Wind Structure Research Articles

Design and analysis of consequent pole permanent magnet synchronous motor with low torque ripple

AbstractPermanent magnet (PM) motor with consequent pole (CP) rotor can improve the PM utilisation ratio. However, one group of PMs with the same polarity is replaced by iron core, which deteriorates the electromagnetic performances of the motor, including asymmetric air‐gap magnetic field and larger torque ripple. To solve this problem, this study analyses the relationship between the torque ripple and the stator‐rotor magnetomotive force (MMF) harmonics, determines the harmonic orders causing the torque ripple of the CP PM (CPPM) motor, and proposes an unequal‐turn four‐layer winding structure which can eliminate the determining harmonics in the stator MMF. Furthermore, the electromagnetic performances of the CPPM motors with the proposed winding structure and traditional CPPM motors are investigated by the finite‐element analysis. It is verified that the CPPM motor with the proposed structure has better motor performances.

The sound of a Martian dust devil

Dust devils (convective vortices loaded with dust) are common at the surface of Mars, particularly at Jezero crater, the landing site of the Perseverance rover. They are indicators of atmospheric turbulence and are an important lifting mechanism for the Martian dust cycle. Improving our understanding of dust lifting and atmospheric transport is key for accurate simulation of the dust cycle and for the prediction of dust storms, in addition to being important for future space exploration as grain impacts are implicated in the degradation of hardware on the surface of Mars. Here we describe the sound of a Martian dust devil as recorded by the SuperCam instrument on the Perseverance rover. The dust devil encounter was also simultaneously imaged by the Perseverance rover’s Navigation Camera and observed by several sensors in the Mars Environmental Dynamics Analyzer instrument. Combining these unique multi-sensorial data with modelling, we show that the dust devil was around 25 m large, at least 118 m tall, and passed directly over the rover travelling at approximately 5 m s−1. Acoustic signals of grain impacts recorded during the vortex encounter provide quantitative information about the number density of particles in the vortex. The sound of a Martian dust devil was inaccessible until SuperCam microphone recordings. This chance dust devil encounter demonstrates the potential of acoustic data for resolving the rapid wind structure of the Martian atmosphere and for directly quantifying wind-blown grain fluxes on Mars.

Numerical Investigations on Natural Ventilation in Atria of China's Southern Yangtze Vernacular Dwellings

The Southern Yangtze Dwellings in South China, have cultivated unique spatial typologies that utilize atrium for natural ventilation in the long-term adaptation to the complex climate of hot summer and cold winter (HSCW), which is of great value to be identified and verified. Therefore, this study presents numerical investigation of natural ventilation in atria of Southern Yangtze Dwellings using a validated Computational Fluid Dynamic (CFD) model. The Reynolds Averaged Navier-Stokes (RANS) modeling approach with the RNG k-ε turbulence model is used for the numerical simulation performed in OpenFOAM. Three architecturally typical forms, namely, the semi-encircled atrium, the centralized atrium and the symmetric atrium are generated by means of drone photography, online modeling and statistical data analysis. A series of CFD simulations as well as horizontal comparison and diachronic analysis of these geometric models are conducted to determine the ventilation mechanism, wind structure and thermal environment in and around the buildings. The findings of the current research give quantitative evidence of the effectiveness of the natural ventilation strategies of atrium under circadian and seasonal situations, and moreover contribute to a comprehensive knowledge for designing modern climate responsive buildings with optimum ventilation function.

