Search Results (420)

Power conversion systems (PCSs) connect dc energy sources to the grid, but background grid-voltage disturbances can degrade grid-current quality. This paper presents a unified derivation and implementation-oriented assessment of proportional grid-voltage feedforward in the abc, αβ, and dq reference frames for an LCL-filtered three-level PCS. The derived disturbance transfer function retains the feedforward term, and attenuation is quantified at the fundamental and selected harmonics. Tests cover gain tuning and voltage harmonics, 10% voltage unbalance, 49–51 Hz operation, SCRs from 10 to 2, ±20% LCL-parameter variation, a 25–50 kW reference ramp, common-mode voltage, and a sixth-harmonic resonant benchmark. With Kff = 0.6, grid-current THD falls from 10.65% to 7.19% in the strong-grid harmonic test; the resonant benchmark reaches 7.05%. At SCR = 3, retuned resonant control gives 20.33% THD versus 11.68% for proportional feedforward, while transferring the strong-grid resonant gain gives 123.02%. The delay-inclusive loop model retains positive stability margins, whereas the switching-model results reveal that the benefit of a fixed feedforward gain is condition-dependent and may diminish or reverse under clean-grid, frequency-deviation, parameter-variation, and weak-grid conditions. Archived 100 kVA waveforms verify stable implementation in all three reference frames. The results clarify the operating conditions under which proportional feedforward is effective, together with its digital implementation requirements and limitations. Full article

Parallel converter operation enables flexible capacity expansion of energy-storage power conversion systems. However, parallel converter interactions, filter-inductor saturation, and grid-strength variations increase the risk of resonance instability. The measured current-inductance characteristic is incorporated into an operating-point-dependent closed-loop Norton model. The grid current of an individual converter is decomposed into self-reference, parallel converter coupling, and grid-voltage-disturbance responses. It reveals that converter-side inductance attenuation shifts the internal and parallel resonances to higher frequencies and increases resonance-instability risk, whereas converter number and grid impedance primarily reshape the parallel resonance. A coordinated active-damping method is then developed: PCC voltage feedforward weakens common-network interaction, and capacitor-voltage feedback increases local LCL-filter damping. Simulation and experimental results validate the feasibility and effectiveness of the proposed control method. Experiments with two parallel converters validated the proposed control method. Stable transient current responses were achieved during a simultaneous current-reference step from 50 to 120 A, while the grid-current THD and power-sharing deviation remained below 3% and 5%, respectively. Full article

Photovoltaic converters operate under varying climatic conditions and non-ideal grid regimes, but factor importance is often assessed either through isolated local metrics or through pooled operating data that hide regime shifts and interaction effects. This study develops a hierarchical framework for sensitivity analysis of operating profiles of grid-connected PV converters under climatic and grid uncertainty. A compact operating-profile formulation is introduced that relates solar radiation, cell and ambient temperature, grid voltage, load, and selected design/control parameters to active power, efficiency, power factor, harmonic distortion, DC bus ripple, clipping behavior, and thermal headroom. The proposed workflow combines local normalized sensitivities for fast ranking around nominal conditions, Morris screening for factor reduction, and Sobol/Saltelli variance-based indices for global prioritization under uncertainty. The framework is demonstrated on a 100 kW synthetic reduced-order benchmark representing a three-phase two-level grid-connected PV inverter with an LCL filter. To clarify the scope of validity, the reduced-order model is cross-checked against switching-level simulations for representative nominal, clipping-prone, high-temperature and grid-stress operating windows. The results show that factor importance is not universal, but depends on the selected KPI, operating regime and uncertainty scenario. In the considered benchmark, grid voltage, cell temperature and equivalent thermal resistance are the dominant total-effect contributors, while the strongest second-order contribution appears between grid voltage and filter inductance under grid-stress conditions. The proposed framework is therefore intended as a reproducible, regime-aware sensitivity workflow rather than as a universal ranking of PV converter parameters. Full article

