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In this paper, a single-layer sequential neural network (SNN) control algorithm has been proposed for managing the power quality (PQ) in the double-stage three-phase grid-integrated solar photovoltaic (SPV) system. The proposed algorithm efficiently extracts the active and reactive fundamental components of the load current, with a higher convergence rate. The extracted reference currents are matched with the sensed source currents to generate gating pulses for the voltage source converter (VSC). To handle power quality issues in distribution networks such as harmonic imbalances, voltage fluctuations (sags/swells), and the need for active and reactive power compensation, the VSC is controlled very precisely. The control algorithm consists of two-stage processes. In the initial stage, the incremental conductance (INC) based DC-DC converter has been incorporated to extract the peak power from the SPV system. In the later stage SNN-based algorithm is used to control the VSC. A 100 KW solar PV system connected to the utility grid has been designed by using a three-leg VSC in the MATLAB/Simulink environment. The system performance has been evaluated by comparing it to existing techniques. The simulation results comfortably meet the requirements of the IEEE-519–2014 and IEEE 1547–2003 standards for utility grid connection. [ABSTRACT FROM AUTHOR]

This paper investigated a multi-variable power quality disturbance identification algorithm (MPQDIA) applying the Stockwell transform (ST), Hilbert transform (HT) and rule based decision tree (RBDT). Voltage waveform with associated power quality disturbances (PQDs) are realized by the mathematical formulation in compliance with standard IEEE-1159. These voltage signals with PQDs are processed applying the ST and HT for computing the index for power quality identification (IPI) and index for power quality location (IPL). IPI and IPL plots effectively identify and locate the PQDs of simple nature and multiple nature. Four features are extracted from data sets of IPI and IPL. These features are considered as input for the RBDT to classify the PQDs. MPQDIA is effectively tested for identification, to locate and to classify the total 21 PQDs of simple as well as multiple natures. Performance of MPQDIA is analysed in terms of rightly and wrongly categorized PQDs in noise free environment and considering noise of 20 dB SNR (signal to noise ratio) level. Efficiency of MPQDIA is compared with the ST and RBDT based algorithm, WT based fast Kurtogram and decision tree powered algorithm, and ST and RBDT powered method in terms of classification accuracy, noise level for which performance is not affected, effectiveness to detect the simple nature and multiple nature PQDs. It is established that MPQDIA effectively recognizes the PQDs on a real time power system network. Study is performed with the help of MATLAB software. • Multivariable PQ identification algorithm (MPQDIA) using ST, HT and RBDT designed. • Index for PQ identification (IPI) and location (IPL) are designed. • Features computed from IPI and IPL are used by RBDT to classify PQDs. • MPQDIA effectively identify, locate and classify PQDs of simple and complex nature. • MPQDIA has better performance with existing methods and recognizes PQD in real time. [ABSTRACT FROM AUTHOR]

• A new methodology to increase power factor for multiple EVs charging. • A Simulink model validate by experimental measurements. • Real time algorithm able to mitigate the power factor decay at the point of delivery. The paper suggests a new methodology to increase the PF of a hub for EV charging. A smart management of the EV charging sessions allows to impose the stand-by operation of a vehicle based on the local PF value at EV charging points. Current harmonics are taken into account to ensure an effective improvement of the hub power quality. The case study of this paper consists of a hub for EV charging with a dedicated MV/LV substation, enriched by an experimental dataset containing measurements of 13 EVs during charging in terms of active and reactive power profiles, current harmonics, PF trends. The model is developed in Simulink environment and the proposed algorithm is implemented in a MATLAB script. The results highlight that in case of multiple EV charging sessions, the algorithm is able to maintain the hub PF value greater than the acceptable PF threshold limit. This scenario is expectable in real conditions, e.g. EV hubs near shopping centres or in cities with high population density. [ABSTRACT FROM AUTHOR]

This paper presents an LCL passive filter design methodology for high voltage direct current systems based on voltage source converters (VSC-HVDC) connected to passive grids. Power quality of passive grids is largely dependent on the VSC operation. Therefore, the filter design should take into consideration power quality issues. The LCL filter model is developed considering its losses and the passive grid impedance. If the grid impedance is considered, a sequential calculation of parameters is not feasible. Therefore, after modeling, parameter calculation algorithms are presented. The algorithms are divided into two steps: a design algorithm called the Multi-Pair Calculation Algorithm and an algorithm that selects the best solution, called the Selection Algorithm. The design methodology and calculation algorithms were exemplified using the IEEE 34 node test system as a passive grid. The results confirm that the proposed algorithms perform an optimal definition of filter parameters and that the quality of the passive grid voltage is a crucial element for the VSC filter design. [ABSTRACT FROM AUTHOR]

