Search Results (63,740)

The proliferation of power converters has posed significant challenges to the simulation of power grids. The unit switching circuit (USC) method provides an approach for power electronics grid simulation, but neglects the situation where the switching action time deviates from the time-step boundary. This article presents novel simulation and solving approaches for converters based on computational equivalence to precisely simulate the power electronics grid. This article also introduces a straightforward calculation method for determining equivalent circuit parameters through port quantity observation to achieve computational equivalence. The qualitative error analysis is given and accompanied by comprehensive discussions on its validity, numerical characteristics, and applicable scenarios. A case study is performed to verify the proposed method’s effectiveness and efficiency, yielding results that demonstrate improved accuracy. Full article

To address the difficulty in accurately characterizing the fault current response of renewable energy grid-connected devices during high-/low-voltage ride-through, this paper proposes a fault current response modeling and parameter identification method based on adaptive nonlinear compensation. First, with the fault voltage and pre-fault operating point as input variables, a basic quadratic equivalent model is established to describe the main variation characteristics of active and reactive currents during high-/low-voltage ride-through. Second, nonlinear compensation terms are introduced into the basic model to correct the response deviation caused by the simplification of fast electromagnetic control links in the electromechanical transient equivalent process, thereby improving the representation capability of the model for complex fault current characteristics. Furthermore, considering that the structural parameters of the nonlinear compensation terms are difficult to directly identify using the traditional least squares method, a differential evolution–ridge regression (DE–Ridge) hierarchical identification method is proposed. In this method, the differential evolution algorithm is used in the outer layer to adaptively optimize the nonlinear structural parameters, while ridge regression is used in the inner layer to solve the corresponding linear coefficients. Case study results show that, compared with the traditional quadratic equivalent model and the fixed nonlinear compensation model, the proposed method further reduces the fault current identification error on the validation set and improves the identification accuracy and generalization capability of fault current responses during high-/low-voltage ride-through. Full article

This review systematically summarizes recent advances in moisture-electric generation technology from four perspectives: functional-material modification, device-structure design, multi-source energy-harvesting strategies, and practical applications. It discusses the classification and modification of moisture-responsive functional materials; analyzes how device architectures regulate ion transport, reviews the mechanisms of coupling moisture energy with solar, thermal, and mechanical energy; and summarizes representative applications of moisture-electric generators (MEGs) in power supply, self-powered sensing, and wearable electronics. The review further compares the advantages and limitations of different material and structural strategies and evaluates challenges related to output performance, environmental adaptability, long-term stability, power management, and scalable fabrication. Finally, future research directions are discussed to support the practical development of MEGs. Full article

This paper presents the experimental validation of a high-frequency full-SiC railway auxiliary converter power module intended as a building block for modular multi-system railway auxiliary converters. The proposed architecture employs a unified SiC-based power conversion platform that integrates an active front-end single-phase PWM rectifier with a galvanically isolated high-frequency DC/DC stage operating at 90 kHz under zero-current switching (ZCS) conditions. Although the converter is designed for both AC and DC traction systems, this study focuses primarily on its operation under single-phase AC railway supply conditions, which are representative of practical applications. A hybrid bipolar–unipolar modulation strategy is used to reduce the RMS voltage stress on the input inductor while preserving controllability of the input current near the voltage zero-crossing regions. Special attention is given to operation under distorted railway supply voltages, which are common in real traction systems. The control structure combines a proportional–resonant (PR) current controller, harmonic compensators, feedforward voltage compensation, and MSOGI-based synchronization to ensure stable synchronization and low-input current distortion even under non-ideal conditions. Experimental validation was performed on a 10 kW laboratory prototype. The results demonstrate a peak efficiency of 98.4% and near-unity input power factor. Under heavily distorted supply conditions ${\mathrm{THD}}_{\mathrm{v}}>30\%$, the input current distortion remained below${\mathrm{THD}}_{\mathrm{i}}=2.3\%$. Harmonic and STFT analyses confirmed the robustness of the proposed synchronization and current control structure. The obtained results indicate that the proposed high-frequency full-SiC converter topology is a promising solution for future modular railway auxiliary converters, offering high efficiency, reduced passive component volume, and high power density. Full-scale high-voltage validation under both AC and DC traction systems remains the subject of further work. Full article

