Effect Of Sag Research Articles

Research on the Effects of Voltage Sags and Harmonics on the Output Characteristics of Switching Power Supply

Switching power supply is widely used in industrial equipment, household appliances, and other fields due to the advantages of high integration and lightweight. Voltage sags can seriously affect the output voltage of switching power supply and the working condition of its power supply equipment; at the same time, the working scenarios of power equipment using switching power supply often have different level of harmonic problems. Considering the continuous innovation of switching power supply technology, the previous analysis and test results on the effect of voltage sags and harmonics on switching power supplies may no longer be applicable. The paper reveals the mechanism of the effect of harmonic alone as well as voltage sag superimposed harmonics on the output voltage of the switching power supply. Then the test research program was developed, and four different brands switching power supplies were selected for the test research, with which the effects of different amplitude voltage sags, harmonics with different frequencies and distortion, as well as voltage sag superimposed harmonics on the output voltage of switching power supplies were investigated. The results show that the tolerance ability of switching power supplies to voltage sags has been improved compared with previous switching power supplies, and the harmonic itself has less effect on the output voltage of switching power supply, but the joint action of harmonics and voltage sags will have a greater effect on the output voltage of switching power supply. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

The Smoothened agonist SAG Modulates the Male and Female Peripheral Immune Systems Differently in an Immune Model of Central Nervous System Demyelination.

Both Hedgehog and androgen signaling pathways are known to promote myelin regeneration in the central nervous system. Remarkably, the combined administration of agonists of each pathway revealed their functional cooperation towards higher regeneration in demyelination models in males. Since multiple sclerosis, the most common demyelinating disease, predominates in women, and androgen effects were reported to diverge according to sex, it seemed essential to assess the existence of such cooperation in females. Here, we developed an intranasal formulation containing the Hedgehog signaling agonist SAG, either alone or in combination with testosterone. We show that SAG promotes myelin regeneration and presumably a pro-regenerative phenotype of microglia, thus mimicking the effects previously observed in males. However, unlike in males, the combined molecules failed to cooperate in the demyelinated females, as shown by the level of functional improvement observed. Consistent with this observation, SAG administered in the absence of testosterone amplified peripheral inflammation by presumably activating NK cells and thus counteracting a testosterone-induced reduction in Th17 cells when the molecules were combined. Altogether, the data uncover a sex-dependent effect of the Hedgehog signaling agonist SAG on the peripheral innate immune system that conditions its ability to cooperate or not with androgens in the context of demyelination.

Evaluating the Effect of Claytone-EM on the Performance of Oil-Based Drilling Fluids.

This study provides a detailed characterization and evaluation of Claytone-EM as a rheological additive to enhance the performance of oil-based drilling fluids (OBDFs) under high-pressure, high-temperature (HPHT) conditions. It also offers a comparative evaluation of the effectiveness of Claytone-EM with an existing organoclay, analyzing their mineral and chemical compositions, morphologies, and particle sizes. A series of experiments are performed to evaluate Claytone-EM's influence on crucial drilling mud properties, such as mud density, electrical stability, sagging tendency, rheology, viscoelastic properties, and filtration properties, to formulate a stable and high-performing OBDF. Results indicated that Claytone-EM had no significant impact on mud density but remarkably enhanced emulsion stability. Claytone-EM effectively mitigated sagging issues under both static and dynamic conditions, leading to improvements in the plastic viscosity (PV), yield point (YP), apparent viscosity (AV), and YP/PV ratio. The PV, YP, AV, and YP/PV ratios were improved by 11, 85, 28, and 66% increments, respectively, compared with those of the drilling fluid formulated with MC-TONE. The addition of Claytone-EM resulted in enhancing gel strength and improving the filtration properties of the drilling fluid. The filtration volume was reduced by 2% from 5.0 to 4.9 cm3, and the filter cake thickness had a 13% reduction from 2.60 to 2.26 mm. These findings highlight Claytone-EM as a valuable additive for enhancing OBDF performance, particularly under challenging HPHT conditions. Its ability to provide emulsion stability, reduce static and dynamic sag, and control filtration holds the potential to enhance drilling operations, minimize downtime, and bolster wellbore stability. This study acknowledges certain limitations, including its temperature range, which could benefit from exploration at extreme temperatures. Additionally, the absence of flow experiments limits a comprehensive understanding of sag effects, and further research and field-scale evaluations are recommended to validate and optimize the application of Claytone-EM in OBDFs.

