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This paper proposes goal-function-based decentralized control of microgrids. In addition to being an instrument for maintaining the grid voltage and frequency stability, each grid-tie inverter generates a current component with the aim of compensating for voltage distortion in the node where it is connected. The designed goal-function does not need to rely on the assumption that a microgrid is dominantly inductive or resistive to derive its control law, as is mostly the case with the droop-based approach. The priorities of the proposed scheme can be adjusted according to user preferences. In addition, the control algorithm is independent of network topology, can be applied in both islanded and non-islanded microgrids, and secure system scalability. The proposed method is verified by detailed simulations. [ABSTRACT FROM AUTHOR]

The presence of non-linear, time-variant loads in power networks introduces harmonics and other power quality issues in voltage and current waveforms. With the growing prevalence of power electronics, managing harmonic distortion has become a significant challenge in modern power distribution systems. This study aims to assess and analyze power quality at various locations within an academic institution (Sultan Qaboos University). The study encompasses the outputs of PV converters, uninterruptible power supplies (UPS), chillers with variable-speed motors, 11 kV/415 V transformers at both the College of Engineering and the Center of Information Systems, as well as two main substations supplying power to the university (33 kV/11 kV). Data collected—such as harmonic content in current and voltage waveforms and Total Harmonic Distortion (THD)—were meticulously analyzed to identify the factors affecting waveform quality. Measurements were conducted using advanced power quality instruments (Fluke 435-II), and the data were analyzed using MATLAB software. The study reveals that most results adhered to both the Oman grid code and international standards. The findings and methodology presented in this paper provide a critical benchmark for guiding standards compliance as Sultan Qaboos University, and other academic institution, undertakes the modernization of aging equipment and the expansion of new high-tech facilities. [ABSTRACT FROM AUTHOR]

Electrical transformers are generally designed to operate from sinusoidal sources. However, increased use of nonlinear loads, such as electric motor drives, lighting, fluorescent lamps, rectifiers, and computers, which generate high values of harmonics, makes this transformer operate in the nonlinear region. This paper discusses and focuses on the effect of the characteristics of a single-phase transformer when it is operated from a non-sinusoidal source with a non-linear load. An experimental 1 kVA single-phase transformer with a voltage of 220V and frequency of 50Hz with linear and nonlinear loads was considered. The results of this investigation show the losses increased by 25% when the transformer was fed from a sinusoidal power supply and the load was non-linear. In addition, the losses and THD for the current reached 40% and 12.4%, respectively, at nearfull load when the transformer was fed from a non-sinusoidal power supply and non-linear loads. The correlation between total harmonic distortion (THD) and these types of power supplies and loads was illustrated. The results showed that increasing the current harmonic distortion will lead to increased transformer losses and thus reduce their life expectancy. [ABSTRACT FROM AUTHOR]

This work aims to design, model and analyse an adaptive control method for voltage source converters (VSCs) under unbalanced PV sources and non-linear load operations. Both utility grids and stand-alone grid systems can use the proposed system. The VSC will inject Solar Photovoltaic(SPV) Power into the grid, to compensate fundamental component and harmonic reactive power, adjust the power factor, and balance the system's three-phase load when there is an imbalanced load. Shunt active power filters (APFs) have proven to be effective in filtering harmonic currents and correcting reactive power for linear/nonlinear loads. This research proposed a unique method for estimating the reference compensation currents of a three-phase shunt active power filter (APF) in a steady state under distorted and unbalanced source voltages (PV Sources). The suggested method is compared with three prior evaluated shunt APF reference compensating techniques. Even when the source voltages are significantly distorted and unbalanced due to variation in temperature and irradiation, the proposed system is compensating reactive power and harmonic/neutral currents of the load more effecetively. Furthermore, the suggested technique results in a simplified design of the shunt APF controller with three phase voltage source converter. [ABSTRACT FROM AUTHOR]

This work proposes an efficient integration method of solar energy with industrial nonlinear loads, accounting for dynamic variations in solar power and load harmonic profiles. The involved dynamics necessitate that the solar interface front-end inverters be equipped to handle both harmonic distortions and active power injection characteristics simultaneously. In this work, an instantaneous load and source characteristic mapping is proposed for the solar-interfaced front-end inverter operated as a shunt active power filter cum active power injector in order to accommodate the dynamic variations of the source and load. As per requirement, to separate the load-demanded and switching harmonics, a new load network time constant-based passive filter design diverging from traditional passive filter design methods is demonstrated. Further, a comprehensive explanation of the current controller modeling methodology is elaborated, considering the essential bandwidth required for proficiently managing load-demanded harmonics in both grid injection and drawing modes of operation. Later, in grid injection mode, the influence of grid and system impedance interactions on the power quality is analyzed for weak grid scenarios to derive the requisite bandwidth conditions to ensure resilient power transfer. Subsequently, the experimental validation of the solar interfaced shunt active power filter (SISAPF) with active power injection capability is carried out in both grid power drawing and injection modes, demonstrating the effectiveness of the enhanced bandwidth in handling load-demanded harmonics and solar power dynamic variations.

