Disturbance Frequency Research Articles

Sex-specific changes in sleep quality with aging: Insights from wearable device analysis.

Prior studies evaluating sleep quality have found that women often have better polysomnography-defined sleep quality than men, but women subjectively report a greater frequency of sleep disturbances. Although these studies can be partially attributed to study design, it is currently unclear what may be causing these discrepancies. In this study, we aim to identify potential differences in objectively assessed sleep quality between men and women with further emphasis on subgroup analysis based on age. We hypothesize that women's sleep worsens after menopause. Sleep quality was assessed by comparing the Sleep Quality Index, Arousal Index, sleep efficiency and apnea-hypopnea index, as provided by the SleepImage Ring@ 2.3.0, between men and women, with a sub-group analysis performed by age (18-40 years, 41-50 years, 51-60 years, 61-70 years, and > 70 years), run separately for women and men. In total, 1444 subjects (704 women and 740 men) with a mean age of 53.6 ± 14.71 years were enrolled in this analysis. In women, a significant drop in Sleep Quality Index was noted after age 51 years. Regression analysis demonstrated that age, Arousal Index, sleep efficiency and apnea-hypopnea index correlated significantly with Sleep Quality Index - with age, Arousal Index and apnea-hypopnea index negatively correlated, and sleep efficiency positively correlated. The highest correlation coefficient was obtained for Arousal Index in both women and men. In women, age older than 50 years was associated with a more rapid decrease of sleep quality than men, as defined by an increase in Arousal Index and apnea-hypopnea index with a concurrent decrease in Sleep Quality Index.

Effects of benzophenone-3 on the liver and thyroid of adult zebrafish

1. Benzophenone-3 (BP-3), commonly known as oxybenzone, is an organic compound that acts as a sunscreen, protecting the skin from UVA and UVB rays. Thus, the objective of this study was to investigate the effects of BP-3 on the liver and thyroid using morphological and biochemical approaches. 2. Adult male zebrafish were randomly assigned to three groups, each with three repetitions (n = 10 per group): water control, solvent control (0.01% ethanol), and 1 μg/L of BP-3, using a static exposure system for 96 hours. After the experiment, histopathological analyses of the liver and thyroid were performed, along with histochemical analyses (glycogen) and biochemical evaluations of the antioxidant enzymes Superoxide Dismutase (SOD) and Catalase (CAT). 3. Exposure to BP-3 resulted in significant histopathological changes in the liver of Danio rerio, increasing the frequency of circulatory disturbances, progressive changes, inflammatory responses, and regressive changes. On the other hand, the thyroid gland did not show any morphological changes during exposure to BP-3, maintaining its typical structure with follicles. There was a significant increase in SOD activity, while CAT showed no changes after 96 hours of exposure. 4. The results obtained demonstrate that exposure to BP-3 causes significant morphophysiological changes in the liver of D. rerio, highlighting not only the negative impacts on the health of these organisms but also the ecotoxicological potential of the substance and its consequences for aquatic biota in contaminated environments.

Comparative Analysis and Improvement of Generalized Droop Control and Virtual Synchronous Generator for Rate of Change of Frequency Constraint and Transient Power Suppression

ABSTRACTSince the microgrid lacks inertia compared to the conventional grid with synchronous generators, the microgrid is unable to address the frequency change issues resulting from the integration of large‐scale distributed generation. Due to the ability to provide virtual inertia, generalized droop control (GDC) and virtual synchronous generator (VSG) control are considered effective solutions for improving frequency regulation. However, in response to external frequency disturbances, the grid‐connected inverters may experience a significant transient active power overshoot caused by GDC and VSG. In this paper, the GDC is used as the fundamental control architecture, and then the small signal models of the GDC and VSG are compared and analyzed under various disturbances. A reduced‐order method for the GDC model is proposed to simplify the analysis of GDC. Additionally, GDC adaptive inertia (GDCAI) and adaptive inertia for operation mode switching (AIOMS) are proposed to mitigate frequency fluctuations and improve active power response. The effectiveness of the two control strategies is verified by MATLAB/Simulink simulation and StarSim hardware‐in‐the‐loop (HIL) experiment.

