Wind Currents Research Articles

Numerical analysis of 40 MW HTS motor electromagnetic characteristics for ship electric propulsion

In recent years, with the development of ship electric propulsion system, High Temperature Superconducting (HTS) motors have gained attention as a promising potential resolution due to their high-power density and the progression of cryogenic refrigeration technology. We present an electromagnetic characteristics numerical analysis of 40 MW, 120 rpm, HTS synchronous motor which is a semi-superconducting motor: in fact, it has a superconducting rotor composed of YBCO material and a conventional stator. Combining electric resistivity variation of rotor copper shielding sleeve in low temperature environment and YBCO coil critical current, the electromagnetic behavior of the 40 MW HTS synchronous motor is analyzed with non-ferromagnetic stator support structure. To assess the effects of varying stator winding currents and thickness on eddy current losses of the copper shielding sleeve, calculations were done, and a preliminary discussion was initiated. This study has certain reference significance for electromagnetic design and optimization of multi-ten MW HTS motors, especially used in ship electric propulsion system.

INFLUENCE OF CONTROL CURRENT WAVEFORM ON ROTOR NUTATION OF THREE-DEGREES-OF-FREEDOM ELECTRIC MACHINE

The design of the electric machine with three degrees of freedom of the rotor with an external magnetic core, containing permanent magnets, and an internal magnetic core is considered. The both magnetic cores are rotating. The stator windings (control winding and two-phase rotation winding) are located in the air gap between the magnetic cores. The windings are powered by alternating current of corresponding phase. The positive property of rotor gyrostabilization in such structure is shown. At the same time, the negative fact consists in the nutation under the conditions of forced change in the orientation of rotation axis. There are no magnetic losses in the structure due to synchronous rotation of both external and internal magnetic cores. The immobility of the center of mass is assumed. There are no losses that give a non-conservative mechanical system. The mathematical model of the mechanic system and magnetic field is developed to compute the electromagnetic torques acting on the rotor. The expressions for electromagnetic torque components are obtained to use them in the Comsol Multiphysics interface. The effect of the sinusoidal and pulse currents in the control winding on the nutation swing is studied. The optimality of the control winding supplied by undisturbed sinusoidal current or the pulse current having square-wave length of about one-third of the period is revealed. References 15, figures 6, table 1.

VIRTUAL MODEL OF THE SYSTEM "INDUCTION MOTOR - SOFTSTARTER WITH TWO CONTROLLED PHASES"

One of the most commonly used start methods of induction motors is starting by gradually increasing the supply voltage. At the same time, softstarters based on thyristors or triacs are used, which are cheaper in comparison with frequency inverters based on IGBT - transistors. In turn, the disadvantage of this method of starting with significant reduction of the starting torque, so the possibility of using such starters for various executive mechanisms requires careful research. In the presence of a limitation of power source power, especially in wartime conditions, the problem of limitation of starting currents, especially in the case of using starters with two adjustable phases, is actual. To take into account the multiplicity of starting currents for different types of mechanisms, a mathematical model of the system " induction motor - softstarter with two controlled phases" was created. The model differs from the known ones by the possibility of limiting the power of the power supply network, the appearance of the mechanical characteristics of the executive mechanism and the starting moment at voltage ramp start mode. Transient processes in relative units for the possibility of estimating the multiplicity of starting currents to determine the required power of the autonomous power source are presented. To assess the adequacy of the mathematical model, a research stand with measuring of motor winding currents using a current transformer and a microprocessor device with an oscillography function was created. In the work, a comparative analysis of the results of modeling and experimental studies on a physical model is carried out, herewith the discrepancy of the results did not exceed 10%. It was determined that when using a soft-start device with two adjustable phases, even with small voltages, the current multiplicity is quite high and requires the use of a power source of greater power, but less than in the case of direct start. Formulated conclusions based on research results and recommendations for further reduction of starting currents.

