Voltage fluctuations

Integration of wind energy into the grid faces a great challenge regarding power quality. The International Electrotechnical Commission (IEC)~61400-21 standard defines the electrical characteristics that need to be assessed in a Wind Turbine (WT), as well as the procedure to measure the disturbances produced by the WT. One of the parameters to be assessed are voltage fluctuations or flicker. To estimate the flicker emission of a Wind Power Plant (WPP), the standard establishes that a quadratic exponent should be used in the summation of the flicker emission of each WT. This exponent was selected based on studies carried out in WPPs with type I and II WTs. Advances in wind turbines technology have reduced their flicker emission, mainly thaks to the implementation of power electronics for the partial or total management of the power injected into the grid. This work is based on measurements from a WPP with 16 type III WTs. The flicker emission of a single WT and of the WPP were calcul...

The purpose of the present paper is to evaluate the sensitivity of modern lighting technologies to different types of RVCs. In order to do that, 27 modern lamps—mainly LED—have been subjected to real RVCs and their response has been assessed. The detection of RVCs on the grid has been performed according to the IEC 61000-4-30 detection method, while the response of the lamps has been measured with a light flickermeter and characterized using the instantaneous flicker perception, as defined in IEC 61000-4-15. The obtained results show a high dispersion in the response of the modern lighting technologies and high values of flicker perception, although with a lower sensitivity than the incandescent lamp. The results led the authors to propose the definition of a new immunity test to be added to the lamp immunity protocol IEC TR-61547-1, to ensure that newly produced lamps cause limited irritation to grid users.

This paper presents an enhancement to the stability of large PV-integrated grids using an advanced power quality control system. The proposed unified power quality conditioner (UPQC) system control technique combines synchronous reference frame (SRF) theory and modified unit vector template generation (MUVTG), supplemented by an additional proportionalintegral-derivative (PID) controller to regulate reactive power flow to the grid. The results indicate a reduction in the total harmonic distortion (THD) levels. The study also demonstrates the system's stability for different harmonic orders and various cases of voltage sag and swell, in compliance with IEEE standards. The proposed approach effectively addresses power quality issues and achieves a THD of 0.30%, meeting the IEEE-519 standards using MATLAB Simulink.

This paper presents a novel approach that integrates an advanced PLL with an ANFIS-optimized PI DVR controller, effectively mitigating voltage sags, swells, and harmonics in accordance with the IEEE 519 (2014b) guidelines for power quality in specialized application systems. The designed hybrid DVR controllers are tested using the hardware-in-the-loop OPAL-RT 4200 real-time simulator powered by an FPGA Kintex unit using the RT-LAB platform. The testing encompasses various loading conditions, including both nominal (100%) and increased (110%) loads. Under nominal loading conditions, the PLL-ANFIS optimized PI DVR controller is able to maintain power quality within acceptable limits. However, when the loading is increased to 110%, controllers based on the PLL-ANFIS optimized PI DVR method fail to meet the required standards. In contrast, the CDSC PLL-ANFIS optimized PI and MDSC PLL-ANFIS-optimized PI controllers perform better, successfully meeting the required limits. However, this achievement comes with a higher computational load and increased costs compared to alternative methods. Given the higher accuracy required to meet the IEEE 519 (2014a) guidelines for specialized applications, these trade-offs are considered acceptable, especially for critical and sensitive applications like healthcare facilities, semiconductor manufacturing plants, and pharmaceutical industries, where maintaining high power quality is crucial.

This paper reports on the impact of PV farm location in Low-Voltage Distribution Networks (LVDNs) in terms of power loss and voltage profile. Simulation results from a five node or bus radial network within the Power Systems Computer Aided Design (PSCAD) software, successfully demonstrate the effect of the solar farm interface at different network buses on the degree of power loss and voltage variation under three load power sizes, namely 5%, 50% and 100% of the rated power. The results also suggest that the generators' phase angle, point of coupling location, inverters and associated converters switching algorithms have great influence on the aforementioned issues. Furthermore, the injected power by the PV farm at the load side will decrease the power demand from the substation. This in turn leads to the loss reduction and voltage profile improvement within the network. However, if the PV farm power generation is more than the load demand, some power may flow towards the substation. Consequently, a voltage rise can be expected along the distribution network. The rise of the voltage limits the amount of penetration level that can be installed in the distribution networks.