Energy-feed power electronic loads can precisely control the phase and magnitude of the power supply output current, achieving the emulation of loads. Moreover, they can feed energy back to the grid for energy regeneration, demonstrating significant research value. This article proposes an energy-fed power electronic load topology and control method that can realize the static and dynamic simulation of linear and non-linear loads and take into account the simulation needs of single-phase, three-phase three-wire, and three-phase four-wire loads. The main circuit uses a two-stage back-to-back AC/DC/AC structure: the front side is a three-phase four-wire split capacitor PWM rectifier bridge, which is used to simulate loads under various operating conditions; the back side is a three-phase three-wire PWM inverter bridge, which realizes the energy feeding back to the grid and reduces the waste of energy; and the intermediate side uses a split capacitor to equalize the voltage and achieve voltage stabilization. The topology is analyzed under the simulation demands of three-phase balanced, three-phase unbalanced, single-phase and non-linear loads. Finally, a MATLAB(R2022a)/Simulink simulation platform is built for a power electronic load with a rated capacity of 200 kVA. The simulation results verify the effectiveness, feasibility, and advancement of the power electronic load proposed in this article. [ABSTRACT FROM AUTHOR]

The increasing presence of electric vehicles (EVs) requires a thorough understanding of their impact on distribution assets. EV chargers are characterized as nonlinear and multi-state loads due to their unique electrical consumption patterns. This paper presents a comprehensive study focused on modelling diverse EV charging units deployed in the industrial, commercial, and residential sectors. To conduct this analysis, a simulation environment utilizing the ETAP tool is employed, taking into account time variations. This approach facilitates the comprehension and anticipation of the effects that EV charging may impose on distribution networks, thereby supporting well-informed decision-making for the adaptation and enhancement of the electrical system. Detailed data on current and voltage from operational EV charging stations were collected to create consumption, current, voltage, and harmonic profiles for these charging units. Subsequently, general models or libraries applicable to Level 1, Level 2 and Level 3 EV chargers available in Colombia were developed. These models underwent rigorous validation and were subjected to a comprehensive analysis using the IEEE 13-bus test system. The research yielded valuable insights and conclusions regarding the integration of EV chargers into the current Colombian distribution systems, as well as the potential impact of adopting these devices on power quality issues within the distribution grid. This study contributes to the improved management of distribution assets, thereby facilitating the integration of sustainable electric mobility in the national electrical system. [ABSTRACT FROM AUTHOR]

Renewable penetration, particularly the increasing deployment of PV by residential customers, organizations, and utilities, is leading to the rapid evolution of the power grid. However, the power system's architectural changes affect the quality of supply and give rise to power quality issues such as harmonics, fluctuations, disturbances, etc., at the point of common coupling (PCC). Therefore, in this work, a power network was modeled to study the impact of PV systems on PCC. At first, a detailed review is presented for on-grid PV systems with different inverter topologies, control techniques, sources of harmonic generation, and their mitigation strategies. After that, several use cases considering various sources of harmonics in a network with on-grid PV are modeled and simulated using MATLAB/Simulink. In-depth research was performed in this work to examine the many variables that affect harmonics, such as solar radiation levels, controller tuning, and load changes. Results with a real-time simulation platform (OPAL-RT) are presented in this paper for several use cases. Lastly, comprehensive discussions are presented from the acquired offline and real-time simulation results. [ABSTRACT FROM AUTHOR]

Most of the loads used in our day-to-day life are non-linear in nature. To investigate the performance of various non-linear loads, a laboratory setup on different load combinations such as light, fan and drive system in this work. The unbalance in supply voltages, supply current and frequency, reduction in power factor and total harmonic distortion for current and voltages are monitored through this lab setup and also the results obtained from these systems are discussed in this paper. To check the nature of voltage, current, reactive power and power factor in real-time systems, a turret punch machine incorporated with several single-phase AC servo motors is considered. The variations in the parameters are recorded using the fluke analyzer. Finally, it is observed that current harmonics at the source side are dominant in both the laboratory setup and the real-time system. Next, shunt active power filters are applied to mitigate the current harmonics. The simulation for the system with compensations is conducted in the Matlab platform and the hardware implementation validates the same.

