Browsing by Author "Darwish, Mohamed M.F."

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Adaptive LFC incorporating modified virtual rotor to regulate frequency and tie-line power flow in multi-area microgrids
(2022-03-22) Abubakr, Hussein; Guerrero, Josep M.; Vasquez, Juan C.; Mohamed, Tarek Hassan; Mahmoud, Karar; Darwish, Mohamed M.F.; Dahab, Yasser Ahmed
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This research investigates a new coordination strategy for both isolated single-area and interconnected multi-area microgrids (MGs) using a modified virtual rotor-based derivative technique supported with Jaya optimizer based on balloon effect modulation (BE). Accordingly, the main concept of BE is to assist the classic Jaya to be more sensitive and trackable in the event of disturbances, as well as to provide optimum integral gain value on the secondary frequency controller adaptively for both suggested MGs. The proposed modified virtual rotor mechanism is consisting of virtual inertia and virtual damping that are added as a tertiary controller within proposed MGs considering full participation of the inverter-based energy storage systems. The proposed virtual rotor mechanism is consisting of virtual inertia and virtual damping that are added as a tertiary controller within proposed MGs to emulate the reduction in system inertia and the enhanced damping properties. Several nonlinearities were proposed in this work such as a dead band of governor, generation rate constraints, and communication time-delay are considered within the dynamic model of the suggested MGs. In addition, the proposed design of multi-area MGs takes the interval time-varying communication delays into account for stability conditions. In this study, A comparative study using unimodal (i.e., Sphere) and multimodal (i.e., Rastrigin) benchmark test functions are conducted to validate the proposed direct adaptive Jaya-based BE. Furthermore, Wilcoxon’s rank-signed non-parametric statistical test using a pairwise comparison was performed at a 5 % risk level to judge whether the proposed algorithm output varies from those of the other algorithms in a statistically significant manner. Thence, the superiority and effectiveness of the proposed method have also been verified against a variety of other metaheuristics optimization techniques, including classic electro-search, particle swarm, multi-objective seagull, and Jaya optimizers. In addition, an operative performance is assessed against the conventional integral controller, coefficient diagram method, and classic Jaya with/without virtual inertia. The final findings emphasize the superiority of the proposed direct adaptive Jaya-based BE supported by a modified virtual rotor and state better performance and stability compared to existing controllers.
Comprehensive Review on Renewable Energy Sources in Egypt - Current Status, Grid Codes and Future Vision
(2022-01-04) Abubakr, Hussein; Vasquez, Juan C.; Mahmoud, Karar; Darwish, Mohamed M.F.; Guerrero, Josep M.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The development of the energy sector in Egypt is considered an urgent issue due to the rapid population rise rate. In particular, renewable energy sources (RESs) applications play an essential role in the coverage of energy demand. Therefore, Egypt has ambitious plans towards RESs to combine a sustainable energy future with economic growth. Egypt has high potentiality for RESs and their applications, nevertheless, the study of this modality remains below the required level. Due to the widespread use of RESs, communities are facing stability issues as the power converters-based RESs create a significant lack of power inertia, causing system instability and power blackouts as well as issues of power quality such as harmonics or resonances due to the power converters and their interactions with the system. This work presents a recent review supported by a statistical analysis about the current situation in Egypt according to the last data carried out from local/global reports. In addition, this review discusses specifications of technical design standards, terms, and equipment parameters for connecting small, medium, and large-scale solar plants, respectively to the Egyptian grid in accordance with the Electricity Distribution Code (EDC), Solar Energy Grid Connection Code (SEGCC), and the Grid Code (GC). Interestingly, the use of hydropower and emergent solar energy is considered the most promising RES variant, besides the wind energy at the coastal sites. This review characterizes the progress in Egypt and classifies interest areas for RESs recent study, e.g., photovoltaic (PV), solar chimney (SC), concentrated solar plant (CSP), and wind energy in Egypt. To maximize the RES hosting capacity in Egypt, various energy storage systems are required to be integrated into the distribution networks. Finally, a view of existing gaps, future visions and projects, and visible recommendations are defined for the Egyptian grid.
