Search Results (4,201)

Offshore wind farms are increasingly and rapidly expanding due to their ability to harness strong and consistent wind energy resources. Large offshore wind farms are connected to mainland grids through High-Voltage Direct Current (HVDC) technology. However, offshore wind farms can often experience disturbances related to sudden wind changes, voltage drops/dips, faults related to converter switching, and unbalanced grid conditions which affect both the HVDC operation and wind turbine output. As a result, there is a growing need for more advanced and reliable modeling and monitoring tools. Moreover, traditional proportional-integral (PI) controllers are widely applied in wind turbines and HVDC systems due to their simple structure, easy implementation, and reliability. However, PI controllers perform poorly under non-linear and abnormal/fast-changing conditions, especially during sudden drops in wind power and grid faults. With this background, this paper first develops a digital twin model of an offshore wind farm that enables remote operation and monitoring of individual wind turbines. Also, an artificial intelligence (AI)-based controller, namely a fuzzy logic controller (FLC), is proposed to maintain transient stability of a full digital twin-based offshore wind farm connected to the HVDC grid under fault conditions. The effectiveness of the proposed FLC is demonstrated by considering a digital twin-enabled 700 MW offshore wind farm. The performance of the proposed FLC has been compared with that of the PI controller. Simulations performed by the MATLAB/Simulink software show that during the moderate voltage dip at 15 s, the PI controller experienced a 29.8% power reduction with a recovery time of approximately 9 s, whereas the FLC reduced the power drop to 23.1% and recovered within 6 s. During the severe converter disturbance at 15 s, the PI controller recorded a 36.9% power reduction compared to 23.4% for the FLC. Similarly, during the short-duration turbulence at 15 s, the PI controller exhibited a 36.73% power drop and recovered in approximately 7 s, while the FLC limited the power reduction to 19.17% and recovered within 5s. Overall, the FLC provided improved voltage stability, faster recovery, reduced oscillations, and superior fault ride-through capability compared with the conventional PI controller, demonstrating its effectiveness for digital twin-enabled offshore wind farm application. Full article

Ultra-high-voltage direct-current (UHVDC) transmission systems impose stringent requirements on the reliability of insulation materials used in converter transformer bushings. Epoxy resin systems are key insulating materials in resin-impregnated paper (RIP) capacitor bushings, and their processing characteristics, curing behavior, and electrical properties directly affect bushing performance. In this study, two epoxy insulation systems used for resin-impregnated paper (RIP) bushings, namely the imported Araldite LY1564/Aradur 3486 system and the domestic EP-2020/CA-3015 system, were systematically investigated through viscosity, curing, and electrical property tests. The results show that the viscosities of both resins decreased significantly with increasing temperature. At 60 °C, the viscosities of Resin A and Resin B were 151.6 mPa·s and 156.3 mPa·s, respectively. The mixed resin–hardener systems exhibited similar viscosity evolution and comparable pot life characteristics. DSC measurements revealed two-stage curing reactions for both materials, with first exothermic peak temperatures of 65.4 °C and 96.3 °C and second peak temperatures of 269.3 °C and 269.8 °C for Materials A and B, respectively. Electrical testing demonstrated that both materials exhibited similar temperature-dependent dielectric and resistivity behavior, with dielectric loss increasing at elevated temperatures and resistivity decreasing as temperature increased. The volume resistivity trends and dielectric characteristics of the two materials remained highly consistent throughout the investigated temperature range. The results indicate that Material B exhibits processing performance, curing characteristics, and electrical insulation properties comparable to those of Material A. Therefore, Material B demonstrates strong potential for application in UHVDC RIP bushing insulation systems and provides a promising alternative for the localization of key insulating materials. Full article

