SMOGN,MFO,and XGBoost Based Excitation Current Prediction Model for Synchronous Machine

The power factor is the ratio between the active and apparent power,and it is available to determine the operational capability of the intended circuit or the parts.The excitation current of the synchronous motor is an essential parameter required for adjusting the power factor because it determines whether the motor is under the optimal operating status.Although the excitation current should predict with the experimental devices,such a method is unsuitable for online real-time prediction.The artificial intelligence algorithm can compensate for the defect of conventional measurement methods requiring the measuring devices and the model optimization is compared during the research process.In this article,the load current,power factor,and power factor errors available in the existing dataset are used as the input parameters for training the proposed artificial intelligence algorithms to select the optimal algorithm according to the training result,for this algorithm to have higher accuracy.The SMOGN(Synthetic Minority Over-Sampling Technique for Regression with Gaussian Noise)is selected for the research by which the data and the MFO(Moth-flame optimization algorithm)are created for the model to adjust and optimize the parameters automatically.In addition to enhancing the prediction accuracy for the excitation current,the automatic parameter adjusting method also allows the researchers not specializing in the professional algorithm to apply such application method more efficiently.The final result indicated that the prediction accuracy has reached“Mean Absolute Error(MAE)=0.0057,Root Mean Square Error(RMSE)=0.0093 andR2 score=0.9973”.Applying this method to themotor control would be much easier for the power factor adjustment in the future because it allows the motor to operate under the optimal power status to reduce energy consumption while enhancing working efficiency.

Two Kinds of Waves Causing the Resuspension of Deep-Sea Sediments:Excitation and Internal Solitary Waves

The resuspension of marine sediments plays a key role in the biogeochemical cycle and marine ecology system.Internal solitary waves are considered to be important driving forces of the resuspension of bottom sediments.In this paper,the movement of turbidity currents,the generation and the effects on the bottom bed of internal solitary waves and excitation waves are studied by flume tests and numerical simulations,and the sediment resuspension are analyzed.The results show that the excitation wave can lead to the resuspension of the bottom sediments under all the conditions,while the internal solitary wave can lead to the resuspension of the sediment only under some special conditions,such as high amplitude or large underwater slope.Under the experimental conditions,the change in the near-bottom velocity caused by the excitation wave is close to three times that of the internal solitary wave.

Effect of excitation current intensity on mechanical properties of ZL205A castings solidified under a traveling magnetic field

The effect of excitation current intensity on the mechanical properties of ZL205 A castings solidified under a traveling magnetic field was studied. The results of the experiment indicate that the excitation current intensity of the traveling magnetic field has a great influence on the mechanical properties of the ZL205 A castings. When the excitation current intensity is 15 A, the tensile strength and elongation of ZL205 A alloy castings increase 27.2% and 67.7%, respectively, compared with those of the same alloy solidified under gravity. The improvement of mechanical properties is attributed to the decrease of micro-porosity in the alloy. Under the traveling magnetic field, the feeding pressure in the alloy melt before solidification can be enhanced due to the electromagnetic force. Moreover, the melt flow induced by the traveling magnetic field can decrease the temperature gradient. The feeding resistance will be increased because the temperature gradient decrease. So traveling magnetic field has an optimum effect on feeding.

The Continuation Power Flow Considering Both Generator Excitation Current Limits and Armature Current Limits

在传统连续潮流算法中,发电机无功限制采用定上、下限值来处理,随着有功负荷增加,无功限值通常不变,得到的电压稳定裕度偏大。根据同步发电机的无功出力特性,提出同时计及发电机励磁电流约束和电枢电流约束的连续潮流模型和方法。当相应参数越限时,将发电机节点转换为励磁恒定模型或者电枢电流恒定模型进行计算。所提PV、PEq、PIa节点类型双向转换逻辑可在潮流迭代内进行发电机限制模式的转换,模拟实际系统无功能力的变化。分岔点类型识别模块可以识别崩溃点类型及关键约束。通过新英格兰39节点算例的仿真,证明所提算法是有效的。

ANALYSIS OF WORKING MODES OF HYBRID EXCITATION DOUBLY SALIENT MOTOR

A more accurate analysis method on working modes is proposed by considering the winding terminal voltage and the eondueting power device as state parameters. For the three-phase hybrid excitation doubly salient machine （HEDSM） motor and its three-phase full-bridge inverter, in the proposed analytical method, all possible working modes are generally listed. Then, with the H_PWM-L_ON control strategy, the working modes are detailed with eorresponding equivalent circuits. Experimental results verify the robustness of the analysis.

