Frequency Stability Prediction of Power Systems Using Vision Transformer and Copula Entropy

This paper addresses the problem of frequency stability prediction (FSP) following active power disturbances in power systems by proposing a vision transformer (ViT) method that predicts frequency stability in real time. The core idea of the FSP approach employing the ViT is to use the time-series data of power system operations as ViT inputs to perform FSP accurately and quickly so that operators can decide frequency control actions, minimizing the losses caused by incidents. Additionally, due to the high-dimensional and redundant input data of the power system and the O(N²) computational complexity of the transformer, feature selection based on copula entropy (CE) is used to construct image-like data with fixed dimensions from power system operation data and remove redundant information. Moreover, no previous FSP study has taken safety margins into consideration, which may threaten the secure operation of power systems. Therefore, a frequency security index (FSI) is used to form the sample labels, which are categorized as “insecurity”, “relative security”, and “absolute security”. Finally, various case studies are carried out on a modified New England 39-bus system and a modified ACTIVSg500 system for projected 0% to 40% nonsynchronous system penetration levels. The simulation results demonstrate that the proposed method achieves state-of-the-art (SOTA) performance on normal, noisy, and incomplete datasets in comparison with eight machine-learning methods.     

A Fault Diagnosis Method Considering Meteorological Factors for Transmission Networks Based on P Systems

Bad meteorological conditions may reduce the reliability of power communication equipment, which can increase the distortion possibility of fault information in the communication process, hence raising its uncertainty and incompleteness. To address the issue, this paper proposes a fault diagnosis method for transmission networks considering meteorological factors. Firstly, a spiking neural P system considering a meteorological living environment and its matrix reasoning algorithm are designed. Secondly, based on the topology structure of the target power transmission network and the action logic of its protection devices, a diagnosis model based on the spiking neural P system considering the meteorological living environment is built for each suspicious fault transmission line. Following this, the action messages of protection devices and corresponding temporal order information are used to obtain initial pulse values of input neurons of the diagnosis model, which are then modified with the gray fuzzy theory. Finally, the matrix reasoning algorithm of each model is executed in a parallel manner to obtain diagnosis results. Experiment results achieved out on IEEE 39-bus system show the feasibility and effectiveness of the proposed method.     

Maximum Correntropy with Variable Center Unscented Kalman Filter for Robust Power System State Estimation

The robust Kalman filter with correntropy loss has received much attention in recent years for forecasting-aided state estimation in power systems, since it efficiently reduces the negative influence of various abnormal situations, such as non-Gaussian communication, changing environment, and instrument failures, and obviously improves the stability of power systems. However, the existing correntropy-based robust Kalman filters usually use the Gaussian function with a fixed center as the kernel function in correntropy, which may not be a suitable choice in practical applications of power system forecasting-aided state estimation (PSSE). To address this issue, a new and robust unscented Kalman filter, called the maximum correntropy with variable center unscented Kalman filter (MCVUKF), is proposed in this paper for PSSE. Specifically, MCVUKF adopts an extended version of correntropy, whose center can be located at any position, to replace the original correntropy in an unscented Kalman filter to improve the performance in PSSE. Moreover, by using an exponential function of the innovation vector to adjust a covariance matrix, an enhanced MCVUKF (En-MCVUKF) method is also developed for suppressing the influence of bad data to the innovation vector and further improving the accuracy of PSSE. Finally, extensive simulations have been conducted on IEEE 14-bus, 30-bus, and 57-bus test power systems, and the simulation results have shown the superiority of the proposed MCVUKF and En-MCVUKF methods compared with several related state-of-the-art Kalman filter methods.     

