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The goal of reducing greenhouse gas emissions and energy transition has created many favorable conditions to promote solar power generation technology. However, from a technical perspective, integrating solar power into the power grid poses many challenges in grid operation. This study investigates the impact of rooftop solar power in terms of power quality in the urban distribution grid in Vietnam. The current study simulated a typical low-voltage distribution grid with single-phase and three-phase loads to evaluate important power quality issues, such as Total Harmonic Distortion (THD) of voltage and current, voltage unbalance, and voltage rises. A grid simulation grid was developed in Matlab/Simulink under different conditions for the penetration level of solar power and the daily variation of loads. These indexes were compared with the limits specified in Vietnamese standards and the relevant international standards of IEEE and IEC. Compliance with the provisions of these standards was provided, even in the case of solar power systems with a high level of penetration into Vietnam's urban distribution grid. [ABSTRACT FROM AUTHOR]

Power industry reorganization, legislation on greenhouse gas emissions and inadequate conventional generation capacity encourage the idea of incorporating Distributed Generation (DG) into the distribution networks as unconventional sources of power generation. High penetration of DG has further increased the complexity of the analysis of small signal stability because the variability of renewable energy sources affects the stability of power system. Therefore, this research work investigates the effect of wind and solar photovoltaic power injection on small signal stability of Nigerian 11 kV power network. Wind and solar photovoltaic were modelled using probabilistic methods and output power at twenty-one different locations within Nigeria was computed. Using the real and reactive power data of the network, Self-Organizing Map (SOM) neural network was trained and tested for the assessment of the small signal stability of the distribution network before and after the injection of renewable power in python virtual environment. The integration of hybrid wind-solar PV distributed generation at 30 %, 60 %, 90 % and 100 % into the studied 11 kV power distribution network improved its small signal stability by 1.4 %, 2.1 %, 2.5 % and 3.2 % respectively. Moreover, increase in the injection of power gotten from wind and solar sources reduces the oscillation frequency of the system from 1.39 Hz to 1.01 Hz and increases the damping from 4.6 % to 13.2 %. Reactive power increment in the range of 5 %-20 % improved the small signal stability of the system by the range 2.4 %-7 %. This improvement will translate to better power transfer capability of the network.

A distributed-power-generating source (DPGS) is intended to locally supply the increased power demand at a load bus. When applied in small amounts, a DPGS offers many technical and economic benefits. However, with large DPGS penetrations, the stability of the transmission system becomes a significant issue. This paper investigates the stability of a transmission system equipped with a DPGS at load centres supplying power to both a constant power (CP) and induction motor (IM) load. The DPGSs considered in the present study are microturbine and diesel turbine power generators (MTGS and DTGS), both interfaced with synchronous generators. The influence of an IM load supplied by the DPGS on small-signal stability is studied by a critical damping ratio analysis. On the other hand, time-domain indicators of the transient response following a short circuit are employed in the analysis. Further, a variance analysis test (VAT) is performed to determine the contribution of IM and CP loads on the system stability. The study revealed that large penetration levels of IM loads significantly affect the stability and depend on the kind of DPGS technology used. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of DSTATCOM on the losses, voltage stability, and voltage deviation of the radial distribution networks (RDNs) at different DSTATCOM penetration levels (DPLs). A novel voltage stability improvement index (VSII) is modeled to assign an index value to represent the proximity of the voltage stability index (VSI) of all the network buses to the ideal value. The VSII allows a fair comparison of the VSI profile obtained for different events of DSTATCOM penetration levels. Due to the numerous buses of the RDN, the new voltage stability index (NVSI) selects the most sensitive buses to reactive compensation for DSTATCOM integration after performing the load flow for the base case before integration of DSTATCOM. The DSTATCOM is placed on the selected bus, turn by turn, and DPL increases from zero to the maximum reactive load of the RDN in the step of 1 %. This methodology was implemented on the standard 33–bus and Nigerian Imalefalafia 32–bus RDNs. The outcome establishes that a DPL of 30–55 % and 70–100 % were attained for standard 33–bus and Imalefalafia 32–bus RDNs respectively without increasing the power loss. The VSII was continually improved, and average voltage deviation index (AVDI) was reduced with increasing DPL.