This paper investigates decentralized demand-side management in renewable energy communities with limited and uncertain renewable energy resources. Consumer interactions are modeled as a Bayesian game in which self-interested consumers schedule flexible loads between daytime and nighttime periods to minimize electricity costs under time-of-use tariffs. Consumer heterogeneity is captured through private information describing both risk preferences and forecasts of renewable energy availability. Analytical conditions under which dominant strategies or mixed-strategy Bayesian Nash equilibria (BNE) exist are derived. Based on this analysis, two distributed algorithms that operate without a central coordinator are developed. The first is an iterative best-reply (BR) algorithm, while the second is a novel Demand Agreement (DA) algorithm that directly exploits the equilibrium conditions to reduce computation and communication requirements. The proposed decentralized mechanisms are compared against a centralized social-cost minimization benchmark. The results further demonstrate that the DA algorithm consistently converges to the minimum-cost equilibrium whenever a BNE exists, while requiring substantially lower communication overhead than BR. In contrast, the BR algorithm may converge even when the BNE conditions are not satisfied. Finally, the analysis quantifies the impact of consumer risk preferences and renewable generation uncertainty on BNE existence, scheduling decisions, and overall system performance. Full article

Photovoltaic (PV)/biomass systems offer stable/continuous power by overcoming solar-energy intermittency with biomass dispatchable energy. Considering gaps in the scientific literature, this article sets out to present information on PV/biomass installations and the eco-profiles of different feedstocks for biogas generation. To this end, this article is split into two parts. The first one outlines some key elements of the literature on PV/biomass systems, highlighting factors that determine feasibility and performance. The second one presents the eco-profiles of three feedstocks. The methodology is based on literature review and Life-Cycle Assessment (LCA). Regarding the first part, the results show that the majority of the prior research placed emphasis on techno-economic analysis and the design/modelling of PV/biomass systems, and there is a dearth of LCA studies on PV/biomass installations. As for the second part, the findings demonstrate that, among the feedstocks examined (manure; waste cooking oil; grass), in most categories, animal waste shows the highest environmental impacts. For instance, considering the total impact of these three feedstocks and based on Environmental Product Declaration (EPD), the results indicate that, in many categories, manure surpasses the percentage values of 40%. Grass exhibits minor percentage shares, with the exception of the “Eutrophication” (54%) and “Acidification” (33%) categories. Full article

This study presents a full-voyage operational validation of a load optimization strategy applied to a Dual-Fuel Diesel-Electric (DFDE) liquefied natural gas (LNG) propulsion system. The proposed approach was evaluated onboard an LNG carrier equipped with five four-stroke dual-fuel engines. The operational validation was conducted exclusively with the generator engines operating in LNG (gas) mode, while operation on conventional liquid fuels was outside the scope of this study. A complete 26-day voyage cycle, including cargo loading, loaded passage, cargo discharge, and ballast passage, was defined. Representative steady-state operating intervals for each operational mode were analyzed under both conventional Power Management System (PMS) load distribution and optimized load allocation. Real-time manual redistribution of engine loads was performed to validate the proposed load optimization strategy under real operating conditions. The results show consistent fuel savings across all operating modes, with the highest reduction observed during ballast passage (1.51%), followed by loaded passage (0.74%). A voyage-scale analysis reveals cumulative fuel savings exceeding 22 metric tons per operational cycle, equivalent to annual reductions of more than 300 metric tons under typical service conditions. These savings consistently reduce both carbon dioxide (CO₂) and nitrogen oxides (NO_x) emissions across all operating modes. Ultimately, the proposed load optimization strategy demonstrated stable performance under the investigated steady-state operating conditions and provides a practical approach to improving ship energy efficiency. The results support the potential application of the proposed strategy in existing ship energy management systems, while further validation under long-term and transient operating conditions is recommended. Full article

Liquid metals are enabling working fluids for several advanced nuclear systems, including fast reactors, accelerator-driven systems, and fusion blankets. System thermal-hydraulic (STH) codes require thermodynamically consistent property tables over pressure-temperature domains, whereas most liquid-metal correlations are available only as functions of temperature at a reference pressure. This paper presents the formulation and the code verification of four liquid-metal working fluids in RELAP5/Mod3.3: lead (Pb), lead-bismuth eutectic (LBE, denoted PbBi), lead-lithium alloy (PbLi, here Pb-17Li at.%), and sodium (Na). The liquid branch is reconstructed from reference correlations for specific volume, sound speed, and isobaric specific heat through a linearized pressure model, whose correction remains below 0.2% for the heavy liquid metals and below 1% for sodium over the whole tabulated pressure range. The reference pressure is set to the saturation pressure at the maximum tabulated temperature, which maximizes the admissible liquid domain, and a van der Waals equation of state closes the vapor branch. Liquid transport properties and selectable low-Prandtl-number heat-transfer correlations are implemented in the Fortran source code. Verification comprises property comparisons and two non-regression tests, a U-tube manometer, and a natural-circulation loop. The vapor model is a table-completion closure and must not be used for boiling-dominated transients. Full article