An Adaptive Line-of-Sight (ALOS) Guidance Law for Path Following of Aircraft and Marine Craft

This brief presents a novel nonlinear adaptive line-of-sight (ALOS) guidance law for path following, compensating for drift forces due to wind, waves, and ocean currents. The ALOS guidance law is proven to have uniform semiglobal exponential stability (USGES) properties during straight-line path following at constant speed. The ALOS guidance law performs similar to the classical integral line-of-sight (ILOS) and adaptive ILOS guidance laws when the sideslip angle is nearly constant. The ALOS guidance law, however, has better tracking capabilities when compensating for rapidly varying sideslip caused by a time-varying disturbance. This is because the integral state of the ALOS guidance law is additive to the unknown sideslip angle (disturbance matching). In contrast, the ILOS guidance laws must compensate sideslip through a saturating arctangent function. The study also includes an input-to-state stable (ISS) reduced-order extended state observer for estimation of the line-of-sight (LOS) crab angle, known as the ELOS guidance law. The performance of the ALOS, ILOS, and ELOS guidance laws is compared by simulating rapid changes in the sideslip angle to stress the critical assumptions of the algorithms. Finally, a case study of the Remus 100 autonomous underwater vehicle (AUV) exposed to stochastic ocean currents is used to compare the performance of the ILOS, ALOS, and ELOS algorithms during normal operation.

Control of Cascaded/Brushless Doubly-Fed Induction Motors With Real-Time Torque Optimization

Brushless doubly-fed induction machines offer a potential alternative to regular doubly-fed induction generators for wind turbines, due to higher reliability and lower maintenance costs. As motors and generators, the brushless machines could also be part of new technological solutions for hybrid-electric propulsion, including aircraft propulsion. A main advantage is that most of the power would be transferred from generators to motors without electronic conversion. The paper proposes a new speed control algorithm that maximizes the available torque within the limits of the control winding currents and ensures anti-windup protection. The maximum torque and the control variables are obtained through simple analytical computations. The derivations of the paper are based on a complex-variable representation that simplifies the mathematical model and the control algorithm. Compact formulas specify the controller parameters as functions of the machine parameters and of the desired closed-loop behavior. The results are tested on a laboratory testbed using a cascaded doubly-fed induction motor and demonstrate fast responses reaching torque limits that are computed in real-time by the algorithm. While control is achieved through the converter interfaced with the control windings, the data shows that most of the active and reactive power is exchanged directly through the power windings. Similar results are obtained in simulations of a larger brushless doubly-fed induction motor.

Analysis of the effect of parametric uncertainty on dynamic performances of doubly fed induction generator-based wind energy conversion system

The wind, stochastic in nature, is one of the fastest-growing and most promising renewable energy resources in the entire world. Thus, this paper investigates the influence of parameter uncertainties upon a dynamic performance of a grid-tied Doubly-Fed Induction Generator (DFIG)-based Wind Energy Conversion System (WECS). The main uncertain parameters found in the study are mutual and rotor winding reactances which occurred due to the variation of the angular positions of the rotor caused by varying wind speeds. The variation in the wind speed caused the generator rotor speed to deviate between 25% and 150%. Consequently, the rotor winding reactance of DFIG changes from its nominal value of 1.31 mΩ to between 0.983 and −0.655 mΩ; and the mutual reactance from its nominal value of 0.941 Ω to between 0.758 and −0.4708 Ω. As a result, the stator and rotor winding voltages and currents of the DFIG are uncertain.

Online learning-based active disturbance rejection control of autonomous surface vehicles with HIL simulations

Modeling and control of autonomous surface vehicles (ASVs) is a challenging task due to the requirement of real-time adaptation to internal hydrodynamic parameter variations and external ocean disturbances induced by wind, waves, and ocean currents. In this paper, an online learning-based active disturbance rejection control method is proposed by combining real-time model learning and anti-disturbance control. Specifically, a filtering learning extended state observer (FLESO) is proposed for online identifying the unknown hydrodynamic parameters, the unknown control input gain, and estimating system uncertainties composed of the unknown external disturbances and dynamic modeling errors, with guaranteed convergence. Then, a self-learning anti-disturbance control law is developed based on the FLESO, enabling self-learning anti-disturbance speed tracking without prior knowledge of model parameters. A salient feature of the proposed method is that the unknown hydrodynamic parameters, the unknown control input gain, and the unknown system uncertainties can be estimated online simultaneously. Lyapunov stability analysis is employed to verify the stability of the closed-loop system. The effectiveness of the proposed online learning-based active disturbance rejection control method is demonstrated through HIL simulations.