Cameroon’s electricity mix is dominated by hydropower sources despite the huge potentials of other sources like solar. The over-dependence on hydropower has led to frequent load shedding especially in the dry season as a result of low water levels. Interestingly, the government plans to diversify her power mix and provide sustainable energy to Cameroonians. It is in this framework that this study evaluates the integration of solar PV into the Southern Interconnected Grid of Cameroon using dynamic analysis. The ETAP tool was used in developing the model. A power loss assessment was done through successive injection of solar PV into the candidate busbars while monitoring the active power losses in the grid. Then, a transient stability analysis was conducted so as to assess the grid’s response to induced instability after the penetration of large-scale solar PV. The study showed that the use of static performance indices to evaluate the solar PV hosting capacity do not safeguard the grid’s technical robustness. The results indicated an optimum solar PV penetration level of 30% (211.8 MW) at the Ngousso 93 kV busbar. The findings will be useful to system operators and regulators in developing low-carbon pathways in the electricity network in Cameroon.

A distributed-power-generating source (DPGS) is intended to locally supply the increased power demand at a load bus. When applied in small amounts, a DPGS offers many technical and economic benefits. However, with large DPGS penetrations, the stability of the transmission system becomes a significant issue. This paper investigates the stability of a transmission system equipped with a DPGS at load centres supplying power to both a constant power (CP) and induction motor (IM) load. The DPGSs considered in the present study are microturbine and diesel turbine power generators (MTGS and DTGS), both interfaced with synchronous generators. The influence of an IM load supplied by the DPGS on small-signal stability is studied by a critical damping ratio analysis. On the other hand, time-domain indicators of the transient response following a short circuit are employed in the analysis. Further, a variance analysis test (VAT) is performed to determine the contribution of IM and CP loads on the system stability. The study revealed that large penetration levels of IM loads significantly affect the stability and depend on the kind of DPGS technology used.

Cameroon’s electricity mix is dominated by hydropower sources despite the huge potentials of other sources like solar. The over-dependence on hydropower has led to frequent load shedding especially in the dry season as a result of low water levels. Interestingly, the government plans to diversify her power mix and provide sustainable energy to Cameroonians. It is in this framework that this study evaluates the integration of solar PV into the Southern Interconnected Grid of Cameroon using dynamic analysis. The ETAP tool was used in developing the model. A power loss assessment was done through successive injection of solar PV into the candidate busbars while monitoring the active power losses in the grid. Then, a transient stability analysis was conducted so as to assess the grid’s response to induced instability after the penetration of large-scale solar PV. The study showed that the use of static performance indices to evaluate the solar PV hosting capacity do not safeguard the grid’s technical robustness. The results indicated an optimum solar PV penetration level of 30% (211.8 MW) at the Ngousso 93 kV busbar. The findings will be useful to system operators and regulators in developing low-carbon pathways in the electricity network in Cameroon. [ABSTRACT FROM AUTHOR]

Countries around the world are looking forward to fully sustainable energy by the middle of the century to meet Paris climate agreement goals. This paper presents a novel algorithm to optimally operate the Egyptian grid with maximum renewable power generation, minimum voltage deviation and minimum power losses. The optimal operation is performed using Corona Virus Algorithm (CVO). The proposed CVO is compared to the Teaching and Learning-Based Optimization (TLBO) algorithm in terms of voltage deviation, power losses and share of renewable energies. The real demand, solar irradiance and wind speed in typical winter and summer days are considered. The 2020 Egyptian grid model is developed, simulated, and optimized using DIgSILENT software application. The results have proved the effectiveness of the proposed CVO, compared to the TLBO, to operate the grid with the highest share possible of renewables. The paper is a step forward to achieve Egyptian government targets to reach 20% and 42% penetration level of renewable energies by 2022 and 2035, respectively.

