Measurement of Synchronous Machine Parameters by a Modified Frequency Response Method - Part II: Measured Results

De Mello and Hannett [1] have proposed a theoretical method for determining the operational inductances of a synchronous machine at low values of generator speeds. Eitelberg and Harley [2] extended these ideas to obtain the inductances and time constants from the Ld(j2w), Lq(j2w) curves by a numerical curve fitting procedure. Part I [3] of this paper broadens these ideas [1-2] by proposing an improved MODIFIED data-processing method which avoids the tedious integration of the d,q axes flux linkages [1]. Part II continues by performing a line-to-line short-circuit test on a 3 kVA, 220 V microalternator at different speeds covering the range which is of interest to subsynchronous resonance (SSR) studies [4]. Measured results illustrate the practical feasibility of this proposed frequency response method [1-3]. Practical problems associated with this test are also mentioned.     

Estimating Synchronous Machine Electrical Parameters from Frequency Response Tests

A method of obtaining synchronous machine d and q axis impedances by test as a function of frequency of d,q components has recently been proposed by de Mello and Hannett [1]. Their proposal ends by determination of the numerical values for the operational inductances Ld(j2w), Lq(j2w) or impedances Zd(j2w), Zq(j2w) at different values of W, the speed of the machine at which the tests are conducted; however, they do not show how the values of actual parameters such as inductances and time constants are to be obtained from the curves of operational inductance versus frequency.     

Lumped modelling of open-circuit turbogenerator operationalparameters

Solid-rotor turbine-generators have commonly been derived from the fitting of curves to terminal characteristics obtained by measurement or from finite element simulations. The paper presents a new method to represent the open-circuit operational inductances of a large turbogenerator of 150 MVA. The method differs from current estimation techniques because the lumped model and its parameters are determined simultaneously. It is based on a finite-element electromagnetic linear analysis of the solid-rotor machine cross section in the frequency domain. Network theory is used to characterise the quadrature-axis model where the problems of model structure and parameter determination are treated. A q-axis equivalent circuit with one damper winding and frequency dependent parameters is found. In addition, an analysis of the machine d-axis is presented. It is based in an electromagnetic study of the “black box” two-port network, where the open-circuit operational inductances are represented by frequency dependent parameters     

Mathematical and experimental method to obtain the inverse modeling of nonsinusoidal and saturated synchronous reluctance motors

This paper presents new inverse modeling for synchronous reluctance motor (SyRM). This modeling is valid when the inductances are sinusoidal or nonsinusoidal and even when the machine is saturated. This technique involves the generation of constant torque curves as a function of two-phase currents in the Concordia's reference frame when the rotor angle is fixed. We also introduce an experimental method to obtain directly the inverse modeling. This practical method takes into account the saturation of the motor. This technique allows the reduction of the low torque ripple in the case of nonsinusoidal inductances.     

木屑气化过程LS-SVM模型改进及优化

用Sigmoid核函数替换了文献[1]模型中的高斯径向基(RBF)核函数,对文献[1]中的木屑气化过程LS-SVM模型做了改进。在建模基础上,分别用遗传算法(GA)和粒子群算法(PSO)对木屑气化过程进行优化计算。优化结果表明,以Sigmoid核函数建立的模型对分别采用K2CO3和Na2CO3催化剂时木屑气化过程拟合的平均相对误差(1.099 7%和1.094 3%)小于文献[1]模型拟合的平均相对误差(1.788 3%和1.38%);当木屑气化温度和催化剂添加量取优化值时,气体产率、气体热值、气化效率均达到最大值。     

Finite-element calculation of leakage inductances of a saturated salient-pole synchronous machine with damper circuits

It is important to understand the relationship between leakage flux distributions and machine characteristics for better design of synchronous machines. This paper presents a calculation method for leakage inductances of saturated salient-pole machines with damper circuits. All leakage inductances are divided into the self-leakage, gap leakage, and winding-differential leakage inductances. The leakage inductances correspond directly to the leakage flux distributions in the machines. Cross-magnetizing inductances are also calculated. The method is applied to a 300-MVA class generator. The relationship between the winding distributions, flux distributions, saturation, and inductances is discussed. Weak magnetic influence of the damper circuits on the armature in the d-axis is quantitatively illustrated through values of the winding-differential leakage inductances. The cross-magnetizing inductances, except for the d-axis damper circuits, are relatively large. Variations of the armature self-leakage inductances with saturation are small, and variations of the field and damper self-leakage inductances are larger.     