基于固态功率控制器的器载配电器的BIT设计技术研究[BT)]

航空航天飞行器发展迅速,用电设备数量增多,飞行任务复杂性增大,对飞行器配电系统的智能程度以及可靠性提出更高要求。配电器是配电系统的核心设备,为飞行器所有用电负载设备分配电能,其性能的优劣直接影响到飞行任务的成败,BIT（Built-In Test）技术是一种能够显著改善系统或设备测试性能和诊断能力的重要手段。研究了以固态功率控制器为核心器件的配电系统总体方案,对固态功率控制器的故障模式与测试方法进行了分析,给出了测试点设计和优选方法,通过故障诊断能力计算结果表明BIT设计技术可提高配电系统的可靠性和智能化程度。     

无人值守变电站电力设备音频监测及故障诊断系统

针对智能变电站的无人值守需求及现有故障诊断系统的不足,提出一种电力设备音频监测及故障诊断系统。根据变电站电力设备音频信号信噪比较低的特点,采用具有强鲁棒性的梅尔频率倒谱系数作为判断音频信号异常的特征参数,在此基础上根据音频特征构成多样本观测序列,并采用隐马尔科夫模型进行故障诊断,通过对比对数似然估计概率的输出值确定故障类型。该方法具有实时性较强的优势,也避免了现有故障诊断方法要求较大样本容量的缺陷。实验结果表明,该故障诊断系统具有较高的识别率和鲁棒性。     

主动式配气系统驱动的低温制冷机理论与实验研究

针对G—M型脉管制冷机传统配气方式中压缩机配气量耗功和不可逆损失较大等缺点,本文提出一种带有中间气库的主动式配气系统。理论分析表明,和传统配气方式相比,主动式配气系统可显著降低压缩机配气量耗功和配气系统熵产。基于自行研制的G—M型脉管制冷机开展实验。当中间气库开启时间比例为30％时,制冷机可获得较低的制冷温度且对制冷性...     

基于极化因子神经网络的火电厂制粉系统故障诊断技术

制粉系统是火电厂的主要设备,其安全稳定运行对发电企业的经济生产具有十分重要的意义。针对制粉系统的运行特性和故障分析,提出了基于极化因子神经网络的火电厂制粉系统故障诊断方法,该方法将故障征兆相应的过程变量作为输入,将制粉系统故障类型作为输出,通过训练神经网络建立其系统故障诊断模型,其中训练过程中采用极化因子来自动调整神经网络的收敛速度,从而在满足误差目标的前提下,防止其陷入局部极小。选取实际火电厂制粉系统3个典型故障及其相对应的9个故障征兆参数进行了实验。结果表明,该方法具有良好的收敛性,完全可以满足火电厂制粉系统现场故障诊断的要求。     

分布式发电系统感性负载的远程混沌同步

对含有大规模感性负载分布式发电系统（DG）的远程同步进行研究.以风力发电机作为DG发电节点,以永磁同步电机作为实际感性负载,建立一个具有网络耦合作用的DG数学模型,分析不同拓扑网络结构（包括星型、多层网络结构型、随机网络结构型、实际电网IEEE39系统）DG系统感性负载的远程同步特性,进行数值仿真.研究表明：感性负载通过发电机组的中继作用可实现远程混沌同步.研究结果对保证分布式发电系统的同步稳定运行具有意义.     

动态故障树在主蒸汽管道破裂事故风险评价中的初步应用研究

冗余设计使核电厂系统广泛存在复杂时序失效行为,而基于静态故障树(Static fault tree, SFT)的事故风险评价无法对时序失效行为进行准确模拟。为解决这一问题,本工作提出一种基于事件树+动态故障树(Dynamic Fault Tree, DFT)的事故风险分析框架,并以典型三代压水堆主蒸汽管道破裂事故为例,开展动态事故风险案例分析。首先,建立主蒸汽管道破裂事故的事件树模型以及相关系统的DFT模型;其次,将系统故障树分为DFT模块和SFT模块,并将DFT树模块替换为超级事件参与后续计算;最后,采用割集法计算案例结果,并在相同条件下与传统SFT方法进行对比。案例分析结果表明：(1)相较于SFT方法,所提方法更为贴近系统的真实失效场景;(2)针对文中案例所提方法可以降低相关系统失效概率与部分事故序列的发生频率、有助于释放保守风险。     