Increasing the penetration level (PL) of renewable energy in the distribution power grids has the potential of fulfilling growing energy demands and curtailing fossil fuel usage along with its economic and technical benefits. Nevertheless, the quantity of electricity supplied to customers cannot be permitted to take precedence over its quality. This is because the high penetration of the renewable-based power generation comes at the cost of power quality deterioration, especially at the point of common coupling (PCC), owing to nonlinear characteristics of renewable-based distributed generation (DG) systems and pre-contamination of modern distribution grids. So, the role of power quality (PQ) improvement technologies inevitably comes into the picture when the required level of renewable energy penetration is constrained by any of the grid PQ performance indices. Passive power filters (PPFs) have proven to be a very successful solution for increasing the harmonic-constrained penetration level (HC-PL) of renewable energy in power systems. However, there is a scarcity of information on how to choose between various passive filters to meet high penetration objective. The purpose of this paper is to look into the problem of filter type selection. The designing of different PPF types is formulated as an optimization problem with an objective to enhance the penetration of a renewable DG system in a distorted distribution power grid and solved by the firefly algorithm (FA). A comprehensive assessment of common PPF types, in terms of effectiveness in increasing renewable energy penetration in a harmonically polluted distribution grid along with their economic aspects, is performed. The simulation results show that the filters under consideration can be ranked from best to worst as composite type, third-order damped, C-type, second-order damped and single-tuned (ST) ones in terms of their performance on the percentage penetration level enhancement of renewable energy. While in terms of per-unit cost, the highest percentage enhancement in penetration is obtained by the ST filter. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) systems have been gaining popularity among distribution network engineers. The integration of these small-scale sources has a variety of benefits for the distribution network. One of the most important benefits is the power loss reduction. However, a high penetration level of PV systems may disrupt the protection coordination of conventional overcurrent relays of the distribution network, reducing the profit of the electricity distribution company (EDC) due to healthy feeder de-energization. This paper determines the optimal penetration level of PV systems in the distribution network considering both power loss reduction profit and protection miscoordination cost to maximize the profit of the EDC. The merits of the proposed methodology are verified through several case studies on a simulation model of the IEEE 33-bus test system in the Electrical Transient Analyzer Program (ETAP) environment considering the reliability data of the IEEE Roy Billinton Test System. [ABSTRACT FROM AUTHOR]

Shunt Capacitor (SC) integration in radial distribution networks is a method utilized to minimize power losses and huge voltage drops. In other to obtain these maximum benefits, they should be optimally allocated. To this effect, researchers have used various optimization methods for solving SC allocation problems but most have not considered how the penetration level of SC into the radial distribution system affects these benefits. The goal of the paper, therefore, is to determine the most sensitive buses to reactive compensation and investigate the effect of the penetration level of SC on the techno-economic benefits. Load flow was performed for the base case to determine the steady-state performance of the system and the most sensitive buses were selected using New Voltage Stability Index (NVSI) technique. The size of the SC was increased in step of these buses, in turn, to determine SC penetration level impact on the techno-economic benefits. The approach was implemented on IEEE 33-bus and practical Nigerian radial distribution networks. The results showed that appropriate penetration of SC on networks leads to reduction of power losses, voltage profile improvement as well cost reduction resulting in high net savings.

Background: The approach to farm animal welfare evaluation has changed and animal-based measures (ABM), defined as the responses of an animal or effects on an animal, were introduced to assess animal welfare. Animal-based measures can be taken directly on the animal or indirectly and include the use of animal records. They can result from a specific event or be the cumulative outcome of many days, weeks, or months. The objective of the current study was to analyze the use of general ABM codified terms in the scientific literature, the presence of their definitions, and the gap mapping of their use across animal species, categories, years of publication, and geographical areas of the corresponding author's institution. The ultimate aim was to propose a common standard terminology to improve communication among stakeholders. In this study, data models were populated by collecting information coming from scientific papers extracted through a transparent and reproducible protocol using Web of ScienceTM and filtering for the general ABM codified terms (or synonyms/equivalents). A total of 199 papers were retained, and their full texts were assessed. The frequency of general codified ABM terms was analyzed according to the classification factors listed in the objectives. These papers were prevalently European (159 documents), and the most represented species was cattle. Fifty percent of the papers did not provide a definition of the general ABM terms, and 54% cited other sources as reference for their definition. The results of the study showed a very low penetration of the general codified ABM term in the literature on farm animal welfare, with only 1.5% of the papers including the term ABM. This does not mean that specific ABM are not studied, but rather that these specific ABM are not defined as such under a common umbrella, and there is no consensus on the use of terminology, not even among scientists. Thus, we cannot expect the stakeholders to use a common language and a standardized terminology. The recognition and the inclusion of ABM in the lists of commonly accepted abbreviations of scientific journals could be a first step to harmonize the terminology in the scientific literature.

