Static-torque Characteristics of Three-phase Hybrid(HB) Stepping Motors and Influence of Way of Winding Connection on Operating Characteristics of Motors of This Kind

The paper presents the static-torque characteristics of three-phase hybrid stepping motors and discusses the influence of way of winding connection on operating characteristics of motors of this kind.

Difference between grid connections of large-scale wind power and conventional synchronous generation

In China, regions with abundant wind energy resources are generally located at the end of power grids. The power grid architecture in these regions is typically not sufficiently strong, and the energy structure is relatively simple. Thus, connecting large-capacity wind power units complicates the peak load regulation and stable operation of the power grids in these regions. Most wind turbines use power electronic converter technology, which affects the safety and stability of the power grid differently compared with conventional synchronous generators. Furthermore, fluctuations in wind power cause fluctuations in the output of wind farms, making it difficult to create and implement suitable power generation plans for wind farms. The generation technology and grid connection scheme for wind power and conventional thermal power generation differ considerably. Moreover, the active and reactive power control abilities of wind turbines are weaker than those of thermal power units, necessitating additional equipment to control wind turbines. Hence, to address the aforementioned issues with large-scale wind power generation, this study analyzes the differences between the grid connection and collection strategies for wind power bases and thermal power plants. Based on this analysis, the differences in the power control modes of wind power and thermal power are further investigated. Finally, the stability of different control modes is analyzed through simulation. The findings can be beneficial for the planning and development of large-scale wind power generation farms.

Study of Steady-state Performances for a Novel Line-start Single-phase Permanent Magnet Synchronous Motor With Three Parallel-connected Windings

对于三相感应电动机的单相运行,学者们已经提出了多种实用的接线方式,比如Smith接法、SEMIHEX接法。然而,对于三相异步起动永磁同步电动机的单相运行,很少有合适的接法提出。将并联式接法应用于三相异步起动永磁同步电动机的单相运行,提出了一种新型三绕组并联式异步起动单相永磁同步电动机。分析了三相异步起动永磁同步电动机同步运行时以及起动瞬间的正序、负序阻抗,基于对称分量法,对该接法电机的对称运行条件进行分析,得出了电容的确定方法,并利用遗传算法对电容值进行优化。提出了该新型电机稳态性能的计算方法;设计了一台高功率因数和一台低功率因数三相异步起动永磁同步电动机作为样机,并分别将其改接为三绕组高效单相永磁同步电动机,进行实验研究。实验结果表明,低功率因数的异步起动永磁同步电动机更适合改接成新型三绕组并联式单相永磁同步电动机。由低功率因数三相永磁同步电动机改接成的单相异步起动永磁同步电动机在额定负载下运行时,具有与同容量三相永磁同步电动机相近的效率和更高的功率因数。

Control Strategy of DC Link Voltage Flywheel Energy Storage for Non Grid Connected Wind Turbines Based on Fuzzy Control

The large-scale development of wind power is an important means to reduce greenhouse gas emissions, alleviate environmental pollution and improve the utilization rate of renewable energy. At the same time, large-scale non grid connected wind power generation theory avoids the technical difficulties of wind power integration [1]. However, due to the randomness and uncontrollability of wind energy, the output power of the wind power generation system will fluctuate accordingly [2]. Therefore, the corresponding energy storage devices are arranged in the non-grid-connected wind power generation system to ensure the power quality, and it has become the key to full utilization of renewable energy. In the case of wind speed fluctuation, the DC bus control strategy of the wind turbine is proposed in this paper. It can reduce the impact on the unit converter and the power load;this ensures safe and stable operation of non-grid connected wind turbines.

Study on Numerical Simulation for Control of Winding Process of Thin Wall Spiral Tube

Being aimed at the inside wall wrinkling and sinking phenomenon of palladium-yttrium alloy thin wall spiral tube used for preparation of high purity hydrogen, extraction of hydrogen isotope, and purification and separation of hydrogen in the winding process, this article analyzed the reasons for above phenomena, established a numerical simulation model of winding process of above tube, using elastic-plastic Finite Element method analyzed the max. tensile stress and max. compression stress and their locations, thereby provides a theory base for the control of working forming course of thin wall spiral tube.