Three-dimensional Simulations of Magnetospheric Accretion in a T Tauri Star: Accretion and Wind Structures Just Around the Star

We perform three-dimensional (3D) magnetohydrodynamic simulations of magnetospheric accretion in a T Tauri star to study the accretion and wind structures in the close vicinity of the star. The gas accreting onto the star consists of the gas from the magnetospheric boundary and the failed disk winds. The accreting gas is commonly found as a multi-column accretion, which is consistent with observations. A significant fraction of the angular momentum of the accreting flows is removed by the magnetic fields of conical disk winds and turbulent failed winds inside and near the magnetosphere. As a result, the accretion torque is significantly reduced compared to the simple estimation based on the mass accretion rate. The stellar spin affects the time variability of the conical disk wind by changing the stability condition of the magnetospheric boundary. However, the time-averaged magnetospheric radius only weakly depends on the stellar spin, which is unlike the prediction of classical theories that the stellar spin controls the magnetospheric radius through the magnetic torque. The ratio of the toroidal to the poloidal field strengths at the magnetospheric boundary, which is a key parameter for the magnetic torque, is also insensitive to the spin; it is rather determined by the disk dynamics. Considering newly found 3D effects, we obtain a scaling relation of the magnetospheric radius very similar to the Ghosh & Lamb relation from the steady angular momentum transport equation.

Site- and building height-dependent design extreme wind speed vertical profile of tropical cyclone

Tropical cyclone (TC) wind is one of the dominant loadings in the design of building structures. The radial distance-dependent vertical profile and prominent jet structure or super gradient of TC winds make the conventional terrain-dependent design profile inadequate for describing TC wind loadings along the height. Herein, a stochastic simulation-based algorithm is developed to determine the design extreme wind speed vertical profile of TC using a quasi-3D TC wind field model. The wind field model is first described and validated by comparing the vertical wind speed profiles with the upper-level dropsonde data and lower-level tower observation results. The evolution of the wind profile during the passage of historical real storms is reproduced by introducing optimal fitting results for the wind field parameters. Ten-thousand-year synthetic tracks are simulated to obtain the design extreme wind speeds for several coastal cities. The design extreme wind speed composite profile and structure height-dependent outer envelope profile (OEP) are proposed, which are applicable to a certain height of interest and buildings with different heights, respectively. These profiles also depend on terrain exposure, return period, and location of the site of interest. The code-suggested profiles are confirmed to underestimate the TC-induced wind loadings along the height, especially at sites with lower roughness lengths. The power law profile is still applicable, but larger power coefficients should be utilized, and the design extreme wind speed at 10m should be increased with an increase in the structure height. This study provides a forward step towards the rational estimation of TC-induced wind loadings for high-rise structures. • The radial distance-dependent vertical profile and prominent jet structure of tropical cyclone winds are reproduced. • The design extreme wind speed composite profile and structure height-dependent outer envelope profile (OEP) for tropical cyclone are proposed. • The inadequacy of current code-suggested wind speed vertical profiles to tropical cyclone winds is discussed. • The design extreme wind speed vertical profiles of tropical cyclone in several coastal cities are developed.

Design and Implementation of an 18-kW 500-kHz 98.8% Efficiency High-Density Battery Charger With Partial Power Processing

The demand for high-density, high-efficiency bidirectional battery chargers is driven by the fast development of energy storage system in renewable energy system, microgrid, and transportation electrification. Isolated dc–dc converter that interfaces a battery with a variable voltage range is one of the critical components. Input-parallel output-series (IPOS) partial power (PP) converter is considered a promising high-efficiency, high-density solution because only a fraction of power is processed via multistage converters to regulate the output voltage. However, due to the tight coupling between two dc transformers (DCXs), the design of PP converter is complicated. To solve this issue, an overall design procedure for a bidirectional soft-switching resonant-type PP converter is proposed. In the parameters design part, a decoupled design method is proposed to simplify the DCXs design. With this method, two DCXs can be designed separately, and a typical optimization method can be easily applied. As for the hardware design part, to minimize the ac loop inductance and resistance, a two-direction (2-D) flux cancellation method and an “intraleaving” winding structure are proposed for circuit layout and high-frequency (HF) transformer to obtain high operation efficiency and power density. Finally, the whole design procedure is verified by an 18-kW-rated, 25-kW peak, prototype operating at 500 kHz. The realized PP converter features a peak efficiency of 98. 8% and a power density of 142 W/in3. This article is accompanied by two videos demonstrating the dynamic voltage regulation test and the efficiency measurement.