Measurement and Identification of Flame Describing Function (FDF) Based on Parallel Subsystem Model

Because of the need for low pollutant emissions, industrial gas turbines typically use partially premixed gases for combustion. However, the nonlinear dynamic characteristics of partially premixed flames have not been studied sufficiently. Therefore, this study focuses on the dynamics of a partially premixed flame generated by a swirler with fuel holes on its surface and designs a flame describing function (FDF) identification method based on the parallel subsystem model. This method can separate the flame dynamic characteristics into a parallel connection of the nonlinear and linear models. The nonlinear model is related to the disturbance frequency and velocity perturbation amplitude, whereas the linear model depends only on the disturbance frequency. This method is verified using a simulation. Finally, experimental research on partially premixed flames is conducted. Based on the experimental data, the identification method successfully separates the FDF into a nonlinear model with saturation characteristics and a linear model with Gaussian distribution characteristics. The flame model obtained by the identification method is the foundation for the analysis of combustion thermoacoustic stability and active/passive control strategy.

On the two approaches for the combustion instability predictions in a long-flame combustor

This paper presents a detailed comparative analysis and discussion of two typical predictive methods for combustion instability in long flame combustion chambers: the coupled method and the decoupled method. Using large eddy simulation (LES), the coupled method directly predicts stability in typical long flame combustion chambers. In the decoupled method, stability in the combustion chamber is predicted by combining a low-order acoustic network for long flames with flame responses and mean parameters from numerical simulations. The research results indicate that the coupled method provides full-field information, while the decoupled method neglects certain factors, such as the coupling between combustion and acoustics. However, the decoupled method can directly determine combustion instability based on the growth rate of oscillation modes. The flow field undergoes periodic changes, with the region of fluctuation in the combustion heat release rate gradually increasing, resembling vortex development, which ruptures upon encountering the wall due to radial constraints. Furthermore, in the decoupled method, the periodic changes in the flow field are controlled by the frequency of incoming flow disturbances, whereas in the coupled method, they are controlled by the acoustic frequency of the combustion chamber. In the coupled method, the coupling among disturbances and the acoustic disturbances at the boundaries amplifies the disturbances, causing the radial scale of the fluctuation region in the combustion heat release rate to increase along the axial direction and approach a fixed value faster than in the decoupled method.

Predicting new-onset persistent conduction disturbance following transcatheter aortic valve replacement: the usefulness of FEOPS finite element analysis

BackgroundDespite the frequency of persistent new-onset conduction disturbances after transcatheter aortic valve replacement (TAVR), few preoperative methods of prediction exist.MethodsPatients who underwent TAVR in the Department of Cardiology of the Second Affiliated Hospital of the Army Medical University from December 2020 to September 2021 and postoperative aortic root modeling via the FEOPS finite element analysis were included in this single-center case–control study, divided into persistent conduction disturbances (PCD) and non-PCD groups according to their pre- and postoperative electrocardiograms in the first month. Risk factors affecting PCD were identified by comparing the baseline data of these two groups, including echocardiograms, computed tomography angiography of the aortic root, surgical decision-making, and FEOPS data. Independent risk factors were screened using logistic regression modeling, and the receiver operating characteristic (ROC) curve was used to test the predictive ability.ResultsA total of 56 patients were included in this study, 37 with bicuspid aortic valve (BAV) and 19 with trileaflet aortic valve (TAV), with 17 cases of PCD. The contact pressure index (CPI) of FEOPS, valve oversize ratio, differences between membranous interventricular septum length and implantation depth (ΔMSID) and valve implantation depth were statistically different (P < 0.05). CPI could be used as an independent risk factor for PCD (P < 0.05), and the ROC curve comparison showed that the CPI was more predictive (AUC = 0.806, 95% CI: 0.684–0.928, P = 0.001).ConclusionsThe CPI of FEOPS has better predictive value for new-onset conduction disturbance after TAVR compared to other known predictors.

