With the large-scale integration of wind power, modern power systems are facing reduced equivalent inertia, weakened primary frequency regulation capability, and insufficient coordination between wind turbines and energy storage during joint frequency support. To address these issues, this paper investigates a wind–storage hybrid system composed of doubly fed induction generators (DFIG) and supercapacitor energy storage and proposes a coordinated primary frequency regulation strategy combining fuzzy logic control (FLC) and model predictive control (MPC). Considering the variations in rotor kinetic energy reserve and frequency support capability under different wind speed regions, a coordinated regulation mechanism is developed for multiple operating conditions. In addition, a variable-coefficient synthetic inertia control scheme with rotor speed safety constraints is designed to adaptively adjust the turbine regulation coefficients, while an SOC-feedback-based adaptive virtual droop strategy is introduced to improve the sustained support capability of the energy storage unit. On this basis, a multi-objective model predictive control framework is established to optimize the reference power allocation between the wind turbine and the energy storage unit in a rolling manner. The proposed method is characterized by three coordinated features, namely, multi-region wind–storage frequency regulation, rotor-speed-safe adaptive support of the wind turbine and SOC-aware adaptive support of the storage unit, as well as MPC-based rolling power allocation. Simulation results show that the proposed strategy improves the frequency nadir, reduces the steady-state frequency deviation, and enhances coordinated power sharing, thereby improving the primary frequency regulation performance and overall frequency stability of the wind–storage hybrid system.

Abstract This study investigates the effects of idealized and realistic terrain on tornado characteristics and behavior. It uses a novel simulation approach, nesting a high-fidelity, ultrafine-resolution, tornado-scale, engineering large-eddy simulation (LES) within a Cloud Model 1 (CM1) simulation of a tornadic supercell. We analyze the effects of terrain on the tornado’s central pressure, horizontal and vertical velocities, vortex shape, and path. Seven idealized terrain configurations are used including 1) a control run with flat ground, 2) and 3) an idealized hill with steep and gradual slopes having the height of 25.4 m, 4) and 5) an idealized escarpment with steep and gradual slopes having the height of 25.4 m, and 6) and 7) an idealized hill having heights of either 50 or 65 m. Furthermore, a real-world, complex terrain configuration of the same height is analyzed as the eighth case. Results suggest that the presence of terrain relief increases the central pressure deficit, the peak wind speed, and the width of the high wind speed region in the tornado swath, enhancing tornado intensity and causing path deviation. Specifically, the horizontal and vertical velocities at 10 m above ground level (AGL) are stronger with terrain and the location of the maximum pressure deficit occurs along the uphill segment for all idealized cases except the steep hill. The precise location of the maximum wind velocities and pressure deficits varies with the terrain shape and slope. The real terrain simulation is similar to the idealized terrain simulations to a certain extent; however, the vertical velocities are lower and the strongest winds occur over a smaller region, demonstrating the complexity of the tornado–terrain relationship. Significance Statement This high-resolution numerical study investigates the effects that idealized hills and escarpments have on tornadoes and offers a comparison with a real-world, complex terrain configuration. This study is particularly novel for three reasons: 1) The nested simulation approach with an ultrafine inner grid (spacing of 0.01 m) facilitates a high-fidelity vortex simulation which reflects the variability of a real-world tornado in time and space, at a reasonable computation cost; 2) the ultrafine-scale LESs resolve turbulent features to this spatial scale and facilitate better characterization of tornadic winds; and 3) an experiment having real-world, complex terrain is successfully executed for the first time in tornado research (to the authors’ knowledge). Results suggest that terrain generally causes tornadoes to become stronger and wider than they otherwise would have been if the ground were flat. However, another important result is that the effects of the real-world, complex terrain on the tornado are not the same as those from simplified terrains.