Due to system interactions, the formation and maintenance of dual squall lines are more complex than for single squall lines. In this study, we use upper-air soundings, ERA5 reanalysis data, high-density surface automatic weather station observations, and Doppler radar data to analyze a dual squall-line system that occurred over North China on 13 June 2022 under the Northeast China Cold Vortex. We focus on the differences between the two squall lines in mesoscale environments, convective triggering mechanisms, and maintenance processes. The main results are as follows: (1) The dual squall-line event occurred in different sectors of the Northeast China Cold Vortex, with both lines exhibiting a “dry-cold aloft, warm-moist below” stratification. However, significant spatiotemporal differences in mesoscale thermodynamic and dynamic conditions across Hebei and Shandong provinces led to distinct evolutionary pathways between the two squall lines. (2) Squall Line 1 (SL1) was triggered by the superposition of cold-pool outflow from convective cells over the Bohai Bay and convergence lines associated with surface cyclonic circulations. Squall Line 2 (SL2) was triggered by the thermal instability in the overlapping region of the temperature and dew-point fronts on the eastern slope of the Taihang Mountains, in conjunction with topographic uplift driven by the easterly flow. (3) This case study shows that squall-line maintenance depends not only on environmental CAPE and vertical wind shear but may also be closely related to the coordinated interplay between local thermal conditions and low-level shear. SL1, situated in a high-CAPE, low-LCL warm-moist environment, experienced relatively weak low-level shear; however, the ratio of cold-pool propagation speed to low-level shear remained near the RKW optimum, favoring persistence. Additionally, cold-pool spreading on the southern flank triggered new convection that merged into the southern end of the squall line, enhancing the cold pool via evaporative cooling and further promoting longevity. By contrast, SL2 displayed a pronounced north–south disparity: the northern segment failed to satisfy RKW balance due to insufficient cold-pool propagation relative to shear, leading to rapid echo dissipation; the southern segment, featuring an overly strong cold pool and low-CAPE, high-LCL conditions, inhibited deep convection. As a result, SL2 gradually split due to the spatial mismatch of thermodynamic and dynamic conditions along its north–south extent. Full article

SLC25A4, solute carrier family 25 member 4, gene is a member of the mitochondrial carrier subfamily within the solute carrier protein family. Pathogenic variants in SLC25A4 are associated with a spectrum of mitochondrial disorders that exhibit variable inheritance patterns and clinical manifestations. Specifically, dominantly inherited variants are typically associated with progressive external ophthalmoplegia with mitochondrial DNA deletions, recessively inherited variants are linked to myopathy and cardiomyopathy, and de novo variants can result in early-onset fatal disease presentations. In this study, we aimed to identify and characterize the disease-causing mutation(s) in a nine-year-old female patient from a consanguineous Saudi family. The patient was asymptomatic until the age of 3 years, when she presented with cardiomyopathy and myopathy. Comprehensive genetic analysis inclusive of whole exome sequencing and segregation analysis using Sanger sequencing identified an SLC25A4 variant (NM_001151.4: exon 2: c.112-1G>C) as the most likely cause of the disease. To assess transcript-level effects, we performed RT-PCR on RNA extracted from the patient’s cultured lymphoblast cell lines (LCLs) and fibroblast cell lines (FCLs). RT-PCR analysis demonstrated that the variant causes aberrant splicing, resulting in a 6 bp in-frame deletion (p.Gln37_Val38del) in the ANT1 protein. Quantitative RT-PCR demonstrated reduced SLC25A4 transcript levels in both FCLs and LCLs. Quantitative PCR analysis of mitochondrial DNA demonstrated a trend toward increased mtDNA copy number in patient-derived FCLs compared with controls, suggesting a possible compensatory response to mitochondrial dysfunction. Furthermore, Seahorse assays revealed marked reductions in both oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) in patient-derived FCLs compared with controls. These findings expand the molecular and functional spectrum of SLC25A4-associated disease and may inform clinical practice, including genetic interventions such as preimplantation genetic diagnosis, premarital genetic screening, targeted genetic counseling, and cascade testing of at-risk family members. Full article

