Power Quality Degradation Research Articles

Impact of Power Quality on the Performance of Distribution Transformers: A Fuzzy Logic Approach to Assessing Power Quality

Power Quality (PQ) is a major factor for utilities to consider when meeting customer demands. Poor PQ can damage sensitive equipment and lead to costly repairs, resulting in lost time, corrupt data, and lower productivity. It also increases losses, raises electricity bills, and reduces the life expectancy of electrical equipment. In this article, a fuzzy system is used to determine PQ for various operating conditions and study its effect on the performance of distribution transformers (DTs). Experiments are performed on a three-phase, 15-kVA, 400/400-V DT. The input supply voltage to the DT is intentionally disturbed by means of a motor-alternator-variacs-triacs assembly to obtain different PQ conditions. A fuzzy system is developed with offline and online approaches. This system has five measurable inputs-supply voltage, load current, frequency, harmonics distortion, and winding temperature-and one output variable, PQ. Offline and online experimental results are compared. Results show that the efficiency of a DT decreases with PQ degradation, and the proposed fuzzy system is able to make accurate diagnoses.

Mitigation of Harmonics in a Grid Connected Photovoltaic Inverter

Photovoltaic energy generation is one of the potential sources of renewable green energy because it is dirt free, unlimited source and requires less maintenance. Implementation of solar PV has been increasingly preferred for both commercial and residential purposes. The power quality issues are very common during the developing and integrating stages of solar PV. Inverters are considered as the main medium which enables the integration of solar PV into the grid. Due to the widespread use of inverters, harmonics are introduced into the system. These harmonics result in the degradation of power quality at the output. This research work is concerned with power quality when grid-connected systems are used. This paper proposes a new passive filter topology for a unipolar pulse width modulated single-phase inverter interfaced with the PV source and the grid. As a source for the system, a 25W photovoltaic panel is chosen. The panel is integrated with the proposed inverter and filter design. A hardware prototype was developed and suitable results were obtained and verified.

Data‐driven disturbance source identification for power system oscillations using credibility search ensemble learning

Low-frequency oscillations in power system degrade power quality and may trigger blackouts. This study identifies the source location of these oscillations using measurements from phasor measurement unit (PMU), offline credibility estimation and classification models. The performance of these classification models is ranked for each reported feature to use highly ranked models during the online stage. This proposed framework named as credibility search ensemble learning was tested and validated with promising results using western interconnection power system in North America (WECC-179). The reliability and robustness of the proposed framework were checked against measurement errors in PMUs as well as for practical topology change scenarios. Experimental results and performance comparison with average weight-based approach proved that the proposed approach is capable enough to predict the source location of oscillations with good accuracy. An interfacing tool, for MATLAB-WEKA, was developed and employed in this work for validation and testing of the proposed approach.

Improved Reference Generation of Active and Reactive Power for Matrix Converter With Model Predictive Control Under Input Disturbances

The existing model predictive control schemes for the matrix converter perform well under ideal input conditions, but are not optimal when source voltages are unbalanced and distorted. The analysis shows that, under input disturbances, the input filter capacitors cause active power fluctuation and further output power quality degradation, which has been ignored in literature. Therefore, a method is proposed to extract the fluctuation with a digital filter and compensate it in the reference generation of source active power, so as to eliminate the output low-frequency harmonics. In the case of input voltage unbalance, a method is proposed to generate the reference source reactive power which could achieve sinusoidal source currents, without the need of separating sequence components. Moreover, effects of source voltage distortions, which degrade the input power quality significantly and are ignored in literature, are suppressed with the proposed generation method of reference reactive power. The extensive experimental results in nine cases have verified the satisfactory steady-state and dynamic performance of the proposed methods.

