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Search Results (2,019)

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Keywords = frequency tuning

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19 pages, 4084 KB  
Article
Searching for Multimode Resonator Topologies with Adaptive Differential Evolution
by Vladimir Stanovov, Sergey Khodenkov, Ivan Rozhnov and Lev Kazakovtsev
Sensors 2025, 25(20), 6447; https://doi.org/10.3390/s25206447 (registering DOI) - 18 Oct 2025
Abstract
Microwave devices based on microstrip resonators are widely used today in communication, radar, and navigation systems. The requirements to these devices may include specific frequency-selective properties, as well as size and production costs. The design of resonators and filters are mostly performed manually, [...] Read more.
Microwave devices based on microstrip resonators are widely used today in communication, radar, and navigation systems. The requirements to these devices may include specific frequency-selective properties, as well as size and production costs. The design of resonators and filters are mostly performed manually, as the process requires expert knowledge and computationally expensive modeling, so practitioners are usually limited to tuning a chosen example from a set of known, typical topologies. However, the set of possible topologies remains unexplored and may contain specific constructions, which have not been discovered yet. In this study we propose an approach to automatically search the space multimode resonator topologies using a zero-order optimization algorithm and numerous computational experiments. In particular, a family of symmetrical resonators constructed out of four rectangles is considered, and the parameters are tuned by the recently proposed L-SRTDE algorithm. We state the problem of building the topology of a microwave device conductor with specified frequency-selective characteristics as an optimization problem, and the minimized function (target function) in this problem is based on the evaluation of the deviation between the specified frequency-selective characteristics and their values obtained via electrodynamic modeling. The experiments with two target function formulations have shown that the proposed approach allows finding novel topologies and automatically tune them according to the required frequency-selective properties. It is shown that some of the topologies are different from the known ones but still demonstrate high-quality properties. Full article
(This article belongs to the Section Electronic Sensors)
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22 pages, 1212 KB  
Article
Enhancing Microparticle Separation Efficiency in Acoustofluidic Chips via Machine Learning and Numerical Modeling
by Tamara Klymkovych, Nataliia Bokla, Wojciech Zabierowski and Dmytro Klymkovych
Sensors 2025, 25(20), 6427; https://doi.org/10.3390/s25206427 - 17 Oct 2025
Abstract
An integrated approach for enhancing microparticle separation efficiency in acoustofluidic lab-on-a-chip systems is presented, combining numerical modeling in COMSOL 6.2 Multiphysics® with reinforcement learning techniques implemented in Python 3.10.14. The proposed method addresses the limitations of traditional parameter tuning, which is time-consuming [...] Read more.
An integrated approach for enhancing microparticle separation efficiency in acoustofluidic lab-on-a-chip systems is presented, combining numerical modeling in COMSOL 6.2 Multiphysics® with reinforcement learning techniques implemented in Python 3.10.14. The proposed method addresses the limitations of traditional parameter tuning, which is time-consuming and computationally intensive. A simulation framework based on LiveLink™ for COMSOL–Python integration enables the automatic generation, execution, and evaluation of particle separation scenarios. Reinforcement learning algorithms, trained on both successful and failed experiments, are employed to optimize control parameters such as flow velocity and acoustic frequency. Experimental data from over 100 numerical simulations were used to train a neural network, which demonstrated the ability to accurately predict and improve sorting efficiency. The results confirm that incorporating failed outcomes into the reward structure significantly improves learning convergence and model accuracy. This work contributes to the development of intelligent microfluidic systems capable of autonomous adaptation and optimization for biomedical and analytical applications, such as label-free separation of microplastics from biological fluids, selective sorting of soot and ash particles for environmental monitoring, and high-precision manipulation of cells or extracellular vesicles for diagnostic assays. Full article
(This article belongs to the Section Physical Sensors)
24 pages, 6140 KB  
Article
Stabilization of DC Microgrids Using Frequency-Decomposed Fractional-Order Control and Hybrid Energy Storage
by Sherif A. Zaid, Hani Albalawi, Hazem M. El-Hageen, Abdul Wadood and Abualkasim Bakeer
Fractal Fract. 2025, 9(10), 670; https://doi.org/10.3390/fractalfract9100670 - 17 Oct 2025
Abstract
In DC microgrids, the combination of pulsed loads and renewable energy sources significantly impairs system stability, especially in highly dynamic operating environments. The resilience and reaction time of conventional proportional–integral (PI) controllers are often inadequate when managing the nonlinear dynamics of hybrid energy [...] Read more.