Short-circuit test based maximum likelihood estimation of stabilitymodel of large generators

This paper presents a time-domain statistical identification method for synchronous-machine linear parameters from the standard line-to-line short-circuit test. The measurements are recorded on a 13.75-MVA hydrogenerator at Hydro-Quebec's Rapide-des-Quinze generating station. A complete mathematical model for synchronous machine asymmetrical test analysis is proposed. An efficient algorithm is built to accurately calculate the standard equivalent circuit from time-constants and operational inductances. The maximum likelihood estimator derived from the generalized least-squares method is then used for parameter identification. Validation of the estimated model response against the measured running-time domain data confirms the effectiveness of the proposed estimation technique     

最优组合预测模型在预压处理地基沉降中的应用研究

[目的] 为了提高预压地基处理沉降预测及固结度推算精度,提出了以原始累积沉降量时间序列为基础建立最优组合预测模型以及模型的精度评价方法。 [方法] 基于传统单一预测模型Compertz模型、灰色G(1,1)模型、Pearl模型,构建最优组合模型,以某天然气热电冷联产项目地基沉降监测时间序列,分别检验各单一模型以及最优组合预测模型(OCP模型)的可靠性与精度,并将三点法,图解法(Asaoka法)及经验双曲线拟合法的预测结果与最优组合预测模型(OCP模型)的计算结果进行了对比分析。 [结果] 研究结果表明：单一预测模型Compertz模型、灰色G(1,1)模型、Pearl模型以及最优组合预测模型(OCP模型)均满足“好”的精度等级要求;与常用的三点法,图解法(Asaoka法),经验双曲线法计算结果相比,最优组合预测模型(OCP模型)计算值更接近实际值; [结论] 在进行预压处理地基的沉降预测以及预压后地基土固结度计算和分析时,采用不同方法,能得出合理的评价指标值;最优组合预测模型(OCP模型)可为在预压处理地基施工控制提供一定的指导作用。     

A new model of saturated synchronous machines for power systemtransient stability simulations

This paper presents a new method to express the main flux saturation in synchronous machines. In the new method, the saturation is expressed by auxiliary currents and unsaturated magnetizing inductances instead of the saturated inductances. The new model using the currents contains only constant coefficients defined in terms of the unsaturated magnetizing inductances     

[FeFe]-hydrogenase gene quantification and melting curve analysis from hydrogen-fermenting bioreactor samples

In this study, quantitative PCR (qPCR) was used to quantify [FeFe]-hydrogenases and subsequently melting curves were analyzed from hydrogen-fermenting, mixed-culture bioreactor samples. Denaturing gradient gel electrophoresis (DGGE) analysis was also performed to the reactor samples revealing a clostridial dominance in the reactor. Primers targeting [FeFe]-hydrogenases were designed based on known clostridial [FeFe]-hydrogenase gene sequences and tested with several clostridial strains. The results show that amplification efficiencies of four different clostridia are highly similar and melting curves of the clostridial strains were within 1 °C of each other. We compared the melting curves to the hydrogen percentage and observed a correlation between the results. The closer the melting curves were to those of clostridia, the better the hydrogen production. Based on these results, the primers and melting curve analysis of [FeFe]-hydrogenase amplicons can be used for analysing hydrogenase genes from bioreactor samples.     

Photovoltaic activity of a PolyProDOT derivative in a bulk heterojunction solar cell