Far-Detuning Laser Frequency Disturbance Suppression for Atomic Sensor Based on Intrinsic Fiber Fabry–Pérot Cavity

Far-Detuning Laser Frequency Disturbance Suppression for Atomic Sensor Based on Intrinsic Fiber Fabry–Pérot Cavity

Onset of global instability in a premixed annular V-flame

We investigate self-excited axisymmetric oscillations of a lean premixed methane–air V-flame in a laminar annular jet. The flame is anchored near the rim of the centrebody, forming an inverted cone, while the strongest vorticity is concentrated along the outer shear layer of the annular jet. Consequently, the reaction and vorticity dynamics are largely separated, except where they coalesce near the flame tip. The global eigenmodes corresponding to the linearised reacting flow equations around the steady base state are computed in an axisymmetric setting. We identify an arc branch of eigenmodes exhibiting strong oscillations at the flame tip. The associated eigenvalues are robust with respect to domain truncation and numerical discretisation, and they become destabilised as the Reynolds number increases. The frequency of the leading eigenmode is found to correspond to the Lagrangian disturbance advection time from the nozzle outlet to the flame tip. The essential role of this convective mechanism is also supported by resolvent analysis, which finds that the same flame-tip disturbance structure and frequency are optimally amplified when the flame is subjected to external white noise forcing. Strong non-modal effects in the form of pseudo-resonance are not found. Nonlinear time-resolved simulation further reveals notable hysteresis phenomena in the subcritical regime prior to instability. Hence, even when the flame is linearly stable, perturbations of sufficient amplitude can trigger limit-cycle oscillations and higher-dimensional dynamics sustained by nonlinear feedback. A Monte Carlo simulation of passive tracers in the unsteady flame suggests a nonlinear non-local instability mechanism. Notably, linear analysis of the subcritical time-averaged limit-cycle state yields eigenvalues that do not match the nonlinear periodic oscillation frequencies. This mismatch is attributed to the fundamentally nonlinear dynamics of the subcritical V-flame instability, where the dichromatic, non-local interaction between the heat release rate along the flame surface and the vortex dynamics in the jet shear layer cannot be approximated as a simple distortion of the mean flow.

Study on the relationship between surface tension and dilational visco‐elasticity with foam stability

AbstractThe replacement of fluorine‐free foam is imminent, but to date, no fluorine‐free foam has reached comparable fire extinguishing performance to AFFF (aqueous film forming foam). The stability of firefighting foam significantly affects its extinguishing performance. In order to better understand the influence of foam formulation physical properties on foam stability, we correlate the foam stability with surface tension and dilational visco‐elasticity based on the AFFF formulation. The results show that, the foam stability rising steadily with the decrease of surface tension, which indicates that low surface tension favors the improvement of foam stability. However, when at the studied highest surface tension, the foam stability elevates slightly instead, demonstrating the surface tension is not the determinant of foam stability. By contrast, the dilational visco‐elasticity shows a closer correlation with foam stability for the consistent tendency. In the case of constantly changing disturbance frequency, the interface dilational elasticity shows a trend of first increasing and then decreasing with the rise of disturbance frequency, whereas the interface dilational viscosity is completely opposite. Different relaxation processes show up for different samples. More attention can be paid to the regulation of dilational visco‐elasticity in the development of fluorine‐free foams, so as to improve their extinguishing ability.

Exploring the distribution pattern of native and alien forests and their woody species diversity in a small Mediterranean city

Recent studies have explored the ecological relationship between native urban forests and self-sown non-native forests in large cities and metropolises but further research efforts dedicated to analyzing this relationship in small cities are still needed. To improve our understanding of the ecology of urban native and alien forests in Mediterranean small cities, we analyzed the woody species richness, the community-weight mean of moisture and nitrogen ecological indicators, and soil disturbance indicators in the main urban wood types of the city of Campobasso (Italy), as well as their spatial distribution pattern across a gradient of cover and aggregation of green areas. The study showed that both native oak forests and Robinia pseudoacacia forests contributed to the maintenance of woody species richness. If we exclude the riparian environment, R. pseudoacacia forests occupied small marginal patches, tolerating soil disturbance and a high disturbance frequency, thus occupying habitats where the native oak forests could not grow. Conversely, R. pseudoacacia forests shared the ecological niche with the native riparian forests, which calls for action to prevent the spread of this alien species along river banks. Our results highlighted that urban remnant forests should be considered important assets for the planning and upkeep of urban green areas.