In DC microgrids, the combination of pulsed loads and renewable energy sources significantly impairs system stability, especially in highly dynamic operating environments. The resilience and reaction time of conventional proportional–integral (PI) controllers are often inadequate when managing the nonlinear dynamics of hybrid energy storage systems. This research suggests a frequency-decomposed fractional-order control strategy for stabilizing DC microgrids with solar, batteries, and supercapacitors. The control architecture divides system disturbances into low- and high-frequency components, assigning high-frequency compensation to the ultracapacitor (UC) and low-frequency regulation to the battery, while a fractional-order controller (FOC) enhances dynamic responsiveness and stability margins. The proposed approach is implemented and assessed in MATLAB/Simulink (version R2023a) using comparison simulations against a conventional PI-based control scheme under scenarios like pulsed load disturbances and fluctuations in renewable generation. Grey Wolf Optimizer (GWO), a metaheuristic optimization procedure, has been used to tune the parameters of the FOPI controller. The obtained results using the same conditions were compared using an optimal fractional-order PI controller (FOPI) and a conventional PI controller. The microgrid with the best FOPI controller was found to perform better than the one with the PI controller. Consequently, the objective function is reduced by 80% with the proposed optimal FOPI controller. The findings demonstrate that the proposed method significantly enhances DC bus voltage management, reduces overshoot and settling time, and lessens battery stress by effectively coordinating power sharing with the supercapacitor. Also, the robustness of the proposed controller against parameters variations has been proven. Full article
(This article belongs to the Special Issue Advances in Dynamics and Control of Fractional-Order Systems)
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11 pages, 2467 KB  
Article
Scatterers of Non-Electric-Dipole Radiation
by Yafei Li, Zhihui Liu, Shuanglong Cheng, Mansha Li, Jianchao Meng, Tao Jiang, Jiani Li, Zhuangzhuang Xu, Xike Qian, Meng Wang and Ze Li
Nanomaterials 2025, 15(20), 1584; https://doi.org/10.3390/nano15201584 - 17 Oct 2025
Viewed by 36
Abstract
We theoretically demonstrate that nonmagnetic silicon nanodisk dimers, under plane-wave illumination, can achieve electric dipole mode-free by suppressing electric dipole responses at magnetic resonance frequencies through structural parameter tuning. This is enabled by the anapole mode, where destructive interference between Cartesian electric and [...] Read more.
We theoretically demonstrate that nonmagnetic silicon nanodisk dimers, under plane-wave illumination, can achieve electric dipole mode-free by suppressing electric dipole responses at magnetic resonance frequencies through structural parameter tuning. This is enabled by the anapole mode, where destructive interference between Cartesian electric and toroidal dipole moments results in low spherical electric dipole scattering. Furthermore, the magnetic resonance responses in this nanostructure are tunable within the visible spectrum and compatible with current nanofabrication technology. Full article
(This article belongs to the Section Physical Chemistry at Nanoscale)
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16 pages, 6023 KB  
Article
Electromagnetic Shielding Performance of Ta-Doped NiFe2O4 Composites Reinforced with Chopped Strands for 7–18 GHz Applications
by Mehriban Emek, Ethem İlhan Şahin, Jamal Eldin F. M. Ibrahim and Mesut Kartal
Nanomaterials 2025, 15(20), 1580; https://doi.org/10.3390/nano15201580 - 16 Oct 2025
Viewed by 141
Abstract
This study reports the synthesis, structural characterization, and electromagnetic shielding performance of tantalum (Ta)-doped nickel ferrite (NiFe2O4) composites reinforced with chopped strands. Ta-doped NiFe2O4 powders were prepared via the conventional mixed-oxide route and sintered at 1200 [...] Read more.
