Feature extraction and power quality event classification using Curvelet transform and optimized extreme learning machine

The increased usage of sensitive equipment by customers led to the importance of the term Power Quality. Classification of power quality events plays an important role to have an effective mitigation. This paper represents a new approach for classification of Power Quality events using S-transform. S-transform is an improved version of wavelet transform that includes phase information as well. S-transform is used for classification of various power quality events like voltage sag, voltage swell, momentary interruption, harmonics which are simulated in MATLAB in accordance with IEEE Std. 1159. The effectiveness of the algorithm is used to identify multiple events. Phase information is also verified for various simulation cases.

This paper presents an effective method for detection and classification of Power Quality Events (PQE), based on Fast Fourier Transformation (FFT) for event identification and Artificial Neural Network (ANN) technique for classifying of these events. Firstly, synthetic data such as pure sine as a reference, voltage sag, voltage swell, flicker, transient, voltage with harmonics are created in MATLAB based on TS EN 50160 standard. Database with 480 PQE waveforms is generated with 80 samples for each of the 6 types of the waveform with randomly different event amplitude, beginning occurrence time, time duration, frequency component and angle according to a type of event. FFT is used to extract features of the events by decomposing the signal. Then, 16384×480 data are reduced to 480×480 data by applying Principal Component Analysis (PCA) that is prevent over-learning, obtain less runtime using less computing power and reduce data and storage space. Finally, a total of 480 PQE are classified by using ANN. 336 of these PQE are used for training cluster, 72 of PQE are used for verification and the remaining 72 are used for testing. Firstly, the ANN has been trained correctly. The classification performance of the ANN in PQE has been examined by inserting the test into ANN. The performance of ANN is 99.8% for these PQE. The purpose of this research is to provide an artificial intelligence assistant that can fast and accurately advise the power system operators for the networks, and the results also show that the goal has been achieved.

This paper presents a new approach for the detection of the power quality events using symmetrical components in time domain. Power quality (PQ) events like sag, swell, interruption, harmonic, flicker, transients, notches, and spike can be easily detected and classified with this method. As this method is free from the computational burden like in wavelets, S-transform and Hubert transform, so it can be easily used for the on-line applications. Single phase PQ event signal is taken along with the two other phases generated 120° and 240° difference using phase locked loop (PLL) so as to calculate the symmetrical components in the time domain. Triggering points for PQ events can be detected easily from the negative symmetric component of PQ event signal and the events can be easily classified from the signatures of the waveforms using the summation of the positive and negative sequence components. Simulated and real time results are presented for a number of power quality events to show the effectiveness of this method for the PQ event detection and classification.

Optimal feature selection for classification of the power quality events using wavelet transform and least squares support vector machines

In this paper a novel and simple approach for detection and classification of wide variety range of power quality(PQ) events based on discrete wavelet transform (DWT) and correlation coefficient is presented. For this purpose, two new indices is proposed and by comparing the values of the correlation coefficient between the value of these indices for pre-stored PQ events and for a recorded indistinct signal, type of PQ events will be detected. This algorithm has advantages of DWT and correlation coefficient which, it does not have disadvantage of neural network or neural network-fuzzy based algorithms such as; training, and high dimension input matrices nor it does not have disadvantage of Fourier transform based approach such as unsuitability for non-stationary signal as it does not track signal dynamics properly due to limitation of fixed window width. The effectiveness of this method has been tested using numerous PQ disturbance and simulation results confirm the competency and the ability of the proposed method in PQ disturbances detection and automatic diagnosis. Compared with the other methods, the simulation under different noises conditions, verify the effectiveness of noise immunity, and relatively better accuracy of the proposed method.

