Transient Stability Analysis of Power System Based on an Improved Neural Network

A new type of ANN (Artificial Neural Network) structure is introduced, and a nonlinear transformation of the original features is proposed so as to improve the learning covergence of the neural network. This kind of improved ANN is then used to analyse the transient stability of two real power systems. The results show that this method possesses better effectiveness and high convergence speed.

Power System Transients Analysis by Wavelet Transforms

In contrast to Fourier transform, wavelet transform is especially suitable for transient analysis because of its time frequency characteristics with automatically adjusted window lengths. Research shows that wavelet transform is one of the most powerful tools for power system transient analysis. The basic ideas of wavelet transform are presented in the paper together with several power system applications. It is clear that wavelet transform has some clear advantages over other transforms in detecting, analyzing, and identifying various types of power system transients.

SELECTION OF TRANSMISSION LINE MODELS USED IN POWER SYSTEM TRANSIENT SIMULATIONS

A method used for determining the number of equivalent π sections oftransmission line model according to the frequency range of interest and the model accura-cy defined herein is proposed.Factors influencing the discrepancies between continuous ordistributed parameter and multiple π or lumped parameter models are discussed.Generalconclusions concerning the π section lengths of line models used in transient stability,faulttransient and switching over-voltage studies are drawn.Time-domain simulation resultsconfirm the effectiveness of this method.

An Advanced FMRL Controller for FACTS Devices to Enhance Dynamic Performance of Power Systems

The parameters of power system slowly change with time due to environmental effects or may change rapidly due to faults. It is preferable that the control technique in this system possesses robustness for various fault conditions and disturbances. The used flexible alternating current transmission system （FACTS） in this paper is an advanced super-conducting magnetic energy storage （ASMES）. Many control techniques that use ASMES to improve power system stability have been proposed. While fuzzy controller has proven its value in some applications, the researches applying fuzzy controller with ASMES have been actively reported. However, it is sometimes very difficult to specify the rule base for some plants, when the parameters change. To solve this problem, a fuzzy model reference learning controller （FMRLC） is proposed in this paper, which investigates multi-input multi-output FMRLC for time-variant nonlinear system. This control method provides the motivation for adaptive fuzzy control, where the focus is on the automatic online synthesis and tuning of fuzzy controller parameters （i.e., using online data to continually learn the fuzzy controller that will ensure that the performance objectives are met）. Simulation results show that the proposed robust controller is able to work with nonlinear and nonstationary power system （i.e., single machine-infinite bus （SMIB） system）, under various fault conditions and disturbances.

Life Prediction Based on Transient Dynamics Analysis of Van Semi-trailer with Air Suspension System

The early fatigue damage in the van-body of the semi-trailer is often caused by the unique mechanical characteristics and the dynamic impact of the loads.The traditional finite element method with static strength analysis cannot support the fatigue design of van-body;thus,the dynamics analysis should be adopted for the endurance performance.The accurate dynamics model to describe the transient impacts of all kinds of uneven road and the proper system transfer functions to calculate the load transfer effects from tire to van-body are two critical factors for transient dynamics analysis.In order to evaluate the dynamic performance,the dynamics model of the trailer with the air suspension is brought forward.Then the analysis method of the power spectral density （PSD） is set up to study the transient responses of the road dynamic impacts.The transient responses transferred from axles to van-body are calculated,such as dynamic stress,dynamic RMS acceleration,and dynamic load factors.Based on the above dynamic responses,the fatigue life of van-body is predicted with the finite element analysis （FEA） method.Applying the test parameters of the trailer with air suspension,the simulation system with Matlab/Simulink is constructed to describe the dynamic responses of the impacts of the tested PSD of the vehicle axles,and then the fatigue life is predicted with FEA method.The simulated results show that the vibration level of the van-body with air suspension is reduced and the fatigue life is improved.The real vehicle tests on different roads are carried out,and the test results validate the accuracy of the simulation system.The proposed fatigue life prediction method is effective for the virtual design of auto-body.

Transient Power and Quality Events Analysed Using Hilbert Transforms

This work presents an advanced mathematical tool applicable to the recognition and classification of power system transients and disturbances. Disturbances without a periodic pattern or with a non-linear pattern require a more suitable tool than the Fourier series （Fast Fourier or Windowed Fourier Transforms）. To overcome these drawbacks, other tools have been broadly used, such as the wavelet transform. However, the wavelet transform also has some drawbacks such as the lack of adaptivity or interpretation of nonlinear phenomena that the Hilbert and Hilbert Huang Transform techniques could mitigate. The Hilbert techniques transform a time domain function into a space representation both in time and frequency. In the paper, the technique is applied to analyse several short-term and steady events, like a short circuit, a capacitor-switching transient, or a line energisation, showing the abilities of the Hilbert-based transforms.

Analysis on Sensitivity of Power System Stability to Generator Parameters

The sensitivity of power system stability (including transient and dynamic stabilities) to generator parameters (including parameters of generator model, excitation system and power system stabilizer) is analyzed in depth by simulations. From the tables and plots of the resultant simulated data, a number of useful rules are revealed. These rules can be directly applied to the engineering checking of generator parameters. Because the complex theoretical analyses are circumvented, the checking procedure is greatly simplified, remarkably promoting the working efficiency of electrical engineers on site.