With the rapid advancement of wearable technologies, high-performance flexible sensors have garnered significant research interest. This study presents a PAM-5 hydrogel characterized by exceptional tensile strain (425%), superior compressive modulus (325 kPa), and notable ionic conductivity (1.1 S/m), serving as a robust mechanical framework and electrical foundation for developing advanced sensors. The PNP-5 integrated hydrogel sensor fabricated from this material demonstrates an extensive sensing range (2–53 kPa), remarkable sensitivity, and rapid response time (~321 ms), with its outstanding performance attributed to the synergistic structural design. Furthermore, the sensor exhibits excellent durability, maintaining consistent voltage output (~6.5 mV) across 1000 compression cycles, confirming its long-term operational stability. Through real-time monitoring of physiological signals and biomechanical movements including finger bending, respiration, and grasping, combined with spatial pressure mapping experiments using a 5 × 5 array touchpad, the device’s potential applications in wearable sensing platforms and human–machine interface systems are effectively demonstrated. This self-powered hydrogel sensor not only advances the performance metrics of flexible electronic devices but also establishes a solid experimental basis for future development of intelligent materials in health monitoring and interactive technologies. Full article

Precise fault localization for high-speed railway continuous transmission lines is indispensable for sustaining power supply reliability and mitigating power outages. This study presents a novel fault localization approach that uses low-voltage information obtained from box-type substations distributed along continuous transmission lines. The proposed scheme relies on the distribution features of the positive-to-negative sequence voltage ratio ($r_{PNV}$) measured at the low-voltage terminals of box-type substations. Results reveal that the magnitude of $r_{PNV}$ gradually declines from the main substation to the fault location in the fault upstream area, while it stays nearly unchanged in the downstream section. Based on this feature, the faulted section is initially determined by means of the nearest neighbor clustering method. Subsequently, the precise fault location is calculated by solving equations that combine the sequence voltage ratio at the fault point with the measurements obtained from the main substation and box-type substations downstream of the fault. The proposed method requires only asynchronous low-voltage measurements, eliminates the need for fault impedance modeling, and is applicable to various asymmetric faults. Simulation tests under different fault types, fault resistances (up to 2000 Ω), noise conditions, and neutral grounding modes demonstrate that the method achieves high accuracy and robustness. Full article

Although garnet-type Li₇La₃Zr₂O₁₂ (LLZO) solid electrolytes are promising candidates for high-energy-density all-solid-state batteries, their practical applications are limited by high-voltage oxidation instability and interfacial degradation. To address these limitations, Al-doped LLZO (Al-LLZO) solid electrolytes were synthesized via a conventional solid-state reaction method, and the effects of PE-ALD-derived Al₂O₃ nanocoatings on electrochemical properties and interfacial stability were investigated. Al₂O₃ nanocoatings with different structures (5 and 10 nm single-side, and 5 nm double-side) were deposited on Al-LLZO pellets using plasma-enhanced atomic layer deposition. The Al₂O₃ coating reduced electronic conductivity by approximately one order of magnitude while maintaining similar ionic conductivity. Linear sweep voltammetry revealed that initial oxidation onset voltage increased from ~4.2 V (bare Al-LLZO) to ~5.0 V (5 nm-coated samples), while the 10 nm-coated sample exhibited the most delayed anodic current response (~5.2 V). The 5 nm double-side coated sample showed the best Li plating/stripping stability with a critical current density of 1.10 mA/cm² and stable long-term galvanostatic cycling behavior over 200 h at 0.05 mA/cm². Thus, ALD-based Al₂O₃ interfacial engineering can simultaneously improve the high-voltage oxidation and Li metal interfacial stabilities of garnet-type Al-LLZO solid electrolytes for practical all-solid-state batteries. Full article

Non-contact magnetic sensing technology is widely adopted in transmission line online monitoring scenarios including current measurement and fault location for its non-contact measurement capability, strong environmental robustness and low deployment cost. However, existing magnetic-sensing-based galloping monitoring methods suffer from two critical limitations: no theoretical guidance is provided for sensor placement, and a high false detection rate is observed under current fluctuation conditions. To address these issues, a novel transmission line galloping monitoring method based on spatial magnetic field distribution features is proposed in this paper. A conductor galloping-power frequency magnetic field coupling model is first established to derive the optimal magnetic sensor array arrangement strategy. Subsequently, a galloping detection algorithm fusing multi-node frequency-domain features and phase difference information is proposed to eliminate current fluctuation induced false detection. Simulations conducted based on actual 500 kV transmission line parameters and verification tests carried out on a scaled-down laboratory platform confirm that reliable galloping detection can be realized by the proposed method under both current low-frequency oscillation and random fluctuation scenarios. With advantages of non-contact deployment, high anti-interference performance and detection accuracy, the proposed method has promising application potential in engineering-oriented high-voltage transmission line monitoring. Full article