Power quality (PQ) events are referred to any abnormal deviation from the standard sinusoidal behavior of power signals within a power system. PQ events are usually studied by tracking the behavior of voltage signals over observation points of the system. IEEE Standards have defined standard categories for PQ events based on their time behavior. Each class of these events may have different level of importance from different contributors' perspective (utilities, system operators, or costumers). Due to increasing the usage of sensitive technological loads such as transportation, banking systems, and databases on one hand in addition to the uncertainty injected to the system from aggregation of renewables on the other hand, the fast and reliable PQ events classification is an important monitoring task in the future smart grid. In this paper, combining the theory of sparse recovery with a new high-dimensional convex hull approximation framework we have developed a fast, reliable, and adaptive PQ events classification methodology named "compressive-informative sparse representation-based" PQ events classifier. Unlike usual classification approaches, the proposed classifier does not need any training procedure while due to its linear mathematical formulation acts inherently fast. Moreover, it can be easily adapted to recognize the challenging combined PQ events in addition to any permanent change in the behavior of PQ patterns.

In power distributed generation system, analysis of power quality is a major issue and hence it is essential to implement an efficient power quality system. To address and end this issue, the proposed work is mainly focused on the detection and classification of power quality disturbances or events by applying Hilbert–Huang transform (HHT) technique. HHT technique is a novel signal processing algorithm that comprises two processes. First is the empirical mode decomposition (EMD), which is an iterative process where N number of power quality signals are decomposed into intrinsic mode functions (IMFs). The second process, Hilbert transform, is applied to each IMF component. The advantage of using these two processes makes it an attractive power tool for quality event analysis. Once the IMF is obtained, it is easy to construct a time–frequency representation model. Then, the significant features are extracted from amplitude, phase and frequency instantly, which are the contour of IMFs of each power quality disturbance. For classification, adaptive neuro-fuzzy system (NFS) classifier is used. It is an intelligent system used for the combination of neural network and fuzzy logic. Power quality features are given as input to the NFS system. The experimental simulation is conducted in a MATLAB environment, and proposed HHT has higher efficiency compared to existing methods.

In this paper a technique for detection of multiple power quality (PQ) events is illustrated. An algorithm based on wavelet transform and Random Forest based classifier is proposed in this paper. The developed technique is implemented on 11 different power quality events consisting of single stage power quality events such as sag, swell, flicker, interruption and multi stage power quality events such as harmonics combined with sag, swell, flicker, interruption. PQ events are simulated in MATLAB using standard IEEE-1159 standard. Significant features of PQ events are extracted using wavelet transform and used to train random forest based classifier. The efficiency of Random Forest Based classifier is compared with other widely used machine learning algorithms such as K-Nearest Neighbour (KNN) and Support Vector Machine (SVM). From confusion matrix of different algorithms it is concluded that Random Forest shows superior classification accuracy as compared to SVM and KNN.

This paper presents a new approach for classification of a power quality disturbances using modified wavelet transform called as Stockwell transform. This is a new tool for classification of power quality events in the world of electrical power systems. In this paper three power quality events are considered namely voltage sag, swell and interruption. After realizing the features extraction using S-transform, artificial neural network with multilayer perceptron (MLP) architecture is used for classification of the PQ disturbances. The simulation results reveal that the combination of S-Transform and ANN can effectively detect and classify different PQ events.

Power quality events recognition using enhanced empirical mode decomposition and optimized extreme learning machine

