The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The changing power system regulations and increased use of power electronics based equipment, has made power quality (PQ) a highly important issue. The conventional Fourier transform based PQ indices work well with stationary disturbances, but fail to indicate or quantify the PQ issues related to non-stationary disturbances. In order to consider the effects of PQ disturbances, that occur for a short...
This paper proposes the application of frequency locked loop (FLL) based Kalman filter (KF) technique for frequency adaptive instantaneous power quality (PQ) analysis. In the proposed technique, the FLL is integrated with the linear Kalman filter (LKF) to estimate the time-varying grid fundamental frequency. The LKF is used to estimate the orthogonal waveforms of fundamental and harmonics components...
This paper demonstrates the effectiveness of S-transform in detecting and classifying multiple/composite power quality (PQ) events compared to the discrete wavelet transform for the accuracy of tracking the amplitude and frequency changes. Five different types of multiple/composite disturbance signals are considered, in this paper, including harmonics with voltage sag, harmonics with voltage swell,...
The paper presented the fundamental of HHT and Fourier transformation through elaborating the theory and simulation experiments on matlab. Giving specific signal, the two transformations were used in application of partial discharge, voltage dip, and harmonic wave. Visualized spectrogram were obtained to compare the two transformations from each other, therefore, HHT and Fourier transformation can...
This paper presents a new power quality detection method based on the improved HHT in microgrid. Hilbert-Huang Transform (HHT) can distill these disturbing signals automatically and time-frequency spectrum can be obtained. However, in the application of this method there are serious end effects that mixed mode phenomenon will appear, affecting the detecting results. In order to suppress the end effects,...
An automated classification based on S-transform as feature extraction tool and Artificial Neural Network as algorithm classifier is presented. The signals generated according to mathematical models have been used to obtain experimental results in two stages, first, with a data set with only simple disturbances and, later, including complex disturbances, more usual in real electrical systems. In both...
In this paper (Part II), a control strategy for a single-phase series-connected inverter with the microgrid is proposed to interface ac loads not only to regulate the load voltage under voltage disturbances, but also to control the load power drawn from the microgrid. The inverter compensating voltage works in such a way that, irrespective of any type of disturbances in the microgrid voltage (such...
This paper researches the intrinsic relationship between inter-harmonics and typical voltage fluctuations of which the enveloping line is sine wave, it analyses the effects to voltage fluctuations of inter-harmonics of different frequencies, including a single inter-harmonic and a pair of inter-harmonics. In this paper, experiments of voltage fluctuations production and compensation are all carried...
In this paper, a new type of controller is proposed for series connected PV inverter for grid voltage compensation. The inverter operates during the day time as an active power compensator as well as load voltage regulator under grid voltage sag, swell or even under normal condition. The compensating voltage provided by the inverter is added vectorially in series with the grid voltage in such a way...
Power quality indices characterize the nature of a power quality problem and serve as the basis for evaluating its negative impact. Due to the limitation of the traditional power quality indices in measuring transient disturbance signals, new power quality indices are developed in this paper based on S-transform. In the accurate time-frequency domain of S-transform, define four indices: instantaneous...
This paper proposed a novel identification method for voltage sags (dips) based on Hilbert-Huang transform (HHT). Different voltage sag has distinct characters of fault time, three-phase amplitude and harmonics. And HHT is an excellent time-frequency representation and very suitable for feature extraction of voltage sags. The time-frequency absolute values of the instantaneous frequency differential...
Classification for short duration power quality disturbance (SDPQD) is the premise for electric power quality improvement. A new classification method for SDPQDs is proposed in this paper. It is based on partial similarity and scale zooming of the module time-frequency matrix (MTFM) by Stransform. All types of disturbances with different durations are standardized by time-frequency scale zooming....
This paper presents a new approach for recognizing nonstationary signals in power quality (PQ) disturbances. Meanwhile the new approach includes the most types of PQ disturbance, such as voltage sags, swells, interruptions, transients and harmonics. The new model mainly includes two steps. Firstly, S-transform is used to analyze power system disturbance signals, and two most distinguishing features...
With the power system development, the application of non-linear power components is becoming more and more extensive, and the power quality situation of power system has become increasingly severe. This paper proposes a novel method based on mathematical morphology (MM) and Hilbert-Huang transform (HHT), which is used to detect and analyze power quality disturbances. To effectively suppress noises,...
The paper proposes improved S-transform (IST) to detect and classify power quality (PQ) disturbances with time-domain analysis. First, the theory of S-transform (ST) is introduced. To enhance the analytic power of ST in different non-stationary signal processing, IST is achieved by adding an adjustable factor to the Gaussian window function of the normal ST. The adjusted factor changes the velocity...
A multifunctional virtual power quality monitoring system is designed and implemented in LabVIEW environment. S-transform is introduced and applied to perform time-frequency analysis on power quality disturbances. The root mean square (RMS) value, the waveforms of three-phase voltage and current, the harmonic components, the total harmonic distortion (THD) and S-transform analysis waveforms of the...
A new method based on generalized S-transform (GST) is presented for detecting and identifying power quality disturbances (PQDs). The GST formula of discrete time series is deduced firstly, and then nine kinds of typical PQDs are formed for GST analysis. As a result of GST analysis, three voltage-based characteristics, one frequency-based characteristic as well as one phase-based characteristic are...
For the extraction requirements of non-linear and non-stationary transient composite disturbance signal of the power system, EMD method is applied to decompose these signals from characteristics of time scale, and to realize the self-adaptive dividing of the signal band, and then on the basis of which, Hilbert transformation is conducted and the characteristics of time, frequency and amplitude of...
In order to solve the detection and classification of power quality disturbances, a new approach combining S-transform and decision tree is proposed. First, some disturbances are decomposed through S-transform time-frequency analysis, three feature functions are defined, then feature components are extracted, and decision rules are found, finally the decision tree approach for disturbances classification...
The S-transformed module time-frequency matrix exactly contains detailed characteristics of short-duration power quality disturbance (SDPQD). The standard S-transformed module time-frequency matrix (MTFM) of different ideal disturbance compares with which of the tested disturbance signals. According to the maximum similarity principle (MSP), the practical tested PQ disturbances are classified into...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.