Comparing Methods to Mitigate the Effect of Grid Voltage Sag and Frequency Variation on the Operation of Variable Speed Drives

In this paper, the effect of unsymmetrical grid voltage sag on the performance of a slip power recovery drive is studied, and two strategies to mitigate its effects are investigated. The first strategy consists of three phase parallel RL impedance connected to the rotor circuit. The second strategy consists of three phase LCL filter connected to the rotor circuit. A PI controller is tuned to test the drive at constant speed. Also, the effect of grid frequency drop on the drive performance is investigated with the same two protection strategies. The proposed systems are modeled with Matlab/Simulink and the simulation results are compared. The drive performance without any protection schemes are compared with its performance with the two proposed strategies. The compared results include the stator voltage and current, the rotor voltage and current, the DC link voltage and current, the electric torque, and the rotor speed.

Management strategy to mitigate voltage sags effects of a multi-motors system using ADALINE algorithm and cascade sliding mode control

Multi-motor systems (MMS) find widespread use in various industrial applications, including plastic, paper, textiles, and steel rolling mills, where synchronized speeds are crucial for optimal operation. However, a significant limitation of these systems is their susceptibility to voltage sags, resulting in speed and synchronization loss, along with peak currents and torques during voltage recovery. This paper presents a comprehensive multi-motors management strategy aimed at attenuating the adverse effects of voltage sags. The proposed technique is based on principles that involve recovering the system’s kinetic energy and leveraging the current reversibility of the converters. The control scheme comprises two main strategies: an adaptive linear neuron or later adaptive linear element (ADALINE)-based voltage sag detection algorithm utilizing least mean square (LMS) adaptation for rapid convergence using artificial neural networks, and a control scheme incorporating sliding mode speed controllers and indirect rotor field-oriented control (IRFOC). Additionally, a logic-based strategy for voltage sag attenuation completes the control framework. The effectiveness and efficiency of the proposed strategy are demonstrated through simulation results obtained using MATLAB/Simulink/SimPowerSystems.

ATP prediction of voltage sag effect on sensitive loads.

The objective of this paper is to analyze the behavior of adjustable speed drives (ASD) connected to the power system under symmetrical voltage sag conditions. An ATP model has been developed to simulate the response of a VSI inverter driving a three-phase induction motor. Speed and voltage control systems are included. The response of mechanical and electrical variables is obtained.

Modified instantaneous power theory control of dynamic voltage restorer powered by photovoltaic system

<span lang="EN-US">Power quality issues have become widespread due to nonlinear electronic converters and loads. Nonlinear components in the power system hamper the power quality, network efficiency and voltage regulation. The power quality issues like sag, swell, and voltage unbalance can be reduced by employing a dynamic voltage restorer (DVR). DVR provides the compensating power from a DC source to minimize the effect of sag, swell, and voltage unbalance. This article presents a power system with DVR using a photovoltaic system (PV) as a DC source instead of a conventional battery source. This article proposes a modified instantaneous power (PQ) control technique to generate the reference signal of load voltage to assure the DVR's superior performance. This modified technique uses an anti-aliasing filter to generate a reference signal. This proposed technique is tested under extreme power quality issues of 80% sag, 20% sag, 120% swell, 170% swell, and voltage unbalance. The DVR is modeled and simulated using MATLAB/Simulink. A comparison is made between the traditional and modified PQ methods from the obtained results. The analyzed results under severe power quality issues suggest that the proposed P-Q control technique is a preferable option for the DVR with PV as a DC power supply.</span>