Inferring Maps of the Sun’s Far-side Unsigned Magnetic Flux from Far-side Helioseismic Images Using Machine Learning Techniques

Accurate modeling of the Sun’s coronal magnetic field and solar wind structures requires inputs of the solar global magnetic field, including both the near and far sides, but the Sun’s far-side magnetic field cannot be directly observed. However, the Sun’s far-side active regions are routinely monitored by helioseismic imaging methods, which only require continuous near-side observations. It is therefore both feasible and useful to estimate the far-side magnetic-flux maps using the far-side helioseismic images despite their relatively low spatial resolution and large uncertainties. In this work, we train two machine-learning models to achieve this goal. The first machine-learning training pairs simultaneous Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager-observed magnetic-flux maps and SDO/Atmospheric Imaging Assembly-observed extreme ultraviolet (EUV) 304 Å images, and the resulting model can convert 304 Å images into magnetic-flux maps. This model is then applied to the STEREO-observed far-side 304 Å images, available for about 4.3 yr, for the far-side magnetic-flux maps. These EUV-converted magnetic-flux maps are then paired with simultaneous far-side helioseismic images for a second machine-learning training, and the resulting model can convert far-side helioseismic images into magnetic-flux maps. These helioseismically derived far-side magnetic-flux maps, despite their limitations in spatial resolution and accuracy, can be routinely available on a daily basis, providing useful magnetic information on the Sun’s far side using only the near-side observations.

CME-related Large Decreases in the Differential Phase Delay of Tianwen-1 DOR Signals

Differential phase delay is calculated for the differential one-way range (DOR) signals transmitted by Tianwen-1, the first Chinese Mars spacecraft that entered into the Mars orbit on 2021 February 10. Large decreases in the differential phase delay are identified in the DOR signals received by ground stations on 2021 March 23 and June 18. The decreases indicate sizable increases of the total electron content (TEC) along the DOR signal path between Tianwen-1 and the ground stations. The TEC increases are estimated to be 85 and 175 TEC units on 2021 March 23 and June 18, respectively. Evidence shows that they are caused by the sheath regions ahead of the coronal mass ejections (CMEs) that traversed the signal path on both days. The results represent the first observations of CME-related structures by the DOR signals and demonstrate the potential of DOR signals in remote sensing the interplanetary plasma structures in the solar wind.

Wire gauge analysis of planar spiral coil and its optimization technique in Wireless Power Transfer system

Planar spiral coil made of solid wire is widely used in wireless power transfer without magnetic core in high frequency operation system. Based on the magnetic field distribution of planar spiral coil and high frequency eddy current loss mechanism, the influence of magnetic field strength, frequency, and wire gauge on the AC resistance of winding are analysed. It reveals that the coil loss can be reduced by designing the wire gauge. Then the magnetic field strength and the winding loss calculation model are built, based on which the double wire gauge for segmental winding structure is proposed. This method can reduce the AC resistance and improve the quality factor on the premise of keeping inductance constant at high frequency. Through simulation and experiment, the AC resistance of coil based on the double wire gauge scheme can be greatly reduced comparing to the traditional method and the efficiency of the prototype is increased by 4%, which verifies the theory analysis to be correct and flexible.

Detecting the Oscillation and Propagation of the Nascent Dynamic Solar Wind Structure at 2.6 Solar Radii Using Very Long Baseline Interferometry Radio Telescopes