电压补偿型超导限流器对电流保护的影响

基于电压补偿型超导故障限流器(SFCL)的工作原理,分析了电网故障时由于限流器限流阻抗串入对电流保护的影响.通过重新整定电流保护的动作值,得到了限流器与电流保护配合的解决方法.以一个10kV中性点不接地配电网为例,分别对引入SFCL前后系统三相短路的电流保护进行仿真,验证了该方法的有效性.     

基于衰减振荡信号特征参数和伪阻抗的电路参数计算方法

本文研究了基于暂态信号中衰减振荡信号的电路参数计算理论和方法.在电力系统线路发生故障时,通过计算暂态信号流通路径电路参数可确定故障位置、推断故障原因,而衰减振荡信号作为暂态信号主要成分,因此分析基于衰减振荡信号的电路参数计算在电力系统故障定位中有重要理论价值和实际工程意义.结合R-L电路和R-C电路,首先推导了时域衰减振荡电压、电流信号特征参数与各元件参数以及电路参数间定量关系;并分析了电路在衰减振荡信号下阻抗特性,结合稳态正弦分量阻抗概念,将电路流经衰减振荡信号时的阻抗特性定义为伪阻抗,并确定了伪阻抗与电路参数和信号特征参数间的关系;同时分析了串并联条件下伪阻抗与元件参数关系.以此为基础分别提出了基于信号特征参数和基于伪阻抗的电路参数计算理论,结合现有衰减振荡信号特征提取方法,提出具体计算方法,为基于衰减振荡信号的电路参数计算理论发展以及实际工程应用奠定了重要基础.通过MATLAB模拟产生故障信号对所提理论和方法进行验证,结果证明了所提理论和方法的正确性和准确性,并以实际电网故障信息为基础,基于PSCAD/EMTDC建立实际配网模型并对实际单相接地故障进行重现,对配网单相接地故障进行定位分析,结果证明了方法的可行性.     

Analysis of cascading failure in electric grid based on power flow entropy

Large-scale blackouts are an intrinsic drawback of electric power transmission grids. Here we propose a concept of power flow entropy to quantify the overall heterogeneity of load distribution and then investigate the relationship between the power flow entropy and cascading failure. Simulation results, from the small-world 300-node test system and the IEEE 300-bus system, show that the power flow entropy has close relations with the cascading failure in terms of both the dynamic propagation course and the static blackout size. Particularly, at the early stage of failure spreading the potential large blackout can be identified according to the power flow entropy. The power flow entropy can serve as an index not only for long-term planning, but also for short-term operational defense to large-scale blackouts.     

激光诱导击穿光谱分析系统中微型同步时序发生器研制

在激光诱谱导击穿光谱技术(laser-induced breakdown spectroscopy,LIBS)中,元素特征光谱信号强度和信噪比在不同采集延时下具有显著差异,直接影响定量分析的结果。LIBS分析系统通常采用通用型延时发生器来控制采集延时,然而其体积大、功耗高、价格昂贵,不利于LIBS仪器的小型化和便携化。为此,采用单片微控制器芯片和简单外围电路设计实现了具有55 ps可调延时精度的多通道微型同步时序发生器(简称LDG3.0),大幅度降低了同步时序发生器的体积、功耗和成本。对比LDG3.0与一种典型通用延时发生器DG535作为同步时序发生器的LIBS系统,以钒钛生铁中微量钒(V)元素定量检测为例进行两种同步时序发生器性能分析。结果表明,采用LDG3.0和DG535的LIBS系统建立的V元素定标曲线拟合系数R2均大于0.997,前者的平均相对标准偏差ARSD略小于后者,达到2.28%;前者检测极限LoD略低于后者,达到19.90 μg·g-1。因此,自主设计的同步时序发生器LDG3.0与DG535在LIBS系统中的精度基本一致,完全满足LIBS系统的实际控制和集成应用需求,特别适合于体积与功耗受限的LIBS仪器。     