The IEC 61000-4-15 standard establishes the functional and design specifications of a flickermeter in order to objectively assess the disturbing light flicker. Some studies reported the unpredictable behavior of the IEC flickermeter when dealing with irregular voltage fluctuations. This deficiency explained the absence of the expected users' complaints at sites where high flicker levels were measured. The present work uses an alternative strategy for flicker measurement, previously tested under laboratory conditions, which overcomes the deficiencies of the IEC flickermeter. The 1 responses of the two strategies are compared under real voltage signals, which are complex and nonuniform in nature. Moreover, subjective experiments were carried out to characterize the irritation perceived by a small group of people when supplying an incandescent lamp with the same real voltage signals. The present work shows that it is possible to provide more reliable measurements in real scenarios and closer to the subjective perceptions than the IEC flickermeter does.

The Callen-Welton formula (fluctuation-dissipation theorem) of voltage and current noise of a resistance are the sum of Nyquist's classical Johnson noise equations and a (quantum) zero-point term with power density spectrum proportional to frequency and independent of temperature. At zero temperature, the classical Nyquist term vanishes however the zero-point term produces non-zero noise voltage and current. We show that the claim of zero-point noise directly contradicts to the Fermi-Dirac distribution, which defines the thermodynamics of electrons according to quantum-statistical physics. As a consequence, the Johnson noise must be zero at zero temperature, which is in accordance with Nyquist's original formula. Further investigation shows that the Callen-Welton derivation has conceptual errors such as neglecting phonon scattering, disregarding the Pauli principle during calculating the transition probabilities and using bosonic (linear oscillator) energies leading to the zero-point noise artifact. Following Kleen's proposal, the possible origin of the heterodyne (Koch -van Harlingen -Clark) experimental results are also discussed in terms of Heffner theory of quantum noise of frequency/phase-sensitive linear amplifiers. Experiments that failed to see the zero-point noise term are also mentioned.

A distribution static compensator (DSTATCOM) is used for load voltage regulation and its performance mainly depends upon the feeder impedance and its nature (resistive, inductive, stiff, non-stiff). However, a study for analyzing voltage regulation performance of DSTATCOM depending upon network parameters is not well defined. This paper aims to provide a comprehensive study of design, operation, and flexible control of a DSTATCOM operating in voltage control mode. A detailed analysis of the voltage regulation capability of DSTATCOM under various feeder impedances is presented. Then, a benchmark design procedure to compute the value of external inductor is presented. A dynamic reference load voltage generation scheme is also developed which allows DSTATCOM to compensate load reactive power during normal operation, in addition to providing voltage support during disturbances. Simulation and experimental results validate the effectiveness of the proposed scheme.

This paper discusses contemporary problems concerning ship microgrids. It focuses on the role of power electronics and power quality issues, both conventional, such as voltage and frequency variations, and new issues, such as waveform distortions ensuing from the wide proliferation of power electronics in ship microgrids. The paper also contains a discussion on the provisions of the Unified Requirements of International Association of Classification Societies and other leading power quality standards in the industry, with an emphasis on Total Harmonic Distortion (THD) definition. An overview of power converters for high power applications in ships and their impact on ship networks is also given. Next, original results of various power quality phenomena recorded in ship microgrids are presented and commented on, followed by a review and recommendations for maritime microgrid modeling and signal processing methods for power quality assessment in the discussed systems. Finally, preliminary proposals for power quality control are presented.

In this paper, voltage sag compensation of point of common coupling (PCC) using a new structure of fault current limiter (FCL) is proposed. The proposed structure prevents voltage sag and phase angle jump of substation PCC after fault occurrence. This structure has a simple control method. Using semiconductor switch (IGBT or GTO) at dc current rout leads to fast operation of the proposed FCL and consequently, dc reactor value is reduced. On the other hand, the proposed structure reduces total harmonic distortion (THD) on load voltage and it has low ac losses in the normal operation. As a result, other feeders which are connected to the substation PCC will have good power quality. Analytical analysis, simulation results using PSCAD/EMTDC software and experimental results are presented to validate effectiveness of this structure. Index Terms─Voltage sag, fault current limiter, power quality, point of common coupling (PCC), semiconductor switch, THD.