Considering the proliferation of power electronics applications and distributed energy resources, modern power grids are facing a significant increase in harmonic currents circulation and supply voltage deterioration, occasionally associated with small frequency variations. In such a context, the understanding of power phenomena in circuits with linear and non-linear loads under non-sinusoidal voltage conditions is nontrivial and still does not allow for an easy interpretation of harmonic sources, harmonic power flow or the identification of the parameters of a proper equivalent circuit. The main challenge is to develop modern theoretical approaches for load characterization, modeling, and parameter estimation so that new techniques can be formulated to provide adequate guiding for the analysis, compensation, revenue metering, accountability and other applications of power systems. Thus, based on the Conservative Power Theory (CPT) and further decomposition of its apparent power and power factor definitions, this paper proposes a novel methodology for estimating equivalent parameters and for proposing proper equivalent circuits capable of representing/modeling the main characteristics of single-phase generic loads (black boxes) and the related power phenomena in terms of passive dipoles (linear loads) or of harmonic voltage/current sources and their intrinsic transimpedances/transadmittances (non-linear loads). Simulation and experimental results were depicted to support and validate the proposed approach, showing that it might be a powerful modeling technique to represent generic loads in a modern power grid scenario, while being used for complex applications such as reactive power compensation or accountability in circuits with nonlinear loads and distorted voltages. [ABSTRACT FROM AUTHOR]

Harmonic pollution is one of the challenging problems facing power networks recently due to the widespread non-linear loads and inverter-based renewables. In this regard, this work presents the optimal design of damped and undamped passive filters using a solver called Mixed-Integer Distributed Ant Colony Optimisation (MIDACO). This solver is employed to obtain an optimal design strategy for single-tuned passive power filters by investigating three primary criteria – minimisation of active power losses of the Thevenin’s resistor, maximisation of the true power factor, and maximisation of the transmission efficiency. Several constrictions associated with the designed filters have been considered, in which the global maximum or minimum criterion was attained by retaining the quality factors of the designed filters within a particular range, damping harmonic resonance, achieving a permissible range of the power factor, limiting voltage harmonic distortion by complying with IEEE Std. 519–2014 restrictions. Besides, the performance limits of capacitors operating in distorted systems have been met while complying with IEEE Std. 18–2012. Further, the results obtained using the MIDACO solver in four different case studies are compared to those obtained using particle swarm optimisation and genetic algorithm. In addition, this work depicts the damping resistor of the inductance in the single-tuned filters. The benefits and drawbacks of damping over an undamped filter are discussed. Finally, the results validate the effectiveness of the MIDACO solver employed in this paper.

Abstract A concern regarding the deterioration in power quality (PQ) has escalated with the high level of integration of renewable energy sources to the utility, primarily in the scenario of a weak distribution grid. This paper presents a modified complex variable filter (MCVF)‐based control to enhance the power quality performance of wind–solar photovoltaic (PV) and battery‐based microgrid under the weak grid and dynamic load conditions. An MCVF attenuates the harmonics and DC bias infected voltage and current and extracts the fundamental components from distorted current and voltage. The control scheme for the voltage source converter (VSC) is presented to meet the active power demand of load/grid and attenuates harmonics to control the power quality issues at the point of common coupling. To achieve the round, the clock operation of the microgrid, a battery is interfaced to support the local loads under off‐grid mode. Therefore, the presented VSC controller supplies the continuous power to the local loads and maintains the total harmonic distortion value of grid current within the PQ Standard IEEE‐519‐2014. The simulated and test results are presented to validate the VSC controller in different operating conditions.

The spread of power electronics-based non-linear loads increase the harmonics distortion level in power systems. Real-time interactive systems are considered the most promising solution to several grid power quality problems. The practical design considerations are the aim of this study. A current sensor in addition to controller circuits is used for instantaneous current measurement. This measured current is including both the fundamental and the harmonics according to the connected loads. A simple mathematical algorithm for estimating the fundamentals is implemented using the microcontroller. By subtracting the fundamental from the measured current one can extract the whole current harmonic waveforms. This current waveform is used as a modulated signal for Pulse Width Modulation-Current Source Inverter (PWM-CSI) connected to the grid. The current source inverter is the most effective technique to inject the same harmonics shifted with 180 degrees for higher harmonics reduction. The PWM-CSI switching frequency will be determined according to the desired harmonic orders to be eliminated. In this work, the 1 kHz is the switching frequency for eliminating up to about the 20th harmonic order. The laboratory experimental results are satisfactory and confirm these obtained from the analytical and the simulation. [ABSTRACT FROM AUTHOR]