We report the photophysical behavior and photovoltaic performance of a poly(3,4-propylenedioxythiophene) (PProDOT) derivative, namely poly-[3,3-dihexyl-3,4-dihydro-2H-thieno(3,4-b)(1,4)dioxepine] (PProDOT(Hx)₂), as an electron donor in bulk heterojunction solar cells blended with the acceptor 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene (PCBM). Devices composed of a 1:4 (w:w) ratio of PProDOT(Hx)₂/PCBM and spin coated from chlorobenzene were characterized by measuring current–voltage characteristics under simulated Air Mass 1.5 (AM1.5) conditions as well as the spectrally resolved photocurrent (IPCE). The influence of different preparation parameters like various blend ratios, spin coating from different solvents, and changing the metal contacts was studied. It was found that the photoluminescence of the polymer is quenched by a factor greater than 100 using blends consisting of PProDOT(Hx)₂ and PCBM (3:2, w:w). Additionally, the photoactive blends were characterized by photoinduced absorption spectroscopy and the results suggest that charge transfer is occurring from PProDOT(Hx)₂ to PCBM. Results from atomic force microscopy reveal that a bicontinuous network, with domain sizes on the order of 100–200 nm, results when a 1:4 blend of PProDOT(Hx)₂/PCBM is spin coated from chlorobenzene.     

Synthesis and photovoltaic properties of a star-shaped molecule with triphenylamine as core and benzo[1,2,5]thiadiazol vinylene as arms

A solution-processable and star-shaped molecule 4-((E)-2-(benzo[1,2,5]thiadiazol-4-yl)vinyl)-N,N-bis(4-((E)-2-(benzo[1,2,5]thiadiazol-7-yl)vinyl)phenyl)benzenamine (TPA-BT) has been designed and synthesized by palladium-catalyzed Heck reaction for the application in organic solar cells (OSCs). The molecule possesses a D-A structure with a triphenylamine core (donor unit) linked with three benzo[1,2,5]thiadiazole (acceptor unit) arms through double bonds. TPA-BT film shows a strong absorption peak in the visible wavelength range from 400 to 560 nm, which could be ascribed to the charge transfer band of the D-A structure of the molecule. The bulk-heterojunction OSCs with the device structure of ITO/PEDOT:PSS/TPA-BT:PCBM/Ca/Al (or Ba/Al) were fabricated by spin-coating the blend solution of TPA-BT and PCBM (1:3, w/w), in which TPA-BT was used as donor and PCBM as acceptor materials. The devices show a high open circuit voltage of ca. 0.9 V and a power conversion efficiency of 0.61%, under the illumination of AM 1.5, 100 mW/cm². The results indicate that TPA-BT is a promising solution-processable organic photovoltaic material.     

Analysis of leakage flux distributions in a salient-pole synchronous machine using finite elements

It is important to understand the relationship between iron core configurations and leakage flux distributions to get a better design of synchronous machines. This paper presents a method for calculating the steadyand transient-state leakage flux distributions in salient-pole synchronous machines. The method provides information on leakage flux distributions that cannot be obtained by terminal quantities. The method analyzes the leakage inductances that properly represent the corresponding leakage fluxes. They are calculated using the gap flux distributions by finite elements with magnetic saturation. The calculated leakage inductances of a synchronous machine under various loads are also shown and the relationship between the inductances and magnetic saturation is discussed.     

Asymmetrical non-imaging cylindrical solar concentrators

Asymmetrical Non-Imaging Cylindrical Concentrators have been proposed recently by Smith[5] and Rabl[6] which are related to the Symmetrical Non-Imaging Cylindrical Concentrators described by Winston [1, 2] and Baranov [3]. In this paper, both Parabolic and Non-Parabolic Asymmetrical Concentrators are examined and compared with symmetrical designs. Among the advantages of asymmetrical systems are: (1) a concentration vs time-of-day relationship which can be designed to compensate for projected solar area fall-off in early morning and late afternoon, allowing more uniform output where this is desirable; (2) greater operational flexibility for accommodating unexpected fluctuations in demand; (3) easier adaptation to vacuum-insulated receivers in one configuration; (4) the possibility of substantially increased concentration and energy collection per unit of mirror area for systems with receivers which can make use of large daily variations in energy input. A higher tracking frequency may be required, but a tilting adjustment every few days should be the maximum required for practical systems.     