基于Powershap特征选择的电力系统暂态稳定评估

为进一步提高暂态稳定评估(transient stability assessment,TSA)的精准度和可靠性,提出一种基于统计学与Shapley值结合的特征选择方法(Powershap),并建立电力系统TSA模型。首先,根据电力系统运行时的稳态分量构建输入特征集,采用Powershap将数据集分为多个数据子集进行训练,筛选出关键特征集;其次,利用关键特征集训练多个CatBoost模型并进行TSA,生成TSA模型;最后,在新英格兰10机39节点系统和加入新能源发电的新英格兰54机118节点系统上进行仿真实验,并给出评估结果。实验得出:在新英格兰10机39节点系统中采用基于Powershap特征选择的方法进行分类,其准确率能够达到99.79%;在改进的新英格兰54机118节点系统上,其准确率能够达到99.49%,说明该方法能够有效进行电力系统暂态稳定评估,并且验证了所提TSA模型具有较好的鲁棒性与泛化能力。

Improvement of Power System Stability by Static Var Compensator and Tuning Employing Genetic Algorithm

The use of power systems as close to their operating limits can cause instability if a disturbance is occurred. The damping of the system’s oscillations can be obtained by conventional means such as voltage and speed regulation but also by Flexible AC Transmission System devices (FACTS). These devices are increasingly used in power systems. This paper presents a systematic procedure for modelling and simulation of a single-machine infinite-bus power system installed with a Static VAR Compensator (SVC). So the impact of the SVC on power system stability can be reasonably evaluated. Genetic algorithm (GA) optimization technique is applied to design robust power system stabilizer and SVC-controllers for single-machine infinite-bus (SMIB) and is employed to search for optimal controller parameters.

基于CDoubleGAN的电网时序暂态数据生成

为解决电力系统人工智能应用中样本数量不足的问题,对时序数据生成方法进行研究,提出一种CDoubleGAN模型。结合编解码器和两对生成器-鉴别器,采用ARFNN替代RNN解决Lipschitz连续性问题,实现使用Wasserstein距离对目标函数的稳定优化。将数据类别标签融入模型中,生成特定类别的样本。在IEEE-39系统的实验结果表明,CDoubleGAN在类别生成上的准确度超过98%,与TimeGAN相比,生成的数据与原数据具有更高的相似度,更好保留了数据原始特性以应用于数据生产。

Mitigation of Transients in Capacitor Coupled Substations Using Traditional RLC Filter Techniques

This article presents an extensive examination and modeling of Capacitor Coupled Substations (CCS), noting some of their inherent constraints. The underlying implementation of a CCS is to supply electricity directly from high-voltage (HV) transmission lines to low-voltage (LV) consumers through coupling capacitors and is said to be cost-effective as compared to conventional distribution networks. However, the functionality of such substations is susceptible to various transient phenomena, including ferroresonance and overvoltage occurrences. To address these challenges, the study uses simulations to evaluate the effectiveness of conventional resistor-inductor-capacitor (RLC) filter in mitigating hazardous overvoltage resulting from transients. The proposed methodology entails using standard RLC filter to suppress transients and its associated overvoltage risks. Through a series of MATLAB/Simulink simulations, the research emphasizes the practical effectiveness of this technique. The study examines the impact of transients under varied operational scenarios, including no-load switching conditions, temporary short-circuits, and load on/off events. The primary aim of the article is to assess the viability of using an established technology to manage system instabilities upon the energization of a CCS under no-load circumstances or in case of a short-circuit fault occurring on the primary side of the CCS distribution transformer. The findings underscore the effectiveness of conventional RLC filters in suppressing transients induced by the CCS no-load switching.

基于主动迁移学习的电力系统暂态稳定自适应评估

构建了一个基于主动迁移学习的框架,基于原始场景数据搭建并训练源域暂态稳定评估(transient stability assessment,TSA)模型。当运行场景变化导致模型性能下降时启动更新机制,通过短时时域仿真生成大量无稳定性标签的样本以及完整仿真生成小批量带标签样本,采用基于变分对抗的主动学习方法学习数据潜在的特征表示空间,根据置信度选择信息量最大的无标签样本并进行标注。迁移基础模型参数并结合有标签样本进行微调,在保证迁移精度的情况下节省更新时间,通过IEEE 39节点验证了所提方法的有效性。

计及动态负荷特性的多馈入直流系统暂态电压强度分析方法

针对由于动态负荷和非同步机电源的暂态复杂特性导致系统暂态电压强度分析困难的问题,提出一种计及动态负荷特性的多馈入直流系统暂态电压强度分析方法。首先,根据电压刚度概念,给出暂态电压刚度的定义;然后,为描述感应电动机、新能源机组及直流等动态元件对系统暂态电压的影响,提取暂态关键时间断面,将复杂的暂态分析转换为关键时间断面的代数求解模型,从而提出暂态电压强度分析方法。最后,以华东电网为例验证所提的暂态电压强度分析方法的有效性,结果表明该方法能够对定量评估多馈入系统的电压支撑强度具有一定的指导意义。