Numerical Simulation of Self-excited Oscillation Switching Current in HVDC MRTB

This paper presents a numerical study of the current self-excited oscillations during the opening of high voltage direct current(HVDC) metallic return transfer breaker(MRTB).The switching arc is simulated using the magneto-hydrodynamics(MHD) theory coupled with the electric circuit variation.The simulation is proved accurate in simulating the current oscillation and the commutation process in MRTB by the good agreement between the calculated results and the experimental results,which are obtained on a MRTB prototype designed to break about 5 kA of DC current.Both kinds of the results show that the current oscillation starts at about 16.5 ms and the total arc time is about 24 ms with a commutation capacitor bank of 72 μF and an inductor of 173 μH.With a further analyze on how circuit parameters influence arc current oscillations,this study helps to improve the current interruption capability of MRTB.

Exploration of magnetic field generation of H_(3)^(2+)by direct ionization and coherent resonant excitation

Coherent electronic dynamics are of great significance in photo-induced processes and molecular magnetism.We theoretically investigate electronic dynamics of triatomic molecule H_(3)^(2+) by circularly polarized pulses,including electron density distributions,induced electronic currents,and ultrafast magnetic field generation.By comparing the results of the coherent resonant excitation and direct ionization,we found that for the coherent resonant excitation,the electron is localized and the coherent electron wave packet moves periodically between three protons,which can be attributed to the coherent superposition of the ground A′state and excited E+state.Whereas,for the direct single-photon ionization,the induced electronic currents mainly come from the free electron in the continuum state.It is found that there are differences in the intensity,phase,and frequency of the induced current and the generated magnetic field.The scheme allows one to control the induced electronic current and the ultrafast magnetic field generation.

Parameters analysis and application of the differential excitation detection technology

A differential excitation probe based on eddy current testing technology was designed. Sheet specimens of Q 235 steel with prefabricated micro-cracks of different widths and of aluminum with prefabricated micro-cracks of different depths were detected through the designed detection system. The characteristics of micro-cracks can be clearly showed after signals processing through the short-time Fourier transform（ STFT）. By changing the parameter and its value in detecting process,the factors including the excitation frequency and amplitude,the lift-off effect and the scanning direction were discussed,respectively. The results showed that the differential excitation probe was insensitive to dimension and surface state of the tested specimen,while it had a high degree of recognition for micro-crack detection. Therefore,when the differential excitation detection technology was used for inspecting micro-crack of turbine blade in aero-engine,and smoothed pseudo Wigner-Ville distribution was used for signal processing,micro-cracks of 0. 3 mm depth and 0. 1 mm width could be identified. The experimental results might be useful for further research on engineering test of turbine blades of aero-engine.

The failure propagation of weakly stable sediment:A reason for the formation of high-velocity turbidity currents in submarine canyons

The long-distance movement of turbidity currents in submarine canyons can transport large amounts of sediment to deep-sea plains.Previous studies show obvious differences in the turbidity current velocities derived from the multiple cables damage events ranging from 5.9 to 28.0 m/s and those of field observations between 0.15 and 7.2 m/s.Therefore,questions remain regarding whether a turbid fluid in an undersea environment can flow through a submarine canyon for a long distance at a high speed.A new model based on weakly stable sediment is proposed(proposed failure propagation model for weakly stable sediments,WS S-PFP model for short)to explain the high-speed and long-range motion of turbidity currents in submarine canyons through the combination of laboratory tests and numerical analogs.The model is based on two mechanisms:1)the original turbidity current triggers the destabilization of the weakly stable sediment bed and promotes the destabilization and transport of the soft sediment in the downstream direction and 2)the excitation wave that forms when the original turbidity current moves into the canyon leads to the destabilization and transport of the weakly stable sediment in the downstream direction.The proposed model will provide dynamic process interpretation for the study of deep-sea deposition,pollutant transport,and optical cable damage.

Performance Study of a Self-Excitation Dual Stator Winding Induction Generator for Renewable Distributed Generation Systems

Renewable power generation is a suitable technology used to deliver energy locally to customers especially in remote regions. Wind energy based on induction generator situates in a foreground position in the total energy produced using renewable sources. In the last few decades, a new self- excitation generator was based on multi-stator induction strongly emerges. This article presents a systematic modelling, a detailed analysis and the performance analysis of self-excitation dual stator winding induction generator (SE-DSWIG). The modelling of the SE-DSWIG was done with taking in account the common mutual leakage inductance between stators and the magnetizing inductance, which played a principal role in the stabilization of the output voltage in the steady state. The generator feeds the end user emulated by an inductive-resistive load. In order to simulate the weather conditions’ variation, a step change of the prime mover speed was applied on the SE-DSWIG. A passive series and shunt compensator was used to mitigate the voltage sag and swell appeared in the power system due to wind variation and the lack of reactive power consumed by the inductive load.