第二届全国青年工程风险分析和控制研讨会简讯

  [目的]  为推动工程风险管理与保险相关的新理论和新技术发展,为青年学者提供学术交流平台,第二届全国青年工程风险分析和控制研讨会于2018年3月30日—31日在武汉召开。  [方法]  会议由中国土木工程学会工程风险与保险研究分会主办,武汉大学、中国地质大学(武汉)、国家重点研发计划项目(2017YFC1501300)和国际土力学与岩土工程学会TC304工程风险评价与管理技术委员会共同承办。  [结果]  会议探讨了国际前沿的工程风险分析与控制理论和方法进展,促进了工程风险领域青年学者间的交流和合作。  [结论]  会议对推动我国工程灾害防治与风险控制学科的发展具有重要意义。     

An improved computational technique of the inductance parameters ofreluctance augmented shaded-pole motors using finite element method

An improved technique for calculating the inductance parameters of reluctance augmented shaded-pole motors, including the saturation effect, is described. The method is based mainly on the use of finite element (FE) field calculation and partly on some analytical derivations. Equations are provided for saturated inductance components in terms of relevant winding currents, in order to facilitate the inclusion of the saturation effect into the performance evaluation. The computed values of several inductances are compared with their measured counterparts for verification     

一维Si/SiO_2光子晶体应用于热光伏的新进展

针对一维(1D)Si/SiO_2光子晶体滤波器在GaSb热光伏电池特征波长处存在较大反射峰的问题,根据等效折射率理论,将其基本结构由(L/2HL/2)~5改进为[1.10(L/2HL/2)](L/2HI/2)~3[1.10(L//2HI/2)].结果表明:改进的滤波器在特征波长处的透过率有较大提高,且抑制了长波光子的透过.辐射器为1250℃的黑体时,采用改进滤波器的TPV系统的光谱效率为33.3%,输出电功率密度为1.06W·cm~(-2),相对于采用原滤波器的TPV系统增长幅度均超过了10%,电池效率也有所提高.     

Nitrogen-doped mesoporous carbon for energy storage in vanadium redox flow batteries

We demonstrate an excellent performance of nitrogen-doped mesoporous carbon (N-MPC) for energy storage in vanadium redox flow batteries. Mesoporous carbon (MPC) is prepared using a soft-template method and doped with nitrogen by heat-treating MPC in NH₃. N-MPC is characterized with X-ray photoelectron spectroscopy and transmission electron microscopy. The redox reaction of [VO]²⁺/[VO₂]⁺ is characterized with cyclic voltammetry and electrochemical impedance spectroscopy. The electrocatalytic kinetics of the redox couple [VO]²⁺/[VO₂]⁺ is significantly enhanced on N-MPC electrode compared with MPC and graphite electrodes. The reversibility of the redox couple [VO]²⁺/[VO₂]⁺ is greatly improved on N-MPC (0.61 for N-MPC vs. 0.34 for graphite), which is expected to increase the energy storage efficiency of redox flow batteries. Nitrogen doping facilitates the electron transfer on electrode/electrolyte interface for both oxidation and reduction processes. N-MPC is a promising material for redox flow batteries. This also opens up new and wider applications of nitrogen-doped carbon.     

Maximum likelihood estimation of synchronous machine parametersfrom standstill time response data

This paper presents a systematic approach for identification of a three-phase salient-pole synchronous machine rated at 5 kVA from standstill time-domain data. Machine time constant models and the equivalent circuit models are identified and their parameters are estimated. The initialization of the estimated parameters is achieved by the Laplace transformation of the recorded standstill time-response data and the derivation of the well-known operational inductances. The estimation is performed using the Maximum Likelihood algorithm. Based on the best estimated equivalent circuit models, simulation studies using the measured on-line dynamic responses are performed to validate the identified machine models     

Effects of toothless stator design on dynamic model parameters ofpermanent magnet generators

The effects of toothless stator design on the dynamic model parameters of permanent magnet (PM) generators are presented. These parameters, which include inductances and induced back EMFs, are determined for a 75 kVA, 208 V, 400 Hz, two-pole, permanent magnet generator. Two particular stator designs, a toothless stator, and a conventional type stator (with iron teeth), are considered. The method which is used to determine these parameters is general in nature and is based on the use of a series of magnetic field solutions. A validation of the computed EMF and inductance values based on experimentally obtained data is given. The results of using these parameters in a state space model in the abc frame of reference to study the effects of a toothless stator design on the PM generator synchronous inductances are presented. Based on that, it is demonstrated that the effects of rotor saliency and armature loading on the machine parameters are minimized in the case of the toothless design