The affinity of vascular plants and bryophytes to forest microclimate buffering

Abstract With recent advances in technology and modelling, ecologists are increasingly advised to use microclimate, not the usual coarse scale macroclimate based on weather stations, to better reflect the proximal conditions that species experience. This is especially relevant in forest ecosystems, where natural disturbances and management create substantial heterogeneity in microclimates. Under dense canopies, species may experience buffered (less extreme) microclimate temperatures relative to macroclimate, as well as increased relative humidity, reduced light and wind. Focusing on understorey plants, we investigated species response curves to the buffering capacity of the canopy layer, measured as the log‐transformed slope parameter of the microclimate to macroclimate linear relationship. If lower or higher than zero, microclimate temperatures are buffered or amplified, respectively, relative to macroclimate. During leaf‐on conditions (July–September 2021), we measured hourly microclimate temperatures in 157 plots across three temperate deciduous forests with contrasted macroclimates. We used paired hourly macroclimate measurements from nearby weather stations to derive the slope parameter, quantifying microclimate buffering. We surveyed vascular plant and bryophyte communities in 400 m2 plots centred on our microclimate sensors. Species were classified into three groups of forest affinity: core specialists; edge specialists; and generalists. We fitted generalized linear mixed‐effects models, by forest affinity group and by species, to obtain logistic response curves of the probability of occurrence against microclimate buffering. The species' optimum was computed as the microclimate effect that maximizes the species' probability of presence. We found contrasted microclimate preferences: Most bryophytes as well as the vascular plants classified as forest core specialists had an optimum in microclimate buffering, while forest edge specialists and generalists among vascular plants had an optimum in microclimate amplification. As canopies undergo increased disturbance frequency and intensity, more generalists and less forest core specialists might thus be expected in understorey communities, especially for bryophytes. Synthesis. Understorey plants have a species‐specific affinity to the forest microclimate, which we quantify for the first time. The investigation of species response curves to microclimate processes—buffering or amplification—can improve our understanding of the ecology of understorey plants, and help us anticipate their redistribution under climate change.

Towards enhanced metamaterials via shape memory alloy-embedded nonlinear resonators

Standard acoustic metamaterials create an attenuation around specific frequency bands. Finite structures, with distinct boundary conditions and a limited number of unit cells, present less attenuation and narrower bands than those predicted by idealized infinite systems. A critical engineering goal is enhancing performance to motivate practical applications. To that aim, this work incorporates shape memory alloys into a quasi-zero stiffness resonator design, allowing the tuning of each cell's internal resonance. Such a feature enables the system reconfiguration to achieve different purposes, from following a disturbance frequency fluctuation to realizing graded nonlinear metamaterials. While the former can work under an adaptive framework, the latter can result in time-invariant locally resonant metamaterials with wideband vibration attenuation. The proposed design combines a frame that axially compresses an SMA beam in the vicinity of its buckling. The critical buckling force changes by thermally activating the SMA, affecting the residual stiffness, hence the unit cell resonant frequency. The unit cell concept is developed analytically and via finite elements, then built and validated experimentally. The promising results indicate the viability of the proposed concept. Preliminary numerical simulations and experiments show the advantages of the proposed smart resonator over a linear time-invariant counterpart.

Uncovering hazards and adaptive capacity: A comprehensive risk assessment study in three conservation areas in Spain