In this research the effect of imbalance and nonlinear load on power quality was investigated via the electronic method with the aid of a Fluke 435 power quality analyser and the results obtained compared with IEEE standards. The study was carried out on 11 kV Pama feeder Kaduna state, Nigeria, which is comprised of Nassarawa, Boro1, Pama 1, Pama 2, and Pama 4 substation. The analyzed result shows an average value of 230 and 1327 times voltage dips and swells, 11.74 % harmonics current, 2.33 % harmonic voltage, 5.96% imbalance voltage and 25% imbalance current respectively. When compared with the IEEE standard limits of 5 % and 2 % harmonic current and voltage, 10 % and 5 % imbalance current and voltage, it could be seen that these results imply the presence of harmonics within the system which are fundamentally due to imbalance and non-linear load, triggering operating complications on the distribution system. These complications include load disruptions, over current, over voltage, heating, leading to forceful outage, increased power losses, faster ageing of insulations, unstable power supply, burnt cables, sockets and connectors, thus reducing capacity and ultimately resulting in premature failure of transformer.

The increasing presence of electric vehicles (EVs) requires a thorough understanding of their impact on distribution assets. EV chargers are characterized as nonlinear and multi-state loads due to their unique electrical consumption patterns. This paper presents a comprehensive study focused on modelling diverse EV charging units deployed in the industrial, commercial, and residential sectors. To conduct this analysis, a simulation environment utilizing the ETAP tool is employed, taking into account time variations. This approach facilitates the comprehension and anticipation of the effects that EV charging may impose on distribution networks, thereby supporting well-informed decision-making for the adaptation and enhancement of the electrical system. Detailed data on current and voltage from operational EV charging stations were collected to create consumption, current, voltage, and harmonic profiles for these charging units. Subsequently, general models or libraries applicable to Level 1, Level 2 and Level 3 EV chargers available in Colombia were developed. These models underwent rigorous validation and were subjected to a comprehensive analysis using the IEEE 13-bus test system. The research yielded valuable insights and conclusions regarding the integration of EV chargers into the current Colombian distribution systems, as well as the potential impact of adopting these devices on power quality issues within the distribution grid. This study contributes to the improved management of distribution assets, thereby facilitating the integration of sustainable electric mobility in the national electrical system.

This study focuses on improving power electronic components and devices, which have gained popularity due to their compact size and precise control over the output voltage and current. They are widely used in renewable energy systems, such as converters and inverters, and in industrial drives as control devices. However, the switching process in power electronic components introduces nonlinear behavior, leading to the generation of harmonics and power quality problems. To address these issues, various methods and techniques recommended by industry standards have been proposed to mitigate or eliminate harmonics and ensure the power quality. These standards provide limits and guidelines for assisting customers and manufacturers in maintaining acceptable power quality levels. Machine-learning algorithms offer a promising approach for improving power quality by leveraging data from a system to make predictions or classifications. In the context of power electronics, machine-learning algorithms can be trained to classify fault types, identify the exact location of faults, predict the remaining life of power electronic components, and detect voltage disturbances. Different machine learning techniques can be employed, depending on the specific application. For example, fault classification and fault location identification can be achieved through supervised learning algorithms, whereas predicting component life and detecting voltage disturbances can utilize techniques such as regression or anomaly detection. By leveraging the power of machine learning, enhanced reliability, performance, and efficiency can be achieved in various applications, thereby contributing to the overall advancement of power electronics technology. [ABSTRACT FROM AUTHOR]

Utilities produce and supply products following local requirements and with the synchronizations which connect subscribers. Harmonics is a power efficiency/quality variable caused by electronic devices that domestic and industrial consumers use. The famous IEEE Standard 519 is maintained to calculate harmonic limits, which ensures power efficiency. In a standard power system, currents and voltages generate pure sine wave signals during regular operations. As harmonics influence the power system, they cause interference in the sine wave signals. So, the best practice method should be used to resolve the harmonics issue. One of the problem-solving techniques of harmonics is the measurement and reduction of harmonics detection, and it uses Fast Fourier Transform (FFT). Therefore, power output should assess in a peer-to-peer Blockchain scheme by measuring and minimizing harmonics detection. This paper uses a Shunt Active Power Filter (SHAPF). It describes the simulation analysis and reduction of harmonics detection in a peer-to-peer interconnected 3-phase power system with the help of an FFT algorithm. This research was carried out to assess the efficiency of the AC signal by collecting, processing, and evaluating power data. Using the shunt active filter, the proposed design outperformed the traditional methods for both six and twelve pulse rectifiers, achieving total harmonic distortion (THD) of only 1.42% and 0.92%, respectively.