This study reports the synthesis, structural characterization, and electromagnetic shielding performance of tantalum (Ta)-doped nickel ferrite (NiFe2O4) composites reinforced with chopped strands. Ta-doped NiFe2O4 powders were prepared via the conventional mixed-oxide route and sintered at 1200 °C for 4 h, resulting in a well-crystallized single-phase spinel structure. Comprehensive structural and chemical analyses were carried out using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), confirming the successful incorporation of Ta into the NiFe2O4 lattice and the uniform microstructural distribution. The ferrite powders were subsequently embedded with chopped strands and epoxy resin through hot pressing to fabricate composites with varying filler contents. The electromagnetic interference (EMI) shielding effectiveness (SE) of the composites was systematically evaluated in the 7–18 GHz frequency range using a network analyzer (NA). The optimized composite, with a thickness of 1.2 mm, demonstrated a maximum SE of 34.74 dB at 17.4 GHz, primarily attributed to interfacial polarization, dipolar relaxation, and multiple scattering effects induced by the chopped strands. The results indicate that the shielding performance of the composites can be precisely tuned by modifying the filler concentration and microstructural characteristics, enabling selective frequency-band applications. Overall, this work highlights the potential of Ta-doped NiFe2O4/chopped strand composites as lightweight, cost-effective, and high-performance candidates for advanced microwave absorption and electromagnetic shielding applications in defense, and next-generation communication technologies. Full article
(This article belongs to the Section Inorganic Materials and Metal-Organic Frameworks)
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19 pages, 3060 KB  
Article
Design and Optimization of a Hybrid Design for Quantum Transduction
by Enrico Bargagna, Julian Delgado, Changqing Wang, Ivan Gonin, Vyacheslav P. Yakovlev, Paolo Neri, Donato Passarelli and Silvia Zorzetti
Sensors 2025, 25(20), 6365; https://doi.org/10.3390/s25206365 - 15 Oct 2025
Viewed by 276
Abstract
This study presents the mechanical design and analysis of a quantum electro-optical transducer engineered to operate at millikelvin temperatures within a dilution refrigerator. The transducer enables bidirectional microwave-optical frequency conversion through a hybrid architecture that integrates a superconducting radiofrequency (SRF) cavity with an [...] Read more.
This study presents the mechanical design and analysis of a quantum electro-optical transducer engineered to operate at millikelvin temperatures within a dilution refrigerator. The transducer enables bidirectional microwave-optical frequency conversion through a hybrid architecture that integrates a superconducting radiofrequency (SRF) cavity with an electro-optic optical cavity. Among several design options investigated, the configuration offering the best thermal and mechanical performance was selected, yielding a robust solution with reduced sensitivity to fabrication tolerances, improved heat dissipation, as well as alignment precision. The design ensures uniform temperature distribution, enabling higher laser pump powers and, thus, increased conversion efficiency, while maintaining mechanical stresses safely below the material yield strength. Electromagnetic simulations further validate the design, demonstrating enhanced coupling between the optical and microwave modes, as well as a broader tuning range achieved with smaller tuner displacements. Full article
(This article belongs to the Section Physical Sensors)
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26 pages, 6031 KB  
Article
Model-Based Design and Sensitivity Optimization of Frequency-Output Pressure Sensors for Real-Time Monitoring in Intelligent Rowing Systems
by Iaroslav Osadchuk, Oleksandr Osadchuk, Serhii Baraban, Andrii Semenov and Mariia Baraban
Electronics 2025, 14(20), 4049; https://doi.org/10.3390/electronics14204049 - 15 Oct 2025
Viewed by 201
Abstract
This study presents a model-driven approach to the design, calibration, and application of frequency-output pressure sensors integrated within an intelligent system for real-time monitoring of rowing performance. The proposed system captures biomechanical parameters of the “boat–rower” complex across 50 parallel channels with a [...] Read more.