Distribution static synchronous compensator (D-STATCOM) has been developed and attained a great interest to compensate the power quality disturbances of distribution systems. In this paper, a novel single-phase control scheme for D-STATCOM is proposed to improve voltage profile at the Point of Common Coupling (PCC). The proposed voltage mode (VM) controller is based on the phase space algorithm, which is able to rapidly detect and mitigate any voltage deviations from reference voltage including voltage sags and voltage swells. To investigate the efficiency and accuracy of the proposed compensator, a system is modeled using Matlab/Simulink. The simulation results approve the capability of the proposed VM controller to provide a regulated and disturbance-free voltage for the connected loads at the PCC.

This paper presents a Multi-Period Optimal Power Flow (MOPF) modeling applied to the minimization of energy losses in Distribution Networks (DNs) considering the reactive power control of Photovoltaic Generation (PVG) that can be applied to both short-term and long-term operation planning. Depending on the PV Power Factor (PVpf) limitations, PVG may provide both active and reactive power. The optimal power factor control on the buses with PVG contributes to an economical and safe operation, minimizing losses and improving the voltage profile of the DN. The proposed MOPF was modeled in order to minimize active energy losses subject to grid constraints and PVpf limitations. The variations of loads and PVG were discretized hour by hour, composing a time horizon of 24 h for day-ahead planning; nonetheless, the methodology can be applied to any other time period, such as a month, year, etc., by simply having generation and load forecasts. To demonstrate the effectiveness and applicabilit...

The Power quality is essential prerequisite of todays required load. Power system has been facing many problems due to variation in loads. Conventional on load tap changer (OLTC) is being used since long time for any momentary changes in load requirement. Conventional tap changers uses mechanical switches for tap changing. Mechanical tap changer has some drawbacks, like they takes more time for operation, arching, mechanical losses, manpower required, continues maintenance. Also sometimes mechanical tap changer get stuck between two taps, which leads to damage of whole system, it affects stability of the system etc. The ceaseless development in utilization of energy using semiconductor gadgets, for example, the TRIAC, Metaloxide-semiconductor field-effect transistor (MOSFET), Insulated gate bi-polar transistor (IGBT) and Gate turn off thyristor (GTO) has helped for the working of OLTC controllers. To eliminate the drawbacks of mechanical tap changer, this paper presents implementation of Automatic Voltage Control on load (AVCL) tap changer for maintaining constant output voltage. The implemented design of AVCL can be suitable in smart grid technology as an advance technology. The designed and fabricated of AVCL system is using tapings on primary side instead of secondary side, which will provides the quick response, no arcing problems, no wear and tear, reduction of losses, safety towards equipment and human beings.

Rapid Voltage Changes (RVCs) are Power Quality (PQ) events characterized by small and fast transitions between two steady-state Root Mean Square (RMS) voltage levels. RVCs occur quite often at the distribution level and are expected to be even more frequent in the future due to the increasing penetration of dynamic loads and renewable-based generators in the smart grid. Unlike other PQ events, RVCs are less critical, but also more difficult to detect than dips/sags and swells, due to their smaller voltage variations. Nevertheless, they can be harmful for generators control systems and electronic equipment in general. Moreover, they strongly affect flicker. The IEC Standard 61000-4-3:2015 clearly describes an algorithm for RVC detection. However, this approach is poorly characterized in the scientific literature. In fact, it suffers from some drawbacks. In this paper, some of them (e.g. rate-dependent detection limits and detection delays) are analyzed in depth. In addition, an alternative approach based on the estimation of the rate of change of RMS voltage is proposed. Multiple simulation results show that the approach considered is more sensitive to noise, but also faster, especially when not so fast RVCs occur. Moreover, it allows to measure the rate of change of RMS voltage, which is currently disregarded in the IEC Standard.

Rapid Voltage Changes (RVCs) are Power Quality (PQ) events characterized by small and fast transitions between two steady-state Root Mean Square (RMS) voltage levels. RVCs occur quite often at the distribution level and are expected to be even more frequent in the future due to the increasing penetration of dynamic loads and renewable-based generators in the smart grid. Unlike other PQ events, RVCs are less critical, but also more difficult to detect than dips/sags and swells, due to their smaller voltage variations. Nevertheless, they can be harmful for generators control systems and electronic equipment in general. Moreover, they strongly affect flicker. The IEC Standard 61000-4-3:2015 clearly describes an algorithm for RVC detection. However, this approach is poorly characterized in the scientific literature. In fact, it suffers from some drawbacks. In this paper, some of them (e.g. rate-dependent detection limits and detection delays) are analyzed in depth. In addition, an alternative approach based on the estimation of the rate of change of RMS voltage is proposed. Multiple simulation results show that the approach considered is more sensitive to noise, but also faster, especially when not so fast RVCs occur. Moreover, it allows to measure the rate of change of RMS voltage, which is currently disregarded in the IEC Standard.