The operation of devices with different load types is related to the occurrence of distortions such as high current and voltage harmonics, phase and power imbalance. Electrical equipment may not operate correctly due to higher harmonics and power and phase imbalance. Neutral current is the result of harmonics and power and phase imbalance. In three-phase systems, current may flow in the neutral conductor due to the imbalance problem caused by the loads or the wrong wiring. Non-linear loads inject harmonic currents into the grid or source. When triple harmonics are present in the network, the neutral current is not zero even if the load is perfectly balanced. This can increase the risk of fire due to overheating of the neutral conductor due to overload. In this study, power parameters were measured by performing five measurements in three phases (Phase A, Phase B and Phase C) in three different facilities. The effects of load unbalance and triple harmonic values on neutral current are compared. Although the power imbalance standard error value in the first and second measurement was close to each other, there was approximately 30% variation between the triple harmonic values, while the difference in neutral current was 13.27 A. For the test system in the current study, it was concluded that triplen harmonics have more effect on the current in the neutral conductor than unbalanced loading. [ABSTRACT FROM AUTHOR]

Alumina production is rather complex technological process of processing mineral raw materials that requires development of effective technological solutions, including in terms of efficiency of using electric energy. The paper is devoted to studying the power supply system of an alumina refinery inLam Dong Province,Vietnam. The tasks that need to be solved for improving the power quality in the power supply system were analyzed. It was shown that non-linear loads significantly degrade the power quality that in turn leads to equipment damage, malfunction and decreasing the refinery productivity. Models of the refinery power supply system were developed and, using which, the quality of power was assessed at the 6 kV voltage utility bus of the power supply system, as well as at the 6 kV and 0.4 kV buses of distribution substations of individual refinery’s subdivisions. Analysis of the simulation findings showed that the nonlinear loads lead to significant distortions of sinusoidal forms of voltages and currents, and decreasing the power factor. Based on the simulation results, it was concluded that voltage harmonics and current harmonics at nonlinear load at the low voltage buses of 0.4 kV and at the buses of 6 kV exceed the permissible limits of the harmonics in accordance with IEEEST519-1992 international standard. Proposals were developed for improving the power quality in the refinery power supply system. For suppressing higher harmonics of current and voltage, it was recommended to use special power quality regulators in the alumina refinery power supply system. It was proposed to use active harmonic filters as the power quality regulators. The proposed solutions allowed obtaining practically sinusoidal forms of voltages and currents in the alumina refinery power supply system.

Total harmonic distortion has become an important subject in power quality, especially after use of power electronic equipment and non-linear loads. Working of electricity systems smoothly and safety depends on the foundation of quantities such as current and voltage which are sinusoidal and 50 Hz frequency. However, these foundation quantities lose their sinusoidal characteristics because of many reasons and this occurs unwanted harmonics in the system.It is a highly preferred methodto use passive filtersfor reduction harmonic and to improve the power factor. The proposed power system is a combination of three-phase voltage supply, power transformer, sixpulse rectifier, passivefilter, and R-L inductive load. A six-pulse uncontrolled rectifier produces 5th, 7th, 11th, 13th, 17th, 19th, etc. current harmonics components. A passive filter is used to reduce the total harmonic distortion of the input current of the three-phase uncontrolled rectifier. Power system is modeled by using Matlab/Simulink program. Simulation results show that both the harmonics are eliminated and the power coefficient is corrected.Before using passive filters the power coefficient was 0.6877, and the THDI value was measured as 12.71 % in the power system. After using passive filters, the power coefficient was 0.99 and the THDI value was measured as 3.591 % in power system.

This paper present grid interaction solar PV-battery systems can handle unbalanced and balanced three-phase four-wire (3P-4W) nonlinear loads as well as single-phase loads of various types. AL-BP control is capable of automatically adjusting complex nonlinear systems including grid-interactive 3-phase, 4-wire systems that have critical imbalance, and feeding highly nonlinear loads, without requiring any additional tuning. A robust control mechanism is needed to improve performance of the system and power quality for solar array solar energy conversion systems. The module neural network management incorporates DSTATCOM functions such as minimizing harmonics, balancing of load, and improving power factor. The fuzzy logic control technique delivers superior precision due to the neural network's combinational neural structure. This validation validates that the system is capable of maintaining power quality, according to IEEE-519 requirements. This type of approach significantly increases the steady-state and dynamic capabilities of a grid-connected 3-phase, 4-wire (3P-4W) PV-battery system. For verification, a real-time DSP processor has been used to implement the AL-BP control technique. [ABSTRACT FROM AUTHOR]

Harmonics at nonlinear loads have different values for each load. These characteristics can be used as identification of the type of load from the harmonic value produced from nonlinear load. Therefore, this paper proposes harmonic load identification using Fast Fourier Transform (FFT) and Artificial Neural Network (ANN). In order to obtain harmonic values, a prototype of measuring instruments is used, while the method for obtaining harmonic values is FFT. The harmonic value obtained will be used as training data and testing data in ANN. Then, the type of training used as the classification of load type is the Levenberq Marquardt. The input of this method is a harmonic value of three types of nonlinear loads with seven combinations. The training process is carried out in MATLAB. Then, the weight and the bias values of each neuron are obtained and programmed in microcontroller. In order to validate the proposed algorithm, testing is conducted by three nonlinear load combinations. The results show that the proposed algorithm has good results in load identification with the highest accuracy of 99.94%. [ABSTRACT FROM AUTHOR]