The high penetration level of distributed generation (DG) units may lead to various problems and operational limit violations in electric power distribution systems if it exceeds a particular limit known as the system's hosting capacity (HC). In this paper, the problem of selecting the optimal conductor for a real radial distribution system in Egypt is investigated using a recent meta-heuristic algorithm, known as salp swarm optimization. First, a constrained optimization problem is introduced to minimize the combined annual cost of energy losses and the investment cost of the conductors while complying with the system voltage limits and conductor thermal capacities. The results obtained show the effectiveness of the algorithm in satisfying the objective function and constraints. However, the optimization results also show that a reduction in the size of some existing conductors should take place, although this is not allowed by the utilities because of practical reasons such as load growth, variations in loading scenarios, and the possibility of connecting DG units with uncertain penetration levels and locations. Hence, a practical feeder reinforcement approach is proposed to maintain the constraints while considering these uncertainties. Further, a novel feeder reinforcement index is proposed to assist the distribution system operators and planners to determine the feeders that first need to be reinforced. The results obtained show that the proposed reinforcement approach attains a better level of HC than can be obtained with the conventional conductor selection approach under the same testing conditions.

As the penetration level of converter-based generators (CBGs) continues to grow in electric power systems, their impact on power system dynamics and control becomes increasingly significant. Maintaining a stable operation of the CBGs is becoming more and more critical. Since their controls and dynamic behaviour differ from synchronous generators, in this study, the transient stability mechanism of CBGs is analysed and the key influencing factors are identified and investigated. Moreover, a stability margin index, which can be obtained analytically, is proposed to identify potential transient stability issues of CBGs and can be used as a screening technique before conducting time-consuming electromagnetic simulation studies. This index can be used for both planning and operations studies and it outperforms the state-of-the-art index of short circuit ratio that is presently used to identify potential CBG instabilities due to weak grid scenarios. Dynamic simulations on a real power system model have been conducted to validate the accuracy and applicability of the proposed stability margin index. [ABSTRACT FROM AUTHOR]

The share of renewable energy is increasing because of environmental concerns and favorable economic conditions. The majority of the distributed energy resources, connected to the low-voltage grid, are inverter-connected units. These inverters are controlled by using specially developed control strategies to determine the power injection between the primary source and the grid. In the past, the connection of distributed energy resources was based on the connect-and-forget principle, but this approach leads to severe power quality problems. Nowadays, more sophisticated control strategies need to be developed, so that ancillary services can be provided to the distribution system operator, which will allow further increase of renewable share in the distribution grids. This article examines the technical capabilities of the three-phase damping control strategy to provide ancillary services to the distribution system operator. Besides the three-phase damping control strategy, the article also compares the classical positive-sequence control strategy. Active power drooping and reactive power exchange are combined with these control strategies and the effect on the annual energy production, power quality, and grid performance is assessed. The simulations are conducted on a Matlab/OpenDSS platform in a time series simulations. [ABSTRACT FROM AUTHOR]

Inverter interfaced distributed generation units contribute limited fault current and thereby the current magnitude‐based protection schemes find limitation for such situations. Change in penetration level of renewable energy sources with time makes available protection schemes more challenging. The distinction between load and fault current is an issue and with high resistance fault, level of fault current and load current becomes comparable. In this paper, local measurement‐based protection technique is proposed that uses current and voltage signals to derive accurate protection decision for a distribution system in the presence of distributed generation units. The method uses real and reactive power calculated at the relay point for the decision. The performance of the algorithm is tested for a 33 bus distribution system simulated using DIgSILENT PowerFactory. Considering such units, the method is tested for both islanded and grid‐connected modes, the varying level of distributed generation penetration and for different fault resistances. The results demonstrate the strength of the proposed method over available techniques. The proposed method is also validated using hardware‐in‐loop testing using Arduino NANO microcontroller and OPAL‐RT simulator in real‐time. [ABSTRACT FROM AUTHOR]

With the increasing load demand and emergence of various types of Distributed Generators (DG) the complexities and challenges for reliable operation of Distribution Network (DN) power system have increased. The major operational challenge in the DN is non-detection of Islanding event, which may cause the system to collapse. In this paper, two Modified Islanding Detection Techniques (MIDT-I \& MIDT-II) are proposed for accurate and early islanding detection in the presence of different types of DGs. These approaches utilizes robust parameters for accurate identification of the islanded bus. The proposed MIDT schemes combines the advantages offered by different existing passive Islanding Detection Techniques (IDTs) for early identification of the islanding event. In the proposed schemes the DGs are installed in the existing DN by Genetic Algorithm (GA) based Multi-Level Optimization (MLO) approach. The installation of DGs is performed to improve the voltage stability margin of the system and for power loss reduction. In the second stage during operation of the network two methods are proposed to detect unintentional islanding. The proposed scheme is demonstrated on IEEE 33 and IEEE 69 standard radial bus system for the effectiveness of the scheme. [ABSTRACT FROM AUTHOR]