This study investigates grinding media behavior and grinding efficiency in a laboratory-scale ball mill under different rotation speeds to identify energy-efficient operating conditions in ball mill grinding operations. Grinding efficiency is evaluated in terms of the effectiveness of energy transfer into particle breakage, as quantified by PBM-derived breakage-rate characteristics, rather than by conventional metrics based solely on energy consumption. Batch grinding tests were conducted at several fractions of the critical speed, and a Population Balance Model (PBM) was calibrated for each operating condition to quantify the corresponding breakage-rate characteristics. In parallel, Discrete Element Method (DEM) simulations were performed to analyze the motion of grinding media as a function of rotation speed. Media motion descriptors derived from DEM were integrated with the PBM-based breakage parameters to interpret efficiency trends. The results show that grinding efficiency does not increase monotonically with rotation speed; instead, an optimal operating region exists within the investigated range due to the balance between impact-dominated and surface-contact-dominated motion regimes. By linking DEM-quantified media behavior indicators with PBM-derived breakage-rate coefficients, the proposed integrated framework enables physics-based estimation of the optimal rotation speed region. This methodology provides a transferable basis for analyzing and improving grinding efficiency in ball mill grinding operations.

When operating a permanent magnet synchronous motor (PMSM) from the base speed region to the field-weakening region in an extremely short time, the excessive voltage overshoot often leads to slim voltage margin, which deteriorates the current control and poses a risk of losing controllability. To mitigate this issue, a smooth transition strategy is proposed to improve the dynamics of the voltage-regulated field-weakening scheme. The voltage trajectory is analyzed and depicted on the voltage plane, featuring the dynamic characteristics during the fast transition from motor standstill to the field-weakening region. Through an asymptotic cutback of voltage reference, the voltage regulator can be desaturated in advance with sufficient voltage margin, and the dynamic performance will be smoothed without sacrificing much rapidity. The proposed method can effectively suppress voltage and torque overshoot during fast acceleration, with experimental validation on a 2.2 kW PMSM test bench.

Flexible rotor is supported on multiple elastic supports to avoid large bending vibrations in critical speed regions. The vibration transmission characteristic of flexible rotor with elastic support is important in the dynamic response of entire rotor system. In this paper, the nonlinear dynamic response and vibration transmission characteristic of three support flexible rotor (TSFR) with active elastic support dry friction dampers (AESDFDs) is studied. Firstly, the dynamic FEM model of TSFR is derived and friction contact model of the AESDFD is built based on trajectory tracking method (TTM). The vibration transmission dynamic model is established by simplifying rolling bearing, elastic support and pedestal as a multi-degree-of-freedom (DOF) system. Then the steady state unbalance response of the AESDFDs-TSFR under acceleration and constant speed conditions were obtained and supporting system dynamic responses were analyzed by using numerical methods. In order to verify the dynamic characteristic of entire system, experimental test rig for the AESDFDs-TSFR was set up. The influence of normal force on the unbalance response curves and resonance peak values of disks and supporting system at the critical speed regions were compared and discussed. It is shown that the unbalance response of the AESDFDs-TSFR could be suppressed effectively by the AESDFDs. The simulated transmitted force of supporting system is suppressed by using AESDFD, the pedestal acceleration signals are reduced too. Then the experimental measured pedestal acceleration signals are reduced at same tendency. The vibration transmission through rolling bearing and elastic support to the pedestal is analyzed by orbit diagram, time waveform and frequency spectrum. The results could provide theoretical guide for vibration transmission analysis of flexible rotor and its supporting system.

This article proposes a control strategy combining adaptive cascaded notch filters and distributed feedforward compensation, which is used to solve the problem of multifrequency vibration suppression and stable critical speed crossing in high-speed active magnetic bearing (AMB) rotor systems. High-speed rotating machinery often faces significant challenges from multifrequency vibrations, which can degrade system performance and stability. The four-degree-of-freedom rigid rotor dynamic model reveals the mechanism of multifrequency disturbance current generation caused by both rotor unbalance and sensor runout. This article introduces a cascaded notch filter topology reconstruction mechanism, which weakens the chattering caused by phase mismatch in the critical speed region by switching the input signal source of the tracking filter. Meanwhile, a dynamic compensation channel for displacement stiffness force is established, which can suppress multifrequency vibration forces without separating fundamental frequency disturbances. Through a cascaded multifrequency suppression structure, the cooperative filtering of 1st to 3rd harmonic disturbances is realized. Extensive simulation and experimental results demonstrate the efficacy of the proposed method: under both constant-speed and acceleration conditions, the strategy significantly reduces the 1st to 3rd harmonic disturbance components, with experimental reductions of up to 62.9%, 58.7%, and 14.4%, respectively at 65 Hz, and effectively improves system stability. This study provides a novel and effective vibration suppression solution for high-performance AMB systems.