Power quality (PQ) event detection and classification is gaining importance due to worldwide use of delicate electronic devices. Things like lightning, large switching loads, non-linear load stresses, inadequate or incorrect wiring and grounding or accidents involving electric lines, can create problems to sensitive equipment, if it is designed to operate within narrow voltage limits, or if it does not incorporate the capability of filtering fluctuations in the electrical supply (Gerek et. al., 2006; Moreno et. al., 2006). The solution for a PQ problem implies the acquisition and monitoring of long data records from the energy distribution system, along with an automated detection and classification strategy which allows identify the cause of these voltage anomalies. Signal processing tools have been widely used for this purpose, and are mainly based in spectral analysis and wavelet transforms. These second-order methods, the most familiar to the scientific community, are based on the independence of the spectral components and evolution of the spectrum in the time domain. Other tools are threshold-based algorithms, linear classifiers and Bayesian networks. The goal of the signal processing analysis is to get a feature vector from the data record under study, which constitute the input to the computational intelligence modulus, which has the task of classification. Some recent works bring a different strategy, based in higher-order statistics (HOS), in dealing with the analysis of transients within PQ analysis (Gerek et. al., 2006; Moreno et. al., 2006) and other fields of Science (De la Rosa et. al., 2004, 2005, 2007). Without perturbation, the 50-Hz of the voltage waveform exhibits a Gaussian behaviour. Deviations from Gaussianity can be detected and characterized via HOS. Non-Gaussian processes need third and fourth order statistical characterization in order to be recognized. In order words, second-order moments and cumulants could be not capable of differentiate non-Gaussian events. The situation described matches the problem of differentiating between a transient of long duration named fault (within a signal period), and a short duration transient (25 per cent of a cycle). This one could also bring the 50-Hz voltage to zero instantly and, generally affects the sinusoid dramatically. By the contrary, the long-duration transient could be considered as a modulating signal (the 50-Hz signal is the carrier). These transients are intrinsically non-stationary, so it is necessary a battery of observations (sample registers) to obtain a reliable characterization. The main contribution of this work consists of the application of higher-order central cumulants to characterize PQ events, along with the use of a competitive layer as the classification tool. Results reveal that two different clusters, associated to both types of transients, can be recognized in the 2D graph. The successful results convey the idea that the physical underlying processes associated to the analyzed transients, generate different types of deviations from the typical effects that the noise cause in the 50-Hz sinusoid voltage waveform. The paper is organized as follows: Section on higher-order cumulants summarizes the main equations of the cumulants used in the paper. Then, we recall the competitive layer’s foundations, along with the Kohonen learning rule. The experience is described then, and the conclusions are drawn.

This paper presents a novel method for analysis and assessment of various power quality events using Hilbert transform based Fuzzy system. Hilbert transform analyzes the distorted kinds of voltage waveforms and then extract their important features. The various kinds of distorted voltage waveforms are developed through the Matlab parametric equation. These extracted features are given to Fuzzy system in order to classify both the single and combined form of power quality events. The results indicates that the Hilbert transform based Fuzzy system can effectively classify the single and combined form of Power Quality events. The classification accuracy of the proposed method are validated by comparing them against Kalman filter, S-transform based fuzzy classifiers.

Recently the usage of voltage-sensitive devices around the world is growing rapidly. These devices are not ideal and may get affected by Power Quality (PQ) events such as Sag, Swell, Harmonics, and Interruptions, etc. In IoT applications, failure of these sensitive devices may cause serious damages. Existing methods classify the disturbances 90–97% accurately with a large feature set. To avoid complexity, this paper deals with the classification of PQ events with a set of wavelet decomposed & direct signal features such as Shannon entropy, mean energy, and total harmonic distortion (THD), etc. Machine Learning (ML) approaches such as Decision Tree (DT) and Support Vector Machine (SVM) classifiers are used for classification. By considering the different training rates, the performance analysis is carried out. Simulation results indicate the supremacy of the proposed DT & SVM classifiers when compared with the already existing methods.KeywordsPQ eventsWTDecision treesSVM classifiers

Review on detection and classification of underlying causes of power quality disturbances using signal processing and soft computing technique

In order to enable voltage ride-through operation, fast and reliable voltage dips detection is necessary. It has been noticed by the analysis of a huge number of measurement results recorded in-field, in laboratory, and obtained by simulation that the voltage dips may be characterized by specific low-order voltage harmonics pattern, which appears at the beginning and at the end of the voltage dips. This feature is named harmonic footprint. This paper proposes a new method of voltage dips detection based on harmonic footprint as part of smart algorithm for detection and classification of power quality events. The aim is to achieve reliable smart voltage dips detection in 1 ms range. Several methods for harmonic estimation in real time were compared in order to choose the optimal one. The footprint is modeled by mathematical function and applied for voltage dips smart detection using recurrent neural network. The proposed method was tested for voltage dips detection analyzing signals from measurement in the real distribution grid (680 records), computer simulations using IEEE-13 bus test grid, and testing in the laboratory. The reliability (detection rate) and speed of voltage dips detection are tested and verified. Furthermore, the future research directions for presented method are outlined.