Synergy scenario for renewable energy production, CO2 and H2 storage in the Baltic offshore structure

CO2 Capture, Transport, Use and Storage (CCUS) is one of the core technologies to mitigate climate change. New techno-economic and techno-ecological concept of a synergy of CO2 geological storage (CGS), CO2 use, hydrogen (H2) production from different eco-friendly renewable energy recovery technologies and underground H2 storage (UHS), which we call here Geological Power Bank (Geo-PB), in Cambrian Deimena Formation sandstones in different compartments of the E6 structure offshore Latvia is presented for the first time. A five-phase circular economy concept of E6 geological structure energy and CO2 storage hub was developed in this study. The workflow is techno-ecological, eco-friendly, self-supporting, cost-competitive, and economically feasible. It consists of (1) CO2 transport by ships to the rig, (2) CO2 injection for CGS and CO2 Plume Geothermal technology (CPG), (3) H2 production, (4) Geo-PB, and (5) H2 transport by the same ships to the customers. The concept is supporting a win8 situation - innovative elements of techno-ecological synergy in one site: (1) CGS, (2) CPG, (3) solar energy, (4) wind energy, (5) sea currents energy, (6) H2 production (7) Geo-PB and (8) H2 transport to consumers. The proposed cycle is closed, demonstrating the principles of circular economy, which will increase the total efficiency of the concept. CGS and CPG are planned in the E6-A compartment of the E6 geological structure with an average CO2 storage capacity of 365 Mt in an optimistic approach and Geo-PB is planned in E6-B with an H2 storage capacity of 119 kt.The Baltic offshore scenario is ambitious and innovative, proposed new technologies, synergy with renewable energy (geothermal, solar, wind and sea current), large storage capacity, including CO2 storage and use captured by a CCUS clusters of emission sources from energy production, cement industry and bio-emissions from Estonia, Latvia and Lithuania. The concept aimed to decrease the artificial impact of climate change by avoiding CO2 emissions to the atmosphere and implementing circular economy principles. It will increase public and policymakers’ acceptance of new underground CO2 and energy storage technologies. The proposed synergy solution for CGS and energy storage projects will make such a business economically feasible and attractive for investors. Our study demonstrates a new era, the next generation of cost-competitive, self-supporting conceptual techno-ecological examples of a possible synergy of storage concepts with renewable energies combined using circular economy approaches.

STRUCTURE AND ORIGIN OF THE BOTTOM RELIEF OF LAKE CHUKHLOMSKOE (KOSTROMA REGION)<a href="#FN1"><sup>1</sup></a>

The article discusses the first results of studying the structure of the bottom topography and bottom sediments of Chukhlomskoe Lake (Kostroma Region, Chukhlomsky District). We analyzed the lake bottom topography based on the results of our bathymetric survey and discovered two hollows with maximum depths diverging from the lake’s center towards the city of Chukhloma. The maximum depth inside the hollows (and for the entire lake) reaches 5.4 m, and the average lake depth is 2.2 m. There are two steps seen in the bottom topography; 2.0–2.4 m and 1.5–1.8 m. The bottom sediment structure of Chukhlomskoe Lake was revealed by drilling from the ice with two boreholes (with lengths of 9.45 and 7.45 m, located in the area of background depths and inside the hollow, respectively). Five radiocarbon AMS dates were obtained for the core from the hollow’s bottom. The sedimentary sequences of the pre-Holocene part of both cores show high similarity in structure and depths of the marker horizons identified by a set of lithological analyses. The structure and thickness of Holocene sediments differ significantly. In the area of background depths, the Holocene organo-mineralogenic silt is 3.8 m, and inside the hollow, the thickness of this layer is only 1.45 m. Moreover, hiatuses in sedimentation were documented in the structure of the Holocene sediment inside the hollow. The age of hiatuses, based on the sedimentary model, was estimated as 10.6–5.3 and 4.9–0.06 thousand years ago. A probable mechanism for the origin of hollows is localized erosion caused by wind currents in a highly shallow lake. An additional erosion factor can be the degassing of bottom sediments, which leads to the loosening of the bottom layer of sediments, which makes them susceptible to erosion. The cutoff of sediment erosion inside the hollow coincided in time with the construction of a dam on the Veksa River and a rise in the lake level by 1.0–1.5 m in the 1960s.