This study presents a model-driven approach to the design, calibration, and application of frequency-output pressure sensors integrated within an intelligent system for real-time monitoring of rowing performance. The proposed system captures biomechanical parameters of the “boat–rower” complex across 50 parallel channels with a temporal resolution of 8–12 ms. At the core of the sensing architecture are parametric pressure transducers incorporating strain-gauge primary elements and microelectronic auto-generator circuits featuring negative differential resistance (NDR). These oscillating circuits convert mechanical stress into high-frequency output signals in the 1749.9–1751.9 MHz range, with pressure sensitivities from 0.365 kHz/kPa to 1.370 kHz/kPa. The sensor models are derived using physical energy conversion principles, enabling the formulation of analytical expressions for transformation and sensitivity functions. These models simplify sensitivity tuning and allow clear interpretation of how structural and electronic parameters influence output frequency. The system architecture eliminates the need for analog-to-digital converters and signal amplifiers, reducing cost and power consumption, while enabling wireless ultra high frequency (UHF) transmission of sensor data. Integrated algorithms analyze the influence of biomechanical variables on athlete performance, enabling real-time diagnostics. The proposed model-based methodology offers a scalable and accurate solution for intelligent sports instrumentation and beyond. Full article
(This article belongs to the Special Issue Wearable Sensors for Human Position, Attitude and Motion Tracking)
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39 pages, 10642 KB  
Article
An Optimal Two-Stage Tuned PIDF + Fuzzy Controller for Enhanced LFC in Hybrid Power Systems
by Saleh Almutairi, Fatih Anayi, Michael Packianather and Mokhtar Shouran
Sustainability 2025, 17(20), 9109; https://doi.org/10.3390/su17209109 - 14 Oct 2025
Viewed by 275
Abstract
Ensuring reliable power system control demands innovative architectural solutions. This research introduces a fault-tolerant hybrid parallel compensator architecture for load frequency control (LFC), combining a Proportional–Integral–Derivative with Filter (PIDF) compensator with a Fuzzy Fractional-Order PI-PD (Fuzzy FOPI–FOPD) module. Particle Swarm Optimization (PSO) determines [...] Read more.
Ensuring reliable power system control demands innovative architectural solutions. This research introduces a fault-tolerant hybrid parallel compensator architecture for load frequency control (LFC), combining a Proportional–Integral–Derivative with Filter (PIDF) compensator with a Fuzzy Fractional-Order PI-PD (Fuzzy FOPI–FOPD) module. Particle Swarm Optimization (PSO) determines optimal PID gains, while the Catch Fish Optimization Algorithm (CFOA) tunes the Fuzzy FOPI–FOPD parameters—both minimizing the Integral Time Absolute Error (ITAE) index. The parallel compensator structure guarantees continuous operation during subsystem faults, substantially boosting grid reliability. Rigorous partial failure tests confirm uncompromised performance-controlled degradation. Benchmark comparisons against contemporary controllers reveal the proposed architecture’s superiority, quantifiable through transient metric enhancements: undershoot suppression (−9.57 × 10−5 p.u. to −1.17 × 10−7 p.u.), settling time improvement (8.8000 s to 3.1511 s), and ITAE reduction (0.0007891 to 0.0000001608), verifying precision and stability gains. Resilience analyses across parameter drift and step load scenarios, simulated in MATLAB/Simulink, demonstrate superior disturbance attenuation and operational stability. These outcomes confirm the solution’s robustness, dependability, and field readiness. Overall, this study introduces a transformative LFC strategy with high practical viability for modern power networks. Full article
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17 pages, 14976 KB  
Article
Hierarchical Porous P-Doped NiCo Alloy with α/ε Phase-Defect Synergy to Boost Alkaline HER Kinetics and Bifunctional Activity
by Lun Yang, Meng Zhang, Mengran Shi, Yi Yao, Ying Liu, Jianqing Zhou, Yi Cao, Zhong Li, Meifeng Liu, Xiuzhang Wang, Zhixing Gan, Haixiao Zhang, Shuai Chang, Gang Zhou and Yun Shan
Nanomaterials 2025, 15(20), 1562; https://doi.org/10.3390/nano15201562 - 14 Oct 2025
Viewed by 213
Abstract
Non-precious catalysts for alkaline hydrogen evolution reaction (HER) face a fundamental multi-scale challenge: lack of synergy between electronic structure tuning for balancing H adsorption and water dissociation, active site stabilization for boosting intrinsic turnover frequency (TOF), and mass transport. Even Pt loses 2–3 [...] Read more.