Abstract: In this paper a digital signal processor (DSP) based real time voltage envelope tracking system is developed and examined. The ADAptive LINEar neuron (ADALINE) and the Recursive Least Square (RLS) algorithms are adopted for envelope tracking. The proposed ADALINE and RLS algorithms give accurate results even under rapid dynamic changes. The paper investigates the effects of different parameters on the performance of the ADALINE algorithm and that of the RLS algorithm. The experimental system is cantered around a Texas Instrument 16bit fixed-point arithmetic (TMS320LF2407A) evaluation board. Both the ADALINE and the RLS tracking algorithms are developed using the DSP-assembly language. A simple voltage flicker generator is implemented to produce various voltage disturbances. Extensive tests of the proposed envelope tracking algorithms are conducted to evaluate their dynamic performance. [Copyright &y& Elsevier]

Abstract: The novel complex filter/recursive algorithm, which are proposed in part 1 of the two-part series, is an improved signal processing technique that can accurately and continuously measure the instantaneous electrical quantities such as the amplitude, phase angle, frequency and power of the fundamental and harmonic components even during power disturbances. This paper, which is part 2 of the series, focuses on the ways to implement the proposed method for real-time applications. Further, the effectiveness and superiority of the proposed method over the well-known Fourier Algorithm (FA) and the Morlet wavelet-based Continuous Wavelet Transform (CWT) are also ascertained in this paper using both simulated and practical power disturbance waveforms. [Copyright &y& Elsevier]

This paper proposes a five level cascaded converter for Distribution Static Compensator (DSTATCOM) implementing a novel modulation algorithm with harmonic mitigation and a PI controller with phase shift modulation for reactive power control. The modulator operates at fundamental frequency and the whole system satisfies grid code requirements using a simple passive output filter tuned with 11th harmonic. The behavior of the proposed system has been successfully compared with another one with multilevel space vector pulse width modulation. Results show its capability of ensuring satisfactory dynamic response at low frequency operations, resulting improved efficiency and reduced output filter requirements over more conventional systems. [ABSTRACT FROM AUTHOR]

Emulation of the rotational inertia of a synchronous generator (SG), in the form of virtual inertia, is possible through the virtual synchronous generator (VSG). This is a power-electronics based device, whose purpose is to damp the frequency oscillations due to disturbances in the power balance of a power system, similarly to the rotational inertia of a SG. This paper identifies Virtual Inertia as a property of the VSG and provides mathematical expressions that relate it to the rotational inertia of an SG using classical mechanics and machine theory. The ideal VSG is introduced and used as reference for comparison with the SG analogue. Two different algorithms that emulate the rotational inertia of a SG are tested and adjusted accordingly to match the performance of the ideal VSG. The comparison shows that slow frequency-tracking limits the performance of both algorithms. [ABSTRACT FROM AUTHOR]

Highlights: [•] This paper proposes a robust method to locate faults and estimate the magnitude of voltage sags using limited information. [•] Statistical analysis was used to find the most likely fault location and sag magnitude at non-monitored busbars. [•] Robust handling of measurement errors reduces the sensitivity of impedance based fault location algorithms. [•] The method eliminates multiple fault location solutions caused by overlapping impedance paths. [•] It is validated on a generic section of the UK's distribution network. [ABSTRACT FROM AUTHOR]