Bayesian forces identification in cable networks with small bending stiffness

The regular monitoring of cable forces is essential for ensuring the safety of cable structures both during construction and throughout their lifetime. This paper aims at developing a vibration-based identification procedure of the axial forces, bending stiffness, and, secondarily, the crossing point position of cable networks. A model constituted by two crossing stays having small bending stiffness and negligible sag effects is considered. The in-plane direct dynamic problem is solved both numerically and through a perturbation approach. The obtained results are compared to the outcomes of a finite element model for verification purposes. The theoretical studies are also supported by experimental tests performed on a real cable-stayed bridge (Haccourt bridge), which provide insights into the dynamics of the system showing that models of cables with small bending stiffness are more appropriate than taut string models. The inverse analysis based on non-linear Bayesian regression is developed and the closed-form asymptotic formulations are used to prove that the bending stiffness, the cable forces, and the crossing point position can be separately identified from a set of observed frequencies. The implemented procedure is then applied to the tested bridge as a proof of concept, showing that the proposed in-plane identification strategy provides satisfactory results.

Sonic hedgehog signaling promotes angiogenesis of endothelial progenitor cells to improve pressure ulcers healing by PI3K/AKT/eNOS signaling.

Pressure ulcer is a severe disease in the paralyzed and aging populations. Endothelial progenitor cells (EPCs) are able to regulate ulcer healing by modulating angiogenesis, but the molecular mechanism is still obscure. Sonic hedgehog (SHH) signaling contributes to angiogenesis in various diseases and has been identified to modulate EPCs function. Here, we aimed to explore the significance of SHH signaling in EPCs function during pressure ulcers. The EPCs were isolated and characterized by the expression of DiI-acLDL and bind fluorescein iso-thiocyanate UEA-1. Cell proliferation was detected by cell counting kit 8 (CCK-8). The DiI-acLDL and bind fluorescein iso-thiocyanate UEA-1 were analyzed by immunofluorescent analysis. The angiogenesis of EPCs was analyzed by tube formation assay. The pressure ulcers rat model was constructed, the wound injury was analyzed by H&E staining and angiogenesis was analyzed by the accumulation of CD31 based on immunofluorescent analysis. The expression of patched-1 and Gli-1 was enhanced by SHH activator SAG but reduced by SHH inhibitor cyclopamine in the EPCsThe PI3K, Akt, eNOS expression and the Akt phosphorylation were induced by SAG, while the treatment of cyclopamine presented a reversed result. The proliferation and migration of EPCs were enhanced by SAG but repressed by cyclopamine or PI3K/AKT/eNOS signaling inhibitor Y294002, in which the co-treatment of Y294002 could reverse the effect of SAG. Thus, we found that SHH signaling activated angiogenesis properties of EPCs to improve pressure ulcers healing by PI3K/AKT/eNOS signaling. SHH signaling may serve as the potential target for attenuating pressure ulcers.

Experimental Investigations on effectiveness of viscous and viscous inertial dampers on reducing the multimodal vibrations of stay cables

The additional damping ratios provided by viscous dampers (VDs) and viscous inertial damper (VID), were tested in the laboratory to estimate the effectiveness of these dampers on mitigating the multimodal vibrations of stay cable. First, two plate eddy current dampers (PECDs), in which the damping coefficients can be conveniently adjusted, were specially designed and manufactured. The mechanical property of these PECDs was obtained by tests and numerical simulations. Second, the natural frequencies of a test stay cable were carefully determined by tests and numerical analysis, and the effect of cable sag was carefully analyzed. Third, a series of tests including 12 test cases were carried out to validate the effectiveness of a single VD, a single VID, and two VDs, in which PECD is a typical VD, an additional mass is attached on the test stay cable near the PECD and the output is similar to that of a VID. The amplitude and frequency of the vibration have little effect on the mechanical properties of PECD. The inherent damping ratios of the first 25 modes are in the range from 0.068% to 0.22%. It appears that low efficiency to simultaneously enhance the damping ratios of the first 25 modes can be found by adding a single VD and a single VID with the installation position of 4.75%l. However, two VDs installing on 2.75%l and 4.75%l has a significant improvement on the damping ratios of the 15th∼25th modes, and should be considered to a reasonable countermeasure to simultaneously reduce the low-order rain-wind induced vibrations and high-order vortex-induced vibration by raising the modal damping ratios.