具有组分梯度的HgCdTe探测器在激光测量中的潜在应用

该文将组分梯度引入HgCdTe探测器结构设计中,提出了一种可以降低PN结附近热激发载流子浓度的方法。建立暗电流机制模型,分析高温下暗电流成份,分析结果表明,降低热激发载流子浓度对结区的影响是提高器件工作温度的关键。利用组分梯度在PN结附近构建不同的电场,不同电场下样品暗电流和噪声电流随温度的变化曲线表明,构建的电场越强,降低结区附近热激发载流子浓度的效果越明显。通过数据分析,提出构建103 V/cm量级的组分梯度内建电场可抑制热激发载流子向结区的扩散运动,有效地降低结区附近热激发载流子浓度。

多变运行工况下混合励磁轴向磁场永磁电机自适应模型预测电流控制

针对多变运行工况下混合励磁轴向磁场永磁(hybrid excited axial field permanent magnet,HE-AFPM)电机中电励磁磁场与电枢磁场之间矢量耦合、端部漏磁等导致的电机参数非线性变化问题,该文提出一种混合励磁轴向磁场永磁电机自适应模型预测电流控制方法。详细分析HE-AFPM电机拓扑结构及参数变化特性;引入多矢量模型预测电流控制,理论推导分析HE-AFPM电机参数对控制系统的敏感性。在此基础上,将多矢量预测模型作为自适应控制的可调模型,降低了控制算法的复杂度和控制系统的计算负荷,提高了控制系统响应速度;依据波波夫(Popov)超稳定理论,引入3个不等式稳定判据设计各参数的自适应律,可实现多变运行工况下的HE-AFPM电机磁链、自感、互感等参数的有效识别,提高了控制模型的准确性和电流跟踪性能。最后,通过实验验证所提出的自适应模型预测电流控制的有效性。

汽轮发电机转子匝间短路对定子热响应特性的影响

本文分析了汽轮发电机转子匝间短路故障前后定子热响应特性,不仅考虑转子匝间短路引起电压下降对发电机强励动作的影响,还研究了热分布不平衡而引起的定子力学响应。首先推导了正常情况和转子匝间短路故障后加强励磁电流下的气隙磁通密度,得到了铁心损耗和绕组铜耗的解析表达式;然后建立了发电机故障前后的三维有限元仿真模型,对不同短路程度故障下的铁心损耗、绕组铜耗与定子温度进行了求解计算;最后实测了CS-5型故障模拟发电机在正常运行和不同短路程度故障下的定子温度,实验结果与理论分析、有限元仿真结果基本一致。结果表明,转子匝间短路故障后由于励磁电流的增强,发电机铁心损耗和绕组铜耗均会增加,定子温度明显上升,并且随着短路程度的增加而加剧;定子端面边缘位置的变形和应力幅值最大并且为热响应下的危险位置。

高频多谐波激励下计及趋肤效应的软磁带材磁滞及损耗特性预测

软磁材料的非线性磁化特性使得软磁带材涡流场分布及其损耗特性分析十分困难。为此,该文采用分段线性的方法对基本磁化曲线进行逼近,基于麦克斯韦方程在每个线性段进行推导,得到单频正弦激励下软磁带材中与涡流损耗相对应的平均磁场强度Hcl表达式,并提出相应的参数辨识方法。进而,基于场分离技术与损耗分离的一致性原理,建立场分离形式的高频动态磁滞模型。根据实际应用中的高次谐波特征,基于磁导率的近似线性特征和场量的叠加原理,构造描述多谐波激励下与涡流损耗相对应磁场强度Hcl的解析表达式,并进一步提出软磁带材在复杂多谐波激励下的动态磁滞预测模型。通过实验结果与仿真结果的对比,验证该文所提方法的有效性和准确性。

磁脱扣器动作响应分析及储能电容匹配设计

驱动电路与磁脱扣器是电磁式漏电保护器的核心组件,磁脱扣器需与储能电容匹配。在电磁式漏电保护器基本工作原理分析的基础上,建立磁脱扣器的数学模型与有限元计算模型,根据激磁安匝变化进行衔铁响应状态分析,仿真不同线圈激励形式下磁脱扣器动作响应状态。研究衔铁角动量与角位移变化特征,根据无激励时衔铁释放临界角动量与角位移关系,确定不同线圈激励形式下的衔铁临界释放条件。研究电容电压激励源下衔铁所受力矩冲量的变化规律,分析电容及其储能对衔铁释放响应状态的影响,根据临界储能最小的原则确定电容匹配,可以降低衔铁可靠释放所需储能。通过对磁脱扣器样机进行实验测试,验证了理论分析与仿真计算的正确性。