Probing the solar corona is crucial to study the coronal heating and solar wind acceleration. However, the transient and inhomogeneous solar wind flows carry large-amplitude inherent Alfvén waves and turbulence, which make detection more difficult. We report the oscillation and propagation of the solar wind at 2.6 solar radii (Rs) by observation of China’s Tianwen and ESA’s Mars Express with radio telescopes. The observations were carried out on 2021 October 9, when one coronal mass ejection (CME) passed across the ray paths of the telescope beams. We obtain the frequency fluctuations (FFs) of the spacecraft signals from each individual telescope. First, we visually identify the drift of the frequency spikes at a high spatial resolution of thousands of kilometers along the projected baselines. They are used as traces to estimate the solar wind velocity. Then we perform the cross-correlation analysis on the time series of FF from different telescopes. The velocity variations of solar wind structure along radial and tangential directions during the CME passage are obtained. The oscillation of tangential velocity confirms the detection of a streamer wave. Moreover, at the tail of the CME, we detect the propagation of an accelerating fast field-aligned density structure indicating the presence of magnetohydrodynamic waves. This study confirms that the ground-station pairs are able to form particular spatial projection baselines with high resolution and sensitivity to study the detailed propagation of the nascent dynamic solar wind structure.

How does the selection of wave hindcast datasets and statistical models influence the probabilistic design of offshore scour protections?

Offshore wind structures often use bottom-fixed foundations that are susceptible to scour phenomena. The design of scour protections for such structures requires defining the physical actions that they must be able to withstand during their lifetime. In this context, hindcasts providing estimates of necessary metocean variables play a key role. However, it is unclear how the selection of hindcast datasets can influence the design of scour protections at a given location. Moreover, defining design actions requires estimating extreme sea states with return periods exceeding the length of hindcast time series, which introduces additional uncertainty in the modelling process, as different statistical models may perform differently when applied to different hindcast datasets. A better understanding of the effects of these modelling choices is therefore necessary for the design and optimization of scour protections. The present study compares different wave hindcasts for the North Sea, and analyses how their selection and the subsequent application of statistical models affect the estimated probabilities of failure of the armour layer for bottom-fixed monopile foundations. Results show that the selection of different hindcast datasets and statistical models can significantly influence the probabilistic-based design of this type of scour protection, based on which practical recommendations are provided.

A Design Methodology for Irregularly Shaped Windings in Inductive Wireless Power Transfer Systems

Inductive wireless power transfer systems often incorporate unconventional, irregularly shaped transmitter windings for the purposes of covering a designated area, fitting into special enclosures and enhancing the tolerance of misalignment. To design and optimise the winding structures, the inductive parameters must be extracted and linked to the design objectives. Conventionally, these parameters can be extracted using three-dimensional finite element analysis, which often requires subjective manual tweaks and prolonged trial and error procedures. The efficacy is therefore greatly dependent on the experience of the designer. In this paper, a case study for modelling and optimising the spatial coverage by scuplturing the winding shape is demonstrated via a Christmas tree model, utilising the parametric formation equations and line-integral based numerical solvers. A cone-shaped winding with variable interturn pitches was used as the transmitter and a receiver winding was designed to be fit into a bubble that can be hung on the tree. A two-stage optimisation method with simplified degree-of-freedom parameters and brutal force search was used to find the optimal design candidate. Heatmaps of receiver output voltages were generated in a time-efficient way, intuitively helping the designers to make adjustments for the winding structures. A practical prototype was built to verify the open loop voltage distribution on the receiving winding at various positions and another demonstration was made to show the continuum of power coverage around the Christmas tree.

Detection of an Incipient Fault for Dual Three-Phase PMSMs Using a Modified Autoencoder

For the detection of incipient interturn short-circuit (IITSC) faults of machines without shutting them down, there are still shortcomings of insufficient incipient fault features and a high false alarm rate. This is especially the case for dual three-phase permanent magnet synchronous motors (PMSMs) with complex winding structures, and this kind of incipient fault detection is more complicated. To solve this detection difficulty, an IITSC detection method for dual three-phase PMSMs is proposed based on a modified deep autoencoder (MDAE). This autoencoder (AE) adopts an improved distribution metric combined with the maximum mean discrepancy (MMD) and the maximum covariance discrepancy (MCD) to extract the fault feature from the common features, which can improve the feature difference between the normal state and the incipient fault state. Then, the permutation entropy of the extracted features is calculated to detect the IITSC faults. The results illustrate that this method can not only detect IITSC faults online effectively and robustly, but also reduce the false alarm rate of the fault detection for dual three-phase PMSMs.