The power generated by photovoltaic solar systems is exposed to high variability of irradiance mainly due to weather conditions, which cause instability in the electrical networks connected to these systems. This study shows the typical behavior of solar irradiance in an Andean city, which presents considerable variations that can reach up to 63% of the nominal power of the photovoltaic system, at time intervals in the order of seconds. The study covers the application of 3 techniques to reduce power fluctuations at the point of common coupling (PCC), with the incorporation of energy storage systems, under the same irradiance conditions. Supercapacitors were used as the storage system, which were selected for their high efficiency and useful life. A state of charge control is also applied by means of a hysteresis band. The three algorithms studied show similar behaviors; however, the ramp control technique has the best performance. The storage system was dimensioned based on the pho...

This paper proposes an approach for integrating Plug-In Hybrid Electric Vehicles (PHEV) to an existing residential photovoltaic system, to control and optimize the power consumption of residential load. Control involves determining the source from which residential load will be catered, where as optimization of power flow reduces the stress on the grid. The system built to achieve the goal is a combination of the existing residential photovoltaic system, PHEV, Power Conditioning Unit (PCU), and a controller. The PCU involves two DC-DC Boost Converters and an inverter. This paper emphasizes on developing the controller logic and its implementation in order to accommodate the flexibility and benefits of the proposed integrated system. The proposed controller logic has been simulated using MATLAB SIMULINK and further implemented using Digital Signal Processor (DSP) microcontroller, TMS320F28035, from Texas Instruments

We demonstrate a simple wafer-scale process by which an individual silicon wafer can be processed into a multifunctional platform where one side is adapted to replace platinum and enable triiodide reduction in a dye-sensitized solar cell and the other side provides on-board charge storage as an electrochemical supercapacitor. This builds upon electrochemical fabrication of dual-sided porous silicon and subsequent carbon surface passivation for silicon electrochemical stability. The utilization of this silicon multifunctional platform as a combined energy storage and conversion system yields a total device efficiency of 2.1%, where the high frequency discharge capability of the integrated supercapacitor gives promise for dynamic load-leveling operations to overcome current and voltage fluctuations during solar energy harvesting.

Grid faults are one of the most severe perturbations in power systems. During these extreme disturbances, the reliability of the grid is compromised and the risk of a power outage is increased. To prevent this issue, distributed generation inverters can help the grid by supporting the grid voltages. Voltage support mainly depends on two constraints: the amount of injected current and the grid impedance. This paper proposes a voltage support control scheme that joins these two features. Hence, the control strategy injects the maximum rated current of the inverter. Thus, the inverter takes advantage of the distributed capacities and operates safely during voltage sags. Also, the controller selects the appropriate power references depending on the resistive-inductive grid impedance. Therefore the grid can be better supported since the voltage at the point of common coupling is improved. Several voltage objectives, which cannot be achieved together, are developed and discussed in detail. These objectives are threefold: a) to maximize the positive sequence voltage, b) to minimize the negative sequence voltage, and c) to maximize the difference between positive and negative sequence voltages. A mathematical optimal solution is obtained for each objective function. This solution is characterized by a safe peak current injection, and by the optimization of the voltage profile in any type of grid connection. Therefore, the proposed control scheme includes advanced features for voltage support during voltage sags, that are applicable to different power facilities in different types of networks. Due to system limitations, a suboptimal solution is also considered, analyzed and discussed for each of the optimization problems. Experimental results are presented to validate the theoretical solutions.

The stochastic behavior of PV together with high PV penetration have given rise to power quality concerns involving voltage dynamic issues such as undervoltage, overvoltage, sag and swell. To ensure the grid’s stability, various methods have been practiced such as a proper sizing of the grid lines and the installation of power quality compensation equipment. However, these measures often require high costs and high control complexity due to additional equipment being involved such as multiple transformers and inverters. Moreover, the current available reactive power compensation equipment has a lesser impact on distribution level networks. Therefore, this work proposes a hybrid control of grid-feeding mode and energy storage with Direct Current (DC) fault detection scheme utilizing fuzzy control to mitigate high PV penetration problems, PV intermittency and faults via active power compensation to maintain the system’s voltage within its nominal range. This hybrid control works on tw...

