Wavelet-based neural network for power disturbance recognition and classification

In this paper, a prototype wavelet-based neural-network classifier for recognizing power-quality disturbances is implemented and tested under various transient events. The discrete wavelet transform (DWT) technique is integrated with the probabilistic neural-network (PNN) model to construct the classifier. First, the multiresolution-analysis technique of DWT and the Parseval's theorem are employed to extract the energy distribution features of the distorted signal at different resolution levels. Then, the PNN classifies these extracted features to identify the disturbance type according to the transient duration and the energy features. Since the proposed methodology can reduce a great quantity of the distorted signal features without losing its original property, less memory space and computing time are required. Various transient events tested, such as momentary interruption, capacitor switching, voltage sag/swell, harmonic distortion, and flicker show that the classifier can detect and classify different power disturbance types efficiently.     

An effective wavelet-based feature extraction method for classification of power quality disturbance signals

This paper presents a wavelet norm entropy-based effective feature extraction method for power quality (PQ) disturbance classification problem. The disturbance classification schema is performed with wavelet-neural network (WNN). It performs a feature extraction and a classification algorithm composed of a wavelet feature extractor based on norm entropy and a classifier based on a multi-layer perceptron. The PQ signals used in this study are seven types. The performance of this classifier is evaluated by using total 2800 PQ disturbance signals which are generated the based model. The classification performance of different wavelet family for the proposed algorithm is tested. Sensitivity of WNN under different noise conditions which are different levels of noises with the signal to noise ratio is investigated. The rate of average correct classification is about 92.5% for the different PQ disturbance signals under noise conditions.     

On distributed computing for on-line power system applications

This paper reviews the state-of-the-art of distributed computing (also called coarse-grained parallel computing) technology, which has rapidly evolved over the last two decades, with emphasis on the trend towards standardization that has occurred in the last few years. The review is focused on on-line power system applications, and excludes fine-grained parallel applications and planning applications. The applications are divided into two categories. The first category consists of applications where the motivation for distributed processing stems from geographical distribution. The second category is the rest of the on-line applications where the parallelism stems from the easily decomposable abstract (mathematical) model of the problem as opposed to being ‘physically based’. Some of the issues in such distributed computing are illustrated using the example of security-constrained optimal power flows. The paper concludes with some projections on the use of this technology in energy management systems (EMS) in the near future.     

A signal processing module for power system applications

This paper presents a unified power signal processor (PSP) for use in various applications in power systems. The introduced PSP is capable of providing a large number of signals and pieces of information which are frequently required for control, protection, status evaluation, and power quality monitoring of power systems. The PSP receives a set of locally measured three-phase voltage and current signals and provides their fundamental components, amplitudes, phase angles, frequency, harmonics, instantaneous and stationary symmetrical components, active and reactive currents and powers, power factor, and the total harmonic distortion. Simplicity and integrity of its structure as well as its robustness with respect to internal parameters and external disturbances and noise render the proposed scheme very attractive for practical implementations.     

Optically powered data link for power system applications

The practicability of an optically powered data link has been demonstrated. The link has moderate bandwidth (1 kHz), accuracy (1%) and dynamic range (>60 dB) over a useful range of ambient temperatures. The link uses commercially available components, including a photodiode array fabricated using the dielectric isolation process in silicon. An application to the measurement of current in a high voltage line by means of a linear coupler is described, and experimental results are presented. Power transmission efficiency is presently low, at about 0.3% overall (electrical-to-electrical) and 5% optical-to-electrical     

On-line detection of power system small disturbance voltageinstability

Small disturbance (SD) voltage stability (or instability) deals with a system's ability to maintain satisfactory voltages following a small disturbance. For an operating condition, a system's SD voltage stability depends on the proximity of the condition to the critical point (or voltage collapse point). A Q angle and Q directional derivatives are proposed for SD voltage instability detection and weak bus identification, respectively. The Q angle index can handle different kinds of loads, e.g., constant P and Q, constant impedance, and constant current, or a combination of them, and is effective in dealing with generator VAr limits. Moreover, the computation speed of the Q angle is fast, which makes it suitable for on-line application. Simulation results using two power systems are provided     

Expert system for classification and analysis of power systemevents

This paper presents an expert system that is able to classify different types of power system events to the underlying causes (i.e., events) and offer useful information in terms of power quality. The expert system uses the voltage waveforms and distinguishes the different types of voltage dips (fault-induced, transformer saturation, induction motor starting) as well as interruptions (nonfault, fault-induced). A method for event-based classification is used, where a segmentation algorithm is first applied to divide waveforms into several possible events. The expert system is tested using real measurements and the results show that the system enables fast and accurate analysis of data from power quality monitors     

基于改进多层前馈神经网络的电能质量扰动分类

电能质量扰动分类是电能质量控制的重要工作之一,主要工作包括信号特征提取和分类器构造两个阶段。采用S变换与改进的多层前馈神经网络相结合,提出一种新的电能质量扰动分类方法。首先利用S变换对原始数据进行处理,提取具有代表性的4类典型特征以表征不同种类的扰动类型的特性,之后使用拟牛顿法和自适应因子改进传统的多层前馈神经网络,将特征作为改进的多层前馈神经网络的输入向量,实现自动的分类识别。实验表明,新方法减少了噪声对分类准确率的影响,学习能力强,能够有效的识别电压暂降、电压瞬升、电压中断、暂态震荡、谐波等5种电能扰动。     

An accurate fault classification technique for power system monitoring devices

This paper presents a novel method of classifying transmission line shunt faults. Most algorithms employed for analyzing fault data require that the fault type be classified. The older fault-type classification algorithms are inefficient because they are not effective under certain operating conditions of the power system and may not be able to accurately select the faulted transmission line if the same fault recorder monitors multiple lines. The technique described in this paper has been proven to accurately identify all ten types of shunt faults that may occur in an electric power transmission system. The other advantage of this technique is that it can be used where multiple transmission lines are present. It is able to identify the faulted line even if secondary effects are recorded in the unfaulted lines.     