功率同步型构网变流器并网系统暂态同步稳定性研究综述

高比例可再生能源接入电力系统使系统呈现低惯量、弱支撑特点。功率同步型构网变流器通过模拟同步发电机运行特性,可提供频率和电压主动支撑能力。但不同于同步发电机,变流器中电力电子器件过流和过热耐受能力有限,由限流控制引发的功率同步型构网变流器多控制环交互作用显著,其引发的暂态同步失稳与闩锁问题严重影响了功率同步型构网变流器并网系统的安全稳定运行和主动支撑能力的发挥。而功率同步型构网变流器同步环呈现出的高度非线性特性使其并网系统暂态同步稳定性难以分析与量化,给暂态同步稳定性的优化控制带来了新的挑战。针对功率同步型构网变流器并网系统在不考虑故障限流时的暂态失稳问题,以及考虑故障限流作用下的暂态失稳与闩锁问题,对系统建模、分析与稳定边界量化方法进行了总结与归纳。基于暂态失稳与闩锁问题的分析与归纳结果,对功率同步型构网变流器并网系统的暂态同步稳定控制方法进行了综述。最后,对未来功率同步型构网变流器并网系统的暂态同步稳定分析与控制研究方向进行了展望。

基于GCN-LSTM的电力系统暂态电压稳定评估

为了提高电力系统暂态电压在系统拓扑结构发生变化时能够稳定评估,以及提高在时空方面的特征提取能力,提出一种图卷积网络与循环神经网络相融合的方法。首先,引入图卷积网络对电力数据进行图表示,将电力系统建模为网络结构,自动学习电压节点的特征表示。其次,提出使用循环神经网络来处理暂态电压数据的时间依赖关系,捕捉暂态电压数据的时序特征。然后,提出自适应增强模块,用于将两个输出特征表示相互融合,提高模型在系统拓扑结构上的时空特征提取能力。最后,通过算例验证表明,相比于传统的评估模型,所提方法具有更高的预测精度和有效性。

考虑风机低穿动态的风火打捆外送系统暂态功角稳定性分析

风火打捆外送系统中,风机的低电压穿越及恢复控制会影响火电机组的转子动态,可能诱发首摆或多摆失稳。建立了风火打捆外送系统的暂态功角稳定性分析模型,揭示了风电场输出功率变化对火电机组暂态功角稳定性的影响机理;基于等面积定则,分析了不同低电压穿越深度、低电压穿越恢复速率以及风机接入位置对功角失稳形态及暂态稳定性的影响;通过单机及多机系统仿真验证了增加风机低电压穿越深度、减缓低电压穿越恢复速度可增强火电机组首摆稳定性,但增大了其多摆失稳的风险。

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.

Determination of Effective Load Shedding Schemes in Electric Power Plants

The ability of power system to survive the transition from preloading state to the gradual increase in load and thereafter reach an acceptable operational condition is an indication of transient stability of the system. The study analyzed load shedding scheme through the use of empirical measurement tools and load-flow simulation techniques. It was geared towards determining effective load shedding strategies to reduce unnecessary overload in order to achieve dynamic stability of the electric power network in the Export Free Trade Zone, Calabar, Nigeria. From the tests and the measurements taken, it was observed that the real and reactive powers from the generator and the mechanical power from the turbine engine were stable when the load shedding controller was switched on, as compared to when it was off. The engine speed, the bus-bar frequency and the output voltage of the generator stabilized within a shorter time (about 8 seconds) when the controller was switched on than when it was on the off condition. Also, there were noticeable fluctuations in the speed of the remaining two generators. It became stable at about 12 seconds after the loss. The variations were 0.3 per cent of the nominal speed value. The excitation voltage fluctuated from 1.2 (pu) to 4.5 (pu) when the bus voltage dipped as a result of additional load. It then came down and stabilized at 1.8 (pu) after few swings. This confirmed that the stability of power system is much enhanced when load shedding controllers are effectively configured on the network.

Technology and engineering application of cross area HVDC interconnection system high-precision simulation modeling based on ADPSS

In recent years, a large number of high voltage direct current(HVDC) transmission projects have been connected to AC systems. This has started to have an impact on AC/DC hybrid power grids, particularly receiving terminal power grids. An HVDC system is a large-scale power electronic integrated nonlinear system, and it includes a primary system and a control and protection system. Hence, the precision and degree of detail of HVDC systems directly affect the actual effect of simulation. In recent years, in the case of the normal operation and failure of AC power grids, the abnormal fluctuation and even locking of HVDC systems caused by the inappropriate strategies of the control and protection system component have strongly affected power grids. This has significantly affected the safety and stability of receiving power grids and normal operation. In this study, the actual engineering HVDC control logic provided by a manufacturer is analyzed and simulated based on the user defined component library of the ADPSS electromagnetic transient calculation program, and an HVDC control model based on an actual system is established. The accuracy of the DC control custom model based on ADPSS is verified through the simulation of an actual power grid.