Acoustical effects of extreme weather events

The transfer of water from evaporating regions to precipitating regions drives the global water cycle, and understanding its dynamics is essential in determining how weather patterns will respond to changes in global climate. An intensification of the global water cycle has been reported using 50-year sea surface salinity data (Durack and Wijffels, 2010, J. Climate) with the consequence of more frequent extreme weather events. However, data under extreme weather conditions over the ocean are rare and a lot of physics remains to be investigated. As part of the Ocean Climate Stations that NOAA is maintaining, the 1-year data presented here are from Ocean Station Papa (50°N, 145°W), including measurements of wind speed, rain rate, currents, wave height and direction, bubble plume spatial structure and dynamics, and ambient noise for wind speeds up to 25 m/s. This full suite of data enables the study of the statistical properties of bubble plumes, their relation to meteorological parameters, and how to take them into account in ambient noise prediction, especially under severe weather conditions. Knowledge gained through this unique dataset can be critical for understanding air–sea interaction, validating satellite rain products, and predicting the ambient noise field under extreme weather conditions.

Sediment exchange between southern yellow sea and Yangtze river Estuary in response to storm events

The pattern of sediment exchange between the Yangtze River Estuary and the southern Yellow Sea constitutes a crucial yet contentious line of scientific inquiry. This conundrum hampers our comprehensive understanding to predict the future morphological evolution of the radial sand ridges and Jiangsu tidal flats. This study investigates various processes, including tides, wind and waves, to identify the dominant factor controlling sediment exchange between the southern Yellow Sea and the Yangtze River Estuary under storm conditions, using a validated numerical model. Our results show that tide is the dominant force controlling hydrodynamics and sediment transport between the two systems. Tidally induced residual currents and sediment fluxes exhibit a consistent northwesterly trajectory, from the Yangtze River Estuary to the southern Yellow Sea. Conversely, the contributions of wind and wave-induced currents under normal wind conditions (Beaufort Scale 3, 3.4 m s−1) adjust net sediment flux by less than 10 and 46–68%, respectively. In particular, the influence of wind and waves on sediment transport varies significantly with wind direction. While southerly or southeasterly winds amplify the tide-induced northwestward sediment transport, northerly or northeasterly winds curtail it. Under strong winter storm conditions, however, the perturbation caused by northerly winds and waves supersedes the influence of tides in controlling sediment transport, leading to a net residual current and sediment flux oriented southeastwards.

Nanomaterials in sunscreens: Potential human and ecological health implications.

Inorganic nanomaterials such as TiO2 and ZnO provide significant benefits in terms of UV protection, and their use generally has increased in commercial sunscreens. However, more recently there have been concerns about their potential human and ecological health implications, mostly driven by perception rather than by formal assessments. The large and increasing body of literature on these nanomaterials indicates that in most circumstances their risk are minimal. Penetration of the human epidermis is minimal for these nanomaterials, significantly reducing the potential effects that these nanomaterials may pose to internal organs. The excess Zn ion dose is very small compared to normal dietary consumption of Zn, which is a necessary element. The levels of residual nanomaterials or released ions in public swimming pools is also low, with minimal effect in case this water is ingested during swimming or bathing. In natural environments with significant water flow due to wind and water currents, the concentrations of nanomaterials and released ions are generally well below levels that would cause effects in aquatic organisms. However, sensitive habitats with slow currents, such as coral reefs, may accumulate these nanomaterials. The number of studies of the levels and effects of nanomaterials in these sensitive habitats is very small; more research is needed to determine if there is an elevated risk to these ecosystems from the use of sunscreens with these nanomaterials.

