuit area. In addition, a curvature compensation circuit is constructed, improving temperature stability. Implemented in 180 μm CMOS the core area of the circuit is 0.0081 mm². Under a 1.8 V supply voltage, post-layout simulations show that the best TC reaches 1.06 ppm/°C over the temperature range of −40 °C to 125 °C, and the line regulation (LR) is 0.36%/V within a supply voltage range of 1.6 V to 2 V. Full article

This work presents a lightweight and interpretable framework for the early warning of voltage stability degradation in distribution networks, based on fractal and spectral features from flow measurements. We propose a Fast Voltage Stability Index (FVSI), which combines four independent indicators: the Detrended Fluctuation Analysis (DFA) exponent α (a proxy for long-term correlation), the width of the multifractal spectrum Δα, the slope of the spectral density β in the low-frequency range, and the $c_2$ curvature of multiscale structure functions. The indicators are calculated in sliding windows on per-node series of voltage in per unit Vpu and reactive power Q, standardized against an adaptive rolling/first-N baseline, and anomalies over time are accumulated using the Exponentially Weighted Moving Average (EWMA) and Cumulative SUM (CUSUM). A full online pipeline is implemented with robust preprocessing, automatic scaling, thresholding, and visualizations at the system level with an overview and heat maps and at the node level and panel graphs. Based on the standard IEEE 13-node scheme, we demonstrate that the Fractal Voltage Stability Index (FVSI_Fr) responds sensitively before reaching limit states by increasing α, widening Δα, a more negative $c_2$, and increasing β, locating the most vulnerable nodes and intervals. The approach is of low computational complexity, robust to noise and gaps, and compatible with real-time Phasor Measurement Unit (PMU)/Supervisory Control and Data Acquisition (SCADA) streams. The results suggest that FVSI_Fr is a useful operational signal for preventive actions (Q-support, load management/Photovoltaic System (PV)). Future work includes the calibration of weights and thresholds based on data and validation based on long field series. Full article

The electrochemical water splitting process represents a promising and sustainable route for generating high-purity hydrogen with minimal environmental impact. The development of efficient and economically viable electrocatalysts is crucial for enhancing the kinetics of the oxygen evolution reaction (OER), which is a major bottleneck in overall water splitting. In this study, a Co₃V₂O₈/PEG-CTAB electrocatalyst was synthesized and systematically evaluated for its OER activity in alkaline conditions. The nanosheet-like architecture of the PEG-CTAB-assisted Co₃V₂O₈ electrocatalyst facilitates effective interfacial contact, thereby improving charge transport and catalytic accessibility. Among the examined compositions, the Co₃V₂O₈/PEG-CTAB catalyst exhibited superior OER performance, requiring a low overpotential of 298 mV to deliver a current density of 10 mA cm⁻² and displaying a Tafel slope of 90 mV dec⁻¹ in 1 M KOH. Furthermore, the catalyst demonstrated outstanding durability, retaining its electrocatalytic activity after 5000 consecutive CV cycles and prolonged chronopotentiometric testing. The Co₃V₂O₈/PEG-CTAB || Pt-C asymmetric cell required a cell voltage of 1.83 V to reach the threshold current density, confirming its ability to efficiently sustain overall water splitting under alkaline conditions. The enhanced performance is attributed to the synergistic effect of the electrocatalyst, which promotes active site exposure and structural stability. These findings highlight the potential of the Co₃V₂O₈/PEG-CTAB system as a cost-effective and robust electrocatalyst for practical water oxidation applications. Full article

Multi-acceptor and all-acceptor polymers solve the fundamental challenge of achieving unipolar electron transport without compromising stability in n-type polymer field-effect transistors. By systematically replacing electron-rich donors with acceptor units, these architectures push LUMO levels below −4.0 eV and HOMO levels below −5.7 eV. Consequently, electron mobilities exceeding 7 cm² V⁻¹ s⁻¹, on/off ratios approaching 10⁷, and months-long ambient operation can be achieved. This review connects the molecular architecture to device function. We assert that short-range π-aggregation matters more than crystallinity—tight π-stacking over 5–10 molecules drives transport in rigid backbones. Device optimization through interface engineering (e.g., amine-functionalized self-assembled monolayers reduce the threshold voltages to 1–5 V), contact resistance minimization, and controlled processing transform the intrinsic material potential into working transistors. Current challenges, such as balancing the operating voltage against stability, scaling synthetic yields, and reducing contact resistance, define near-term research directions toward complementary circuits, thermoelectrics, and bioelectronics. Full article