In light of the strong expansion of renewables, electrolysis may act as an alternative to conventional grid enforcement to overcome grid constraints in a timely and effective manner, as it creates additional flexible load and thus enables renewable production peaks to be absorbed. This paper examines whether hydrogen electrolysis can serve as a cost-effective alternative to conventional grid reinforcement in Austrian electricity distribution networks. It goes beyond the current state of the art by using three real-world case studies in Styria, using an integrated techno-economic framework combining distribution-grid simulations, market optimisation, PEM electrolysis modelling and cost–benefit analysis to compare the grid-supportive electrolysis against conventional grid enforcement. The results demonstrate that grid-supportive electrolysis can become competitive under suitable hydrogen market conditions. When operated in grid-supportive mode only, the capacity factor for the electrolysis lies below 5%. Economic viability emerges only when electrolysers are allowed to combine grid-supportive operation with market-driven hydrogen production. Thereby, the hydrogen price proves to be the key determinant: a hydrogen price above approximately 6 EUR/kg incentivises market-based operation and naturally resolves grid congestion without further intervention by the DSO. In some locations, smaller electrolysers (around 20–60% of the theoretically required size) deliver the best economic performance, recovering most curtailed renewable energy while limiting investment costs compared to conventional grid extension. Full article

Efficient utilization of agricultural residues plays an important role in advancing sustainable bioenergy development in China. This study established a multi-criteria evaluation framework integrating energy quality, economic performance, and environmental impact to assess three representative straw-to-energy pathways: direct combustion for power generation, anaerobic digestion for biogas production, and lignocellulosic ethanol production. The Analytic Hierarchy Process (AHP) was applied to determine indicator weights and calculate composite scores using operational and pilot-scale data obtained for each pathway. The results showed that anaerobic biogas achieved the highest overall performance (composite score 0.41), with balanced performance in economic viability, energy utilization efficiency, and environmental performance. Direct combustion demonstrated favorable economic performance (0.37) but exhibited higher process emissions, whereas lignocellulosic ethanol showed superior environmental performance but suffered from low energy conversion efficiency and negative economic returns (0.00). Sensitivity analysis confirmed the stability of the pathway ranking and highlighted the dominant influence of economic and energy-related indicators on the overall sustainability assessment. The study demonstrated that anaerobic biogas exhibited the most balanced performance among the evaluated pathways under the investigated technological and economic conditions, while integrated biorefining approaches, such as co-production of ethanol and biogas, showed potential for further enhancing resource efficiency and sustainability. Full article

Molybdenum carbide (MoC) thin films were deposited by dual-target magnetron co-sputtering and investigated as platinum-free counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The effects of Mo target power and film thickness on structural evolution, electrical transport properties, and photovoltaic performance were systematically examined. Raman analysis revealed progressive modifications in the carbon bonding structure, accompanied by variations in the G-band position and an overall reduction in the I_D/I_G ratio. These structural changes were correlated with increased hardness, reduced electrical resistivity, and decreased surface wettability, indicating improved structural integrity and electrical transport characteristics of the MoC films. The optimized films exhibited a resistivity as low as 2.04 mΩ·cm and improved charge-transport behavior. DSSCs employing the optimized MoC CEs achieved a maximum power conversion efficiency of 4.13%. The photovoltaic performance trends were consistent with the evolution of the electrical transport properties of the MoC thin films, suggesting a close relationship between electrode structure, charge transport, and device operation. The results demonstrate that sputtered MoC thin films are promising functional materials for Pt-free DSSC CEs and provide insight into structure–transport–performance correlations relevant to sustainable photovoltaic energy-conversion systems. Full article

The lightning withstand performance of transmission lines is critically affected by grounding impulse characteristics, particularly for river-crossing towers where soil conditions are complex. This study develops a coupled seepage–electric field model to evaluate these characteristics under dynamic hydrological influences. A complex soil model is constructed integrating Bernoulli’s laminar flow equation with Richards’ equation for unsaturated seepage; long-term finite-element iterations simulate seepage dynamics, yielding distributed soil conductivity parameters that vary with river flow velocity, water depth, and impermeable layers. These parameters are then coupled with an electroquasistatic Maxwell framework to model impulse current dispersion. Validation against experimental data confirms the model’s accuracy. Results show that seepage increases moisture and lowers resistivity. Increasing flow from static to 10 m/s reduces riverbed pressure from 5.61 × 10⁴ Pa to 1.86 × 10⁴ Pa, shifting the 0 Pa isobar downward by 5.1 m, weakening seepage and raising impulse resistance. A shallower impermeable layer deflects seepage laterally, reducing nearby resistivity. Raising water depth from 5 m to 10 m increases pressure from 1.96 × 10⁴ Pa to 5.61 × 10⁴ Pa, enhancing seepage and lowering resistivity. These findings indicate that grounding design must holistically account for flow velocity, water depth, and subsurface barriers to ensure reliable lightning current dissipation and stable grid operation. Full article