The increase in the frequency, duration and severity of disturbances can disrupt forest composition and structure, posing threats to ecosystem services. Adaptive forest management has the potential to adjust forests to future disturbance regimes, by reducing their susceptibility to these threats and, therefore, increasing their adaptation capacity. However, few comprehensive studies have integrated the factors involved in adaptive forest management by comparing the biomass of national parks of the same region, or examined how global change might affect them in the near future. In this study, we integrate data of forest inventories, wildfires, high-resolution climate and pests information in climate model projections to assess climate-sensitive risks associated with key abiotic disturbances (such as fires, droughts and pests) in coniferous Mediterranean mountain forests, considering various forest management approaches and climate scenarios in three Spanish national parks. We employed the conceptual framework introduced by Lecina-Diaz et al. (2021a) to evaluate risks to forests and considered Exposed values (E), Hazard Magnitude (HM), Susceptibility (S) and Lack of Adaptive Capacity (LAC). We applied statistical weights using expert weights and the analytic hierarchy process (AHP) as the basis for determining the global ranking score of each indicator of the risk components. We extracted information about the climatic scenarios from the Coupled Model Intercomparison Project Phase 6. Three forest management scenarios were generated, named “low intervention», «traditional silviculture”, and "reduction of climate vulnerability", and mapped the risks of carbon sequestration for the different scenarios. The importance of each component was estimated using the AHP. HM was most significantly affected by the Aridity Index and the Fire Risk Index, with weights of 27.7 % and 24.2 %, respectively; S was affected by fuel load (29.0 %) and the Suppression Difficulty index (21.0 %), and LAC was influenced by forest management (32.0 %) and resprouting capacity (22.0 %). The three forest management scenarios exhibited different risk values that decreased with increasing intensity of the intervention in the three protected areas. Likewise, when two climate scenarios were considered, risk increased in the protected areas (Teide National Park, 10.69 %; Sierra Nevada National Park, 10.9 %; Sierra de las Nieves National Park, 6.17 %). Patterns of spatial arrangement of risk, which included HM, S and LAC, were consistent with the risk level, with the highest risk values being concentrated in the buffer areas (natural parks), with areas with a greater presence of coniferous plantations. The risk maps allowed us to identify areas that are critical under extreme conditions and where the greatest disturbance events may occur. Our study underscores that risks of disturbances in mountain ecosystems dominated by conifers within protected areas can be mitigated by forest management. The application of forest management adaptation strategies in national parks and buffer areas has proven effective in reducing risks of disturbances and preserving certain ecosystem services, such as carbon sequestration.

Combining thinning and diverse plantings to adapt to climate-change-induced timber supply shortage in British Columbia

Forestry is an important component of Canada’s economy with British Columbia (BC) contributing almost half to the national roundwood production. Yet, the country’s timber supply and forest economy are threatened by climate change, with increased frequency and severity of natural disturbances and changes in forest productivity. Mountain pine beetle ( Dendroctonus ponderosae) outbreaks are endemic in BC, but the latest climate change-driven outbreak has resulted in a cumulative loss of over half of all merchantable pine, leading to a mid-term timber supply shortage. In this study, we investigate the potential of commercial thinning and alternative planting regimes based on species diversification and assisted species migration to mitigate the anticipated decrease in timber supply in BC. We simulated the long-term effects of these management options in a case study area in interior BC, using a toolbox that combines management- and research-oriented data and models. We found that combining commercial thinning and species diversification has the best potential to mitigate future timber supply shortages in BC. We discuss the limits of this toolbox approach and identify research needs and recommendations for future studies aiming at modelling cumulative effects of management, climate change, and natural disturbances on timber supply.

B-319 Kappa and Lambda Free Light Chains Quantification in Serum Samples with 3 or 4 Monoclonal Components Detected by Serum Immunofixation

Abstract Background Serum free light chain (FLC) quantification is a diagnostic criterion for monoclonal gammopathy. Oligoclonal expansion is defined when two or more small bands are detected in the gamma region of serum protein electrophoresis (SPEP) or immunofixation (SIFE) within the context of infectious diseases, autoimmune diseases, or some lymphoproliferative processes. This study aims to investigate the frequency of FLC disturbances in samples with oligoclonal pattern of 3 or 4 monoclonal bands observable in SIFE. Methods We have analyzed 7553 consecutive samples during the period of January to December 2023 in which both determination of FLC and SIFE were ordered in a large central laboratory at São Paulo, Brazil. FLC quantification and SIFE analysis were performed with FreeLite assay and Optilite system (The Binding Site, UK) and SPIFE 3000 (Helena Laboratories, USA), respectively. Results In our analysis, 119 samples (50 males, 69 females, median age 69 years (range 37-90)), with 3 or 4 monoclonal bands were identified, constituting 1.57% of the overall study population. These samples were then categorized into two groups. The first group had normal FLC Ratio (range 0.26 to 1.65) and the second group had altered FLC Ratio (outside 0.26-1.65 range). Seventy-seven samples (65%) had altered FLC ratio, with kappa elevation being the most common alteration (51 samples). Within these samples, median FLC ratio was 2.99 (range 1.72-719.05). Lambda elevation was present in 26 samples, with median FLC ratio 0.04 (range 0.005-0.16). Conclusions Presence of 3 or more oligoclonal bands in SIFE analysis may be indicative of various pathological processes (benign and malignant) and also be observed in post-transplantation. In this study, we have observed that most of these samples present altered FLC ratio, which indicate monoclonal disturbances in the production of free light chains. Those disturbances may be associated with a lymphoproliferative disease (e.g. multiple myeloma) or may be transient. Clinicians should be aware of the need for follow-up of these cases.