Ultra-short-term wind power forecasting based on the MIFCformer model and a critical low wind speed region power revision strategy

Objective Motorcycle crashes, one of the major contributors to worldwide road traffic crashes (RTCs), remain a critical public health issue often in several low- and middle-income countries, where data limitations hinder comprehensive safety assessments. Existing studies have largely relied on police-reported data, which often underrepresents crash severity and lacks detail on post-crash recovery. To address the gap, this study aims to utilize hospital-based data for examining the distribution of patients across demographic, vehicular, situational and crash dynamics related factors; and to provide a severity-based assessment across several variables, such as patient’s age, impact speed, collision type, and impacted body region. Furthermore, it aims to evaluate severity-based post-crash outcomes, focusing on patient’s 30-day recovery status. Methods The study used a questionnaire-based interview to collect data from 509 motorcycle crash victims admitted in two major hospitals, over a nine-month period in Dhaka, Bangladesh. The Abbreviated Injury Scale (AIS) was employed to provide a standardized assessment of injury severity, while the data summarization and visualization was achieved using R software package. Results Findings reveal a high frequency of motorcycle crashes among males in the 11–40 age bracket, middle-income individuals, and students or service-holders, with most incidents occurring at moderate speeds and head-on collisions on single-lane roads. Severity-based analysis highlights that injuries in AIS 2 (moderate) and 3 (serious) are predominant, with a trend of increasing proportion of injuries with severity of AIS 3 or above correlated with older age groups, high-speed crashes, and specific collision types like rear-end and head-on. Lower extremity, specially the legs, are the most susceptible body part to injuries across all severity categories. Moreover, recovery rates (proportion of injured patients who fully or partially recover from their injuries after 30-days) decrease with higher injury severity, with permanent disabilities being more common among severely injured patients. Conclusions The data distribution reveals how crash frequency, and severity varies across several key factors while also divulging how injury severity impacts recovery trajectories. The results are expected to provide a foundation for future research and policy development toward reducing motorcycle crash risks and improving post-crash recoveries in similar urban settings.

Bi-level framework for cost effective robustness and responsiveness to enhance infrastructure resilience of transmission network against cyclones

As a critical link connecting upstream and downstreamsectors inthe petrochemical industry, crude oil storage tank farms serve asvital hubs for production, transfer, and import/export operations,where safety management presents unique complexities. However, currentsafety regulations have failed to keep pace with the rapid developmentof the petrochemical sector, leading to frequent oil-gas leakage incidents.This study investigates the stress states of hydrocarbon components(both near-leakage sources and far-field) and their mixing characteristicswith air under complex turbulent flow conditions. We establish a numericalmodel and solution algorithm capable of describing cross-scale oil-gasdispersion and cloud evolution dynamics. The model is applicable to(1)­High-speed regions near leakage sources (<300 m/s, without shockwavestructures); (2)­Far-field environments where atmospheric turbulencedominates hydrogen dispersion concentration fields. Through numericalsimulations studies conducted at an actual crude oil, we systematicallyanalyze the “leakage-mixing, cloud formation, dispersion-migration,and flow-dilution” processes under various scenarios. The workquantifies the spreading range and concentration distribution of hydrocarbonclouds at different stages, providing theoretical guidance for quantitativerisk assessment of oil-gas leaks in storage areas and Emergency responsedesign.

Abstract Around the world, wind turbines are essential to the production of power. However, running micro-scale wind generators comes with several difficulties. This affordable, clean, and renewable energy is something that many countries aim to achieve. Malaysia’s low wind speeds, which generally make it more challenging to deploy wind turbines nationwide and provide significant obstacles to efficiently harvesting wind energy, impact this goal. This study investigates the use of miniature wind turbines to overcome this problem. Using an electric blower, two different turbine designs, the S-200 W and S-800 W models, were tested extensively in a controlled laboratory setting. The trials reached a maximum wind speed of 6 m/s despite the challenges of controlling low wind speeds. The analysis found significant variations between the S-200 W and S-800 W turbines, especially in power output and coefficient. To maximize turbine performance under low wind circumstances, a particular MPPT technology was created that draws additional power from a battery as needed. While the S-800 W turbine demonstrated a lower power coefficient of 52%, the S-200 W turbine exceeded a 75% power coefficient, beyond its operating limit and necessitating the intervention of the MPPT system to control energy. To guarantee the next experiment’s accuracy and dependability, the study supports the use of wind tunnels because they can create controlled high-speed wind conditions, improving the validity of experimental results and making it easier to make well-informed decisions about wind turbine technology.