Abstract There has been a worldwide rise in installations of grid-connected variable renewable energy (VRE) systems over the past few years. However, with the increasing share of these systems comes additional complexities that can affect planning and operation of a power system within a specific region. Several studies have been conducted across different regions with the general aim to identify the impacts of integrating high shares of VRE in the respective power grids. However, each region is different in terms of available renewable resources, VRE targets and grid characteristics. Therefore, the results of VRE integration studies are generally context specific and the impacts observed in one region might not be relevant to another. Given that conducting a full range of detailed VRE integration studies for each grid is costly, there is value in effectively identifying likely issues relevant to the specific region under consideration, towards a smaller set of detailed VRE integration studies. This paper presents a literature review based on international experience that aims to provide an understanding on the VRE integration impacts within the context of generator type, penetration level and grid characteristics. This can be used to identify the VRE integration impacts that are relevant to the region under consideration. Highlights • Review on how generator type, penetration level and grid characteristics contributed to VRE integration issues. • Local VRE integration issues can affect the power system at any penetration level. • Balancing operation is affected when the VRE instantaneous penetration level is above 20%. • Countries with high share of VRE have some strategy to maintain flexibility in the power system. • Transient and frequency stability is affected when the VRE instantaneous penetration level is above 50%. [ABSTRACT FROM AUTHOR]

Highlights • Double-layered intelligent energy management approach for optimal PEV integration. • PEVs are utilized to provide both real and reactive power support to the grid. • First layer involves real power management to minimize the PEV (dis)charging cost. • Second layer involves reactive power management to minimize system power losses. Abstract This paper proposes a double-layered intelligent energy management (DIEM) approach for optimal integration of plug-in electric vehicles (PEVs) into a distribution system. The proposed approach involves two optimization layers for real and reactive power management of PEVs which take place at nodal and system level, respectively. The first optimization layer for real power management is designed from nodal aggregator's perspective and aims to minimize the daily total cost incurred for PEV (dis)charging. The second optimization layer for reactive power management is designed from distribution system operator's perspective where the objective is to minimize the system power loss utilizing the reactive power capacity provided by PEVs. The DIEM approach is implemented for PEV integration in a 33-bus distribution system and its performance is assessed against a single-layered intelligent energy management (SIEM) approach which involves only first optimization layer, i.e. real power management of PEVs. The simulation results indicate that utilizing reactive power services of PEVs allows the proposed approach to provide voltage regulation and hence the ability to integrate higher PEV penetration within permissible voltage limits. Furthermore, the simulation results clearly demonstrate the effectiveness and superiority of the proposed DIEM approach in comparison to the SIEM approach. [ABSTRACT FROM AUTHOR]

Wind turbines' installed capacity is expected to increase significantly in future power grids due to environmental concerns. Reductions in the power system inertia and frequency response due to increasing penetration levels of wind energy lead to a decrement in the frequency stability margin. This paper focuses on the frequency stability issue in power grids with high penetration level of wind turbines. The maximum allowable wind generation penetration level is first formulated as a function of primary frequency response and system inertia with/without considering operating reserve limits. Following that, the possibility of participation of wind turbines in the frequency stability improvement is investigated and the minimum required wind turbine participation is estimated as a function of wind energy penetration level. In this trend, a time-independent formulation for power system frequency response is utilized to increase the accuracy and reduce the computational complexity. A comprehensive analysis is performed on IEEE 39-bus test system to investigate the proposed methodologies. As results confirm, participation of wind turbines in the frequency control task leads to more secure operation of the power system. • Our research focuses on dynamic changes in power systems due to high penetration of renewable energy, particularly wind generation. • Increasing wind power integration necessitates adjustments to power system frequency stability constraints. • As wind energy penetration rises, traditional power sources alone can't manage frequency regulation. Wind turbines must contribute for stability. frequency stability. • Our work shows that incorporating wind turbines into frequency regulation significantly improves power system stability. • We emphasize the need for operational adaptation in power systems to accommodate more renewables, providing crucial insights for sustainable power system evolution. [ABSTRACT FROM AUTHOR]