Combined fuzzy-logic wavelet-based fault classification technique for power system relaying

This paper presents a new approach to real-time fault classification in power transmission systems using fuzzy-logic-based multicriteria approach. Only the three line currents are utilized to detect fault types such as LG, LL, and LLG, and then to define the faulty line. An online wavelet-based preprocessor stage is used with data window of ten samples (based on 4.5-kHz sampling rate and 50-Hz power frequency). The multicriteria algorithm is developed based on fuzzy sets for the decision-making part of the scheme. Computer simulation has been conducted using EMTP programs. Results are shown and they indicate that this approach can be used as an effective tool for high-speed digital relaying, as the correct detection is achieved in less than half a cycle and that computational burden is much simpler than the recently postulated fault classification techniques.     

多机系统励磁的非线性L2增益干扰抑制控制

针对多机电力系统，基于严格耗散理论，提出了一种新的能够实现干扰抑制的励磁鲁棒非线性控制策略，在实现过程中不需要任何线性化方法。对三机系统的仿真结果表明，提出的励磁控制策略可提高电力系统暂态稳定性。     

Transfer function identification in power system applications

The authors present an introduction to concepts and applications of transfer function identification in power systems. They begin with a brief introduction to transfer function identification methods using least-squares approaches and then discuss applications which include static VAR compensators, model validation applications, and software validation. A comparison is also made between eigenvalues obtained from transfer function identification and small signal analysis. Methods for testing the validity of identified transfer functions are also discussed     

板级电源系统ADM1166的电源管理应用研究

电源是影响电子产品可靠性和耐用度的重要指标。产品性能的提升在很大程度上依赖于电源管理技术,因此需要从系统上对电源进行综合管理。基于电源管理芯片ADM1166,研究了电源管理的基本功能,包括多电源上电时序控制、电源电压异常监控功能,并研究了电源电压在线调节功能。结合实际的应用案例,对上述功能进行了测试和验证。     

Wavelet transform applications in power system dynamics

This paper proposes the use of the discrete wavelet transform (DWT) to analyze and locate the low frequency oscillations of power systems, which can result in a loss of stability or in a black-out. The proposed DWT applied to active power signal is tested and compared with more conventional approaches of Prony and Eigenvalue analyses. The DWT also enables estimation of the total active power imbalance of a system. Estimation performances of different wavelet families are tested. Based on the proposed DWT of electromechanical transient oscillations, the DWT is also applied to identify the network nodes in the neighbourhood of the original disturbance. The performance of the proposed DWT is evaluated on the New England (NE) 39-bus test system.     

Bulk power system reliability concepts and applications

While it is pointed out that probabilistic methods for the reliability assessment of composite generation and bulk transmission in electric power systems are still under development, an overview is given of the purposes and uses of power systems reliability studies. Probabilistic indices and reliability criteria are discussed. The features of a comprehensive reliability program to compute these indices are listed, and of these features, those required in selected applications are examined. Modeling and computational difficulties are discussed, and the necessity of balancing program accuracy and computing effort is stressed     

WiMAX在电力通信中的应用探讨

WiMAX具有容量大、传输距离长、可靠性高、频谱利用率高等特点,在电力系统通信中有一定的应用潜力。分析了WiMAX技术的特点、优势和定位,并结合电力行业的特点,阐述了WiMAX在无线城域网、变电站接入备用通信、应急通信和配网自动化等方面的应用。     

McWiLL技术及其在电力系统通信中的应用

介绍了电力系统对无线通信的需求,分析了McWiLL无线宽带系统的技术特点及技术优势,结合配网通信和应急通信的业务需求提出了McWill无线网络的电力系统解决方案;分析了McWill无线网络在电力系统的应用前景,并指出了研究重点。     

WiMAX技术及其在电力系统通信的应用

WiMAX具有容量大、可靠性高、传输距离长等特点,在电力系统通信中有一定的应用潜力。文章从物理层、链路层、大覆盖范围、QoS性能等4个方面,对WiMAX的技术展开分析,并结合电力行业的特点,阐述了WiMAX在无线城域网、变电站接入备用通信方式、应急通信、配网自动化等方面的应用,表明了WiMAX可以作为下一代宽带无限接入技术应用于未来的电力系统通信。     

Enhancing the human-computer interface of power system applications

This paper examines a topic of increasing importance: the interpretation of the massive amount of data available to power system engineers. The solutions currently adopted in the presentation of data in graphical interfaces are discussed. It is demonstrated that the representations of electric diagrams can be considerably enhanced through the adequate exploitation of resources available in full-graphics screens and the use of basic concepts from human-factors research. Enhanced representations of electric diagrams are proposed and tested. The objective is to let the user “see” the behavior of the power system, allowing for better interpretation of program data and results and improving user's productivity     

Wavelet based on-line disturbance detection for power qualityapplications

This paper introduces a new online voltage disturbance detection approach based on the wavelet transform. The proposed approach: (1) identifies voltage disturbances; and (2) discriminates the type of event which has resulted in the voltage disturbance, e.g. either a fault or a capacitor-switching incident. The proposed approach is: (1) significantly faster; and (2) more precise in discriminating the type of transient event than conventional voltage-based disturbance detection approaches. The feasibility of the proposed disturbance detection approach is demonstrated based on digital time-domain simulation of a power distribution system using the PSCAD/EMTDC software package