This paper presents the design of an embedded control system and its implementation on a DC-AC bidirectional converter for the interconnection of a DC Microgrid (MG) with the AC Main Network (MN). This control system was designed in LabVIEW and implemented on the NI myRIO platform, and it was used for the synchronization of the MG with the MN. Its main goal is to keep the stability of the DC bus when energy is supplied to or extracted from the MN. The MG is composed of two 500 W photovoltaic panel arrays (PAs), each with a Boost DC-DC converter to generate a DC bus of 190 V, and a DC-AC bidirectional converter that interconnects the MG with the MN. The control system was tested considering nonl-inear loads such as computers, commercial fluorescent lamps, and LED, with the aim to analyze the response of the system to real life conditions. Results show that the embedded control system is capable to stabilize the DC bus at a voltage level of 190 V ± 5% when interacting with the different non-linear loads connected to the MG. This is an improvement on the control of the voltage variation previously presented in the literature of 190 V ± 10%. [ABSTRACT FROM AUTHOR]

• To reduce the distortion in multi-microgrid system, a 63 level inverter with reduced switches are used. • The multi-microgrid system is controlled by using a stationary frame control theory. • The stability in frequency of grid and microgrid is achieved by using two-degree of freedom based fractional order proportional resonant controller optimized by weighted mean of vectors optimization. A 63-level inverter with fewer switches is proposed to reduce harmonics in the multi-microgrid scenario. Since the multi-microgrid is connected with varying loads, synchronizing the output of the multi-level inverter and controller is developed, which works by having a data testing phase. The weighted mean of vector optimization acquires the multi-microgrid data to feed the control variable to the controller. Multi-microgrid issues are managed by two degrees of freedom based on a fractional order proportional resonant controller. As a result, the proposed inverter scheme has yielded a very low THD when subjected to a renewable based DC supply. This improves the performance of the 63-level inverter by 20.1 % compared to the asymmetric 63-level inverter. [ABSTRACT FROM AUTHOR]

This paper discusses the design, modelling and analysis of a single-phase grid-tied photovoltaic (PV) system feeding a variety of loads. Normally, the phase-locked loop (PLL) circuits are used for synchronisation purposes and generation of in-phase and quadrature templates. However, this paper presents an interesting application of PLLs for achieving load compensation for power quality improvement as well as estimation of phase and frequency. Three PLL algorithms are considered which include the conventional Delay PLL, Enhanced PLL and Second-Order Generalised Integrator Frequency-Locked Loop (SOGI-FLL). Design and modelling of controllers using these PLLs for achieving power quality improvement is also presented in the paper. Suitable comparisons are drawn to investigate the performance of different PLLs for two purposes viz. grid synchronisation and achieving compensation in a single-phase grid-tied PV system. Finally, the application of SOGI-FLL for control of a 5 kW PV interfaced single-phase compensator for power quality improvement is presented. Appropriate experimental results are shown along with simulation results for suitable comparison. [ABSTRACT FROM AUTHOR]

This paper describes experimental verification of progressive control strategies for shunt active power filters (SAPF) in common single-phase systems. Normalized least mean squares (NLMS) and QR decomposition-based least squares (QR-RLS) were used as SAPF control adaptive algorithms. The functionality was verified on real data using a measuring system based on virtual instruments (modules NI 9225 and NI 9227 were inserted into the cDAQ 9185 chassis). Commonly household devices (TV, energy saving lamp, PC power supply unit), which represent a non-linear load were tested. Different variables were thoroughly tested for both presented algorithms: filter length, forgetting factor λ for QR-RLS and filter length, convergence constant µ for NLMS. The results were evaluated based on total harmonic distortion (THD), signal-to-noise ratio (SNR) root mean square error (RMSE) and percentage root mean square difference (PRD). The contribution of the article is to verify the functionality of NLMS and QR-RLS algorithms, especially the influence of individual parameters on successful harmonic compensation. [ABSTRACT FROM AUTHOR]