The negative stiffness electromagnetic tuned inerter damper for damping enhancement of stay cables

Long stay cables may be subject to vortex-and rain-wind-induced vibrations. To suppress the two types of vibrations simultaneously, integrating the advantages of negative stiffness and inerter-based damper, a new negative stiffness electromagnetic tuned inerter damper (NSETID) is proposed in this study. The equivalent mechanical model of the NSETID is presented according to its working principle. On this basis, non-dimensional analytical equations of the cable with NSETID are developed. Subsequently, the optimum parameters of the NSETID are identified by optimizing the damping ratio of the tuned cable mode. The effects of the cable sag and flexural stiffness on the control performance and optimum parameters of the NSETID are also taken into consideration. In addition, the benefits and damping enhancement of the NSETID for mitigating single-mode and multi-mode cable vibrations are illustrated by comparing with tuned inerter damper (TID), negative stiffness damper (NSD), and negative stiffness inerter damper (NSID). Finally, the damping enhancement mechanism of the NSETID for cable multi-mode is explored through its stiffness and damping properties. The results highlight the superior damping enhancement capabilities of the NSETID in mitigating single-mode and multi-mode cable vibrations. The better control performance of the NSETID can be attributed not only to its negative stiffness behavior but also to the adaptability of its equivalent damping and negative stiffness coefficients to the cable mode order.

Sequence extraction-based low voltage ride-through control of grid-connected renewable energy systems

Various faults can cause voltage sag in the power grid at different voltage levels across the network. Balanced or unbalanced voltage sags lead to grid instability by tripping off a large number of wind or solar power plants from the electric power network. This is particularly problematic to maintain the stability of renewable energy-rich converter-dominated modern power systems. To mitigate the adverse effects of voltage sag, grid-connected converters (GCCs) need to be capable of operating in self-healing and fault-tolerant mode by embedding low voltage ride-through (LVRT) capability into the control system of GCCs. In order to facilitate the implementation of LVRT capabilities for unbalanced faults, fast and accurate frequency-adaptive sequence extraction of grid voltages and currents is essential. This motivated the present work of making a systematic comparison of adaptive observer-based sequence extraction techniques to provide LVRT capabilities into the control system of GCCs. In order to show the effectiveness of each observer, various comparative analyses were performed through Matlab-based numerical simulation. Different observers were benchmarked by the dynamic performance improvement during the low-voltage fault period. Experimental results using a laboratory-scale prototype GCC show that adaptive observers are a suitable choice of sequence extractors for LVRT operation of grid-connected converters in unbalanced and distorted grids. The results obtained in this work will contribute to enhancing the stability of modern power systems that are getting more and more converter-dominated.

Mitigation of Power Quality Problems Using Fuzzy Logic-Based Unified Power Quality Conditioner (UPQC)

This suggested research work provided a distributed generator-based unified power quality conditioner with a decreased rating and a star-connected transformer as a means of enhancing power quality. The unified power quality conditioner (UPQC), a Y-connected transformer, and an LC filter are all included in this work. When the source voltage is out of balance, the hybrids of the approach greatly enhance UPQC performance. The quality conditioner that is suggested here is intended to correct issues with the voltage and current quality of delicate loads and to reduce load current harmonics when the supply is distorted. In this case, the DC link control method has been implemented using a fuzzy logic-based controller. A 500 kVA grid model is taken into consideration, along with an analysis and description of the suggested solution. The results were produced using the power system block set toolboxes in the MATLAB/Simulink environment. According to the thorough simulation results, hybrid UPQC with distributed generation has a greater ability to reduce the voltage sag effects and swell and to suppress the load current harmonics, phase current harmonics, and neutral current when the supply is distorted. To validate the results generated by the proposed method, the hybrid methodology yields better results when compared to the traditional UPQC method.

