Experiment in metal disturbance during advanced detection using a transient electromagnetic method in coal mines

Tunneling machines, or excavators, are large and good conductors and affect the reliability of data gathering and interpretation in advanced detection using transient electromagnetic methods. In our experiment, we used a coincident-loop and central loop type of configuration, where the coil plane l） vertical to and 2） parallel to the working face. A SIROTEM instrument at different locations was used to observe the transient electromagnetic responses of the excavator and to analyze the response amplitudes. The result shows that the tunneling machine affects the advanced detection data and is related to the way the coil is coupled. When the excavator is 6 m from the observatory, the interference of tunneling machine can be ignored.

Characteristic Analysis of Transient Electromagnetic Disturbance Data in Substation

Characteristic analysis of transient electromagnetic disturbance data is very important. In this paper, the time-domain and frequency-domain characteristics of transient electromagnetic disturbance caused by switching operations in substations are analyzed. Two methods are adopted in time-domain analysis. One method is histogram and the other one is normality test. An appropriate procedure for the normality test is proposed. Furthermore, the method used in frequency- domain analysis is to obtain overall envelope. These statistical characteristic analysis methods are showed to be of great value in analyses of the measured samples. The simulation results showed that these methods are effective.

基于优化窗函数改进S变换的低频振荡暂态检测方法

低频振荡暂态是电力系统中常见的一种电能质量扰动,其直接影响电力系统的安全、稳定运行。通过对影响时频分析算法检测精度的窗函数进行了研究,提出一种基于优化窗函数改进S变换的低频振荡暂态检测方法。首先,对时频分析算法中窗函数随检测频率变化的改变特性进行分析,确定了适用于低频振荡暂态扰动检测的优化窗函数,并利用其构造了改进S变换算法;其次,通过利用卷积定理、Fourier变换及其逆变换,推导了改进S变换算法快速实现的计算表达式,获取了包含信号幅值、相位信息的二维时频矩阵,给出了改进算法的实现流程;最后,采用包含低频振荡暂态扰动的电网信号对改进算法进行了测试。该优化算法对低频振荡暂态扰动表现出相对最佳的时频能量聚集性能,实际实验中所测得扰动中心频率为600 Hz,与扰动的生成频率相吻合,验证了改进算法的可行性和有效性。

高空台进气环境模拟系统固定时间自抗扰复合解耦控制

针对高空台进气环境模拟系统(IESS)存在压力与温度双变量强耦合及发动机快速过渡态试验带来的强总和扰动问题,设计一种新型固定时间滑模控制器(FxTSMC)并结合固定时间扩张状态观测器(FxTESO),提出一种固定时间自抗扰复合解耦控制(FxT-ADRCDC)方法。具体地,采用静态解耦方法将IESS解耦为两个单输入、单输出系统,实现IESS温度和压力的独立控制。在总扰动估计与抑制方面,利用固定时间扩张状态观测器快速准确估计系统状态与包含系统动态耦合在内的总扰动,并提出一种能够避免奇异问题且快速收敛的新型FxTSMC,将总扰动补偿到FxTSMC中,得到FxT-ADRCDC方法。设计Lyapunov函数证明了闭环控制系统的固定时间稳定性,得到不依赖于初始条件的稳定时间上限。搭建高置信度IESS仿真平台开展发动机过渡态飞行任务试验,对比了本文所提出方法与线性自抗扰解耦控制(LADRDC)方法。结果显示,FxT-ADRCDC方法控制下的进气压力、温度的绝对积分误差比LADRDC方法平均减少约70.3%和70.7%,且阀门摆动量符合实际工程要求,有效实现了进气压力、温度的高品质解耦控制,为提升IESS的快速、精确的动态模拟能力提供有力的技术支撑。

GCN-LSTM Based Transient Angle Stability Assessment Method for Future Power Systems Considering Spatial-temporal Disturbance Response Characteristics