The share of renewable energy is increasing because of environmental concerns and favorable economic conditions. The majority of the distributed energy resources, connected to the low-voltage grid, are inverter-connected units. These inverters are controlled by using specially developed control strategies to determine the power injection between the primary source and the grid. In the past, the connection of distributed energy resources was based on the connect-and-forget principle, but this approach leads to severe power quality problems. Nowadays, more sophisticated control strategies need to be developed, so that ancillary services can be provided to the distribution system operator, which will allow further increase of renewable share in the distribution grids. This article examines the technical capabilities of the three-phase damping control strategy to provide ancillary services to the distribution system operator. Besides the three-phase damping control strategy, the article also compares the classical positive-sequence control strategy. Active power drooping and reactive power exchange are combined with these control strategies and the effect on the annual energy production, power quality, and grid performance is assessed. The simulations are conducted on a Matlab/OpenDSS platform in a time series simulations.

Summary: Increasing integration of local generators is a challenge in the planning, design, and operation of the distribution system. The distributed energy resources, especially renewable ones, have caused dispersion of generation units along the feeder. This paper presents a dual index combination of the penetration level and the dispersion factor of distributed generation. Maximum penetration level of distributed generation was determined by a multiobjective function of the proposed dual index. This function has subroutines based on voltage stability, active and reactive power flows, voltage profile limits, and power loss that are restricted by technical constraints associated system with shunt compensator. A limited memory quasi‐Newton trust‐region algorithm was developed to optimize the objective function by using the first‐ and second‐order sensitivities of the nonlinear objective function and a trust region based on the constraints. Two networks were used for testing, and obtained results revealed accuracy and validity of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, smart charging strategies incorporating a unified grid-to-vehicle and vehicle-to-grid charging framework are proposed for optimal integration of plug-in electric vehicles (PEVs) within the existing distribution system infrastructure. Two smart strategies with objective functions considering minimization of total daily cost and peak-to-average ratio, respectively, are developed to study the impact on PEV charging from an economic and technical perspective. The proposed strategies are implemented for PEV charging at workplace car parks located in a 37-bus distribution system and an analytical study is presented to evaluate the maximum possible PEV penetration that the existing distribution infrastructure can accommodate corresponding to the two strategies. A comparative analysis of the two strategies is performed in terms of various economic and technical benefits that are derived. Moreover, a performance comparison of the two strategies in presence of slow and fast charging of PEVs is also presented. Finally, an investigative study is conducted for both the strategies to evaluate the maximum PEV penetration that can be integrated in the upcoming years without infrastructure reinforcement. The simulation results present a comprehensive evaluation of the two proposed strategies. [ABSTRACT FROM PUBLISHER]

In the field of dermal protection, the use of chemical protective clothing (CPC) (including coveralls) are considered as the last barrier against airborne engineered nanomaterials (ENM). In the majority of cases, Type 5 CPC, used against solid particles (ISO 13982-1), perform well against ENM. But in a recent study, a penetration level (PL) of up to 8.5% of polydisperse sodium chloride airborne nanoparticles has been measured. Moreover, in all the previous studies, tests were performed on a sample of protective clothing material without seams or zippers. Thus, the potential for permeation through a zipper or seams has not yet been determined, even though these areas would be privileged entry points for airborne ENM. This work was designed to evaluate the PL of airborne ENM through coveralls and specifically the PL through the seams on different parts of the CPC and the zipper. Eight current models of CPC (Type 5) were selected. The samples were taken from places with and without seams and with a zipper. In some cases, a cover strip can be added to the zipper to enhance its sealing. Polydisperse nanoparticles were generated by nebulization of a sodium chloride solution. A penetration cell was developed to expose the sample to airborne nanometric particles. The NaCl particle concentration in number was measured with an ultrafine particle counter and the PL was defined as the downstream concentration divided by the upstream concentration. The results obtained show that the PL increased significantly in the presence of seams and could reach up to 90% depending on the seam's design. Moreover, this study classifies the different types of seams by their resistance against airborne ENM. As for the penetration of airborne NaCl particles through the zipper, the PL was greatly attenuated by the presence of a cover strip, but only for certain models of coveralls. Finally, the values of the pressure drop were directly linked to the type of seam. All of these conclusions provide recommendations to both manufacturers and users. [ABSTRACT FROM AUTHOR]