Investigations of the Bump Foil Bearing With Thick Top Foil Based on Contact Mechanics

AbstractTraditional bump foil bearing, though widely used, is considered to have the problem of inadequate load capacity due to the effect of foil sag between adjacent bumps. In this paper, the thick top foil is applied to cope with the heavy load conditions, which has one order of magnitude larger top foil thickness than traditional top foil. Thick plate and curve shell models are developed to calculate the load-carrying performance of thick top foil bearing based on contact mechanics, and the sag ratio is introduced to describe the degree of foil sag and estimate the bearing load capacity. The impacts of top foil thickness on the stiffness of bearings in different sizes as well as on the adaptability to rotor tilt are discussed. The results indicate that the thick top foil (tt = 2 mm) bearing performs a nearly 100% enhanced load capacity at small gas film thickness whether rotor tilts or not. Thick top foil will increase the bearing stiffness of small size (d = 35 mm) and tends to have little influence on large-size bearing stiffness (d = 70 mm).

Hedgehog signal activates Ampk via Smoothened to promote autophagy and lipid degradation in hepatocytes.

Studies in the past decade have shown that lipid droplets stored in liver cells under starvation are encapsulated by autophagosomes and fused to lysosomes via the endocytic system. Autophagy responds to a variety of environmental factors inside and outside the cell, so it has a complex signal regulation network. To this end, we first explored the role of HH in autophagy and lipid metabolism. Treatment of normal mouse liver cells with SAG and GDC-0449 revealed elevated phosphorylation of AMPK and increased lipidation of LC3. SAG and GDC-0449 were agonist and antagonist of Smo in canonical Hedgehog pathway respectively, but they played a consistent role in the regulation of autophagy in hepatocytes. We further knocked down the Smo and found that the effects of SAG and GDC-0449 disappeared, indicating that the non-canonical Hedgehog-Smo pathway was involved in the regulation of autophagy in hepatocytes. In addition, SAG and GDC-0449 promoted lipid degradation and inhibited lipid production signals. Knockdown of Smo slowed down the rate of lipid degradation rather than Sufu or Gli1, indicating that Hh signaling regulated the lipid metabolism via Smo. In summary, Hedgehog activates Ampk via Smo to promote autophagy and lipid degradation.

A FBG pull-wire vertical displacement sensor for health monitoring of medium-small span bridges

With the increase of service life, a growing number of medium-small span bridges have suffered degradation and even serious damage, and the vertical displacement is one of the significant parameters for their safety condition and performance evaluation. In terms of medium-small span bridges, to solve the difficulty for long term vertical displacement measuring and the demand for low-cost monitoring, this paper proposes a fiber Bragg grating (FBG) pull-wire vertical displacement sensor, which owns advantages of low cost, high accuracy and convenient installation. Firstly, the calibration and temperature correction of the sensor were carried out. Secondly, the influences of the fixed angle and sag effect of the sensor on measuring results were investigated. Finally, the sensor was installed in an in-service hollow slab bridge and the static and dynamic load experiments were carried out. Results show that the linearity of the proposed sensor is 0.998, the sensitivity is 7.87 pm/mm, the hysteresis error is 1.54 %, the temperature correction coefficient is 18.08 pm/°C, the relative combined uncertainties are within 4 %; the fixed angle of this sensor is recommended to choose in the range of 15°-30° in order to obtain higher measuring accuracy; when θ = 15° and the radius of the external wire is 0.3 mm, the limit of the external wire length can be set to 19.5 m to avoid the influence of the wire sag effect on measuring results; the sensor is feasible in vertical displacement measurement of in-service medium-small span bridge, and the relative measuring errors in both static and dynamic load experiments are less than 5 %.