Abstract: This paper takes us a step forward with respect to previous definitions for the measurement of electric power quantities under non-sinusoidal conditions. A new decomposition of voltage, current and power is presented in order to determine the extent to which the distribution company and the electrical energy consumer are each responsible for the harmonic distortion measured at the point of common coupling, PCC. This gives us three different quantities: fundamental frequency, frequencies associated with the distribution system distortion and frequencies associated with consumer distortion. These magnitudes can also be measured in relation to power factor compensation and harmonic elimination problems in power distribution systems. In addition to this, the power factors resulting from the new decomposition are also analyzed and the decomposition algorithm implemented on a measurement platform based on a digital signal processor, DSP. Finally, the general structure of the system, focusing on both hardware and software, is also discussed. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a new approach for the detection and classification of single and combined power quality (PQ) disturbances is proposed using fuzzy logic and a particle swarm optimization (PSO) algorithm. In the proposed method, suitable features of the waveform of the PQ disturbance are first extracted. These features are extracted from parameters derived from the Fourier and wavelet transforms of the signal. Then, the proposed fuzzy system classifies the type of PQ disturbances based on these features. The PSO algorithm is used to accurately determine the membership function parameters for the fuzzy systems. To test the proposed approach, the waveforms of the PQ disturbances were assumed to be in the sampled form. The impulse, interruption, swell, sag, notch, transient, harmonic, and flicker are considered as single disturbances for the voltage signal. In addition, eight possible combinations of single disturbances are considered as the PQ combined types. The capability of the proposed approach to identify these PQ disturbances is also investigated, when white Gaussian noise, with various signal to noise ratio (SNR) values, is added to the waveforms. The simulation results show that the average rate of correct identification is about 96% for different single and combined PQ disturbances under noisy conditions. [ABSTRACT FROM AUTHOR]

Abstract: It is important to accurately estimate instantaneous voltage flicker magnitudes and frequencies in order to correctly evaluate voltage fluctuations. Voltage flicker is a problem in electric power quality. Different approaches used to determine the magnitude of the voltage flicker have been presented: measurement methods generally use a flickermeter device. Simulation methods require a computer model of the disturbing load and the flickermeter. Calculation methods necessitate a simplified empirical formula. Estimation algorithms are based on the estimation of the voltage flicker components. In this paper, two models of voltage flicker are discussed: L p estimation algorithms utilizing L 1, L 2 and L ∞ norms are used to estimate the voltage magnitudes of the flicker signals as well as the fundamental voltage magnitude. The main result is that it is possible to design an L p estimator to identify flicker frequency and amplitude from time series measurements. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a new methodology to estimate unbalanced harmonic distortions in a power system, based on measurements of a limited number of given sites. The algorithm utilizes evolutionary strategies (ES), a development branch of evolutionary algorithms. The problem solving algorithm herein proposed makes use of data from various power quality meters, which can either be synchronized by high technology GPS devices or by using information from a fundamental frequency load flow, what makes the overall power quality monitoring system much less costly. The ES based harmonic estimation model is applied to a 14 bus network to compare its performance to a conventional Monte Carlo approach. It is also applied to a 50 bus subtransmission network in order to compare the three-phase and single-phase approaches as well as the robustness of the proposed method. [Copyright &y& Elsevier]

Abstract: Enhancement of power distribution system reliability requires of a considerable investment in studies and equipment, however, not all the utilities have the capability to spend time and money to assume it. Therefore, any strategy that allows the improvement of reliability should be reflected directly in the reduction of the duration and frequency interruption indexes (SAIFI and SAIDI). In this paper, an alternative solution to the problem of power service continuity associated to fault location is presented. A methodology of statistical nature based on finite mixtures is proposed. A statistical model is obtained from the extraction of the magnitude of the voltage sag registered during a fault event, along with the network parameters and topology. The objective is to offer an economic alternative of easy implementation for the development of strategies oriented to improve the reliability from the reduction of the restoration times in power distribution systems. In the application case for an application example in a power distribution system, the faulted zones were identified, having low error rates. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: For power quality detection, several techniques have been proposed in the literature. In the paper, some shortcomings of the conventional methods that are usually used to analyze the power quality issues are firstly pointed out. A kind of artificial neural network, adaline, and its new algorithm for analysis of power quality are presented. The new algorithm has the advantages of being simply calculated and easily implemented through hardware. The simulating results of voltage quality disturbances detection and especially frequency tracking demonstrate that the new adaline and its algorithm can be applied to the precise analysis for power quality. [Copyright &y& Elsevier]

Abstract: A simple model for uncontrolled rectifiers with capacitive filter working in discontinuous current mode is developed in this paper. The presented model allows the rectifier ac line current harmonics to be obtained in an easy way. Previously, both the width and the peak value of the ac current pulse are calculated by means of analytical equations. This model is obtained when the rectifier working point is defined by dc current consumption or dc power consumption. In the first case, the expressions of the width and peak value are analytical, whereas in the second case they are non-linear; thus, an iterative algorithm is proposed to solve them. The rectifier behaviour is also graphically characterised in both cases from the previous equations normalisation. Several examples of the proposed model application are presented. Lastly, it is exposed that the model allows harmonic current emission to be studied in an easy, friendly way, according to the present regulations for both rectifiers. [Copyright &y& Elsevier]