Traditional transient angle stability analysis methods do not fully consider the spatial characteristics of the network topology and the temporal characteristics of the time-series disturbance.Hence,a data-driven method is proposed in this study,combining graph convolution network and long short-term memory network(GCN-LSTM)to analyze the transient power angle sta-bility by exploring the spatiotemporal disturbance char-acteristics of future power systems with high penetration of renewable energy sources(wind and solar energy)and power electronics.The key time-series electrical state quantities are considered as the initial input feature quantities and normalized using the Z-score,whereas the network adjacency matrix is constructed according to the system network topology.The normalized feature quan-tities and network adjacency matrix were used as the inputs of the GCN to obtain the spatial features,reflecting changes in the network topology.Subsequently,the spa-tial features are inputted into the LSTM network to ob-tain the temporal features,reflecting dynamic changes in the transient power angle of the generators.Finally,the spatiotemporal features are fused through a fully con-nected network to analyze the transient power angle stability of future power systems,and the softmax activa-tion cross-entropy loss functions are used to predict the stability of the samples.The proposed transient power angle stability assessment method is tested on a 500 kV AC-DC practical power system,and the simulation results show that the proposed method could effectively mine the spatiotemporal disturbance characteristics of power sys-tems. Moreover, the proposed model has higher accuracy, higher recall rate, and shorter training and testing times than traditional transient power angle stability algo-rithms.

Non-Stationary Random Process for Large-Scale Failure and Recovery of Power Distribution

This work applies non-stationary random processes to resilience of power distribution under severe weather. Power distribution, the edge of the energy infrastructure, is susceptible to external hazards from severe weather. Large-scale power failures often occur, resulting in millions of people without electricity for days. However, the problem of large-scale power failure, recovery and resilience has not been formulated rigorously nor studied systematically. This work studies the resilience of power distribution from three aspects. First, we derive non-stationary random processes to model large-scale failures and recoveries. Transient Little’s Law then provides a simple approximation of the entire life cycle of failure and recovery through a queue at the network-level. Second, we define time-varying resilience based on the non-stationary model. The resilience metric characterizes the ability of power distribution to remain operational and recover rapidly upon failures. Third, we apply the non-stationary model and the resilience metric to large-scale power failures caused by Hurricane Ike. We use the real data from the electric grid to learn time-varying model parameters and the resilience metric. Our results show non-stationary evolution of failure rates and recovery times, and how the network resilience deviates from that of normal operation during the hurricane.

综合提升新能源高占比受端电网小干扰和暂态电压稳定性的SVG优化配置方法

由于新能源发电设备的弱支撑性,新能源高占比的受端电网的电压支撑强度难以满足系统安全稳定运行的要求。为了解决现有静止无功发生器(static var generator,SVG)配置方法未能充分提升系统小干扰电压稳定性和暂态电压稳定性的问题,提出了一种综合考虑系统小干扰电压稳定和暂态电压稳定的SVG优化配置方法。首先,在第一阶段考虑SVG投资运行总成本和系统小干扰电压稳定裕度,在第二阶段引入SVG接入对系统故障后暂态电压稳定裕度的影响。然后,利用基于组合赋权法和相对熵距离的改进理想解法得到最优配置方案。最后,应用PSDBPA对新能源高占比受端电网算例进行分析,验证了所提配置方法能充分发挥SVG对系统电压稳定的提升作用。

基于SVD-ILMD的暂态电能质量扰动定位检测方法

为实现对电网非平稳扰动信号的快速、准确分析,提出了融合SVD(奇异值分解)与ILMD(优化局部均值分解)的暂态电能质量扰动定位检测方法。首先,通过ILMD与模糊隶属度函数阈值处理噪声信息,削弱噪声干扰;然后,构造差值信号并利用滑窗SVD增强扰动特征,进一步抑制噪声干扰;最后,基于特征增强信号提出一种自适应阈值截断的暂态电能质量扰动定位检测方法。经仿真分析与算法对比,验证了所提方法定位准确、抗噪性强、计算量小,对过零与微弱扰动也有较好的定位效果。

100 Mbps以太网端口的电快速瞬变脉冲群抑制装置

为了解决智能网联产品以太网端口的通信性能在电快速瞬变脉冲群试验中出现的非预期降级问题,研制了一款用于100 Mbps以太网端口的瞬态脉冲抑制装置。该装置的应用解决了以太网端口在±4 kV的电快速瞬变脉冲群干扰试验中出现的连接中断问题,并将±4 kV的电快速瞬变脉冲群干扰电压抑制至38.8 V,且不会引起以太网链路通信性能的明显下降。该研究为智能网联产品以太网端口的电快速瞬变脉冲群敏感度的准确判定提供了理论和技术支撑。