This paper presents the use of PHEVs with photovoltaic sources as an implementation of Vehicle to Grid (V2G) technology for designing a photovoltaic shunt active filter (PV-AF) system to improve power quality of photovoltaic generation. A system model with photovoltaic generation and a dynamic model of PHEVs are introduced here based on third order battery model. A simple battery scheme is proposed for the control of the charging and discharging of the PHEVs using a power electronic interface. The active filter controller is designed based on the instantaneous power theory (p-q theory) to improve the PV cell's performance. Simulations have been carried out and demonstrate that PHEVs have the potential to work as an active filter of photovoltaic generation to improve power quality, dynamic power factor correction and harmonics current compensation.

The power generated by photovoltaic solar systems is exposed to high variability of irradiance mainly due to weather conditions, which cause instability in the electrical networks connected to these systems. This study shows the typical behavior of solar irradiance in an Andean city, which presents considerable variations that can reach up to 63% of the nominal power of the photovoltaic system, at time intervals in the order of seconds. The study covers the application of 3 techniques to reduce power fluctuations at the point of common coupling (PCC), with the incorporation of energy storage systems, under the same irradiance conditions. Supercapacitors were used as the storage system, which were selected for their high efficiency and useful life. A state of charge control is also applied by means of a hysteresis band. The three algorithms studied show similar behaviors; however, the ramp control technique has the best performance. The storage system was dimensioned based on the pho...

The power generated by photovoltaic solar systems is exposed to high variability of irradiance mainly due to weather conditions, which cause instability in the electrical networks connected to these systems. This study shows the typical behavior of solar irradiance in an Andean city, which presents considerable variations that can reach up to 63% of the nominal power of the photovoltaic system, at time intervals in the order of seconds. The study covers the application of 3 techniques to reduce power fluctuations at the point of common coupling (PCC), with the incorporation of energy storage systems, under the same irradiance conditions. Supercapacitors were used as the storage system, which were selected for their high efficiency and useful life. A state of charge control is also applied by means of a hysteresis band. The three algorithms studied show similar behaviors; however, the ramp control technique has the best performance. The storage system was dimensioned based on the pho...

The stochastic behavior of PV together with high PV penetration have given rise to power quality concerns involving voltage dynamic issues such as undervoltage, overvoltage, sag and swell. To ensure the grid’s stability, various methods have been practiced such as a proper sizing of the grid lines and the installation of power quality compensation equipment. However, these measures often require high costs and high control complexity due to additional equipment being involved such as multiple transformers and inverters. Moreover, the current available reactive power compensation equipment has a lesser impact on distribution level networks. Therefore, this work proposes a hybrid control of grid-feeding mode and energy storage with Direct Current (DC) fault detection scheme utilizing fuzzy control to mitigate high PV penetration problems, PV intermittency and faults via active power compensation to maintain the system’s voltage within its nominal range. This hybrid control works on tw...

A novel designing approach of a grid-connected residential photovoltaic (PV) system containing a plugin hybrid electric vehicle (PHEV) load along with a feasible power management mechanism are presented in this paper. In this system, PV arrays and battery packs are cascaded to supply power to the load. Solar energy is harvested by PV arrays, the terminal voltage of PV arrays is regulated by a DC/DC converter to track maximum power point (MPPT) using the incremental conductance method. Battery packs work as the energy storage system and the current controlled bi-directional DC/DC converter regulates the power flow between grid and battery. The interfaced inverter is also a bidirectional inverter.

The stochastic behavior of PV together with high PV penetration have given rise to power quality concerns involving voltage dynamic issues such as undervoltage, overvoltage, sag and swell. To ensure the grid’s stability, various methods have been practiced such as a proper sizing of the grid lines and the installation of power quality compensation equipment. However, these measures often require high costs and high control complexity due to additional equipment being involved such as multiple transformers and inverters. Moreover, the current available reactive power compensation equipment has a lesser impact on distribution level networks. Therefore, this work proposes a hybrid control of grid-feeding mode and energy storage with Direct Current (DC) fault detection scheme utilizing fuzzy control to mitigate high PV penetration problems, PV intermittency and faults via active power compensation to maintain the system’s voltage within its nominal range. This hybrid control works on tw...