Y型沟谷桥址区风特性的数值模拟研究

复杂山区的风场特性不同于平原地区,风场十分复杂,没有较为统一的规律,对大跨度桥梁的结构振动影响较大。为了研究复杂山区地形对桥址区风场特性的影响规律,以某座位于多条沟谷交汇谷口的斜拉桥桥址区为工程背景,基于ALOS数字高程地形模型,通过CFD数值模拟的方法,计算了不同风向来流下桥位处的风场特性。分析了桥址区主要的几条沟谷和桥位处局部地形对沿主梁横桥向平均风速、风攻角、风偏角及桥梁跨中竖向风剖面等风特性的影响。研究了横桥向平均风速大小和风攻角之间的关系,定性讨论了存在风速放大效应的来流工况和桥址区地形特点之间的关系。结果表明:Y型沟谷桥址区风特性不同于一般的山区桥址区,当来流沿着几条比较顺直的沟谷时桥位处平均风速较大,其他风向桥位处风速较小;沟谷的弯曲致使沿着沟谷的来流产生回流和改向,这时桥位处的风攻角较大,沿着主梁的风偏角变化范围较大,水平风速较小,不存在风速峡谷放大效应;桥位处交汇的沟谷局部地形对桥梁跨中竖向风剖面影响较大。研究结果为桥梁设计风速的确定提供了依据,可为定性判断Y型沟谷口桥位处风特性提供指导。

嵌岩单桩水平静力加载现场试验及 p-y 曲线研究

为研究风化花岗岩地质条件下嵌岩单桩的受荷响应和p-y曲线规律,本文基于现场试验,开展了水平静力荷载作用下嵌岩单桩的荷载-位移关系、弯矩、桩身变形及p-y曲线响应研究。试验表明:在所研究的相对深度范围内,随着z/D的增加,岩土阻力和相应位移都减小,上部荷载很难传递到深部岩层;桩身最大弯矩在3~4倍桩径之间,极限荷载主要取决于桩身强度而不是岩土体。将p-y曲线分别与一般双曲函数和双曲正切函数进行拟合,评估现有p-y曲线模型在风化花岗岩地基中的适用性,修正了模型在风化岩层中的参数取值。结果表明:一般双曲函数在较浅区域拟合良好,相对深度较大的区域数据离散性较强;双曲正切函数在各深度处拟合优度均较好。分析结果简化了现场p-y曲线的预测程序。

Infl uence of structural parameters on dynamic characteristics and wind-induced buffeting responses of a super-long-span cable-stayed bridge

A 3D finite element （FE） model for the Sutong cable-stayed bridge （SCB） is established based on ANSYS. The dynamic characteristics of the bridge are analyzed using a subspace iteration method. Based on recorded wind data, the measured spectra expression is presented using the nonlinear least-squares regression method. Turbulent winds at the bridge site are simulated based on the spectral representation method and the FFT technique. The influence of some key structural parameters and measures on the dynamic characteristics of the bridge are investigated. These parameters include dead load intensity, as well as vertical, lateral and torsional stiffness of the steel box girder. In addition, the influence of elastic stiffness of the connection device employed between the towers and the girder on the vibration mode of the steel box girder is investigated. The analysis shows that all of the vertical, lateral and torsional buffeting displacement responses reduce gradually as the dead load intensity increases. The dynamic characteristics and the structural buffeting displacement response of the SCB are only slightly affected by the vertical and torsional stiffness of the steel box girder, and the lateral and torsional buffeting displacement responses reduce gradually as the lateral stiffness increases. These results provide a reference for dynamic analysis and design of super-long-span cable-stayed bridges.

Overview of the Rectangular Wire Windings AC Electrical Machine

The rectangular wire winding AC electrical machine has drawn extensive attention due to their high slot fill factor,good heat dissipation,strong rigidity and short end-windings,which can be potential candidates for some traction application so as to enhance torque density,improve efficiency,decrease vibration and weaken noise,etc.In this paper,based on the complex process craft and the electromagnetic performance,a comprehensive and systematical overview on the rectangular wire windings AC electrical machine is introduced.According to the process craft,the different type of the rectangular wire windings,the different inserting direction of the rectangular wire windings and the insulation structure have been compared and analyzed.Furthermore,the detailed rectangular wire windings connection is researched and the general design guideline has been concluded.Especially,the performance of rectangular wire windings AC machine has been presented,with emphasis on the measure of improving the bigger AC copper losses at the high speed condition due to the distinguished proximity and skin effects.Finally,the future trend of the rectangular wire windings AC electrical machine is prospected.