Non-precious catalysts for alkaline hydrogen evolution reaction (HER) face a fundamental multi-scale challenge: lack of synergy between electronic structure tuning for balancing H adsorption and water dissociation, active site stabilization for boosting intrinsic turnover frequency (TOF), and mass transport. Even Pt loses 2–3 orders of magnitude activity in alkaline media due to inefficient water dissociation, a synergistic gap unresolved by the Sabatier principle alone. Existing strategies only address isolated aspects: phase engineering optimizes electronic structure but not active site stability; heteroatom doping introduces defects unlinked to mass transport; and nanostructuring enhances mass transfer but not atomic-level activity. None of them address multi-scale mechanistic synergy. Herein, we design a hierarchically porous P-doped NiCo alloy (hpP-NiCo) with an aim of achieving this synergy via integrating α-FCC/ε-HCP phases, P-induced defects, and 3D porosity. The formed α/ε interface tunes the d-band center to balance H adsorption and water dissociation; and the doped P stabilizes metal-vacancy sites to boost TOF. In addition, porosity matches mass transport with active site accessibility. In 1 M KOH, hpP-NiCo reaches 1000 mA cm−2 at 185 mV overpotential and has a Tafel slope of 43.1 mV dec−1, corresponding to electrochemical desorption as the rate-limiting step and verifying Volmer acceleration. Moreover, it also exhibits bifunctional oxygen evolution reaction (OER), achieving 100 mA cm−2 at potential of 1.55 V. This work establishes a mechanistic synergy model for non-precious HER catalysts. Full article
(This article belongs to the Section Energy and Catalysis)
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19 pages, 2192 KB  
Article
Robust Online Rotor Time Constant Tuning Method with High-Frequency Current Injection for Indirect Field-Oriented Induction Motor Drives
by Yongsu Han
Symmetry 2025, 17(10), 1729; https://doi.org/10.3390/sym17101729 - 14 Oct 2025
Viewed by 132
Abstract
For an induction motor operating as a symmetric three-phase system, the performance of indirect field-oriented vector control relies heavily on the accuracy of the rotor time constant. Any inaccuracies result in severe torque errors and compromise dynamic performance because of the coupling between [...] Read more.
For an induction motor operating as a symmetric three-phase system, the performance of indirect field-oriented vector control relies heavily on the accuracy of the rotor time constant. Any inaccuracies result in severe torque errors and compromise dynamic performance because of the coupling between the flux and torque controls. Although conventional IFOC methods are intended to compensate for the rotor time constant error, they rely on induction machine parameters such as the mutual and leakage inductances. This paper proposes an online method for tuning the rotor time constant independent of other parameters. First, an active power model of three-phase symmetric induction motor is selected to estimate the stator resistance based on a model reference adaptive system, which requires only the rotor time constant. Additionally, high-frequency current injection and torque ripple estimation without phase delay or amplitude decay are introduced to compensate for the rotor time constant. When a high-frequency current is injected, the rotor time constant and stator resistance can be simultaneously tuned without depending on other parameters. A high-frequency current is injected only when a rotor time constant error is detected from the estimated stator resistance. This behavior is enabled by the correlation between the stator resistance and the rotor time constant. Simulation results using MATLAB/Simulink regarding the symmetric three-phase induction motor validate the proposed method. Full article
(This article belongs to the Special Issue Applications of Symmetry Three-Phase Electrical Power Systems)
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18 pages, 6226 KB  
Article
PSO-Based Supervisory Adaptive Controller for BESS-VSG Frequency Regulation Under High PV Penetration
by Raffaella Assogna, Lucio Ciabattoni and Gabriele Comodi
Energies 2025, 18(20), 5401; https://doi.org/10.3390/en18205401 - 14 Oct 2025
Viewed by 176
Abstract
High photovoltaic (PV) penetration challenges grid frequency stability due to reduced system inertia. Virtual Synchronous Generators (VSGs), particularly when paired with Battery Energy Storage Systems (BESSs), can mitigate this by emulating synchronous machine dynamics. This study focuses on improving frequency response during PV [...] Read more.