To limit the maximum rotor thrust in the near-rated wind speed region, this paper proposes a novel rotor thrust control scheme for large-scale wind turbines operating. It contains a rotor thrust identificator, a rotor thrust control loop, and a feedforward blade pitch controller. A simplified blade model is first proposed to achieve rotor thrust identification. Based on blade element momentum theory, the rotor thrust can be identified by the blade root out-of-plane bending moments. The rotor thrust control loop is then designed with the identified rotor thrust. Then, a feedforward blade pitch saturator is designed, called Nonlinear Dynamic Inversion based minimum Pitch Saturator (NDI-PS). It is realized by nonlinear dynamic inversion of the thrust coefficient curve. The simulation results exhibit outstanding performance of the proposed control scheme. Compared with existing controllers of NREL and Goldwind, power output is increased by 1% to 1.5%, while blade root and tower bottom loads are mitigated by about 4%.

To investigate the influence of three-dimensional (3D) static wind nonlinear effects on the nonlinear flutter of long span bridges, a multimodal coupled nonlinear flutter analysis method considering 3D static wind nonlinear effects is established, taking a double-deck steel truss girder suspension bridge as a case study. First, amplitude-dependent flutter derivatives under different wind angles of attack (AoAs) are obtained by identifying free-vibration wind tunnel test results of a section model. Additionally, the 3D additional wind AoAs for the main girder are derived from analyzing the bridge's 3D static wind response. Finally, the influence mechanisms of multimodal coupling and 3D static wind nonlinear effects on the bridge's nonlinear flutter performance are investigated through 3D multimodal coupled nonlinear flutter analysis. The results show that lateral flutter derivatives and the first-order symmetric lateral-bending mode influence the 3D nonlinear flutter response, with their effects modulated by the initial wind AoA. The two-dimensional (2D) closed-form solution based on the “strip assumption” significantly underestimates the steady-state amplitude by neglecting the 3D spanwise amplitude effect in large-amplitude nonlinear flutter analysis. Higher-order vertical modes influence the steady-state amplitude by altering modal damping while also modifying the amplitude distribution pattern. Modes coupled with a weak torsional mode suppress the torsional amplitude. The 3D static wind nonlinear effect impacts nonlinear flutter performance by introducing nonuniform 3D static wind additional AoAs. Moreover, this effect exhibits significant dependence on the initial wind AoA, demonstrating substantial influence on large-amplitude nonlinear flutter in high wind speed regions under an initial AoA of 3°.

Abstract This paper focuses on the application of special motors in low wind speed regions of wind power generation, and discusses in depth the research status of their intelligent control strategies. Firstly, it introduces the important position of wind energy resources development in low wind speed areas in wind power generation and the key role of special motors in it. In view of the characteristics of low wind speed, the principle and implementation of intelligent control strategies based on advanced maximum power point tracking (MPPT) algorithm and model predictive control (MPC), as well as the mechanism of real-time optimization and adjustment of motor speed and torque, are studied in depth, and it is analyzed how these strategies can improve the efficiency and stability of power generation for the entire wind power system and reduce its impact on the power grid in areas with low wind speeds.. By analyzing the current literature in the theoretical analysis, simulation research and actual cases of the comprehensive presentation and research status, for the further development and application of special motors in low wind speed wind power generation to provide a comprehensive and in-depth reference basis, to promote the advancement of wind power generation technology in the low wind speed region is of great significance.

In the traditional speed adaptive full-order observers of induction motor (IM), since the actual value of rotor flux is unattainable, the flux error term is usually ignored in the speed adaptive law. This would cause instability at low-speed during regenerating load. To mitigate this issue, an improved speed adaptive law strategy is proposed by introducing the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i>-axis current error term. Compared with the conventional speed adaptive law, the studied method maintains stability across the wide speed range based on the Routh–Hurwitz stability criterion. Notably, the studied method necessitates only a single parameter design, enhancing its practical applicability. Furthermore, the formula of the improved speed adaptive law is solely dependent on the motor inductance parameter. Consequently, even with variations in inductance, it can still retain its stable operation area. Experimental results from a 2.2 kW IM platform validate the effectiveness of the studied method.