单电压环构网型并网逆变器暂态稳定性分析

随着电力电子化电力系统的快速发展,构网型并网逆变器作为新型电源得到了广泛关注,其中单电压环构网型并网逆变器因具有更强的小信号稳定性而在新能源并网中具有独特优势。同时,构网型并网逆变器在大扰动下呈现与同步电机不同的暂态响应,容易产生暂态失稳。针对这一问题,以单电压环构网型并网逆变器大扰动模型为基础,采用相平面图的方法分析了大扰动下功率控制环、电压控制环对逆变器的暂态作用,给出了关键控制器参数对暂态稳定性的影响,刻画了功角的暂态响应特性。同时,揭示了有功控制环、无功控制环和单电压环在暂态期间会改变功角超调量、逆变器输出电压幅值和变化率,进而影响并网逆变器的暂态稳定性。基于上述分析,给出了减小有功和无功下垂系数,增大电压积分系数和低通滤波器截止角频率的控制参数优化方法,可增强单电压环构网型并网逆变器暂态稳定性。最后,通过Matlab/Simulink仿真验证了分析的准确性与可行性。

基于智能体的电力系统分布式自适应抗干扰控制

针对多机电力系统中不可避免存在非线性、不确定特性和动态干扰等问题,基于径向基神经网络(RBFNN)和非线性干扰观测器(NDO)提出一种分布式自适应抗干扰控制器,以增强多机电力系统的暂态稳定性和鲁棒性。采用RBFNN处理系统中的未知非线性问题,并基于神经网络的输出设计NDO以实现对复合扰动的在线估计;在多智能体框架下为多机电力系统提出一种分布式自适应抗干扰控制策略,实时接收通信网络测量的数据并控制储能装置动作,在外部扰动下实现各电机转速的快速同步与跟踪,并利用Lyapunov稳定性理论证明闭环系统信号的收敛性。仿真实验表明:所提策略有效可行。

FLEXURAL-GRAVITY WAVES DUE TO TRANSIENT DISTURBANCES IN AN INVISCID FLUID OF FINITE DEPTH

The dynamic response of an ice-covered fluid to transient disturbances was analytically investigated by means of integral transforms and the generalized method of stationary phase. The initially quiescent fluid of finite depth was assumed to be inviscid, incompressible, and homogenous. The thin ice-cover was modeled as a homogeneous elastic plate. The disturbances were idealized as the fundamental singularities. A linearized initial-boundary-value problem was formulated within the framework of potential flow. The perturbed flow was decomposed into the regular and the singular components. An image system was introduced for the singular part to meet the boundary condition at the fiat bottom. The solutions in integral form for the vertical deflexion at the ice-water interface were obtained by means of a joint Laplace-Fourier transform. The asymptotic representations of the wave motion were explicitly derived for large time with a fixed distance-to-time ratio. The effects of the finite depth of fluid on the resultant wave pattems were discussed in detail. As the depth increases from zero, the critical wave number and the minimal group velocity first increase to their peak values and then decrease to constants.

Transient power quality disturbance denoising and detection based on improved iterative adaptive kernel regression

The denoising and detection of transient disturbances are two important subjects for power quality monitoring and analysis. To effectively denoise and detect transient disturbances under noisy conditions, an improved iterative adaptive kernel regression method is proposed in this paper. The proposed method has advantages that itdoes not need to estimate the noise variance or a filter threshold, and has both denoising and detection capabilities for transient disturbances. Simulation results demonstrate that the proposed method provides excellent denoising effects, which can not only suppress noise effectively but also preserve disturbance features of sudden change points well. Additionally, it provides good detection and location performance for single and combined transient disturbances, even under strong noise conditions. Finally, the effectiveness of the proposed method is further verified by using real disturbance data.

Impact of welding equipment on power quality

In an industrial facility,many electrical consumers can affect the quality of electricity.Therefore,the freedom from interference sources of these devices and equipment can be crucial for quality and uninterrupted electricity supply.Electric welding equipment is also a possible source of interference.The electrical harmonic injections created by welding equipment into the electrical network can affect the operation of other consumers connected to the given distribution points and cause unjustified overheating and shutdowns of some network components.The aim of the research is to analyse the current harmonic injection of welding equipment of different types and modes of operation connected to the internal distribution network of the industrial facility.The effectiveness of the active harmonic filter built into the welding equipment was also examined in the paper.The results showed that the built-in active harmonic filter of the DC045 laser welding equipment was ineffective because the total harmonic distortion(THD)was about three times the 8%allowed by IEEE 519−2022 standard.The current harmonic injection of MIG 320 and MM403 type welding equipment was more than five times the permissible value of 5%.The current harmonic distortion of the PLAS140 type plasma-jet cutter equipment was below the 5% value allowed in the standard,thus it complied with it.Based on the measurement results,it can be concluded that the use of protection against harmonics is also necessary for welding equipment.Finally,proposals were made in the paper to reduce the effect of harmonics.