Positivity preserving semi-Lagrangian discontinuous Galerkin formulation: Theoretical analysis and application to the Vlasov–Poisson system

Semi-Lagrangian (SL) methods have been very popular in the Vlasov simulation community , , , , , ,  and . In this paper, we propose a new Strang split SL discontinuous Galerkin (DG) method for solving the Vlasov equation. Specifically, we apply the Strang splitting for the Vlasov equation [6], as a way to decouple the nonlinear Vlasov system into a sequence of 1-D advection equations, each of which has an advection velocity that only depends on coordinates that are transverse to the direction of propagation. To evolve the decoupled linear equations, we propose to couple the SL framework with the semi-discrete DG formulation. The proposed SL DG method is free of time step restriction compared with the Runge–Kutta DG method, which is known to suffer from numerical time step limitation with relatively small CFL numbers according to linear stability analysis. We apply the recently developed positivity preserving (PP) limiter [37], which is a low-cost black box procedure, to our scheme to ensure the positivity of the unknown probability density function without affecting the high order accuracy of the base SL DG scheme. We analyze the stability and accuracy properties of the SL DG scheme by establishing its connection with the direct and weak formulations of the characteristics/Lagrangian Galerkin method [23]. The quality of the proposed method is demonstrated via basic test problems, such as linear advection and rigid body rotation, and via classical plasma problems, such as Landau damping and the two stream instability.     

基于Dymola软件及Modelica语言的飞机供电系统建模与仿真

飞机供电系统的布局设计与控制逻辑是飞机系统设计的重要环节,且其对系统的可靠性、容错供电和余度等特性具有一定影响。对飞机电源系统进行仿真建模研究,在支持各种物理系统建模的Dymola平台下搭建了数字仿真模型,包括交流发电机、变压整流器、电源系统接触器和过欠压、过欠频检测模块等部件模型,并利用各个部件模型搭建了供电系统模型,同时利用Modelica语言完成系统逻辑设计,对整个系统进行仿真。数字仿真结果表明电源系统模型基本能够完成自动配电、自动隔离故障,达到设计要求,为飞机系统设计提供了理论支持。     

A time-domain Discontinuous Galerkin method for mechanical resonator quality factor computations

Numerical simulations are becoming increasingly important in the design of micromechanical resonators, in particular for the prediction of complex frequency response in high quality devices where damping is controlled by anchor losses. Frequency based approaches have been shown to predict these accurately, however, they require the solution of eigenvalue problems or the inversion of Helmholtz-type operators which are known to be very difficult for large-scale iterative solvers. We propose using a time-domain approach instead, where a broadband input signal is propagated through the system with a local explicit time-stepper. This is achieved using a new high-order Discontinuous Galerkin (DG) discretization for the linear elasticity equations, in particular a second-order formulation with Compact DG fluxes and a Runge–Kutta time integrator, where the block-diagonal mass matrices allow for efficient, stable, and accurate time stepping. Our solver scales well on distributed parallel computers, even in three spatial dimension and for large problem sizes. The resulting output signal is analyzed using a well-known filter diagonalization method, which is capable of finding accurate frequencies and quality factors for as little as a hundred periods of data. We validate the properties of our scheme on model problems, and demonstrate the feasibility of our proposed analysis process on two high quality factor disk resonators, using an axisymmetric formulation as well as full three dimensional simulations which is shown to scale well.     