Power Quality Improvement in Microgrids Under Critical Disturbances Using an Intelligent Decoupled Control Strategy Based on Battery Energy Storage System

The concept of microgrids (MGs) provides the flexibility to integrate renewables into the power network. Nevertheless, the transience of most renewable energy sources (RESs) exacerbates the power quality of the grid network. Furthermore, the unpredictability of RESs additionally becomes challenging in case of high magnitude disturbances. The deployment and optimal utilization of energy storage systems, to act as an energy buffer are hence pertinent. In this paper, a control strategy for a battery energy storage system (BESS) is formulated based on two intelligent decoupled controllers. The objective is the restoration of system voltage and frequency considering a wide range of disturbances and hence circumvent the power quality degradation. The proposed controller is based on hybrid differential evolution optimization and artificial neural network (DEO-ANN). The controller parameters are tuned online by training the ANN with the sets of input and output data obtained during the process of optimizing the two controllers under low and high disturbances using DEO. Finally, the effectiveness of the proposed controller is validated on a power network consisting of a synchronous generator, photovoltaic power system, and BESS. The simulation results prove the robustness of the proposed control approach as compared with a benchmark controller.

Harmonic‐signature‐based islanding detection in grid‐connected distributed generation systems using Kalman filter

Islanding in power systems is a challenge that results in various uncertainties in the system parameters, degrades power quality, and may endanger the maintenance workers. This study presents a new passive islanding detection approach for grid-connected distributed generation (DG) units. The proposed method employs a Kalman filter (KF) to extract and filter the harmonic contents of the voltage signal measured at DG terminals. A three-phase voltage signal is measured at the point of common coupling and taken as a test signal for islanding detection. First, a residual signal is generated using the KF to detect different changes in the power system. In the second step, multiple harmonic contents are estimated by the KF to calculate a criterion named selected harmonic distortion (SHD). The variation of SHD classifies between islanding and normal conditions. The IEEE 13-bus test system simulated in Matlab/Simulink is used as a testbed to assess the performance of the proposed approach. The proposed method is extensively analysed under various islanding and non-islanding scenarios. The results demonstrate that the proposed method can successfully differentiate between islanding and non-islanding events. Moreover, it provides high reliability by eliminating the non-detection zone and stands robust against the false operation.

The Shunt Active Power Filter to Compensate Reactive Power and Harmonics with optimized PI controller in a 3 Phase 3 Wire Distribution System

In this paper is to study the denomination Power quality and large refers to maintaining a proximal sinusoidal power distribution bus voltage at rated magnitude and frequency. This is mainly affected by the generation of harmonics. Even though electronic and non-linear devices are flexible, economical and energy efficient, they may degrade power quality by creating harmonic currents and consuming excessive reactive power. This paper shows the method of improving the power quality using shunt active power filter with proposed optimized PI. The proposed topic comprises of PI controller, filter hysteresis current control loop, dc link capacitor. The switching signal generation for filter is from hysteresis current controller techniques. With the all these element shunt active power filter reduce the total harmonic distortion. Its source current, compensating current and THD values are studied, then PI control strategy is applied then the differences in THD are compared. The PI feedback compensation design starts with the small signal system's transfer function. Then an optimum constant of PI for a Shunt-APF is proposed and implemented to enhance its response to compensation of harmonics of linear and non-linear loads. The obtained results have demonstrated the ability to compensate the current harmonics effectively under distorted source conditions. The fluctuation in the dc bus voltage of the filter depends on the compensation speed of the outer loop that regulates the dc bus voltage. harmonics. The model is made in MATLAB / SIMULINK and successfully reduces the harmonic in the source current.

Power quality problems mitigation using dynamic voltage restorer (DVR) with pi controller and fuzzy logic controller

The existence of non-standard currents, frequencies and voltages enhances the Power Quality (PQ) problems. Power consumed by the consumers and losses occurred in power system are deciding factors for the utility to determine the performance of the power system in terms of Power Quality. These Power Quality problems lead to failure of end user equipments as well as creates disturbances in power distribution network, thereby deteriorates residual life assessment of major equipments used in substation. The PQ problems can be characterized as voltage surges, sags, swells, harmonic distortions, etc. There are many reasons for the determination of Power Quality. The loads used by the consumers of electricity abnormally leads to deprove the Power Quality. Low power factor loads are taken care of by the utilities in the form of financial penalty. However, occurrence of harmonics, voltage swells and sags in the system is the most powerful reason behind degradation of Power Quality. To mitigate these issues, use of Custom Power Devices (CPD) in the distribution network is the most significant solution. Paper presents the design of the CPD like Dynamic Voltage Restorer (DVR) using two control strategies i.e. PI Controller and Fuzzy Logic Controller (FLC). MATLAB/SIMULINK is used to analyze the effectiveness of these control strategies.