ISLA DE CALOR Y SU INTENSIFICACIÓN EN LA VIVIENDA PERIFÉRICA DE MÉRIDA HEAT ISLAND AND ITS INTENSIFICATION IN THE PERIPHERAL HOUSING OF MÉRIDA

Extreme temperatures and heat waves trigger considerable problems to the population and the environment, making the inhabitants of urban areas the most vulnerable to this situation. The impacts generated are identified from a general increase in the demand for water and energy, health problems and greater air pollution. In this sense, the influence that cities have on their own climate has long been recognized, which is typically hotter than its nonurban surroundings, this phenomenon is called Urban Heat Island (ICU), and its main causes are due to the urbanization process. One of the mitigation measures is the increase in intraurban vegetation areas; You are filtering the wind currents, decrease the air temperature through evapotranspiration and intercept solar radiation before being absorbed by the waterproof materials of the city. This work explores the intensification of the UHI in the city of Mérida, Yucatán. Its objective is to determine the thermal behavior of the housing areas on the periphery of the city and conurbation. On the one hand, the results obtained show the convenience of the methods used to characterize the problem, on the other, they reveal that the housing sectors located on the periphery have temperature patterns that range between 47 and 55 degrees Celsius. The above reflects the need to establish land use policies and housing development, contributing to the process of adaptation to climate change.

Judgment Basis and Mechanical Analysis of Current Collector Failure in the Winding Process of a Lithium-Ion Battery

The winding process is one of the essential processes in the manufacturing of lithium-ion batteries (LIBs). Current collector failure frequently occurs in the winding process, which severely increases the production cost and reduces production efficiency. In order to solve this problem, we first analyze the relationship between different process parameters and the failure of the current collector, and put forward the standard to determine the failure of the current collector. Moreover, we conducted tensile experiments to validate the differences in the mechanical performance of the current collector under different thicknesses. Finally, the circumferential stress and strain of the current collector winding were calculated using finite element analysis. The accuracy of the proposed criterion for determining current collector failure was verified through experimental measurements of stress and strain. The results demonstrate that the criterion proposed in this study can accurately calculate the maximum stress during the current collector winding process, providing a powerful tool for addressing the issue of current collector failure in the winding process.

Coordinated Control for Seamless Integration of Wind Energy Conversion System With Small Hydrogenerator Through Modified Notch Filters

This paper deals with the seamless integration of doubly fed induction generator (DFIG) based wind energy conversion system (WECS) with local grid constituted by a permanent magnet based small hydrogenerator (PMHG). The seamless integration is carried out using a solid state static transfer switch (SSSTS). The WECS-PMHG system is operated using a coordinated control strategy based on modified notch filters. The modified notch filters are adopted for the computation of (a) sensorless speed and position of the DFIG rotor, (b) fundamental constituents of unbalanced/nonlinear load current and (c) filtered DFIG stator voltages and phase angle. Moreover, the notch filters are also used for mitigating the effects of unbalance/nonlinearity in load currents on the stator and rotor currents of DFIG as well as PMHG currents. Additionally, the control methodology ensures no power interaction between the WECS and the PMHG during the synchronization process. This enables transient-free WECS and PMHG currents. Further, the coordinated control regulates the amplitude and frequency of system voltages even amidst wide variations in wind speed and load. The DFIG stator and wind currents are injected at unity power factor with the system voltages, while the excitation requirement of the DFIG is met by its machine side converter. The validness of the control is demonstrated experimentally through a developed laboratory-scale test bench.

Novel Harmonic Current Controller for DC-Biased Vernier Reluctance Machines Based on Virtual Winding

Direct current-biased vernier reluctance machine (DC-biased VRM) adopts a doubly salient structure and sinusoidal phase currents. It has better performance than switched reluctance machines and variable flux reluctance machines. The back electromotive force (EMF) waveforms of DC-biased VRMs contain low-order harmonics. It leads to harmonic currents in phase windings. The current harmonics increase the losses and worsen controller performance. The suppression of current harmonics has become a hot research topic in literatures. However, the existing harmonic suppression methods have their inherent defects. In this paper, a novel harmonic current controller based on virtual winding is proposed. Harmonic currents are decoupled and transformed into different harmonic planes, and independent closed-loop control is realized. The characteristics of harmonic planes and the relationship between them are analyzed. According to the analysis, the method of choosing valid planes and harmonic distribution is introduced. The major advantage of the proposed method is that, harmonic current sampling and control can be realized without the use of filters, and it avoids complicated design of controller parameters. Experimental results based on a DC-biased VRM are presented. It verifies that the proposed current control strategy based on virtual winding shows excellent harmonic control performance.