High photovoltaic (PV) penetration challenges grid frequency stability due to reduced system inertia. Virtual Synchronous Generators (VSGs), particularly when paired with Battery Energy Storage Systems (BESSs), can mitigate this by emulating synchronous machine dynamics. This study focuses on improving frequency response during PV power reductions through the adaptive tuning of an extensive set of VSG parameters. A double-phase Supervisory Controller is developed: in the first phase, Particle Swarm Optimization (PSO) computes multiple sets of optimal VSG parameters for various PV curtailment and load demand change scenarios; in the second phase, the system determines the most appropriate parameters based on current operating conditions to minimize frequency deviations, using the first phase as a foundation for adaptive decision making. The proposed Supervisory Controller reduced the Integral of the Absolute Error (IAE) of 151.55% in the case of a 65% irradiance drop. At 55%, the IAE decreased from 0.4605 to 0.2227, and at 25% from 0.0791 to 0.0546. In the low-disturbance scenario at a 25% drop, the IAE was maintained below 0.06. Supervisory Controller performance led to a reduced settling time and improved frequency recovery. These results demonstrate that the Supervisory Controller improves frequency regulation in both mild and severe irradiance reduction events. Full article
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20 pages, 9011 KB  
Article
The Effect of HiPIMS Pulse Conditions on the Microstructural, Mechanical, and Tribological Properties of TiB2 Coatings on Steel Substrates
by Daniel Kottfer, Karol Kyzioł, Mária Kaňuchová, Marta Kianicová, Michal Žitňan, Ewa Durda, Marianna Trebuňová, Dávid Medveď and Patrik Kľučiar
Materials 2025, 18(20), 4699; https://doi.org/10.3390/ma18204699 - 13 Oct 2025
Viewed by 432
Abstract
This study examines the impact of varying pulse conditions on the properties of titanium diboride (TiB2) coatings deposited by high-power impulse magnetron sputtering (HiPIMS). The coatings were prepared on steel substrates using an industrial-scale system. During the experiments, the HiPIMS frequency [...] Read more.
This study examines the impact of varying pulse conditions on the properties of titanium diboride (TiB2) coatings deposited by high-power impulse magnetron sputtering (HiPIMS). The coatings were prepared on steel substrates using an industrial-scale system. During the experiments, the HiPIMS frequency and pulse width were systematically varied to examine their influence on the coating’s microstructural, mechanical, and tribological properties. The obtained results show a correlation between process parameters and coating performance. A maximum hardness of 39.7 GPa and a coefficient of friction (CoF) as low as 0.68 were achieved. The best combination of mechanical properties was observed for coatings prepared in a frequency range of 600–1000 Hz and with a pulse width of 50 µs. Notably, the optimal tribological properties and surface roughness were obtained at 800 Hz and a 50 µs pulse width. This work demonstrates that fine-tuning HiPIMS pulse conditions is crucial for achieving high-quality TiB2 coatings with enhanced functional performance. Full article
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19 pages, 8882 KB  
Article
A Robust Design Strategy for Resonant Controllers Tuned Beyond the LCL-Filter Resonance Frequency
by Xin Zhao, Chuan Xie, Josep M. Guerrero and Xiaohua Wu
Electronics 2025, 14(20), 3991; https://doi.org/10.3390/electronics14203991 - 12 Oct 2025
Viewed by 205
Abstract
Compared to the L-filter, the LCL-filter provides superior high-frequency harmonic attenuation for a given inductance. However, it also introduces resonance issues that can compromise system stability. Consequently, the bandwidth of the inner current loop must be maintained well below the resonant frequency [...] Read more.