Low-speed permanent magnet synchronous motors (LS-PMSM) have been widely adopted in fields such as mining and oil extraction due to their excellent stability and high efficiency. In practical applications, current harmonics cause a decline in motor control performance and, in severe cases, can damage the motor. This paper analyzes the mechanism of harmonic generation in LS-PMSM and derives a mathematical model for these harmonics. To address the 5th and 7th harmonics, which are particularly prominent, an improved harmonic voltage compensation module was added to the efficiency-optimized control system. The current averaging method was employed to extract harmonic currents in real time, and a fuzzy PI controller was used to perform closed-loop control of the harmonic currents, thereby obtaining accurate harmonic voltage compensation values. Finally, the control effectiveness of the harmonic voltage compensation was analyzed through simulation. The results indicate that this method can effectively suppress 5th and 7th harmonics and reduce torque ripple. Furthermore, the improved algorithm enhances the accuracy of harmonic current extraction and improves the dynamic performance of the controller. Full article

In cold, humid environments, even a small amount of ice accumulation on the blade surface can degrade aerodynamic performance, increase drag, induce premature stall and vibration, and raise the risks of shutdown, fatigue, and ice throw. Existing blade anti-icing and de-icing strategies (such as passive coatings, electrothermal heating, hot-air systems, and hybrid designs) struggle to simultaneously meet the requirements of lightweight construction, low-voltage rapid heating, conformability to curved surfaces, erosion resistance, long-term durability, and scalable manufacturing. MXenes, particularly Ti₃C₂T_x, have attracted attention due to their high electrical conductivity, broadband optical absorption, solution processability, tunable interfacial chemistry, and good compatibility with polymer matrices. However, their oxidation issue and blade-scale deployment challenges (coating chemistry, scalable fabrication, real-world testing) remain obstacles. Based on this, this review discusses Ti₃C₂T_x-based anti-icing, de-icing, and defogging strategies for wind turbine blades, with emphasis on material properties, functional mechanisms, coating architectures, fabrication routes, durability, and scalability, and highlights their potential for lightweight and energy-efficient all-weather blade protection. Finally, future research directions for Ti₃C₂T_x-based blade anti-icing and de-icing are prospected. This review not only aims to identify key knowledge gaps in current research but also strives to provide a theoretical reference for the application of Ti₃C₂T_x in the complex service environment of real wind turbine blades, thereby moving beyond idealized laboratory conditions. Full article

This study proposes a barrier-oriented application of conventional failure mode and effects analysis (FMEA) and fuzzy weighted geometric mean (FWGM)-based fuzzy-FMEA for laboratory-scale solvent-based electrospinning. The process was decomposed into 14 sequential steps, and one representative failure mode was defined for each step. Severity, occurrence, and detection were rated by a five-member expert panel, and hazard-type-specific weights were assigned to chemical-dominant, electrical-dominant, fire/static-dominant, and combined-dominant hazards. Conventional FMEA identified material review/approval, equipment setup, pre-start inspection, and response to abnormalities as the highest-risk steps (RPN = 60). FWGM-based fuzzy-FMEA re-ranked tied RPN groups and identified response to abnormalities and equipment setup as the joint highest-FRPN failure modes (FRPN = 79.35), followed by pre-start inspection (77.39) and material review/approval (75.89). Barrier-oriented interpretation revealed four dominant mechanisms: upstream information-based hazards, direct high-voltage access, pre-start combined hazards, and intervention under abnormal or residual-energy states. Scenario-based post-control analysis showed that grounded enclosures, interlocks, de-energize-discharge-verify procedures, pre-start checklists, and bonding/grounding measures reduced FRPN by 25.88–43.79% for prioritized failure modes. The proposed framework supports SOP development, equipment improvement, training prioritization, and laboratory risk-assessment documentation for solvent-based nanofiber manufacturing. Full article