It is well known that genetic variants contribute to cellular sensitivity to chemotherapeutic agents and ionizing radiation (IR). The aim of this study was to identify single nucleotide polymorphisms (SNPs) and genes associated with the spectrum of normal cellular sensitivity of lymphoblastoid cell lines (LCLs) towards ionizing radiation and mitomycin C (MMC). In the first step, we determined the viability of LCLs established from male participants of the Berlin Aging Study II (BASE-II) aged ≥62 years following treatments with increasing doses of IR (n = 137 cell lines) or MMC (n = 140 cell lines) using the alamarBlue assay. Results from intra-experimental triplicates and three independent experiments for each cell line and treatment were used to calculate the area under the curves (AUCs) representing the specific sensitivity to IR and MMC of each LCL. The data from these experiments were subsequently used as outcomes in genome-wide association studies (GWASs). In addition, we calculated polygenic risk scores (PGS) from UK Biobank GWAS results for four cancer-related phenotypes and assessed the extent to which the variance in the IR and MMC sensitivity is explained by these PGS. The GWAS analyses revealed one variant, rs74728080, located in CDH13 on chromosome 16, to show genome-wide significant (p < 5 × 10⁻⁸, ß = 2.81) association with cellular viability after treatment with IR. In the GWAS on MMC sensitivity the most interesting signal was elicited by SNP rs113978558 in an intron of the PLD5 gene on chromosome 1 (p = 9.232 × 10⁻⁸; ß = 1.44). Several other SNPs with statistically suggestive (i.e., p < 1 × 10⁻⁵) evidence of association with IR or MMC sensitivity were identified. PGS calculations from GWAS of four cancer-related traits in UKB explained ~5% and ~3% of phenotypic variance in IR- and MMC-induced cell viability, respectively. The genome-wide significant association of rs74728080 with IR sensitivity and the location of this variant in CDH13 is interesting and functionally highly plausible given its known involvement in oxidative stress response and function as a tumor suppressor. Taken together, our novel data suggest that CDH13 may be genuinely involved in regulating cellular IR sensitivity. Full article

Grid-connected photovoltaic (PV) systems paired with battery storage are becoming a core element of low-carbon distribution networks. This paper develops a complete closed-form formulation together with an independent, simulation-based verification of a single-phase grid-connected PV-battery microgrid sized for high-irradiance residential conditions in Saudi Arabia, using measured solar-resource and tariff data for Riyadh. A 6.25 kW monocrystalline array feeds a 400 V DC link through a perturb-and-observe boost stage; a bidirectional converter couples a 13.5 kWh LiFePO₄ battery; and an IEEE 1547 smart inverter interfaces a 230 V grid through an LCL filter. Governing equations for every subsystem are derived and evaluated numerically, and a Python re-implementation of the phasor power-flow model verifies the analysis over a 24 h cycle run to periodic steady state, reproducing the reference design values with a mean absolute error of 0.5%. Using measured monthly solar-resource and temperature data for Riyadh, a full twelve-month analysis gives an annual self-sufficiency of 51.8% and a PV self-consumption of 72.9% for the optimised energy-management scheme. A dedicated time-domain switching simulation with FFT analysis shows that the LCL filter limits grid-current total harmonic distortion to 0.8%, far below the L-filter value of 6.2% and below the 5% current-distortion reference of IEEE 519 (full compliance additionally requires the PCC short-circuit ratio). Twelve-month, battery-size and load-sensitivity studies confirm robustness, and a techno-economic assessment based on the Saudi Electricity Company residential tariff quantifies levelized cost, payback and battery degradation, showing that economic viability hinges on tariff reform. Full article

LCL-type grid-connected inverters face problems including complex modeling, sampled current distortion from harmonics and negative-sequence components, and reduced control accuracy of conventional deadbeat predictive current control (DPCC) due to its heavy reliance on precise system parameters. To solve these issues, this paper proposes a model-free DPCC (MF-DPCC) using an adaptive-gain extended state observer (AGESO). Firstly, an ultra-local model is established to avoid dependence on accurate mathematical models. Secondly, an AGESO is designed to overcome conventional ESO drawbacks (initial differential peaking, inflexible bandwidth tuning, and tracking-noise immunity trade-off) by adopting adaptive gains to real-time estimate the ultra-local model’s lumped disturbance and state variables. Finally, a double second-order generalized integrator (DSOGI) purifies sampled currents and extracts fundamental positive-sequence components, reducing harmonic disturbance on the AGESO, allowing for higher bandwidth operation without excessive noise amplification, and indirectly enhancing resonance suppression by including LCL resonance-induced disturbance in the lumped term. Full article