Existing grid-connected photovoltaic (PV) systems with grid-following (GFL) control rely on phase-locked loop (PLL)-based grid synchronization, which may become unstable under weak grid conditions. By contrast, grid-forming (GFM) retrofits are regarded as promising solutions for improving the stability of GFL-based PV integration. However, existing retrofit methods often require comprehensive replacement or substantial modification of the existing GFL controller or hardware, thereby increasing retrofit costs and maintenance complexity. To address these issues, a non-intrusive configuration with a battery-backed GFM branch comprising a charging rectifier and a GFM inverter is proposed for retrofitting implemented GFL PV power plants in this paper. With the proposed configuration, the existing GFL PV inverters retain their original hardware and GFL control. The charging rectifier branch absorbs surplus PV power from the PV inverter output, whereas the proposed battery-backed GFM branch is connected at the point of common coupling (PCC) to provide voltage- and frequency-forming supports. To utilize the available branch capacity under normal grid conditions, selected auxiliary functions, i.e., harmonic compensation and Volt–VAR support, are incorporated subject to the available inverter operating margin. The effectiveness of the proposed configuration and the corresponding control scheme is validated through different operating scenarios, including PV/load mismatch charging, nonlinear load harmonic compensation, reactive load Volt–VAR support, grid frequency and grid voltage disturbances under different grid strength conditions, and combined dynamic operating disturbances at weak grids. Full article

This paper presents a short-term traction-load forecasting method that fuses optimization-driven dual-scale decomposition and multiscale information fusion (ODE-MMF) with TimeXer-Mamba to address non-stationary prediction difficulties caused by intermittent and volatile traction loads. A correlation analysis module is first constructed for adjacent feeding sections, where mutual information quantifies cross-arm load transfer induced by train operations and extracts key spatial features. In the ODE-MMF signal processing module, an improved whale migration algorithm searches for the optimal parameters of optimization-driven dual-scale decomposition, enabling multiscale decomposition of load features. Multiscale transfer entropy is then used to measure information flow among decomposed components, and highly redundant components are adaptively merged into complementary feature subsequences. In the TimeXer-Mamba prediction module, TimeXer enhances exogenous variables such as holidays, whereas Mamba captures long-range dependencies through the selective state-space model. A gated fusion mechanism integrates the two representations, after which the merged subsequences are predicted in parallel and reconstructed to obtain the final forecast. Experiments conducted on real-world traction-load data demonstrate that the proposed model consistently outperforms all evaluated baselines. Relative to the best-performing baseline, LSTM-Transformer, it achieves reductions of 9.61%, 9.32%, and 9.81% in mean absolute error, root mean square error, and mean absolute percentage error, respectively, while maintaining high computational efficiency and demonstrating strong potential for practical deployment in railway power supply systems. Full article

Virtual synchronous generator (VSG) control is widely used to improve the frequency stability of low-inertia microgrids. However, most existing adaptive VSG strategies tune the virtual inertia and damping coefficient mainly according to local frequency deviations of the energy storage converter, while the effect of supplementary wind turbine frequency support on the admissible VSG parameter range is rarely considered. To address this limitation, this paper proposes a wind–storage coordinated frequency control strategy that combines an energy storage fuzzy VSG with active-power-frequency droop support from a doubly fed induction generator (DFIG). The scientific contribution of this study is that the DFIG droop support term is incorporated into a reduced-order wind–storage small-signal model, and an admissible scheduling region for the virtual inertia and damping coefficient is constructed according to prescribed damping ratio and natural angular frequency constraints. This region is used to constrain the online fuzzy parameter scheduling of the energy storage VSG. In addition, bell-shaped membership functions are introduced to obtain smoother parameter variation and are compared with triangular membership functions under the same operating conditions. MATLAB/Simulink simulations are conducted under grid-connected/islanded transition, load switching, and renewable-power fluctuation conditions. Compared with the benchmark strategies, the proposed method reduces the maximum and average frequency deviations to 0.181 Hz and 0.016 Hz, respectively. The maximum discharge power, RMS power, and cumulative energy throughput of the energy storage system are reduced to 236.853 kW, 155.822 kW, and 5.751 kWh, respectively. These results indicate that the proposed coordinated strategy improves frequency regulation while reducing the transient regulation burden of the energy storage system within the investigated operating conditions. Full article