This paper discusses contemporary problems concerning ship microgrids. It focuses on the role of power electronics and power quality issues, both conventional, such as voltage and frequency variations, and new issues, such as waveform distortions ensuing from the wide proliferation of power electronics in ship microgrids. The paper also contains a discussion on the provisions of the Unified Requirements of International Association of Classification Societies and other leading power quality standards in the industry, with an emphasis on Total Harmonic Distortion (THD) definition. An overview of power converters for high power applications in ships and their impact on ship networks is also given. Next, original results of various power quality phenomena recorded in ship microgrids are presented and commented on, followed by a review and recommendations for maritime microgrid modeling and signal processing methods for power quality assessment in the discussed systems. Finally, preliminary proposals for power quality control are presented. INDEX TERMS Measurement, power electronics, power quality, power system modeling, ship microgrid.

The purpose of the present paper is to evaluate the sensitivity of modern lighting technologies to different types of RVCs. In order to do that, 27 modern lamps—mainly LED—have been subjected to real RVCs and their response has been assessed. The detection of RVCs on the grid has been performed according to the IEC 61000-4-30 detection method, while the response of the lamps has been measured with a light flickermeter and characterized using the instantaneous flicker perception, as defined in IEC 61000-4-15. The obtained results show a high dispersion in the response of the modern lighting technologies and high values of flicker perception, although with a lower sensitivity than the incandescent lamp. The results led the authors to propose the definition of a new immunity test to be added to the lamp immunity protocol IEC TR-61547-1, to ensure that newly produced lamps cause limited irritation to grid users.

Electric Springs (ES), a converter topology connected in series with non-critical loads, has been recently developed to restore bus voltages to their reference value in case of voltage sag/swell by injecting/absorbing reactive power into/from grid. In this paper, a dual-function ES is proposed with an enhanced decoupled controller, offering additional capability of Renewable Energy Sources (RES) grid integration. Hence, the proposed ES controller is capable of simultaneously injecting active power, extracted from a PV arrays, into grid and mitigating bus voltage fluctuations. Simulation results verify the proposed ES effectiveness when varying irradiance level and bus voltage states. Variables Nomenclature V s Nominal feeder voltage V o Non-critical load voltage V es ES injected voltage S s Grid apparent power S nc Non-critical load apparent power S c Critical load apparent power I s Non-critical load current-Smart load current Z nc Non-critical load impedance Z c Critical load impedance I.

Voltage fluctuations caused by fast changes of industrial loads have been a major concern for both power companies and customers in the area of power quality. The fast response of the Static Compensator (STATCOM) makes it an efficient solution for improving power quality in distribution systems. This paper describes a simplified model for a PWMbased STATCOM used in a distribution system for mitigation of voltage fluctuations produced by an Electric Arc Furnace (EAF). The analyzed system is modeled using MATLAB/SIMULINK Power System Blockset (PSB), including a complete STATCOM model with its power circuits and its control system. Static and dynamic performance of STATCOM is evaluated and voltage fluctuation mitigation studies are performed and discussed. The voltage fluctuation mitigation is obtained by simulations and according to international standards.

Expansion of high-voltage dc (HVdc) systems to multi-terminal HVDC (MT-HVDC) systems/grids considerably increases the short circuit levels. In order to protect the emerging MT-HVDC systems/grids against fault currents, proper DC fault current limiters (FCLs) must be developed. This paper proposes an innovative high inductance solid-state DC-reactor based fault current limiter (HISS-DCRFCL) to be used in HVDC applications. In fact, during the HISS-DCRFCL normal operation, its inductance value is extremely low, and its value becomes considerably high during the fault period, which decreases the fault current amplitude. The proposed HISS-DCRFCL performance is analyzed by MATLAB/Simulink and the simulation results are verified and confirmed by laboratory experimental results using a scaled-down laboratory prototype setup.

The simultaneous mitigation of slow and fast voltage fluctuations caused by The simultaneous mitigation of slow and fast voltage fluctuations caused by rooftop solar PV by controlling the charging/discharging of an integrated battery rooftop solar PV by controlling the charging/discharging of an integrated battery energy storage system energy storage system

The stochastic behavior of PV together with high PV penetration have given rise to power quality concerns involving voltage dynamic issues such as undervoltage, overvoltage, sag and swell. To ensure the grid’s stability, various methods have been practiced such as a proper sizing of the grid lines and the installation of power quality compensation equipment. However, these measures often require high costs and high control complexity due to additional equipment being involved such as multiple transformers and inverters. Moreover, the current available reactive power compensation equipment has a lesser impact on distribution level networks. Therefore, this work proposes a hybrid control of grid-feeding mode and energy storage with Direct Current (DC) fault detection scheme utilizing fuzzy control to mitigate high PV penetration problems, PV intermittency and faults via active power compensation to maintain the system’s voltage within its nominal range. This hybrid control works on tw...