High efficiency and low-cost Static Frequency Changer (SFC) converters are widely used in electronic industry. SFC known as cycloconverter is installed to obtain variable output AC voltage or frequency. Fast dynamic response and slight size made these converters to occupy the potential space in switching world. Cycloconverter generates harmonics when connected to different types of loads. These harmonics pollute the purity of sinusoidal waveform and affect the quality of power system. Harmonic current is produced when an electrical device draws current in a nonsinusoidal manner. The harmonic voltage develops as harmonic current traverses the electrical system. Harmonic and current orders are inversely proportional to each other, respectively. These harmonics affect the execution of switching devices and causes breakdown of cable insulation, circuit breaker tripping, power transformer failures, limits on generator efficiency and UPS capacity. This paper comprises of odd harmonics that takes place in different load contiguous with cycloconverter. The 3rd, 5th, 7th and higher order harmonics are diagnosed by employing MATLAB platform. Simulation studies are depicted and proved the importance of single phase step down bridge - cycloconverter. [ABSTRACT FROM AUTHOR]

In this paper, a new power factor correction circuit known as bridgeless Single Ended Primary Inductor Converter (SEPIC) is designed for universal input voltage applications. Now-a-days, entire electrical grid is connected with non-linear loads, so there is a need to improve power factor implied on the grid as well as power quality. The main drawbacks of the conventional SEPIC PFC is lower efficiency due to the conduction losses of the diodes. To improve efficiency of the system, a modified bridgeless SEPIC converter is proposed in this paper. The proposed modified PFC converter offers higher operating efficiency with high gain. The high gain is obtained by multiplier circuits. The main advantages of the proposed system are that diode bridge circuits is completely eliminated for conventional circuits and also the control circuit is very simple. The proposed converter is analysed in terms of THD and also gain of the converter is analysed with respect to the different duty cycle varying from 10% to 90%. The proposed converter is analysed with mathematical expressions. The results of the modified PFC have been verified using MATLAB Simulink. [ABSTRACT FROM AUTHOR]

This study aims to comparatively evaluate the widely known five passive harmonic filters as single-tuned, double-tuned, triple-tuned, damped-double tuned and C-type ones by regarding their contribution on the loading capability improvement of the transformers under non-sinusoidal conditions. For the comparative evaluation, the studied filter types are optimally designed to minimize the harmonic loss factor index, which is defined as a tool to determine the transformer’s permissible loading capability under non-sinusoidal current conditions in IEEE C.57.110 standard. According to the harmonic distortion limitations and the reactive power compensation level recommended in IEEE 519 standard, the individual and total harmonic distortions of voltage and current at point of common coupling and displacement power factor are considered as constraints of the studied optimal filter design problems. Whales optimization (WO) algorithm, which has recently been introduced in the literature, is used to find the optimal filter solutions. To show the validity of the obtained optimal filter designs, the results are also provided via Particle Swarm Optimization (PSO) algorithm. The simulation results show that the studied filters can be ranked from the best to worst as triple-tuned, damped double-tuned, double-tuned, C-type and single-tuned ones in terms of their performance on the transformer’s loading capability improvement. It is also seen from the simulations that the results of WO and PSO algorithms are very close to each other, and WO algorithm achieves optimal design solutions with considerably lower iteration numbers and run times. [ABSTRACT FROM AUTHOR]

The importance of considering the effects of harmonic distortion on electrical installations becomes more relevant because of the proliferation of so-called "non-linear" loads. This phenomenon contaminates the electrical network of an installation and can affect the operation of the devices connected to it when it exceeds certain limits. Therefore, the objectives sought in the article are to perform a study in the Sonangol - Namibe Industrial System components of harmonics that influence the same, propose the method (s) and procedures of elimination as are the passive filters used to reduce the distortions originated, From the electrical survey of the installation. A general review is also presented on the indicators related to harmonics and generators in electrical networks, using reference documents such as: IEEE 519-1992 recommendations, IEC-61000, NRS 048-2 and EN 50160. [ABSTRACT FROM AUTHOR]

PhotoVoltaic (PV) microgeneration ( μG ) located close to the end-users is gradually increasing and is expected to increase more in the future. However, a high μG penetration level may cause overvoltage issues in the Low Voltage (LV) distribution grid. On the other hand, these μG PV generators are usually placed in residential houses, composed by nonlinear loads that generate harmonics. The use of the harmonics compensation capabilities provided by modern PV systems can be an added value, as this function improves the voltage profile and reduces losses on the LV distribution network. This paper proposes an additional contribution to the subject by studying the impact of the use of PV systems harmonics compensation features to mitigate the harmonics produced by residential nonlinear loads. The assessment tool is a suitable algorithm created to compute an unbalanced three-phase power flow in the presence of harmonics. This is based on the Common Object Model (COM) interface of two software tools, MATLAB and OpenDSS. Three case-studies are proposed: harmonic compensation disabled, harmonic compensation enabled and reactive power control. The last one is introduced for comparison purposes. The assessment is made for a typical summer day, on a highly unbalanced test radial LV distribution network with high μG penetration and harmonic pollution. The obtained results allow the conclusion that the PV system harmonic compensation capability is able to attenuate the harmonics, therefore improving the voltage profile, and reducing the power losses and voltage drop on the LV distribution network. [ABSTRACT FROM AUTHOR]