Effect of tornado near-ground winds on aerodynamic characteristics of the high-speed railway viaduct

The tornado is in direct contact with the underlying surface, which causes damage and indicates the vortex structure close to the ground. Accordingly, the maximum wind velocity generally could occur near the ground, potentially exposing the infrastructure to higher wind loads. However, one of the biggest challenges facing tornado research is characterizing the wind structure very near the surface due to the limitation of the data by using Doppler weather Radar. Considering the advantage of the high-fidelity computational fluid dynamics (CFD) models, this study aims to investigate the aerodynamic characteristics of a high-speed railway viaduct under tornado near-surface winds. More specifically, in light of limited full-scale data to arrive at a consensus on quantifying key parameters characterizing the tornado flow and near-surface winds, firstly. Secondly, tornado radar-measured data and a theoretical analysis model were utilized to validate the accuracy of the numerical method adopted in this study. Thirdly, the wind pressure distribution on the bridge is validated using the wind tunnel experimental data in Central South University(CSU), and the comparison between the simulational bridge and the measured data under crosswind was satisfactory. Finally, a comprehensive modeling strategy comprehensively investigates the aerodynamic characteristics of a high-speed railway viaduct under a tornado near-surface wind.

Analysis and Design of Monopile Foundations for Offshore Wind and Tidal Turbine Structures

This paper aims to design an integrated offshore structure capable of supporting a hybrid assembly of one wind plus two tidal turbines. The monopile has been found to be a suitable foundation type as the most inexpensive solution in water depths of less than 30 m. The Cook Strait in New Zealand is an ideal location for wind and tidal renewable energy sources due to its strong winds and tidal currents. Finite element analysis was performed to determine the displacement of the structure for different types of soils using OPTUM G3. After that, a macro-element model for soil was represented, considering the monopile as a Euler–Bernoulli beam model. The results enable the finding of optimum dimensions of monopiles with allowable tilt and deflection. Based on this, the diameter, thickness, and length of the monopile can be 6, 0.083, and 60 m, respectively. The maximum load occurs in extreme wind load scenarios when wind and waves move in same direction.

Modality analysis and algorithm design of stator short-circuit fault set for large compressed air energy storage generators

Using salt caverns and caves to build compressed air energy storage power stations is an important development direction in the field of large-scale energy storage. With the continuous maturity of technology, compressed air energy storage generators have gradually developed into large-scale units with a single-unit capacity of 300 MW. Due to the increase of single-unit capacity, the internal short-circuit fault of the stator will cause very serious losses. In addition, the compressed air energy storage generator has complex operating conditions and is more prone to various internal short-circuit faults. In order to effectively ensure its safe and reliable operation, it is particularly necessary to study the effective main protection configuration scheme. The optimal design of the main protection configuration scheme is based on the analysis of the possible internal short-circuit faults of the generator. At present, the stator windings of large-scale compressed air energy storage generators generally adopt double-layer wave winding or double-layer tap winding structures. For these two winding structures, this paper analyzes in detail the characteristics of all fault modalities that may occur inside the large-capacity compressed air energy storage generator and designs a general algorithm that can form their respective fault sets. Finally, the application of the algorithm in the analysis of the stator fault modality in a compressed air energy storage power station is introduced.

Thermal Network Model of High-Power Dry-Type Transformer Coupled with Electromagnetic Loss

Based on thermoelectric analogy method, a thermal network model coupled with electromagnetic loss is presented. According to the actual structure of dry-type transformer windings, an accurate thermal network is established. Considering the distribution characteristics of heat source along the cooling ducts inside the dry-type transformer, the thermal parameters such as heat flux and convective heat transfer coefficients are calculated by finite element method (FEM) analysis and computational fluid dynamics (CFD). Based on the temperature rise experiment, the hottest spot located at the top of the outmost high-voltage (HV) winding is 151.8 °C, which verified the correctness of thermal network model.