Sustainable integration of wind and grid resources for electric vehicles charging in low wind speed region: A techno-economic assessment

Starting mode of a synchronous motor is an integral part of all production processes, determining the controllability of industrial production in general. At the same time, starting processes lead to special consequences, cause an increase in the accident rate of electromechanical equipment and an increase in various types of resource costs, which significantly affect the technical and economic performance of the enterprise. Since in the asynchronous starting mode the excitation winding is a current source, an increase in the value of the starting resistor or the capacitive resistance of the energy storage device leads to a significant overvoltage on the excitation circuit, so limiting overvoltages on this circuit is an important scientific and practical task. Existing methods and devices for asynchronous starting of a synchronous motor are based on compensation of electromagnetic inertia of the excitation circuit by including resistors, energy storage devices, decoupling the excitation winding from capacitors, and compensating electromotive force, which complicates the devices and reduces the reliability of the device. The inclusion of an energy storage device with a constant capacity in the excitation circuit improves the asynchronous characteristics of a synchronous motor in some limited slip range, while in other slip zones, a significant deterioration in the motor's starting properties can occur, up to the appearance of braking torques in the semi-synchronous speed region. To improve the characteristics, a multi-stage energy storage device is used, which somewhat complicates the design. Based on experimental studies of the asynchronous starting modes of a synchronous motor, it is proved that the inclusion of the electric capacity of the energy storage device in the excitation circuit with different data of starting and shunt resistors can significantly increase the electromagnetic torque of a synchronous motor, and when the electric capacity of the energy storage device and the starting resistor are connected in series, the starting and maximum torques of the synchronous motor increase significantly: when the electric capacity of the energy storage device and the resistor are connected in parallel, the starting and maximum torques of the synchronous motor increase These features make it possible to create highly efficient excitation circuit control systems for synchronous electric drives of technological mechanisms with a significant static resistance torque at sub-synchronous speed.

Abstract In this paper, the wind-gathering performance of wind-gathering impeller grilles of wind-gathering type wind turbines under different working conditions is investigated in conjunction with Computational Fluid Dynamics (CFD) simulations, and its working mechanism is analyzed. The mechanistic study of the concentrated wind turbine by SolidWorks modeling at wind speeds of 3 m/s, 5 m/s, and 8 m/s, respectively, shows that its unique design allows it to achieve higher energy conversion in the low wind speed region. This paper analyzes the flow field characteristics of the wind gathering blade grill of the wind gathering type wind turbine. It provides theoretical support for the design of wind-pooling wind turbine and practical guidance for the application and development of future wind energy equipment.

The design of the wind turbine blades has a significant impact on the operation of the wind turbine. Therefore, the cross-sectional structure of the airfoil needs to be simulated by specialized software to evaluate the impact on the performance of the wind turbine, especially in the low wind speed region. This paper studies the aerodynamic characteristics such as lift coefficient (CL), drag coefficient (CD) and ratio (CL/CD) in the attack angle ranges from -8 degrees to 10 degrees of the S4110 airfoil model under low wind velocity (3 m/s) using QBLADE and XFLR5 software with Reynolds coefficient margin conditions of 200000, Mach coefficient of 0.3 and Ncit coefficient of 9. Evaluate the ability to analyze aerodynamic parameters. The purpose of the study is to verify the accuracy of the two software in wind turbine design under low wind velocity by comparing the simulation results with experimental data from Airfoiltool. The results showed that both the QBLADE and XFLR5 achieve high accuracy at small attack angles (from -4.5 degrees to 4 degrees), with an error of less than 5%. Besides, the optimal angle of attack of the model is determined with the value of 4 degrees and a Ratio (CL/CD) value of 80.02

We study transition path properties such as the transient probability density, transition path time and its distribution, splitting probability, coefficient of variation, and the transition path shape of active run and tumble particles for unconstrained motion. In particular, we provide the theoretical description of the transition path properties using forward and backward master equations. The theoretical results are supported by Monte Carlo simulations. In particular, we prove that the system dynamics do not feature a symmetry breaking in the transition path properties for the case of run and tumble particles considered here. The symmetry of the transition path properties is shown to emerge for variations of the particle tumbling rate, particle speed, and transition path region.