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Harmonic pollution is one of the challenging problems facing power networks recently due to the widespread non-linear loads and inverter-based renewables. In this regard, this work presents the optimal design of damped and undamped passive filters using a solver called Mixed-Integer Distributed Ant Colony Optimisation (MIDACO). This solver is employed to obtain an optimal design strategy for single-tuned passive power filters by investigating three primary criteria – minimisation of active power losses of the Thevenin's resistor, maximisation of the true power factor, and maximisation of the transmission efficiency. Several constrictions associated with the designed filters have been considered, in which the global maximum or minimum criterion was attained by retaining the quality factors of the designed filters within a particular range, damping harmonic resonance, achieving a permissible range of the power factor, limiting voltage harmonic distortion by complying with IEEE Std. 519–2014 restrictions. Besides, the performance limits of capacitors operating in distorted systems have been met while complying with IEEE Std. 18–2012. Further, the results obtained using the MIDACO solver in four different case studies are compared to those obtained using particle swarm optimisation and genetic algorithm. In addition, this work depicts the damping resistor of the inductance in the single-tuned filters. The benefits and drawbacks of damping over an undamped filter are discussed. Finally, the results validate the effectiveness of the MIDACO solver employed in this paper. [ABSTRACT FROM AUTHOR]

Voltage quality issue and invariably power quality has become an important issue in distribution power system operation due to presence of increased use of nonlinear loads (computers, microcontrollers and power electronics systems). Voltage sags and swells as well as harmonics are problems for industrial, commercial and residential customers with sensitive loads, which need urgent attention for their compensation. In this paper, the modeling and simulations of a dynamic voltage restorer (DVR) was achieved using MATLAB/Simulink. The aim was to employ artificial intelligence to provide smart triggering pulses for the DVR to mitigate and to provide compensation against voltage sags and swells. The Artificial Neural Network (ANN) was trained online by data generated via a 3-phase programmable voltage generator and these were used as inputs to the ANN, fault conditions were simulated to create voltage sags and swells in the source supply, while faultless condition of the system was simulated and the data obtained from it was used as targets of the ANN. A net fitting, feed forward back propagation, Lavenberg-Marquardt training algorithm and mean square error performance were used. ANN Simulink block was used as control for the gate of the full wave 3-phase Insulated Gate Bipolar Transistor (IGBT) inverter employed in constructing the DVR. Three single phase injection transformers were employed to regulate the output amplitude voltage from the DVR, while filters were used to reduce the harmonics from 11.09% to 3.5%. At the end, voltage sags and swells were effectively mitigated and harmonics in the system reduced to 3.5%, which is within the maximum acceptable IEEE standard 519 of 1992 for harmonic distortion. [ABSTRACT FROM AUTHOR]

Three-phase four-leg inverters are commonly employed to supply unbalanced loads avoiding the use of a transformer. A suitable output filter is necessary to improve the harmonic content of the output voltage and current waveforms. To this aim, different kind of filters, presenting both symmetrical and asymmetrical phase-to-phase and phase-to-neutral behavior, can be used. The paper discusses and analyzes the effects of different carrier-based modulation techniques, based on the independent control of the fourth leg from that of the other phases, with reference to the different filter topologies. The comparison, performed through extensive simulations and experimental tests, have demonstrated that in case of the asymmetrical filter utilization, such as the active split dc-bus (also known as split-link), the conventional continuous and discontinuous space-vector modulations produce a significant harmonic content in the output voltages even at no-load condition. Moreover, the analysis is extended considering the interaction between the modulation strategy and load characteristics as linear, nonlinear, balanced and unbalanced loads. The problem is discussed in detail and a specific design procedure for the active split dc-bus is presented. [ABSTRACT FROM AUTHOR]

This paper deals with the integration of distribution energy resource (DER) connected to a three-phase grid connected system feeding a variety of loads. The DER is controlled to provide power quality improvement capabilities viz. power factor correction, harmonic reduction, voltage regulation, and load balancing, and it is realized as a voltage source converter (VSC). The developed controller is based on Synchronous Reference Frame (SRF) Theory and an energy based controller that also includes additional features viz. filtration of fundamental voltage extracted from the polluted utility grid voltages. This new controller, realized as an energy controller, is implemented over the square of the DC link voltage of the DER. The control algorithm has been tested for several power quality improvement features and works well for power factor correction, voltage regulation, harmonic reduction, and operation under unbalanced load conditions. Extensive simulation and hardware results are demonstrated on a prototype developed in the laboratory. [ABSTRACT FROM AUTHOR]