Power converters are essential for solar energy systems but achieving over 96% efficiency at 1 kW and 300 kHz with compact magnetic and EMC compliance remains challenging for high-power-density PV applications. This study presents the design, modeling, and experimental validation of a 1 kW two-phase interleaved boost converter operating from 12 V input to 48 V/20 A output, featuring a single EE32 Litz-wound coupled-core inductor with coupling coefficient k = −0.475 that reduces per-phase current ripple to just 120 mA (0.6% relative) at full load, a load-selective active zero-current switching (ZCS) circuit activated above 5 A threshold via DCR sensing to minimize switching losses without light-load penalties, and digital peak-current control with 2P2Z compensator implemented on an XMC4200 microcontroller, ensuring robust stability. Experimental results demonstrate peak efficiency of 98.6% at approximately 190 W load, full-load efficiency of approximately 96% with total losses limited to 40 W dominated by conduction rather than switching, thermal rise below 80 °C on key components, voltage regulation with less than 1% deviation down to 2 A minimum load, and full compliance with electromagnetic compatibility standards, including EN 55014-1/2 and EN 61000-4-2 ESD testing. The novel integration of selective ZCS, single-core magnetic, and high-frequency operation outperforms prior interleaved boost converters, which typically achieve 94–97% peak efficiency at lower switching frequencies of 20–100 kHz using multiple inductors or complex always-active resonant networks, making this solution particularly suitable for compact photovoltaic micro-converters, electric vehicles, and industrial power supplies requiring high efficiency, reliability, and regulatory compliance. Full article

In power systems with a high penetration of renewable energy, integrating battery energy storage systems can enhance frequency regulation capabilities. However, in “islanded” operation mode, the lack of large grid interconnection support may cause significant frequency fluctuations or even instability when the system faces fault disturbances. To ensure the dynamic stability of the grid-forming energy storage system, this paper proposes a virtual synchronous machine (VSM) control parameter tuning and adaptive switching strategy. A control model is developed, which incorporates virtual inertia, damping, droop control, and transient virtual impedance. An optimization model for control parameter tuning is established for two typical disturbances: generator disconnection and three-phase symmetrical short-circuit fault. Additionally, a control parameter adaptive switching mechanism is designed based on voltage threshold and recovery time criteria. The application of this method to a simulation of an islanded power system demonstrates that high damping (e.g., greater than 15 pu) is suitable for generator disconnection disturbances, while a combination of low inertia (0.1 s) and high damping (50 pu) is appropriate for three-phase short-circuit disturbances. The control parameter tuning for three independent and aggregated scenarios successfully achieves effective frequency support. The adaptive switching criteria are set with a voltage threshold of 0.4 pu and a recovery time of 2 s, ensuring that the system frequency recovers within the specified range (48.5–51.5 Hz) within 1 s under short-circuit disturbance. The proposed method shows great potential for improving the operational stability of grid-forming energy storage systems. Full article

This work focuses on the development of a diagnostic approach for detecting and localizing sensor faults in an autonomous photovoltaic system. The considered system is composed of a photovoltaic module and a resistive load. However, an adaptation stage formed by a DC/DC voltage boost converter is necessary to transfer energy from the source to the load. The diagnostic scheme is based on a sliding mode observer (SMO) that is robust to uncertainties and parametric variations. The SMO incorporates adaptive gains optimized via parametric adaptation laws, with stability rigorously verified through Lyapunov analysis. The method effectively identifies both independent and simultaneous sensor faults, employing an optimized threshold selection strategy to balance detection sensitivity and false alarm resistance. Simulation results under varying environmental conditions, system parameter fluctuations, and noisy measurement demonstrate the approach’s superior performance, achieving a 20% reduction in mean absolute percentage error (MAPE) and 90% faster settling time compared to existing techniques. These enhancements immediately increase the dependability, efficiency, and lifetime of the PV system, which are critical for lowering carbon emissions and ensuring the economic feasibility of solar energy investments. Key innovations include a novel residual generation mechanism, seamless integration with backstepping sliding mode maximum power point tracking (MPPT) control, and enhanced transient response characteristics. Full article

To enhance the electrical performance of MgZnO-TFTs, this study employed radio-frequency (RF) magnetron sputtering to fabricate MgZnO/ZTO thin films. Using these films as the channel layer, bottom-gate top-contact MgZnO/ZTO-TFT devices were constructed. The thin films were characterized using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). After optimization, the MgZnO/ZTO-TFT exhibited a high field-effect mobility of 16.80 cm²·V⁻¹·s⁻¹, high Ion/off of 7.63 × 10⁸, threshold voltage of −1.60 V, and subthreshold swing as low as 0.74 V·dec⁻¹. Bias stress stability tests were conducted under positive bias stress (PBS) and negative bias stress (NBS) conditions with a source-drain voltage of 20 V and gate bias stresses (VGS) of +10 V and −10 V, respectively, for a duration of 1000 s. The resulting threshold voltage shifts were only +0.58 V and −0.15 V, respectively, indicating excellent bias stability. These results suggest that the ZTO film, serving as the lower channel layer, effectively enhances carrier transport at the MgZnO/ZTO interface, thereby improving the field-effect mobility and on/off current ratio. Meanwhile, the MgZnO film as the upper channel layer adjusts the device’s threshold voltage and enhances its bias stability. Full article