Reconfiguration of NPC Multilevel Inverters to Mitigate Short Circuit Faults Using Back-to-Back Switches

The main focus of this paper is to propose a reconfiguration method to mitigate short circuit faults in a neutral point clamped multilevel inverter which is widely used as a power conversion system with distributed energy resources. Existing reconfiguration methods use either a redundant strategy or need a large number of additional devices pre-installed in the circuit; these will increase the bulk and complexity of the system. Most existing control-strategy-based methods distort the phase-toneutral voltage, which results in degradation of power quality. To maintain control-strategy-based reconfiguration, avoid significant change to the circuit topology, and avoid phase voltage distortion, a new and practical reconfiguration method is proposed in this paper. The proposed method is applicable to neural point clamped (NPC) multilevel inverters at any voltage level and can mitigate short circuit faults in any device. A technique of switching series connected switches is selected to combine with the proposed reconfiguration method since it's a practical design consideration for realistic implementation. MATLAB/Simulink is used to simulate a five-level NPC inverter with non-idealities to verify the proposed reconfiguration method. A five-level NPC is also built and tested to experimentally verify the proposed method. Short circuit faults are injected to different devices and the proposed method is verified to quickly and effectively recover the NPC inverter from these faulty conditions.

Harmonic Modelling of the Wind Turbine Induction Generator for Dynamic Analysis of Power Quality

Given the increasing integration of wind-based generation systems into the electric grid, efforts have been made to deal with the problem of power quality associated with the intermittent nature of these systems. This paper presents a new modelling approach oriented towards harmonic distortion analysis of the induction machine for wind power applications. The model is developed using companion harmonic circuit modelling, which is a natural approach for analysis of the adverse effects of harmonic distortion in electric power systems, and represents an easier solution method than the well known dynamic harmonic domain, since it solves algebraic equations instead of state-space differential equations. The structure of the companion circuits simplifies both the formulation and solution for power systems with wind-based generation systems. This approach is especially useful for analysis of the harmonic interaction in transient and steady states between the wind power generator and the power system, whose interconnection is made through electronic converters. The proposed model allows us to compute the dynamics of the wind turbine, which are influenced by disturbances such as changes in the wind velocity, voltage fluctuations, electric waveform distortion, and mechanical vibrations, among other factors. Moreover, the cross-coupling between harmonic components at different frequencies is considered. The proposed model represents an integral framework of the electrical and mechanical subsystems of a wind turbine, allowing for analysis of the interactions between them, and understanding power quality degradation behaviour as well as causes and consequences, while also giving useful information on the field of simulation and control. To test the performance of the proposed model, a test power system is used to obtain the behaviour of a wind turbine induction generator in response to typical power quality disturbances, i.e., harmonic distortion, and voltage sags and swells. Then, the dynamics of the variables considering their harmonic interactions are analysed.

An islanding detection methodology combining decision trees and Sandia frequency shift for inverter‐based distributed generations

Distributed generations (DGs) for grid-connected applications require an accurate and reliable islanding detection methodology (IDM) for secure system operation. This study presents an IDM for grid-connected inverter-based DGs. The proposed method is a combination of passive and active islanding detection techniques for aggregation of their advantages and elimination/minimisation of the drawbacks. In the proposed IDM, the passive method utilises critical system attributes extracted from local voltage measurements at target DG locations as well as employs decision tree-based classifiers for characterisation and detection of islanding events. The active method is based on Sandia frequency shift technique and is initiated only when the passive method is unable to differentiate islanding events from other system events. Thus, the power quality degradation introduced into the system by active islanding detection techniques can be minimised. Furthermore, a combination of active and passive techniques allows detection of islanding events under low power mismatch scenarios eliminating the disadvantage associated with the use of passive techniques alone. Detailed case study results demonstrate the effectiveness of the proposed method in detection of islanding events under various power mismatch scenarios, load quality factors and in the presence of single or multiple grid-connected inverter-based DG units.