Electrospun sulfonated polyketone (PK) nanofiber membranes were prepared to investigate the sulfonation-time-dependent structure–property relationships of hydrocarbon-based polymer electrolyte membranes for PEMFC (Polymer Electrolyte Membrane Fuel Cell) applications. NaCl addition to the electrospinning solution increased solution conductivity and enabled the formation of uniform PK nanofibers with an average diameter of approximately 270 nm. Subsequent sulfonation introduced sulfonic-acid-related groups into the PK nanofiber framework, and the resulting membrane properties were strongly governed by sulfonation time. Among the tested membranes, PK-NC16 exhibited the highest proton conductivity of 0.107 ± 0.031 S cm⁻¹ and an ion exchange capacity of 2.82 m_eq g⁻¹, exceeding or comparable to those of Nafion 115 under the tested conditions. FTIR-based analysis indicated that the relative sulfonation index increased up to 16 h, whereas extended sulfonation for 24 h generated additional sulfone/sulfonate-related bands, suggesting possible side reactions or structural changes under prolonged acid treatment. The high water uptake of PK-NC16 enhanced proton transport but also revealed a hydration-sensitive polymer network, as reflected by a voltage degradation rate of approximately −590 μV h⁻¹ during a 100 h short-term stability constant-current test. These results demonstrate that sulfonation time is a key parameter controlling the balance among ionic functionality, hydration, mechanical response, proton conductivity, and PEMFC-relevant single-cell performance in electrospun PK nanofiber membranes. Full article

In the context of the “dual-carbon” target, the large-scale integration of renewable energy sources leads to an increased risk of transient voltage instability at the high voltage direct current (HVDC) transmission receiving end. The HVDC transmission system possesses fast and accurate power regulation capability. After a fault occurs near the inverter station, reducing the DC current enables the reactive power from the compensation devices to be released and injected into the receiving-end power grid, thereby providing emergency voltage support for the receiving-end grid. To reduce control costs, an optimization model constrained by transient voltage violation is established, and the DC current modulation is acquired via an online solution. To maintain system stability and meet the requirements of online applications, it is crucial to rapidly solve the optimization model based on the grid operating mode and contingency information to update the emergency control strategy table in the special protection system (SPS). Conventional global orthogonal collocation (GOC) and adaptive orthogonal collocation (AOC)-based solution methods transform the optimization model in the continuous time domain into a nonlinear programming (NLP) problem for solution, which addresses the low efficiency of traditional rolling optimization. However, the GOC- and AOC-based solution methods improve the discretization accuracy of the model by pursuing global uniform densification of collocation points, making it difficult to balance solution accuracy and solution efficiency. To this end, this paper proposes an efficient interval partition dynamic adaptive orthogonal collocation (IP-DAOC)-based solution method. Firstly, the overall optimization time window is interval-partitioned into multiple initial intervals, and an interval-partitioned transient voltage stability emergency control optimization model is established. Furthermore, the interval length and the number of collocation points are dynamically adjusted according to the curvature of interpolation polynomials at collocation points in different intervals. Finally, after interval adjustment, the dynamic equations discretized in adjacent intervals are made continuous by reconstructing the differential matrix. This solution method reduces the total number of collocation points, thereby decreasing the scale of the NLP problem and narrowing the search space, significantly improving solution efficiency while ensuring solution accuracy. To verify the effectiveness of the proposed solution method, simulations are carried out on a modified IEEE 14-bus system. The results are compared with those of the traditional GOC- and AOC-based solution methods, which further demonstrate the superiority of the proposed solution method. Full article

In this study, charge-trapping memory (CTM) transistors were developed using indium gallium zinc oxide (IGZO) as the oxide semiconductor channel and high-k HfO₂ as the charge-trapping layer, aiming for next-generation nonvolatile memory applications. To evaluate the impact of plasma exposure on film quality and device performance, HfO₂ thin films were deposited via atomic layer deposition (ALD) using both direct plasma (DP) and remote plasma (RP) modes. Post-deposition annealing (PDA) was applied to the IGZO and HfO₂ layers, with experiments conducted at various annealing temperatures to enhance the interfacial stability between the HfO₂ layer and the IGZO channel. Electrical characterization results demonstrated that the RP-processed devices exhibited a wider memory window, reduced gate leakage current, and improved threshold voltage stability compared with the DP-processed devices. Thermal treatment effectively reduced the interfacial defect density and enhanced the crystallinity at the dielectric–channel interface. These findings underscore that the selection of the plasma process and annealing conditions is critical in determining the electrical characteristics and reliability of oxide semiconductor-based CTM devices. Full article