Compared to the L-filter, the LCL-filter provides superior high-frequency harmonic attenuation for a given inductance. However, it also introduces resonance issues that can compromise system stability. Consequently, the bandwidth of the inner current loop must be maintained well below the resonant frequency of the filter. This paper proposes a robust controller design strategy for LCL-filtered converters to extend the harmonic control range under wide variations in grid impedance. An analysis of the resonant controller phase-frequency characteristics reveals its capability to provide phase compensation up to 2π. Building on this finding, the damping ratio and phase leading angle are systematically optimized through a joint analysis of the phase characteristics introduced by the resonant controller and active damping, thereby enhancing system robustness. With these optimized parameters, the center frequency of the resonant controller can be tuned above the LCL-filter resonance frequency without inducing instability. In contrast to conventional methods, the proposed approach allows the LCL-filter to be designed with a lower resonance frequency. This enables improved attenuation of switching-frequency harmonics without compromising the tracking performance for higher-order harmonics. Such a capability is particularly beneficial in high-power and weak-grid scenarios, where the filter resonance frequency may fall to just a few hundred hertz. Experimental results validate the effectiveness of the proposed design strategy. Full article
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24 pages, 7481 KB  
Article
Loop Shaping-Based Attitude Controller Design and Flight Validation for a Fixed-Wing UAV
by Nai-Wen Zhang and Chao-Chung Peng
Drones 2025, 9(10), 697; https://doi.org/10.3390/drones9100697 - 11 Oct 2025
Viewed by 154
Abstract
This study presents a loop-shaping methodology for the attitude control of a fixed-wing unmanned aerial vehicle (UAV). The proposed controller design focuses on achieving desired frequency–domain characteristics—such as specified phase and gain margins—to ensure stability and robustness. Unlike many existing approaches that rely [...] Read more.
This study presents a loop-shaping methodology for the attitude control of a fixed-wing unmanned aerial vehicle (UAV). The proposed controller design focuses on achieving desired frequency–domain characteristics—such as specified phase and gain margins—to ensure stability and robustness. Unlike many existing approaches that rely on oversimplified plant models or involve mathematically intensive robust-control formulations, this work develops controllers directly from a high-fidelity six-degree-of-freedom UAV model that captures realistic aerodynamic and actuator dynamics. The loop-shaping procedure translates multi-objective requirements into a transparent, step-by-step workflow by progressively shaping the plant’s open-loop frequency response to match a target transfer function. This provides an intuitive, visual design process that reduces reliance on empirical PID tuning and makes the method accessible for both hobby-scale UAV applications and commercial platforms. The proposed loop-shaping procedure is demonstrated on the pitch inner rate loop of a fixed-wing UAV, with controllers discretized and validated in nonlinear simulations as well as real flight tests. Experimental results show that the method achieves the intended bandwidth and stability margins on the desired design target closely. Full article
(This article belongs to the Section Drone Design and Development)
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27 pages, 7418 KB  
Article
Walrus Optimization-Based Adaptive Virtual Inertia Control for Frequency Regulation in Islanded Microgrids
by Akeem Babatunde Akinwola and Abdulaziz Alkuhayli
Electronics 2025, 14(20), 3980; https://doi.org/10.3390/electronics14203980 - 11 Oct 2025
Viewed by 159
Abstract
Microgrids with high renewable energy penetration face critical challenges in frequency stability due to reduced system inertia and the presence of parameter uncertainties. This study introduces a novel adaptive virtual inertia control strategy utilizing a combination of the Walrus Optimization Algorithm (WaOA), a [...] Read more.
Microgrids with high renewable energy penetration face critical challenges in frequency stability due to reduced system inertia and the presence of parameter uncertainties. This study introduces a novel adaptive virtual inertia control strategy utilizing a combination of the Walrus Optimization Algorithm (WaOA), a recent metaheuristic optimization technique, and Proportional–Integral–Derivative (PID) controllers (WaOA-PID) to improve frequency regulation in islanded microgrids under diverse operating conditions. The proposed method is evaluated across three scenarios: medium inertia, low inertia, and parametric uncertainty. Comparative analyses with conventional, IMC-tuned PID and H∞ Vector Internal Controllers (VIC) reveal that the WaOA-PID controller achieves the lowest overshoot, undershoot, and rate of change of frequency (RoCoF), while maintaining acceptable settling times in all cases. At an estimated load deviation of 0.18, the demand is varied from 200 MW to 250 MW to evaluate the system’s performance. The proposed technique yields an Integral Time Absolute Error (ITAE) of 0.000576, with PID gains of Ki = 0.9994, Kd = 0.185, and Kp = 0.774. Compared to traditional methods, the proposed controller demonstrates high reliability and efficiency in maintaining load frequency control and enhancing power system management, validating its suitability for real-time renewable energy-integrated microgrid applications. Full article
(This article belongs to the Section Systems & Control Engineering)
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