The high penetration level of photovoltaic (PV) generation in distribution networks not only brings benefits like carbon savings, but also induces undesirable outcomes, like more harmonic components and voltage fluctuations. Driven by decreasing costs of energy storage, the focus of this paper is to investigate the feasibility of applying energy storage in the grid-connected PV system to mitigate its intermittency. Firstly, to appreciate the functionality of storage, a generic PV-battery-supercapacitor model was simulated in MATLAB/Simulink, and a flat load profile was obtained to enhance predictability from the network management point of view. However, the usage of supercapacitors at the residential level is limited, due to its high startup costs. Secondly, a detailed residential PV-battery model was implemented in the System Advisor Model (SAM) based on local data in Dubai. The optimal sizing of a battery system was determined by assessing two criteria: The number of excursions, and average target power, which are contradictory in optimization process. Statistical indicators show that a properly sized battery system can alleviate network fluctuations. The proposed sizing method can be also applied to other PV-storage systems. Finally, economic studies of PV-battery system demonstrated its competitiveness against standalone PV systems under appropriate tariff incentives.

In this paper, the impact of integrating photovoltaic plants (PVPs) with high penetration levels into the national utility grid of Egypt is demonstrated. Load flow analysis is used to examine the grid capacity in the case of integrating the desired PVPs and computer simulations are also used to assess the upgrading of the transmission network to increase its capacity. Furthermore, the impact of increasing the output power generated from PVPs, during normal conditions, on the static voltage stability was explored. During transient conditions of operation (three-phase short circuit and outage of a large generating station), the impact of high penetration levels of PVPs on the voltage and frequency stability has been presented. Professional DIgSILENT PowerFactory simulation package was used for implementation of all simulation studies. The results of frequency stability analysis proved that the national grid could be maintained stable even when the PVPs reached a penetration level up to 3000 MW of the total generation in Egypt. Transmission network upgrading to accommodate up to 3000 MW from the proposed PV power plants by 2025 is suggested. In addition, analysis of voltage stability manifests that the dynamic behavior of the voltage depends remarkably on the short circuit capacity of the grid at the point of integrating the PVPs.

The global interest in encouraging the use of renewable energy has triggered a massive opening unconventional generation units. In view of the current incentives at country level for the installation of photovoltaic panels (PFV), it is possible to foresee that in the future there will be high penetration of distributed generation of this type connected to the electrical system. In our province, Cayo Santa Maria isolated system has three areas for the installation of PFV. As stated above and considering that high penetration levels of photovoltaic generation produces static and dynamic effects in connected isolated systems, it is essential to conduct studies systemically to determine the impact that would produce this connection, taking into consideration its location, technology, modeling and penetration level. The analysis allows to know how beneficial or harmful the installation of photovoltaic generators can be in that system. [ABSTRACT FROM AUTHOR]

Increasing the penetration level of distributed generation (DG) may lead to improper protection coordination. Previous work introduced a protection coordination index (PCI) that can quantify the impact of installing a DG at individual locations. This paper extends on previous work and proposes a generalized approach for calculating PCI considering multiple DG locations simultaneously. Furthermore, this paper proposes a solution for enhancing the PCI using fault current limiters (FCL). The problem is formulated as a mixed-integer nonlinear programming problem to determine the optimal FCL size and location as well as enhanced PCI. [ABSTRACT FROM AUTHOR]

This study explores the patterns of the global mobile divide and the factors that influenced it. It proposes a comprehensive framework to explain mobile phone adoption by integrating technology acceptance model (TAM) and economic consumption analysis. The empirical analysis is conducted using the data from more than 150 countries. The results show that the gaps of mobile phone penetration among different groups of income level countries have decreased during the past 23 years. Average income had a negative correlation with mobile phone adoption rate, represented by the slope of mobile phone diffusion curve. However, average income had a positive correlation with mobile phone penetration, suggesting that there are still gaps of mobile phone penetration between rich and poor countries. Besides average income, other factors, such as legacy phone system, population density, and education level, were also demonstrated to have influence on mobile phone penetration. The framework and findings of this study suggest the potentials for the integration among consumption analysis, diffusion of innovation theory (DIT), and TAM. Strategies for further bridging the global mobile divide are suggested based on the empirical findings. [ABSTRACT FROM AUTHOR]