The research utilizes Ansys Maxwell 2024 R2, a 3D Finite Element Analysis (FEA) software, to compare the electromagnetic coil parameters, losses, and efficiency of planar spiral circular, square, and round-cornered square (RCS) coils for wireless power transfer (WPT) systems in electric vehicle (EV) applications. This study focuses on key coil parameters such as self-inductance, mutual inductance, and the coupling coefficient, which are crucial for determining power transfer and system efficiency. While analytical calculations for these parameters are straightforward for air-core transformers, they become complex and inaccurate when ferrite cores are incorporated to improve efficiency. Ansys Maxwell overcomes this challenge by employing a numerical method. Simulation results indicate that RCS coils offer uniform magnetic field distribution and reduced losses, similar to circular coils. They also exhibit better coupling and good misalignment tolerance, akin to square coils. These characteristics suggest that RCS coils are a superior choice for WPT applications. Electro-thermal management (ETM) co-simulation of the RCS coil is performed and analyzed using Ansys Icepak 2024 R2. Furthermore, an Ansys Twin Builder 2024 R2 co-simulation of a double-sided LCL-compensated WPT system, incorporating the reduced-order model of the RCS coil, is performed. Under standardized EV conditions, say 85 kHz, 35 mm, and 50 Ω load, the RCS coil achieves an efficiency of 94.81%. The research also includes loss analysis and misalignment tolerance studies, confirming the superiority of RCS coils. Full article

This paper proposes a three-dimensional prescribed-time hierarchical cooperative guidance law (3-D PTHCGL) for rapid and reliable head-on encirclement in cooperative interception of high-speed targets under incomplete directed communication topology, target maneuvers, and limited terminal engagement time. The proposed method consists of a distributed estimator layer (DEL) and a local controller layer (LCL), addressing three key issues in head-on encirclement formation: information acquisition, rapid convergence, and geometric configuration. In the DEL, a distributed prescribed-time estimator (DPTE) is developed to enable followers without direct communication with the leader to estimate the leader’s states from neighborhood information within a prescribed time. In the LCL, a prescribed-time extended state observer (PTESO) and a three-dimensional prescribed-time cooperative guidance law (3-D PTCGL) are designed to estimate target-maneuver-induced disturbances and unknown states, and to guarantee prescribed-time convergence of estimation and cooperative tracking errors. Furthermore, virtual line-of-sight (LOS) angles are introduced based on a three-dimensional head-on interception kinematic model to characterize the head-on encirclement configuration, and range-to-go together with radial relative velocity are adopted instead of time-to-go to reduce sensitivity to time-estimation errors. Simulation results demonstrate the effectiveness and robustness of the proposed method in achieving prescribed-time head-on encirclement and simultaneous attack without a speed advantage. Full article

The main purpose of this study is to overcome the difficulty of maintaining high-quality zero-voltage switching (ZVS) in resonant converters over wide operating ranges. Conservative designs ensuring light-load ZVS inevitably generate excessive reactive current, causing severe circulating losses and body diode conduction under heavy loads. To resolve this intrinsic trade-off, this paper proposes an active closed-loop optimal ZVS control strategy utilizing a DC-biased variable resonant inductor. The core mechanism actively shifts the tank impedance to dynamically reshape the primary current. By integrating the primary current during each dead time, the real-time integrated charge is actively regulated to track an optimal reference limit defined by the switch parasitic capacitance and dc-bus voltage. Consequently, the variable inductor continuously regulates the tank current toward the optimal ZVS boundary, ensuring the parasitic capacitance is completely discharged just before the turn-on instant. Validations via simulation and a 192 W hardware prototype confirm the method’s efficacy. The strategy completely eliminates light-load hard switching and significantly suppresses heavy-load body diode conduction without compromising output voltage regulation. Compared to conventional active schemes, this approach achieves full-range optimal ZVS without requiring additional high-frequency switching devices, establishing a highly efficient shift from passive parameter design to active boundary tracking. Full article

Lateral column lengthening (LCL) calcaneal osteotomy is a well-established surgical procedure used in flexible flatfoot reconstructive surgery. The effects of LCL on subtalar joint (STJ) range of motion (ROM) have not been thoroughly explored in the literature. Our study aimed to objectively measure the average decrease in the total ROM of the STJ following LCL. A retrospective cohort study was conducted on 15 patients (20 feet) who underwent LCL for various indications. Data for STJ ROM was collected from both the preoperative and postoperative periods. Mean follow-up for the cohort was 12 weeks postoperatively. The mean total preoperative STJ ROM was 39.65 ± 2.52 degrees, while the mean total postoperative STJ ROM was 19.17 ± 2.62 degrees (p < 0.001). This represents a statistically significant reduction of 20.48 degrees (48% decrease) in STJ ROM from preoperative to postoperative measurements. This study provides the first objective measurement of the STJ ROM decrease following LCL calcaneal osteotomy on patients in vivo. The findings highlight the substantial impact of the procedure on the ROM in the STJ. These results have important implications for patient management and should be considered when evaluating the outcomes of LCL procedures. Further research is warranted to explore the functional consequences and long-term effects of the reduced STJ ROM and to develop strategies for optimizing foot function in patients undergoing this procedure. Full article