Effects of Wind-Wave Misalignment on a Wind Turbine Blade Mating Process:Impact Velocities,Blade Root Damages and Structural Safety Assessment

Most wind turbine blades are assembled piece-by-piece onto the hub of a monopile-type offshore wind turbine using jack-up crane vessels.Despite the stable foundation of the lifting cranes,the mating process exhibits substantial relative responses amidst blade root and hub.These relative motions are combined effects of wave-induced monopile motions and wind-induced blade root motions,which can cause impact loads at the blade root’s guide pin in the course of alignment procedure.Environmental parameters including the wind-wave misalignments play an important role for the safety of the installation tasks and govern the impact scenarios.The present study investigates the effects of wind-wave misalignments on the blade root mating process on a monopile-type offshore wind turbine.The dynamic responses including the impact velocities between root and hub in selected wind-wave misalignment conditions are investigated using multibody simulations.Furthermore,based on a finite element study,different impact-induced failure modes at the blade root for sideways and head-on impact scenarios,developed due to wind-wave misalignment conditions,are investigated.Finally,based on extreme value analyses of critical responses,safe domain for the mating task under different wind-wave misalignments is compared.The results show that although misaligned wind-wave conditions develop substantial relative motions between root and hub,aligned wind-wave conditions induce largest impact velocities and develop critical failure modes at a relatively low threshold velocity of impact.

Renewable Energy Based Grid Connected Battery Projects around the World—An Overview

The environmental pollution,as well as gradual depletion of mineral resources has encouraged the world to move into renewable energy sources for generation of electricity.At present,the cost of using renewable energy sources,such as sunshine and wind in electricity generation has significantly reduced.This has led to higher penetration of renewable energy into the grid.However,both wind and solar energy photovoltaics are unpredictable energies which reduce the reliability and resiliency of the grid.The integration of battery energy storage system in the grid is one of the proficient solutions to the problem.There are numerous grid connected renewable energy based battery projects that have been deployed in different countries around the world for research,development and commercial application.This review paper will discuss some of the projects based on the battery connected wind and solar energy power generation systems that can operate both in grid connected and grid independent modes.The projects discussed in this paper are selected based on the availability of information.The battery energy storage system(BESS)incorporated in each of the project is found to increase the stability and performance of the grid by addressing the mismatch between power generation and the load of the grid created due to intermittent nature of renewable energy sources.

砂土地基海上风电大直径单桩基础的p-y曲线研究

依托福建某海上风电项目现场试验,对大直径单桩有限元模型的有效性进行验证,进一步研究砂土地基中不同桩径大直径单桩的破坏模式、初始刚度、极限抗力随桩径与深度的变化规律,并分别考虑桩径的尺寸效应与埋深对双曲线模型进行修正。结果表明:不同桩径下大直径单桩的破坏模式主要为浅层土体的楔形破坏;API规范、双曲线模型计算得到的p-y(地基土水平抗力-桩水平位移)曲线与数模得到的p-y曲线误差较大,而修正双曲线模型与数模结果吻合较好,优于其他模型的计算结果。

High Performance Double-Interleaved Dual Boost Converter and 3 Phase Grid Connected Converter for Wind Turbine

This paper proposes a high performance double-interleaved dual boost （DIDB） technique to solve the problems of high ripple current, large inductor size and the requirement of step-up transformer in many case found in the conventional DC-DC boost converter. The 3-phase grid connected converter with decoupling control give an independent control between active and reactive power using the load current feed-forward. With this technique, the disturbance rejection and the output power quality can be improved. Experiments are conducted with three case studies： 1） a test of the DIDB converter to determine current ripple and voltage gain, 2） a test of the 3-phase grid connected converter to determine DC-link voltage regulation, power factor and total harmonic distortion （THD）, and 3） a test of the overall system with a 7.5 kW wind turbine simulator by step and various input wind speeds to determine the output power at the grid side and verify the maximum peak power tracking （MPPT） performance. The results can confirm that the DIDB converter gives lower ripple current and higher voltage gain than the conventional converter. For the grid side, the 3-phase grid connected converter can regulate the DC-link with fast dynamic response to disturbance rejection and low overshoot while complying with the THD standard defined in IEEE 519-1992. In addition, the MPPT controller is able to achieve the maximum energy capture with the various input wind speeds.