Aqueous zinc–manganese dioxide (Zn–MnO₂) batteries are undergoing a paradigm shift from traditional ion-insertion mechanisms to a reversible deposition/dissolution process. By leveraging a two-electron transfer (Mn²⁺/MnO₂), this electrolytic system achieves a high theoretical capacity of 616 mAh g⁻¹ and a theoretical operating voltage of 1.99 V. However, the accumulation of dead Mn, electrically isolated inactive phases, and dynamic interfacial pH fluctuations remain critical barriers to cycle life and practical energy density. This review systematizes a trinitarian strategy to overcome these bottlenecks, focusing on interfacial engineering, redox mediator-assisted recovery, and advanced electrode architectures. We evaluate how anion engineering and pH-buffering stabilize reaction pathways, and how diverse mediators (e.g., halogens, metal ions, and organic molecules) chemically rescue inactive manganese. Furthermore, we examine the integration of 3D carbon networks and low-cost hybrid electrodes to sustain high-areal-capacity deposition. To elucidate these complex mechanisms, we highlight multiscale analytical approaches combining synchrotron X-ray techniques and density functional theory (DFT). Finally, we outline a roadmap for applications ranging from grid-scale flow batteries to flexible wearable electronics. This work provides a comprehensive perspective on realizing sustainable, safe, and high-performance zinc-based energy storage. Full article

The increasing penetration of renewable energy sources and converter-interfaced loads has intensified the need for fast and reliable grid-support services. Although electric vehicle (EV) battery chargers have emerged as promising resources for Vehicle-to-Grid (V2G) applications, existing solutions typically focus on individual services such as virtual inertia or frequency regulation, while limited attention has been given to the coordinated provision of multiple ancillary services within a unified framework. Furthermore, the use of batteries alone for fast frequency support may accelerate battery degradation due to frequent high-power transients. To address these challenges, this paper proposes a hybrid energy storage-based EV battery charger architecture and a coordinated multi-timescale control strategy capable of simultaneously providing virtual inertia support, long-term frequency regulation, reactive power compensation, and harmonic mitigation. The proposed approach utilizes a DC-link capacitor to deliver fast inertial response while the battery supplies sustained frequency support, thereby reducing battery stress and improving energy management efficiency. An enhanced frequency estimation method based on a phase-locked loop combined with a low-pass filter is also introduced to improve dynamic performance. Simulation results demonstrate the effectiveness of the proposed strategy under various grid disturbances. The system achieves an equivalent virtual inertia constant of approximately 1.85 s and delivers up to 786 W of transient inertial support within 80 ms during frequency events. The enhanced frequency estimation method significantly reduces transient overshoot, while harmonic compensation limits the grid current and voltage total harmonic distortion to 1.50% and 3.23%, respectively. In addition, the controller provides up to 400 VAR of reactive power support during voltage disturbances while maintaining stable battery operation. These results demonstrate that the proposed EV battery charger can function as a multifunctional grid-support resource, enhancing frequency stability, voltage regulation, power quality, and overall V2G capability in future smart grids. Full article

With the integration of high-penetration distributed renewable energy sources and grid-forming inverters, AC microgrids face significant challenges in maintaining autonomous voltage and frequency stability. While traditional droop control can achieve autonomous power allocation, it introduces inherent steady-state deviations when load change. To address this, this paper proposes a distributed secondary control strategy for AC microgrids based on a consensus algorithm, aiming to achieve high-precision coordinated correction of voltage and frequency and improve power quality. In the proposed strategy, each grid-forming inverter autonomously generates dynamic secondary compensation signals based solely on local measurements and limited information exchange with neighboring nodes, eliminating the need for a central controller and enhancing robustness, scalability, and fault tolerance. Stability is proven via Lyapunov function construction. Simulation results show that the strategy effectively eliminates steady-state errors, with frequency deviations within ±0.01 Hz and voltage deviations below 0.5% of the rated value. Rapid and precise regulation is achieved under various load disturbances and network conditions, validating its effectiveness and application potential. Full article