The sensory effects of light on the electric organ discharge rate of Gymnotus omarorum.

Gymnotiformes are nocturnal fishes inhabiting the root mats of floating plants. They use their electric organ discharge (EOD) to explore the environment and to communicate. Here, we show and describe tonic and phasic sensory-electromotor responses to light distinct from indirect effects depending on the light-induced endogenous circadian rhythm. In the dark, principally during the night, inter-EOD interval histograms are bimodal: the main peak corresponds to the basal rate and a secondary peak corresponds to high-frequency bouts. Light causes a twofold tonic but opposing effect on the EOD histogram: (i) decreasing the main mode and (ii) blocking the high-frequency bouts and consequently increasing the main peak at the expense of removal of the secondary one. Additionally, light evokes phasic responses whose amplitude increases with intensity but whose slow time course and poor adaptation differentiate from the so-called novelty responses evoked by abrupt changes in sensory stimuli of other modalities. We confirmed that Gymnotus omarorum tends to escape from light, suggesting that these phasic responses are probably part of a global 'light-avoidance response'. We interpret the data within an ecological context. Fish rest under the shade of aquatic plants during the day and light spots due to the sun's relative movement alert the fish to hide in shady zones to avoid macroptic predators and facilitate tracking the movement of floating plant islands by wind and/or water currents.

Multi-stage Drive of Switched Reluctance Motor Based on Ring Winding Structure

A new ring winding structure can drive switched reluctance motors (SRMs). It uses a full-bridge power converter circuit to drive SRMs and is significant for developing SRMs. For this structure, this paper proposes an optimization strategy. A voltage regulator is used to boost the winding current during the motor starting phase to ensure the average starting and low-speed operation of the motor. After the motor speed reaches a specific value, the passive device replaces the voltage regulator, which ensures the stable operation of the SRM while reducing the frequency of the voltage regulator and improving the service life of the regulator. This paper simulates the optimization strategy of the ring winding structure and derives the calculation method for switching speed.

The cycle of seagrass life: From flowers to new meadows.

Understanding sexual reproduction and recruitment in seagrasses is crucial to their conservation and restoration. Flowering, seed production, seed recruitment, and seedling establishment data for the seagrass Posidonia australis was collected annually between 2013 and 2018 in meadows at six locations around Rottnest Island, Western Australia. Variable annual rates of flowering and seed production were observed among meadows between northern and southern sides of the island and among years. Meadows on the northern shore consistently flowered more intensely and produced more seeds across the years of the survey. Inter-site variation in clonal diversity and size of clones, seed production, wind and surface currents during pollen and seed release, and the large, but variable, impact of seed predation are likely the principal drivers of successful recruitment into established meadows and in colonizing unvegetated sands. The prolific but variable annual reproductive investment increases the probability of low levels of continuous recruitment from seed in this seagrass, despite high rates of abiotic and biotic disturbance at seedling, shoot, and patch scales. This strategy also imparts a level of ecological resilience to this long-lived and persistent species.

TWO- DEGREE-OF-FREEDOM ELECTRIC MACHINE AND ITS OPERATION MODES

This paper is devoted to the problems of developing an electric machine with two-degrees-of-freedom (2-DOF) of rotor movement and its control system. The structure of the machine with the possibility of rotation of the rotor along two angular coordinates in a limited range of rotation angles is considered. The machine is designed to control the position of the axis of the optical beam along the line and frame trajectories. Based on the electrodynamic state model of the 2-DOF electric machine, a block diagram of the servo system was developed to control the trajectory of the rotor in two coordinates. Relationships between the time constant of the angle controller and the time constants of the high-frequency part of the amplitude-frequency characteristic of an open-loop system are determined. The dependences of the effective values of the currents in the control windings on the frequency of the frames and the duration of the linear part of the triangular signal are obtained. The dependences of the modules of relative accuracy of the rotor movement along a given trajectories on the system tunings are obtained. Ref. 12, fig. 8. Key words: two-degree-of-freedom electric machine, control system, scanning device, line trajectory, frame trajectory.