The effect of a constant electric field in an undisturbed plasma on the stability of the electron beam–gas discharge collisional plasma system

This work is devoted to the study of a fast non-relativistic electron beam–gas discharge plasma system within the framework of the kinetic theory of stability. The influence of a constant electric field, collinear beam velocity, on the stability of the system in an undisturbed plasma is studied. It is shown that even a relatively small electric field, which does not significantly affect the energy of the electron beam, can lead to significant changes in the parameters of harmonic disturbances propagating in the electron beam–plasma system in the region of its instability. It was found that the reason for such changes is the drift of plasma electrons, which, as a consequence, leads to a change in the frequency of disturbances in the coordinate system associated with the plasma due to the Doppler effect. The results obtained are demonstrated by calculations based on the kinetic theory of perturbation parameters in a low-voltage beam discharge in rare gases, which is used in the development of plasma electronics devices. The effect of electron-atomic collisions on the stability of the electron beam–plasma system is investigated and compared with the results of other authors' works.

Droughts Amplify Soil Moisture Losses in Burned Forests of Southeastern Amazonia

AbstractSoil moisture is a crucial variable mediating soil‐vegetation‐atmosphere water exchange. As climate and land use change, the increased frequency and intensity of extreme weather events and disturbances will likely alter feedbacks between ecosystem functions and soil moisture. In this study, we evaluated how extreme drought (2015/2016) and postfire vegetation regrowth affected the seasonality of soil water content (0–8 m depth) in a transitional forest in southeastern Amazonia. The experiment included three treatment plots: an unburned Control, an area burned every three years (B3yr), and an area burned annually (B1yr) between 2004 and 2010. We hypothesized that (a) soil moisture at B1yr and B3yr would be higher than the Control in the first years postfire due to lower transpiration rates, but differences between burned plots would decrease as postfire vegetation regrew; (b) during drought years, the soil water deficit in the dry season would be significantly greater in all plots as plants responded to greater evaporative demand; and (c) postfire recovery in the burned plots would cause an increase in evapotranspiration over time, especially in the topsoil. Contrary to the first expectation, the burned plots had lower volumetric water content than the Control plot. However, we found that droughts significantly reduced soil moisture in all plots compared to non‐drought years (15.6%), and this effect was amplified in the burned plots (19%). Our results indicate that, while compounding disturbances such as wildfires and extreme droughts alter forest dynamics, deep soil moisture is an essential water source for vegetation recovery.

Optimizing PID controller parameters for robust automatic voltage regulator system through indirect design approach-2

Automatic voltage regulators (AVR) are designed to manipulate a synchronous generator’s voltage level automatically. Proportional integral derivative (PID) controllers are typically used in AVR systems to regulate voltage. Although advanced PID tuning methods have been proposed, the actual voltage response differs from the theoretical predictions due to modeling errors and system uncertainties. This requires continuous fine tuning of the PID parameters. However, manual adjustment of these parameters can compromise the stability and robustness of the AVR system. This study focuses on the online self-tuning of PID controllers called indirect design approach-2 (IDA-2) in AVR systems while preserving robustness. In particular, we indirectly tune the PID controller by shifting the frequency response. The new PID parameters depend on the frequency-shifting constant and the previously optimized PID parameters. Adjusting the frequency-shifting constant modifies all the PID parameters simultaneously, thereby improving the control performance and robustness. We evaluate the robustness of the proposed online PID tuning method by comparing the gain margins (GMs) and phase margins (PMs) with previously optimized PID parameters during parameter uncertainties. The proposed method is further evaluated in terms of disturbance rejection, measurement noise, and frequency response analysis during parameter uncertainty calculations against existing methods. Simulations show that the proposed method significantly improves the robustness of the controller in the AVR system. In summary, online self-tuning enables automated PID parameter adjustment in an AVR system, while maintaining stability and robustness.