Abstract: A novel robust algorithm to harmonic and interharmonic analysis based on support vector machines (SVM) and solved by iterative reweighted least squares (IRWLS) algorithm to overcome the difficulty of exponential computation complexity, is proposed in the paper. It has a good precision for analyzing harmonics and interharmonics without synchronized sampling that is essential for fast Fourier transform (FFT). By introducing a specific loss function, the method can mitigate the infection of outliers and noises and exhibits robustness characteristics. Its IRWLS-based implementation makes it efficient and suitable for harmonic and interharmonic analysis of electric power system. The case studies showed its high precision and robustness of the SVM spectral analysis algorithm. [Copyright &y& Elsevier]

Active power filters (APF) can be employed for harmonic compensation in power systems. In this paper two algorithms are proposed for optimum allocation and sizing of APFs. In the first algorithm, the aim is to minimize the voltage harmonic distortion while in the second; the aim is to meet the harmonic standard levels by minimum injection of APF currents. Both algorithms are solved using genetic algorithm (GA) as the optimization tool. The performance of the proposed approaches are assessed and appreciated by various case studies on an 18-bus test system. [Copyright &y& Elsevier]

• Development of Nonparametric Variable Step-Size NLMS (NPVSS-NLMS) control technique for distribution static compensator (DSTATCOM). • Development of laboratory prototype of DSTATCOM for verification of real time performance of the NPVSS-NLMS control technique for power quality problems at distribution system. • Several power quality problems such as harmonic distortion, excessive reactive power and load unbalancing are compensated using developed test setup. • Improved performance of developed NPVSS-NLMS control technique is demonstrated by comparing with existing control techniques. The development of distribution static compensator (DSTATCOM) using nonparametric variable step-size normalized least mean square (NPVSS-NLMS) based control technique is presented in this paper. Numerous features of DSTATCOM such as harmonic alleviation, reactive power compensation and load balancing are demonstrated using NPVSS-NLMS controller. The laboratory prototype of shunt compensator is developed using a dSPACE DS1104 R&D controller having TMS320F240 as a slave DSP. Both MATLAB/SIMULINK based simulations and experimental test results are presented for demonstrating the steady state as well as dynamic performance of DSTATCOM. The developed control technique is compared with variable step size LMS (VSS-LMS) and modern control techniques viz. sliding mode controller (SMC) and model predictive control (MPC) in terms of filter type, weight convergence, complexity, harmonic compensation and sampling time taken. The NPVSS-NLMS based control algorithm for shunt compensator is performing satisfactory in all the above mentioned terms over conventional VSS-LMS controller. The scheme is found to be effective in reducing the total harmonic distortion (THD) of supply current as per IEEE-519 standard. [ABSTRACT FROM AUTHOR]

• Proposing an accurate modelling of OUPQC and its integration in backward/forward sweep load flow. • Evaluation of OUPQC operation capabilities in voltage sag compensation. • Proposing an improved reactive compensation method for enhancing the series unit capability by contribution of shunt units in voltage sag condition. • Evaluation of the proposed method in two distribution network: IEEE 69-bus and practical 95-bus Iranian distribution networks. Voltage and current deficiencies in distribution network (DN) necessitate the improvement of power quality (PQ). Custom power devices (CPDs) compensate for these deficiencies. Recently, in presence of communication infrastructure in smart distribution network, open unified power quality conditioner (OUPQC) is attracted the attention of DN researchers and operators. OUPQC is utilized in DN to improve voltage and current deficiencies by operation of series unit (SEU) and shunt unit (SHU), respectively. In this paper, an accurate modelling of OUPQC and its integration in backward/forward sweep load flow (BFSLF) is proposed. In addition, it is confirmed that SEU performance which is responsible for voltage sag compensation, is limited. Hence, an operational method of the OUPQC is proposed to improve the performance of SEU. In the proposed method, SHUs contribute in voltage sag compensation by modifying their reactive power injection. The proposed method, determines the reactive power injection of SHUs and make the SEU possible to compensate the voltage sag by quadrature injection of series voltage (e.g. reactive power injection). The proposed method is utilized in two DNs: IEEE 69-bus and practical 95-bus Iranian DN. Results confirms that the performance of OUPQC in healthy and especially in voltage sag condition is deeply improved. The proposed method can be utilized in designing the operational algorithm of OUPQC. [ABSTRACT FROM AUTHOR]