基于改进结构的自激式直流空气断路器小电流开断能力提升方法

大容量自激式直流空气断路器(SE-DCCB)广泛应用于轨道交通电力系统中,其可以快速切断大等级短路电流。但是SE-DCCB分断几百安小电流时自激磁场较小,导致电弧燃弧时间较长甚至开断失败。该文通过耦合自激线圈磁场的改进磁流体动力学(MHD)模型,仿真得出双气流涡旋和弧根黏滞是SE-DCCB开断小电流失败的主要原因。为了提高SE-DCCB开断小电流的能力,对其结构进行改进,改进结构SE-DCCB采用安装导磁条的导磁板,并减小跑弧道转弯角半径,可以加快弧根运动速度、削弱小电流开断时的双气流涡旋和弧根黏滞现象,从而缩短燃弧时间。同时,改进结构SE-DCCB降低了电弧熄灭时刻灭弧室入口处的温度,能够减小电弧熄灭后重燃的概率,提升其开断小电流的性能。该研究揭示了SE-DCCB小电流难以开断的物理本质,可为轨道交通用空气断路器提供研发指导。

汽轮发电机转子绕组匝间短路故障恶化的影响因素研究

转子绕组匝间短路是大型同步发电机的常见故障,在发电机的电气故障中占据了较高的比例,也是影响机组安全运行的主要原因之一。本文针对转子绕组匝间短路伴随的局部过热问题,分别研究了短路点过渡电阻、短路点电流集束效应以及短路点的反复通断过程对其的影响。以一台300MW汽轮发电机为例,仿真获取了短路回路电流和功率损耗、短路点附近励磁电流密度以及被短路回路的暂态电压规律。本研究为确定转子绕组匝间短路故障的过热现象原因奠定了理论基础,也为进一步研究故障演化过程提供了分析思路。

基于联合仿真的电励磁同步电机线性自抗扰控制

针对电励磁同步电机(EESM)在车用电机控制方向的研究,通过Maxwell设计EESM有限元模型,基于Simulink搭建电机控制系统模型。然后,根据凸极EESM的电机特性和电磁转矩分析,在控制系统中采用最大转矩电流比(MTPA)矢量控制方式在Simulink-Maxwell进行EESM控制系统的联合仿真验证。同时,控制系统电流环应用线性自抗扰控制(LADRC),基于电机已知参数在LADRC中设计模型辅助—扩张状态观测器(MA-LESO),以观测和消除系统扰动变量。仿真实验表明,采用MTPA矢量控制的电机在带载时转速波动降低,带载能力增强;在电流环中采用MA-LESO的LADRC控制器能使电机转速在稳态时波动更小,在带载时的抗干扰性能更强,电机运行过程相对稳定;电机负载转矩和定子电流在空载、负载时的波形更稳定,显著提升了电机运行性能。

并联热敏电阻对半导体桥换能元直流响应的影响研究

并联热敏电阻是提升半导体桥(SCB)火工品临界熔断电流的有效措施。本研究利用恒流电源和红外测试系统,对不同直流激励条件下并联热敏电阻对半导体桥响应的影响进行了试验研究。试验测试了换能元桥区温度及临界熔断电流,结果表明,并联负温度系数(NTC)热敏电阻能显著提高SCB的临界熔断电流至原来的1倍以上,同时使桥区温度最大降低68%。经计算,NTC热敏电阻的分流效果范围为34.4%~74.4%。本研究不仅验证了并联NTC热敏电阻对提高3Ω敏感型SCB火工品安全性的显著效果,而且为SCB火工品在复杂电磁环境下的应用提供了技术支撑。

海洋平台结构损伤涡流热成像检测激励线圈设计

海上平台作为海上石油开发的重要设施,处在海水浸泡、冲击等恶劣环境中,很容易出现损伤,影响其安全性。管节点作为高应力集中的部位是海上平台结构中更易产生损伤的地方,因此对管节点进行检测十分重要,为适应海上平台管节点这种特殊结构的损伤检测,利用涡流热成像技术,考虑管节点结构、在管节点表面感应出的涡流分布情况等因素,设计出了圆台形线圈、三角形线圈、扁平双线圈三种形式的线圈,并通过COMSOL、SolidWorks完成了相应的仿真模拟,为了符合实验室需求,又构建出了等比例待测工件及线圈的实际模型,通过实验模拟、MATLAB数据处理验证了仿真模拟的准确性及所设计线圈的有效性。结果表明,扁平双线圈对海上平台管节点的加热效果更佳,能够用于对其损伤缺陷的检测。