结合特征根及模态分析法的逆变器多机并网系统谐波扰动响应分析

为了从本质上解释逆变器多机并网系统受到宽频谐波扰动后的动态行为,该文理论推导特征根与系统稳态和暂态响应的解析解,进而利用单个逆变器并网的实例验证了采用特征根分析系统谐波响应的可行性。针对逆变器多机并网系统,阐明特征根与谐振模态的对应关系,使得利用模态分析方法既能解析系统内部支路对不同谐振模态的可激励性和可观测性,又能视系统为一个整体对其稳定性进行分析。最后,通过仿真与实验验证了结合特征根分析逆变器并网系统动态行为的正确性及有效性。

短时电压振荡下矿区供电变电所电能质量小波暂态扰动检测方法

短时电压振荡下矿区供电变电所电能质量小波暂态扰动在检测的过程中存在扰乱类型较多和噪声环境复杂的现象,在进行检测的同时需要及时处理噪声信号,导致检测的效率低,效果较差。针对该问题,对矿区供电变电所电能质量小波暂态扰动进行检测,首先对噪声环境进行小波去噪处理,减少外界环境对检测结果的影响;并基于PCA算法对数据降维处理,调整数据暂态形式,建立识别机制,提高检测精度;最终结合去噪的阈值进行内部检测,获取检测数据。根据实验结果可知,该电能质量小波暂态扰动检测方法具有较高的检测精度,与预设参数吻合度较高,检测效果良好。

基于集中式电子电气架构的沿电源线电瞬态传导脉冲研究

对于汽车电子沿电源线电瞬态传导抗扰试验,ISO 7637-2标准规定了多种模式下的典型脉冲波形以及试验要求,但并不能覆盖汽车上所有的瞬态类型。随着新能源汽车的发展,汽车电子电气架构由分布式架构转向集中式域控架构,供电方式也与传统的方式不同。本文首先分析了集中式架构对于标准中典型脉冲波形的影响,然后实车采集了域控架构下的电源线上的一些瞬态脉冲波形,并对这些脉冲波形进行拟合,最后使用autowave设备将拟合后的波形注入到整车电气件,验证了这类脉冲波形会对一些电器件产生干扰问题。因此,在产品开发时需针对异常脉冲进行设计预防,从源头规避潜在风险。车企及零部件厂商也应更加关注新电气架构下存在的电磁兼容风险。

采用改进多分辨率快速S变换的电能质量扰动识别

噪声干扰是影响电能质量暂态扰动识别准确率的最重要因素。经过S变换后获得的扰动信号的模时–频矩阵具有灰度图像特点。因此,可通过二维数学形态学方法,滤除噪声干扰,获得更高的识别准确率。首先,针对扰动信号时–频分布特点,设计具有不同时–频分辨率的多分辨率快速S变换方法以降低运算量、提高特征表现能力;之后,在阈值滤波基础上,根据信号时–频分布特点,选择线段型、零角度结构元进行灰度级形态学开运算,进一步滤除高频频域噪声;最后,从原始信号、信号傅里叶谱、多分辨率快速S变换模矩阵中提取5种特征建立决策树分类器,识别含噪声信号与6种复合扰动信号在内的12种电能质量信号。通过仿真对比实验发现,新方法具有更好的抗噪能力,更加适用于低信噪比环境下的电能质量信号识别。

基于提升复小波的暂态电能质量扰动的检测与定位

针对暂态电能质量扰动信号的检测与定位,提出一种基于第2代小波变换的提升复小波的提升算法。通过Euclidean分解算法得到复小波提升方案;利用该方案对常见的几种扰动信号进行提升变换,将变换后的幅值和相位信息用于暂态电能质量扰动的定位检测及扰动幅度估计;并与第1代小波变换进行比较。仿真结果表明,所提算法具有简单、运行速度快、检测精度高等优点,能够准确定位暂态电能质量扰动信号和计算扰动信号的变化幅度。