In this work, a voltage regulation scheme to stabilize voltage variation in the consumer side is proposed. The voltage regulation scheme uses IGBT-based onload tap changer (OLTC) and nonlinear hysteresis control algorithm. The proposed switching algorithm establishes the commutation of the taps without redundant short circuit operation of the taps. The experimental results of the designed system show accurate voltage regulation at the consumer side and high ability of the designed system to fix voltage sag and voltage swell in maximum of one cycle period. The paper considers the consequences of fault in the drive circuit of the IGBT tap changer and discusses its reliability. The analysis and the experimental results of the faults in the drive circuit show that the loss of one drive signal results in a large circulating DC current in the primary circuit and may result in fault current of value more than three times the operated current, which leads to unavailability of the system. INDEX TERMS On load tap changer, voltage regulation, distribution transformer, IGBT, OLTC fault analysis.

Introduction. Nowadays, power quality issues are of considerable interest to both utilities and end users as they cause significant financial losses to the industrial customers. Due to this, power quality assurance in power distribution systems is very important, when considering commercial and industrial applications. Problem Statement. Unfortunately, sudden faults such as sag, transients, harmonics distortion and notching in the power system create disturbances and affect the load voltages. Out of these, voltage sag and harmonics seriously affect sensitive devices. Harmonics in the power system cause increased heating of equipment and conductors, misfires in variable speed drives, and torque pulsations in motors. Harmonics reduction is considered desirable. Methodology. This paper presents an efficient and robust solution to this problem by using dynamic voltage restorer in series with distribution system. Dynamic voltage restorer is economical and effective solution for protectin...

This research introduces the simulation of photovoltaic (PV) array to track the peak point (MPPT) using fuzzy logic control. Therefore, real time simulation is performed in MATLAB/Simulink based on a PV model, boost converter and fuzzy logic-based tracker. A comparative study is carried out against perturb and observe (P&O) controller. The fuzzy logic technique based tracker can successfully track the maximum power point very fast and has precise control when compared to the P&O algorithm. The overall we
conclude that the MPPT using the fuzzy logic technique takes a fast response and can improve the performance of the PV system.

Increased government funding and incentives in recent years has led to an increase in the number of grid-tied renewable energy sources as their economic benefits become more renowned. Unfortunately, the outputs of these renewable resources are often highly variable, resulting in undesirable voltage disruptions that are harmful to sensitive loads. In addition to the energy variability of renewable energy sources, random voltage sags, swells and disruptions are already a major issue in power systems. Recent advances in power electronic devices have provided a platform for new solutions to the voltage support problem in power systems. One promising solution is the Dynamic Voltage Regulator (DVR), a series compensating device used to protect a sensitive load that is connected downstream from voltage sag or swell. For this thesis, the design, modeling, and analysis of a DVR system were performed using PSCAD software. Results from simulation demonstrate the DVR's effectiveness in protecting a sensitive load from load and source side voltage disturbances as well as regulate the load bus voltage to its rated value.

The purpose of the present paper is to evaluate the sensitivity of modern lighting technologies to different types of RVCs. In order to do that, 27 modern lamps—mainly LED—have been subjected to real RVCs and their response has been assessed. The detection of RVCs on the grid has been performed according to the IEC 61000-4-30 detection method, while the response of the lamps has been measured with a light flickermeter and characterized using the instantaneous flicker perception, as defined in IEC 61000-4-15. The obtained results show a high dispersion in the response of the modern lighting technologies and high values of flicker perception, although with a lower sensitivity than the incandescent lamp. The results led the authors to propose the definition of a new immunity test to be added to the lamp immunity protocol IEC TR-61547-1, to ensure that newly produced lamps cause limited irritation to grid users.