Locking Frequency Band Detection Method for Islanding Protection of Distribution Generation

An islanding condition refers to an undesired event in which a portion of utility system, including both distributed generator(s) (DG) and local loads, remains energized while the main grid is disconnected. Unintentional islanding incident can result in serious personnel safety issues, interference to grid-protection facilities, power quality degradation, and equipment damage. Accordingly, anti-islanding protection for DG system is required by standard and utility codes. In this paper, an active islanding protection method is proposed called locking frequency band detection. The proposed method functions by introducing a virtual detection band only based on local grid frequency measurements at the point of common coupling. Hence, it has little or no impact on DG output and its power quality, and it does not get affected by a number of DGs. In addition, the proposed protection method eliminates the dreaded nondetection zone for DG systems typically observed during most severe power system transient conditions. In this paper, detailed description of the algorithm is explained and its performance and efficacy are evaluated through simulation and hardware experiments for different load quality factors.

Optimal Control of PEVs with a Charging Aggregator Considering Regulation Service Provisioning

Plug-in electric vehicles (PEVs) are considered the key to reducing fossil fuel consumption and an important part of the smart grid. The plug-in electric vehicle-to-grid (V2G) technology in the smart grid infrastructure enables energy flow from PEV batteries to the power grid so that the grid stability is enhanced and the peak power demand is shaped. PEV owners will also benefit from V2G technology, as they will be able to reduce energy cost through proper PEV charging and discharging scheduling. Moreover, power regulation service (RS) reserves have been playing an increasingly important role in modern power markets. It has been shown that by providing RS reserves, the power grid achieves a better match between energy supply and demand in presence of volatile and intermittent renewable energy generation. This article starts with the problem of PEV charging under dynamic energy pricing, properly taking into account the degradation of battery state-of-health (SoH) during V2G operations as well as RS provisioning. An overall optimization throughout the whole parking period is proposed for the PEV and an adaptive control framework is presented to dynamically update the optimal charging/discharging decision at each hour to mitigate the effect of RS tracking error. As more and more PEVs are being plugged into the power grid, the control or management issue of PEV charging arises, since mass unregulated charging processes of PEVs may result in degradation of power quality and damage utility equipments and customer appliances. To solve this problem, this article also presents an SoH-aware charging aggregator design, which decides the control sequences of a group of PEVs. An energy storage system is used in the charging aggregator to do a peak power shaving, and future parking PEVs are properly taken care of. Experimental results show that the proposed optimal charging algorithm minimizes the combination of electricity cost and battery aging cost in the RS provisioning power market. Experimental results also show that the introduction of charging aggregator can significantly reduce the peak power consumption caused by simultaneous PEV charging.

Electrical characteristics of an energised conductor under various weather conditions

When a transmission line is subjected to adverse weather conditions, rain drops or ice can be formed on its surface, leading to discharge phenomena known as corona. The corona discharge increases corona loss, leakage conductance, and capacitance, the latter two effects facilitating harmonic conditions and power quality degradation. This study investigates the electrical characteristics of an energised conductor under rain, rime, and glaze ice conditions. The experiments were carried out in a climate room using a corona cage. It was found that the leakage conductance of a corona-cage configuration was at its highest under glaze ice condition and at its lowest under rime condition for the same background surface electric field. With the presence of icicles, the change in capacitance under glaze ice accretion was complex. From the experimental results, it can be concluded that the corona-cage configuration is mainly characterised by its capacitive nature before the corona onset. When the corona discharge occurs, the corona cage exhibits a resistive–capacitive nature. With the increase of applied voltage, the configuration becomes more resistive.

Improvement of Power Quality Using a Robust Hybrid Series Active Power Filter

The degradation in power quality causes adverse economical impact on the utilities and customers. Harmonics in current and voltage are one of the most commonly known power quality issues and are solved by the use of a hybrid series active power filter (HSAPF). In this paper, a new controller design using sliding-mode controller-2 is proposed to make the HSAPF more robust and stable. An accurate averaged model of a three-phase HSAPF is also derived in this paper. The design concept of the robust HSAPF has been verified through simulation and experimental studies, and the results obtained are discussed.