The National Hurricane Center Tropical Cyclone Model Guidance Suite

Abstract The National Hurricane Center (NHC) uses a variety of guidance models for its operational tropical cyclone track, intensity, and wind structure forecasts, and as baselines for the evaluation of forecast skill. A set of the simpler models, collectively known as the NHC guidance suite, is maintained by NHC. The models comprising the guidance suite are briefly described and evaluated, with details provided for those that have not been documented previously. Decay-SHIFOR is a modified version of the Statistical Hurricane Intensity Forecast (SHIFOR) model that includes decay over land; this modification improves the SHIFOR forecasts through about 96 h. T-CLIPER, a climatology and persistence model that predicts track and intensity using a trajectory approach, has error characteristics similar to those of CLIPER and D-SHIFOR but can be run to any forecast length. The Trajectory and Beta model (TAB), another trajectory track model, applies a gridpoint spatial filter to smooth winds from the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) model. TAB model errors were 10%–15% lower than those of the Beta and Advection model (BAM), the model it replaced in 2017. Optimizing TAB’s vertical weights shows that the lower troposphere’s environmental flow provides a better match to observed tropical cyclone motion than does the upper troposphere’s, and that the optimal steering layer is shallower for higher-latitude and weaker tropical cyclones. The advantages and disadvantages of the D-SHIFOR, T-CLIPER, and TAB models relative to their earlier counterparts are discussed. Significance Statement This paper provides a comprehensive summary and evaluation of a set of simpler forecast models used as guidance for NHC’s operational tropical cyclone forecasts, and as baselines for the evaluation of forecast skill; these include newer techniques that extend forecasts to 7 days and beyond.

A Winding Structure of Air-Core Planar Inductors for Reducing High-Frequency Eddy Currents

High-frequency converters with high power density have shown promise in recent years. Air-core planar inductors built with printed circuit boards can eliminate problems associated with the use of magnetic materials, such as iron loss and magnetic saturation. However, conventional air-core planar inductors suffer from eddy current loss. Eddy currents affect the resistance and inductance of the inductor. This article proposes a stranded wire structure to reduce eddy currents more than that in the conventional spiral wire structure. Eddy currents can be reduced by splitting the windings as well as currents of each split winding are balanced in the proposed structure. Seven types of air-core planar inductors were built, and their resistances, inductances, and impedances were measured to evaluate the effects of different structures on eddy currents. Furthermore, the temperature distribution of the planar inductors was measured while supplying a sinusoidal voltage with a power amplifier. The experimental results demonstrate the usefulness of the proposed stranded wire structure. Furthermore, the experimental result shows that the stray capacitance of the inductor can be reduced as a by-product of the proposed stranded wire structure.

An All Silicon Carbide 3 kV/540 V Series-Resonant Converter for Electric Aircraft Systems

In this work, an all silicon carbide (SiC) series-resonant converter (SRC) design is proposed and demonstrate to achieve a single stage dc-to-dc conversion from 3 kV to 540 V (±270 V) for future electric aircraft applications. The proposed SRC consists of a neutral-point-clamped converter using 3.3-kV SiC MOSFETs on the primary side, an H-bridge converter using 900-V SiC MOSFET on the secondary side and a high-frequency (HF) transformer. The detailed design methods for the SRC power stage and the HF transformer are presented. Especially, a tradeoff between the complexity for the cooling system and the need for high power density and voltage insulation is addressed in the transformer design, leading to a novel multilayer winding structure design to enhance the insulation capability and also the mechanical robustness. The proposed bobbin design is realized using additive manufacturing. The detailed analysis and modeling of the parasitic capacitance between sections introduced by fringe electrical field are presented. To validate the effectiveness of the proposed SRC design, a 25-kW converter prototype using 3.3-kV SiC discrete devices has been developed with a peak efficiency of 99.08% achieved in experimental studies.