This paper presents fast screening techniques and process for grid interconnection of wind-storage systems. In a smart grid, the wind turbines are likely installed accompanying with battery energy storage systems, called “wind-storage system”, to largely increase the penetration of renewable energy. A fast screening approach based on a genetic algorithm with self-adaptive evolution provided from a commercial software, OPTIMUS, is applied to predetermine the maximum power output of a wind farm. The total power generation of a wind farm can be greatly increased without violating these limitations through the assistant of a battery energy storage system. Time-varying distribution system operating status make the operation problem of a wind-energy system further complicated. The results show that the maximum power output of a wind farm and the required capacity of the battery energy storage systems in a wind-storage system mainly depend on the system short-circuit capacity at the interconnection point of the wind-storage system. This paper confirms the effectiveness of the proposed algorithm using actual wind farm data and a physical distribution system of Taiwan. The outcomes of this paper are of value to fast screening the grid-interconnection applications of wind-storage systems. [ABSTRACT FROM AUTHOR]

In recent years, wind energy has a remarkable growth, and the power systems tend to increase the integration of wind power source. However, the existing power systems are not compatible with the effects resulted by the highly integrated wind power sources. Because of the transmission congestion, available produced wind power is not able to be fed into the grid. This paper presents the application of flexible AC transmission system (FACTS) devices for mitigating the wind power curtailment. A framework of multi period optimal power flow problem (MPOPF) is derived for a wind integrated power system. FACTS devices are utilized in such a way that the total wind curtailment during a specific time horizon is reduced. The proposed MPOPF is tested on modified IEEE 30-bus load flow test system. It is shown that the amount of curtailed wind power is significantly reduced when FACTS devices are optimally allocated. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Due to the increased penetration of distributed generations in distribution systems, transient stability is one of the major concerns to be analyzed. This article presents a support vector machine based approach for transient stability detection using post-disturbance signals extracted from the optimally located distributed generations in a distribution system having distributed generation. Initially, distributed generations are placed optimally, and their optimal sizes are found with objectives of loss reduction and reliability improvement for various distributed generation penetration levels, system configurations, and system loading conditions. Various asymmetrical and symmetrical faults at different locations in the system are simulated to calculate the critical clearing times. The post-disturbance values of terminal voltage, active power, reactive power, and speed obtained from the distributed generations for both stable and unstable cases are used as input features of the support vector machine for finding the transient stability status. The dynamic simulations are carried out on IEEE 33-node and IEEE 69-node radial distribution test systems with four distributed generations, modeled in DIgSILENT power factory software (DIgSILENT GmbH, Germany). The proposed support vector machine based approach predicts the post-disturbance transient stability of the distribution system accurately. [ABSTRACT FROM PUBLISHER]

Owing to increasing the penetration level of the inverter‐based distributed generations (IBDGs) in power systems, their fault ride‐through (FRT) capability has become one of the essential issues of new grid codes. This study proposes a novel DC‐link fault current limiter (DLFCL)‐based FRT scheme to improve the FRT capability in IBDG units. The DLFCL module has almost no effect on normal operation of IBDG. When a short‐circuit fault occurs in power system, the DLFCL module effectively limits the inverter output current and protects its switching devices. The employed DLFCL does not need any control, measurement and gate driving system. Also, it has simple configuration and it is not mandatory to use a superconductor inductor in its power circuit so, it has low initial cost. By using the proposed scheme, it is possible to provide continues operation of IBDG even at zero grid voltage. Analytical analysis is presented in details. The effectiveness of the proposed approach is approved through extensive simulation studies in PSCAD/EMTDC environment. An experimental setup is used to verify the main concept of the proposed approach. [ABSTRACT FROM AUTHOR]

The penetration level of solar photovoltaic (PV) generation in a distribution system is often limited by the constraint on voltage variation due to large intermittent power injection. This paper investigates the penetration levels of PV systems in distribution feeders by taking into account the mutual coupling effect between phase conductors. The equivalent circuit models for distribution line segments, including the grounding effect and the mutual coupling between phase conductors and the grounded neutral line, are applied to computer simulation. Two practical Taipower distribution feeders are selected for system analysis to study the maximum PV penetration with the proposed precise modeling of the feeder network. The increase of allowable PV penetration by executing the transposition of phase conductors to improve the three-phase balance is also analyzed. [ABSTRACT FROM AUTHOR]