Application of the Fuzzy Computational Intelligence in Power Quality Data Management

In Electrical Power Distribution System the sustained availability and quality of electric power are the main challenge they need to satisfy so overcoming the power quality (PQ) degradation became an asset. This Paper addresses the perfect load management using the computational techniques by analyzing the data of the system taking into account the density of the feeding nodes and its distribution also the classification of major Power quality degradations such as power factor and harmonics in the System and The methodology will be illustrated, simulated and evaluated using the fuzzy technique clustering the data and on an Artificial Neural Network (ANN) to achieve the optimum utilization of the energy loads and perfect load management and optimization. Simulation results demonstrate the effectiveness of the proposed algorithm in reducing the power and energy losses, improving the quality of the electric power system.

On power quality and reliability of supply

Power quality determines reliability of electrical equipment operation, performance of the assigned functions by it, service life. In the last years problem of power quality attracted increased attention because of power quality degradation and a great number of consumer complaints. Many problems of power quality control, such as determination of liabilities and responsibility of power suppliers and consumers for its quality, call for solution. The paper presents the types of damages caused by harmonics and the results of an analysis of harmonic active power at the node connecting an aluminum smelter block to a supply network. The analysis is performed on the basis of measurements. Measured current and voltage were used to calculate harmonic active power. It was found out that the aluminum smelter block generates the harmonic active power to the supply network only during part of the measurement time. For the other part harmonic active power flows from the supply network to the aluminum smelter block. The paper presents the proposals on the use of harmonic active energy for determination of the power quality distortion source and its contribution.

Classification of Power Quality Events Using Wavelet Analysis and Probabilistic Neural Network

<p>Power quality studies have become an important issue due to widespread use of sensitive electronic equipment in power system. The sources of power quality degradation must be investigated in order to improve the power quality. Switching transients in power systems is a concern in studies of equipment insulation coordination. In this paper a wavelet based neural network has been implemented to classify the transients due to capacitor switching, motor switching, faults, converter and transformer switching. The detail reactive powers for these five transients are determined and a model which uses the detail reactive power as the input to the Probabilistic neural network (PNN) is set up to classify the above mentioned transients. The simulation has been executed for an 11kv distribution system. With the help of neural network classifier, the transient signals are effectively classified.</p>

Particle motion around open mixing screws: optimal screw angular velocity

Purpose The analysis of the effect of screw angular velocity on the mixing efficiency of open mixing screws. Design/methodology/approach Measurements and discrete element method based simulations. Findings There is an optimal screw rotation angular velocity above which there is no reason to operate the mixing apparatus, as the mixing efficiency does not increase with the increase of screw angular velocity. Research limitations/implications By using discrete element method based optimization of open mixing screw apparatus, the effective mixing of agricultural grains can be achieved. The quality degradation of the dried product can be reduced. Practical implications The causeless increase of screw angular velocity results higher power consumption and quality degradation because of the increasing value of contact forces arising between the mixed particles. Originality/value Our article shows that by using discrete element based simulations, the optimal working parameters of open mixing screws can be evaluated.

Effects on Light Efficiency in Discharge and Solid-State Lighting Operation, Supplied by Non-Sinusoidal Voltage

The widespread use of discharge lamps and solid-state lighting is justified by its high-energy efficiency. However, the massive use causes degradation of power quality provided. In this context, the objective was the evaluation and discussion of the effect of harmonic voltage distortion (THDv) in view of the electrical system electrical operation of discharge lamps and solid state. More specifically, they were tested lamps of various types available in Brazil and evaluated rate of harmonic distortion current (THDI), current crest factor (CF), power factor (PF), luminance and bulb temperature before Feeds distorted with THDv 0 per cent, 12.6 per cent, 14.4 per cent and analyzed the effects on brightness and bulb temperature. The results showed that compact fluorescent lamps are the most sensitive to distorted power while the lamps for use in street lighting with magnetic ballasts are the least sensitive.