This paper discusses contemporary problems concerning ship microgrids. It focuses on the role of power electronics and power quality issues, both conventional, such as voltage and frequency variations, and new issues, such as waveform distortions ensuing from the wide proliferation of power electronics in ship microgrids. The paper also contains a discussion on the provisions of the Unified Requirements of International Association of Classification Societies and other leading power quality standards in the industry, with an emphasis on Total Harmonic Distortion (THD) definition. An overview of power converters for high power applications in ships and their impact on ship networks is also given. Next, original results of various power quality phenomena recorded in ship microgrids are presented and commented on, followed by a review and recommendations for maritime microgrid modeling and signal processing methods for power quality assessment in the discussed systems. Finally, preliminary proposals for power quality control are presented. INDEX TERMS Measurement, power electronics, power quality, power system modeling, ship microgrid.

Power quality improvement of low voltage grid is a great challenge that confronts the sophisticated power applications, because their performance is highly sensitive to the quality of power supply. Dynamic Voltage Restorer (DVR) used widely as an efficient and skillful device to adjust electrical disturbances of the distribution grids. This paper introduces an overview of the components of the 3-phase dynamic voltage restorer and design its own control circuit. The performance of DVR was developed on the basis of the appropriate selection of Photovoltaic (PV) module instead of the present conventional designs. Through this design, the need of series converter (DVR) for the current from an electrical grid will end and the problems of power losses will curb. The PV-module is selected to meet the requirements of the DVR during voltage sag/swell on voltage line. The proposed system is mimicked in MATLAB software/Simulink and the findings are presented to prove the success of the design in terms of full congruence of the load voltage waveform with source voltage waveform, attaining 0.77% of THD analysis for the load voltage and the waveforms of PV system.

The high penetration of photovoltaic (PV) systems and fast communications networks increase the potential for PV inverters to support the stability and performance of microgrids. PV inverters in the distribution network can work cooperatively and follow centralized and decentralized control commands to optimize energy production while meeting grid code requirements. However, there are older autonomous inverters that have already been installed and will operate in the same network as smart controllable ones. This paper proposes a decentralized optimal control (DOC) that performs multi-objective optimization for a group of PV inverters in a network of existing residential loads and autonomous inverters. The interaction of independent DOC groups in the same network is considered. The limit of PV inverter power factor is included in the control. The DOC is done by the power flow calculation and an autoregression prediction model for estimating maximum power point and loads. Overvoltage ...

The purpose of the present paper is to evaluate the sensitivity of modern lighting technologies to different types of RVCs. In order to do that, 27 modern lamps—mainly LED—have been subjected to real RVCs and their response has been assessed. The detection of RVCs on the grid has been performed according to the IEC 61000-4-30 detection method, while the response of the lamps has been measured with a light flickermeter and characterized using the instantaneous flicker perception, as defined in IEC 61000-4-15. The obtained results show a high dispersion in the response of the modern lighting technologies and high values of flicker perception, although with a lower sensitivity than the incandescent lamp. The results led the authors to propose the definition of a new immunity test to be added to the lamp immunity protocol IEC TR-61547-1, to ensure that newly produced lamps cause limited irritation to grid users.

The power generated by photovoltaic solar systems is exposed to high variability of irradiance mainly due to weather conditions, which cause instability in the electrical networks connected to these systems. This study shows the typical behavior of solar irradiance in an Andean city, which presents considerable variations that can reach up to 63% of the nominal power of the photovoltaic system, at time intervals in the order of seconds. The study covers the application of 3 techniques to reduce power fluctuations at the point of common coupling (PCC), with the incorporation of energy storage systems, under the same irradiance conditions. Supercapacitors were used as the storage system, which were selected for their high efficiency and useful life. A state of charge control is also applied by means of a hysteresis band. The three algorithms studied show similar behaviors; however, the ramp control technique has the best performance. The storage system was dimensioned based on the pho...

An increase in the number of Plug-in Hybrid Electric Vehicles (PHEVs) might negatively affect the performance of Microgrid (MG) such as, reducing power quality and efficiency, increasing power losses and voltage variations, and increasing customers' energy prices. An effective selection of the capacity and location of charging stations helps in reducing such negative impact. This paper proposes a method for finding the optimal location and capacity of PHEVs charging stations along with the optimal location of renewable energy sources (RESs). A multi-objective function including charging/discharging costs, losses, and voltage profile is adopted to formulate the paper problem. Differential Evolution algorithm is used to solve the proposed objective function. By applying the proposed method into a 69-bus network its performance is assessed. The simulation results support the effectiveness of the proposed method.