Optimization of the cable forces of completed cable-stayed bridges with differential evolution method

Long-span cable-stayed bridges have been massively erected worldwide in recent decades, and reasonable cable forces play an essential role in achieving the desired configurations of completed bridges. In the current research, a differential evolution (DE) algorithm is adopted to optimize the cable forces considering the counterweight. An asymmetrical cable-stayed bridge is taken as a case study, and the numerical model of the bridge is established with the OpenSees platform. The cable sag effect and geometric nonlinearity are considered in the numerical model. The weighted total bending energy of the girder and pylons is taken as the objective function of the optimization problem. In addition, the constraints of the cable forces, the range and magnitude of the counterweight, and the bearing reaction forces at the transition and auxiliary piers are considered. The numerical results reveal that the proposed framework is efficient and stable for optimizing the cable forces, and several optimum solutions can be obtained. In addition, the performance of the proposed optimum algorithm is less sensitive to the values of the initial parameters (feasible regions and population size). Moreover, the proposed algorithm automatically determines the control parameters (scaling factor and crossover rate) of the DE method, which makes it easy to use in practical engineering. In addition, the proposed algorithm can be used to optimize the cable forces in the final stage and the construction stages.

Requirements and limitations of the pulsed wire technique for measuring short-period long undulators’ magnetic field

The pulsed wire method is an attractive option to measure the magnetic field in insertion devices, mainly for those with restricted access (e.g., small gaps, in-vacuum/cryogenic environments, etc.). Besides first and second field integrals, experiments have proved the feasibility of reconstructing the magnetic field profile. Undulators with a small gap and short period are — and are planned to be — used at diffraction-limited storage rings and free-electron lasers. This contribution outlines the pulsed wire system’s requirements to perform magnetic field reconstruction in such undulators. We examine the main expected limitations, particularly the dispersive, finite pulse-width, discretization error, and sag effects. Furthermore, we present the current status of developing the pulsed wire system at the European XFEL.

Natural vibration characteristics of short-span submarine power cables with bending stiffness and sag

Based on a continuum model that governs the dynamics of submarine power cables, analytical solutions of the natural frequencies and modal shapes for free spanning cables are derived. The effects of sag, axial and bending stiffness are all included. The cable sag calculation has considered the effects of bending stiffness on the static profile. The accuracy of the derived solutions is validated by the results from a laboratory experiment. The applicable ranges of these solutions and that of Ricciardi (Ricciardi and Saitta, 2008) [15] are determined. Also, the effects of static profile, boundary conditions and non-dimensional parameters (ξ and λ2) on the cable natural frequencies and modal shapes are discussed. The results show that the static profile and boundary conditions have significant effects on the modal properties for free spanning submarine power cables. It must be noted that, for lower ξ values, the frequencies of the symmetric modes show a non-monotonic dependence on bending stiffness. The single-degree-of-freedom approach is adopted to further analyze the mechanisms of the non-monotonic behavior.

Experimental validation of the design formulas for vibration control of stay cables using external dampers

Transversely installing the dampers on the stay cable has been widely adopted to control its excessive vibration. However, the optimum damper size and its damping efficiency is subject to the effect of damper parameters, including the damper coefficient, damper inner stiffness and support stiffness, damper concentrated mass. Based on the attainable damping-ratio formulas of the stay cable–damper system proposed by authors, this study carries out a serials of experimental study on the cable-damper system to investigate the effect of the above-mentioned damper parameters and to consolidate the accuracy of the proposed damping-ratio equation. A scaled sagged stay cable has been built, and a small-size shear-mode viscoelastic damper has been developed. Results indicate that the larger damper stiffness and the lower support stiffness degrade the achievable damping ratio. Increasing the damper mass properly seems to improve the achievable damping ratio but still needs more full-scale test verification. The sag effect of the cable reduces considerably the attainable damping ratio for the first-order mode while affect marginally for the higher mode. Experimental results of the attainable damping-ratio considering the effect of the damper parameters commonly align with the theoretical values from the design formula. Therefore, the design formula is qualified to facilitate the design of the damper size.