Maiden application of mountaineering team-based optimization algorithm optimized 1PD-PI controller for load frequency control in islanded microgrid with renewable energy sources

Load Frequency Control (LFC) is essential for maintaining the stability of Islanded Microgrids (IMGs) that rely extensively on Renewable Energy Sources (RES). This paper introduces a groundbreaking 1PD-PI (one + Proportional + Derivative-Proportional + Integral) controller, marking its inaugural use in improving LFC performance within IMGs. The creation of this advanced controller stems from the amalgamation of 1PD and PI control strategies. Furthermore, the paper presents the Mountaineering Team Based Optimization (MTBO) algorithm, a novel meta-heuristic technique introduced for the first time to effectively tackle LFC challenges. This algorithm, inspired by principles of intellectual and environmental evolution and coordinated human behavior, is utilized to optimize the controller gains. The effectiveness of the proposed methodology is rigorously evaluated within a simulated IMG environment using MATLAB/SIMULINK. This simulated IMG incorporates diverse power generation sources, including Diesel Engine Generators (DEGs), Microturbines (MTs), Fuel Cells (FCs), Energy Storage Systems (ESSs), and RES units like Wind Turbine Generators (WTGs) and Photovoltaics (PVs). This paper employs the Integral Time Multiplied by the Squared Error (ITSE) and Integral of Time Multiplied By Absolute Error (ITAE) indicators as the primary performance metrics, conventionally used to mitigate frequency deviations. To achieve optimal controller parameter tuning, a weighted composite objective function is formulated. This function incorporates multiple components: modified objective functions related to both ITSE and ITAE, along with a term addressing overshoot and settling time. Each component is assigned an appropriate weighting factor to prioritize specific performance aspects. By employing distinct objective functions for different aspects of control performance, the derivation of optimized controller gains is facilitated. The efficacy and contribution of the proposed methodology are rigorously demonstrated within the context of RES-based IMGs, featuring a comparative analysis with well-known optimization algorithms, including Particle Swarm Optimization (PSO) and the Whale Optimization Algorithm (WOA). These algorithms are used to optimize the 1PD-PI controller, resulting in three control schemes: 1PD-PI/MTBO, 1PD-PI/WOA, and 1PD-PI/PSO. The effectiveness of these control schemes is evaluated under various loading conditions, incorporating parametric uncertainties and nonlinear factors of physical constraints. Three case studies, presented in eight scenarios (I-VIII), are utilized to comprehensively assess the efficiency, robustness, and sensitivity of the proposed approach. This analysis extends beyond the time domain, considering the stability evaluation of the proposed control scheme. Simulation results unequivocally establish the superior performance of the MTBO algorithm-optimized 1PD-PI controller compared to its counterparts. This superiority is evident in terms of minimized settling time, reduced peak undershoot and overshoot, and enhanced error-integrating performance characteristics within the system responses. Improvements are observed in both the high range and within the 80–90% range for criteria such as overshoot, undershoot, and the numerical values of the objective functions. This paper underscores the practicality and effectiveness of the 1PD-PI/MTBO control scheme, offering valuable insights into the management of frequency disturbances in RES-based IMGs.

Modeling method of photovoltaic power generation grid connection based on particle swarm optimization neural network

Aiming at the complex structure, numerous equipment, intricate control and protection logic, as well as the existence of numerous unmodeled dynamics and black-box device models in photovoltaic (PV) grid-connected systems, a modeling method based on Particle Swarm Optimization Neural Network (PSO-NN) is proposed to address the inability of pure mechanism models to accurately simulate their operational dynamics. Utilizing the differences in active power response waveforms under Voltage-Frequency (Vf) control, Power-Reactive Power (PQ) control, and Droop control as criteria for control strategy identification, a PSO-NN model is constructed for PV grid-connected systems, with inputs comprising temperature, humidity, light intensity, voltage, and frequency disturbances, and outputs being active and reactive power. To validate the model's effectiveness, a PV grid-connected system model is built in a self-developed simulation software and connected to an IEEE 14-bus distribution network for simulation verification. The results demonstrate that the proposed PV grid-connected model can effectively identify the types of Vf control, PQ control, and Droop control strategies, and accurately reflect the dynamic response characteristics of active and reactive power under various voltage and frequency disturbances.