黏土中大直径钢管桩p-y曲线法适用性研究

大直径钢管桩作为常用的海上风机基础形式,其水平承载性能是风机基础结构设计中最关键的一环。API规范建议的p-y曲线法是目前计算钢管桩水平承载力最主流的方法,但其对大直径刚性桩及刚柔性桩的适用性有待探讨。通过开展数值模拟方法,研究了不同长径比水平受荷桩的桩身变形规律及桩周土体破坏规律,提出了基于长径比的刚柔性桩判断标准,并通过比较不同长径比下钢管桩水平极限承载力,得到了传统p-y曲线的适用范围。研究结果发现传统p-y曲线模型由于仅考虑了水平向的土阻力,适用于计算长径比≥15的刚柔性桩及柔性桩;而对于长径比<9的刚性短桩,其误差最高可达63%,严重低估了单桩的水平向承载力;对于长径比在9~15之间的刚柔性桩可适当使用API规范进行计算。

Y-Δ接法分数槽永磁电机断相故障电流特征分析与诊断方法研究

星-三角(Y-△)接法的分数槽永磁电机(fractional-slot permanent magnet machine,FS-PMM)因其谐波分量低、转矩脉动小等优点在电动汽车领域具有较好的应用前景。但由于该电机中的△接绕组位于电机内部,其电流无法直接测量,故障时难以被及时发现。该文针对Y-△接法的FS-PMM内层△接绕组单相断相故障,提出一种基于电流三次谐波幅值的故障诊断方法。首先,建立△接绕组单相断相故障下的数学模x相故障的检测与故障相定位。经实验验证,所提方法能够实时准确地实现△接绕组单相断相故障诊断,且具有良好的鲁棒性。

Wind Energy Conversion System from Electrical Perspective—A Survey

This paper focuses on the wind energy conversion system (WECS) with the three main electrical aspects: 1) wind turbine generators (WTGs), 2) power electronics converters (PECs) and 3) grid-connection issues. The current state of wind turbine generators are discussed and compared in some criteria along with the trends in the current WECS market, which are ‘Variable Speed’, ‘Multi-MW’ and ‘Offshore’. In addition, the other crucial component in the WECS, PECs will be discussed with its topologies available in the current WECS market along with their modulation strategies. Moreover, three main issues of the WECS associating with the grid-connection, fault-ride through (FRT) capability, harmonics/interharmonics emission and flicker, which are the power quality issues, will be discussed due to the increasing responsibility of WECS as utility power station. Some key findings from the review such as the attractiveness of BDFRG are presented in the conclusion of this paper.

基于现场试验的海上风电大直径钢管桩p-y曲线特性分析

作为美国石油协会(API)推荐的规范方法,p-y曲线法在水平受荷桩的计算分析中得到了广泛应用。随着海上单桩基础尺寸的增大,基于柔性长桩得出的API规范p-y曲线的适用性受到了越来越多的质疑。以中国某海上风电场大直径单桩基础水平静载试验为工程背景,分析了试桩的水平受荷变形特性。基于实测数据,对比了4种较为常见的p-y曲线方法的计算效果。结合三维有限元模拟分析了基础尺寸对p-y曲线形式的影响,并探讨了上述p-y曲线的适用工况。结果表明:API法不适用于大直径桩的分析计算;4种方法中,Sullivan法的预测值与实测值最为吻合。同时根据现场试验与有限元分析的结果提出了修正的p-y曲线计算方法。文中研究成果能为相似海域内大直径单桩水平承载变形特性设计提供一定参考。

新媒体语言中“一言不合就Y”的语义演变及功能解析

网络热用语“一言不合就Y”就本义而言是“一X就Y”中,“X”的论域局限于“语言或意见相左”的下位变体;当代汉语系统中“一言不合就Y”的意义可以看作是从“逻辑意义的顺理承接”到“小化前提、大化结果的反差承接”,再到“意义的无厘头对接”的连续统,而后两种意义是“一言不合就Y”应用中的强势表达。三种意义演变的过程中,“一言不合就Y”从“表义实体”演变为“话语标记”。

多Y绕组同步电机瞬态参数的频域法数值计算

为计算多Y绕组同步电机任意部分Y绕组供电时的瞬态参数,提出多Y绕组同步电机瞬态参数的频域法算法。通过分析全Y或部分Y绕组供电时的派克方程,得到电机等效电路,进而定义单Y与多Y瞬态参数。通过分析各Y绕组空间合成电流矢量,得到定子各相绕组脉振电流的确定方法。此外,给出运算电抗频率特性的拟合方程。以双Y绕组同步电机为例,计算双Y绕组同步电机单Y与双Y瞬态参数,计算结果与实验结果基本吻合。计算结果表明,其单Y自感抗比单Y互感抗大,电抗差随频率增加发生波动变化,瞬态之初差异最大,稳态时差异最小。所提方法可适用于定子含多套非Y型对称绕组同步电机的瞬态参数计算。