计及地磁暴影响的电力系统事故链仿真模型

地磁暴影响下地磁感应电流(GIC) 流过变压器中性点, 引起变压器无功损耗增加, 在强地磁暴环境中, 系统的无功补偿装置可能过载, 母线电压下降, 可能引发连锁故障, 继而导致大停电事故。对比事故链各环节特点和因磁暴导致的电力系统停电事故的发展规律, 使用事故链模型来仿真实现地磁暴条件下的电网停电过程。基于自组织临界理论和非故障线路的安全稳定裕度来确定连锁故障的传播路径。结合IEEERTS79系统参数, 估算各母线的地理位置, 借助PowerWorld仿真软件, 以该系统为例, 研究结果验证了所提事故链模型可以反映给定电网条件下, 地磁暴参数对电力系统事故链集与薄弱环节辨识的影响, 研究结果可为量化和防治磁暴电网灾害提供依据。     

Dual-gate lateral double-diffused metal—oxide semiconductor with ultra-low specific on-resistance

A new high voltage trench lateral double-diffused metal-oxide semiconductor (LDMOS) with ultra-low specific onresistance (R on,sp ) is proposed. The structure features a dual gate (DG LDMOS): a planar gate and a trench gate inset in the oxide trench. Firstly, the dual gate can provide a dual conduction channel and reduce R on,sp dramatically. Secondly, the oxide trench in the drift region modulates the electric field distribution and reduces the cell pitch but still can maintain comparable breakdown voltage (BV). Simulation results show that the cell pitch of the DG LDMOS can be reduced by 50% in comparison with that of conventional LDMOS at the equivalent BV; furthermore, R on,sp of the DG LDMOS can be reduced by 67% due to the smaller cell pitch and the dual gate.     

A low on-resistance triple RESURF SOI LDMOS with planar and trench gate integration

A low on-resistance(Ron,sp) integrable silicon-on-insulator(SOI) n-channel lateral double-diffused metal-oxide-semiconductor(LDMOS) is proposed and its mechanism is investigated by simulation.The LDMOS has two features:the integration of a planar gate and an extended trench gate(double gates(DGs));and a buried P-layer in the N-drift region,which forms a triple reduced surface field(RESURF)(TR) structure.The triple RESURF not only modulates the electric field distribution,but also increases N-drift doping,resulting in a reduced specific on-resistance(Ron,sp) and an improved breakdown voltage(BV) in the off-state.The DGs form dual conduction channels and,moreover,the extended trench gate widens the vertical conduction area,both of which further reduce the Ron,sp.The BV and Ron,sp are 328 V and 8.8 m.cm2,respectively,for a DG TR metal-oxide-semiconductor field-effect transistor(MOSFET) by simulation.Compared with a conventional SOI LDMOS,a DG TR MOSFET with the same dimensional device parameters as those of the DG TR MOSFET reduces Ron,sp by 59% and increases BV by 6%.The extended trench gate synchronously acts as an isolation trench between the high-voltage device and low-voltage circuitry in a high-voltage integrated circuit,thereby saving the chip area and simplifying the fabrication processes.     

A novel power allocation strategy for cooperative PDMA systems

Cooperative communication technology is of great importance for increasing the user reachable rate, further improving throughput and reducing the outage probability of non-orthogonal multiple access (NOMA) systems. This paper mainly studies the power allocation optimization method based on amplify-and-forward (AF) pattern division multiple access (PDMA) to obtain the maximum achievable throughput. We formulate an optimization problem of user power allocation in a downlink PDMA system with cooperative relaying, the exact expressions of system throughput and user outage probability of the AF-PDMA system are derived, and a novel power allocation optimization method based on uniform distribution and restricted constraints is proposed. The effectiveness of the restricted constraints and optimization method is verified by theoretical analysis and simulation. The studies we have performed showed that the proposed scheme with uniform distribution and restricted constraints can be significantly improved in terms of the system throughput in comparison to the case with a genetic algorithm (GA) and fixed power allocation scheme. Concerning the proposed method, the search space is reduced to 1/3 of the original feasible region, and the runtime of the algorithm accounts for only 20% of the GA runtime.