Conventional active disturbance rejection control (ADRC) schemes for grid-connected inverters (GCIs) suffer from performance degradation under grid frequency fluctuations and voltage distortions, primarily due to the limited bandwidth of conventional extended state observers (ESOs) and their reliance on fixed-frequency internal models. To address these issues, this paper proposes a second-order repetitive ADRC (SRC-ADRC) strategy for LCL-type single-phase GCIs. The proposed method integrates a second-order repetitive extended state observer (SRC-ESO) and a frequency-adaptive proportional-quasi resonant (FPQ) controller. By cascading an additional internal model into the repetitive control-based ESO, the SRC-ESO achieves higher internal model gain and wider resonant bandwidth, significantly improving periodic disturbance estimation accuracy under off-nominal grid frequencies. The FPQ controller ensures reference current tracking without phase error and amplitude attenuation, while the control law and observer are decoupled for independent parameter design. The robustness and frequency adaptability of the SRC-ADRC are verified through theoretical stability analysis and frequency-domain evaluation. Experiments on a 1.5 kW LCL-type single-phase GCI platform show that SRC-ADRC provides better frequency robustness, stronger harmonic mitigation, and improved current-tracking performance than the comparison methods. Full article

Voltage source converters (VSCs), together with their inner current and outer power/voltage control loops, are fundamental building blocks in the modern, converter-dominated power systems, particularly within high-voltage DC (HVDC) frameworks. Selecting effective control methods for VSCs is essential to ensure the stability, power quality, and dynamic performance of HVDC grids. This paper seeks to advance the current body of research by delivering an in-depth, consistent, unified framework and systematic examination of VSC control architectures within HVDC networks. It thoroughly explores various control strategies for VSCs interfacing with HVDC grids, such as grid-following and grid-forming strategies, with particular emphasis on both stationary ($\alpha \beta$) and synchronous (dq) reference frames. Moreover, the paper provides a comprehensive analysis of the theoretical underpinnings and decoupled control strategies, like the feedforward decoupling of the d- and q-axis currents in the dq frame and the inherently decoupled structure of the αβ frame. Additionally, advanced filtering techniques, including Moving Average Filter (MAF), Cascaded Delayed Signal Cancellation (DSC), and LCL filters, are analyzed. In addition, harmonic mitigation strategies, like parallel/multiple resonant (PR) terms in the αβ frame and cascaded notch filters in the dq frame, are presented. Furthermore, precise power control approaches and synchronization methods are discussed in detail. Also, this paper presents a detailed comparison of the performance characteristics of phase-locked loop (PLL) and frequency-locked loop (FLL) in response to grid frequency variations. Moreover, this paper proposes circuit representations and VSC models in both synchronous and stationary reference frames. The simulation results corroborate the theoretical insights discussed in the paper under various operational conditions, including initial responses, grid disturbances, three-phase-to-ground temporary fault scenarios, harmonic distortions, and load imbalances, in terms of overshoot, settling time, active- and reactive-power fluctuation reduction, voltage unbalance factor, total harmonic distortion, and post-fault convergence time, all evaluated in accordance with the limits defined in EN-50160. This comprehensive comparison of the presented control strategies facilitates researchers in identifying the most appropriate controller depending on their specific application requirements. Full article

Large-scale integration of renewable energy sources and power-electronic equipment introduces substantial background harmonics into the grid and, at the same time, gives rise to weak-grid operating conditions with a low short-circuit ratio, thereby degrading the power quality and stability of grid-connected converters. This paper investigates a three-phase LCL-type grid-connected converter and establishes a dq-domain admittance model that incorporates the DC-voltage outer loop, the phase-locked loop (PLL), and grid-voltage feedforward. On the basis of admittance-reshaping theory, a method is proposed to suppress the influence of background harmonics and enhance system stability. First, the frequency coupling caused by the structural asymmetry of the PLL and the voltage outer loop is decoupled to reduce the harmonic components in the grid current. Then, based on the decoupled model, the grid-voltage feedforward path is compensated to eliminate the negative-damping region in the converter output admittance and thus improve system stability under weak-grid conditions. Finally, simulation and experimental results verify the effectiveness of the proposed method. Full article