Condition Assessment of Natural Ester–Mineral Oil Mixture Due to Transformer Retrofilling via Sensing Dielectric Properties
(2023-07) Karaman, Hesham S.; Mansour, Diaa Eldin A.; Lehtonen, Matti; Darwish, Mohamed M.F.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Mineral oil (MO) is the most popular insulating liquid that is used as an insulating and cooling medium in electrical power transformers. Indeed, for green energy and environmental protection requirements, many researchers introduced other oil types to study the various characteristics of alternative insulating oils using advanced diagnostic tools. In this regard, natural ester oil (NEO) can be considered an attractive substitute for MO. Although NEO has a high viscosity and high dielectric loss, it presents fire safety and environmental advantages over mineral oil. Therefore, the retrofilling of aged MO with fresh NEO is highly recommended for power transformers from an environmental viewpoint. In this study, two accelerated aging processes were applied to MO for 6 and 12 days to simulate MO in service for 6 and 12 years. Moreover, these aged oils were mixed with 80% and 90% fresh NEO. The dielectric strength, relative permittivity, and dissipation factor were sensed using a LCR meter and oil tester devices for all prepared samples to support the condition assessment performance of the oil mixtures. In addition, the electric field distribution was analyzed for a power transformer using the oil mixtures. Furthermore, the dynamic viscosity was measured for all insulating oil samples at different temperatures. From the obtained results, the sample obtained by mixing 90% natural ester oil with 10% mineral oil aged for 6 days is considered superior and achieves an improvement in dielectric strength and relative permittivity by approximately 43% and 48%, respectively, compared to fresh mineral oil. However, the dissipation factor was increased by approximately 20% but was at an acceptable limit. On the other hand, for the same oil sample, due to the higher molecular weight of the NEO, the viscosities of all mixtures were at a higher level than the mineral oil.
Effective Transmission Congestion Management via Optimal DG Capacity using Hybrid Swarm Optimization for Contemporary Power System Operations
(2022) Gupta, Prashant; Sarwar, Md; Siddiqui, Anwar Shahzad; Ghoneim, Sherif S.M.; Mahmoud, Karar; Darwish, Mohamed M.F.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Managing transmission congestion had been a major problem with growing competition in the power networks. Accordingly, competitiveness emerges through the network's reconfiguration and the proliferation of secondary facilities. Congestion of transmission lines is a critical issue, and their regulation poses a technical challenge as the power system is deregulated. Therefore, the present research illustrates a multi-objective strategy for reaching the optimal capabilities of distributed generators (DG) like wind power plants and geothermal power-producing plants to alleviate congestion throughout the transmission network. Goals such as congestion management during power delivery, power loss reduction, power flow improvement with the enhancement of voltage profile, and investment expenditure minimization are considered to boost the network's technological and economic reliability. The congestion management is achieved using the locational marginal price (LMP) and calculation of transmission congestion cost (TCC) for the optimal location of DG. After identification of congested lines, DG is optimally sized by particle swarm optimization (PSO) and a newly proposed technique that combines the features of modified IL-SHADE and PSO called hybrid swarm optimization (HSO) which employs linear population size reduction technique which improves its performance greatly by reducing the population size by elimination of least fit individuals at every generation giving far better results than those obtained with PSO. In addition, optimal rescheduling of generations from generators has been done to fulfill the load demand resulting in alleviation of congested lines thereby enhancing the performance of the network under investigation. Furthermore, the performance of the proposed methodology of HSO and PSO has been tested successfully on standard benchmark IEEE-30 & IEEE-57 bus configurations in a MATLAB environment with the application of MATPOWER power system package.
Emerging applications of IoT and cybersecurity for electrical power systems
(2023-10) Darwish, Mohamed M.F.; Elsisi, Mahmoud; Fouda, Mostafa M.; Mansour, Diaa Eldin A.; Lehtonen, Matti
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Enhancement of the underground cable current capacity by using nano-dielectrics
(2024-09) Gouda, Ossama E.; Darwish, Mohamed M.F.; Thabet, Ahmed; Lehtonen, Matti; Osman, Gomaa F.A.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In most underground power cables, cross-linked polyethylene (XLPE) is utilized as the main insulating material, while polyvinyl chloride (PVC) is usually used as a nonmetallic sheath or jacketing for the cable. Accordingly, improving the electrical and thermal characteristics of these materials leads to an increase in cable dielectric strength, besides a rise in the current capacity of the underground power cables. Thus, enhancing the thermal characteristics of cable insulation is the goal of many research studies. In this regard, increasing the current capacity of underground power cables is an essential topic for electrical distribution and transmission networks. This usually occurs by increasing the cross-sectional area of the cable conductor, which means raising the cost of transmitting electrical energy. Another proposed alternative may be to improve the thermal properties of the dielectric material using nanotechnology to allow better dissipation of heat resulting from the cable losses. This article proposes the use of nano-composite dielectrics to increase the current capacities of underground power cables. Nano-fillers are used to enhance the thermal and electrical characteristics of XLPE and PVC, which represent cable dielectric materials. Accordingly, in this paper, many experiments are conducted on various nano-dielectric materials to choose the most appropriate nano-dielectrics for improving both the thermal and electrical properties. Hence, measurements are performed on the thermal and electrical properties of dielectric nano-materials manufactured in the laboratory. Further, calculations of the cable's current capacities by the use of the measured properties of nano-dielectrics are done considering several backfill soils. From the obtained measurements and calculations carried out on cable capacities, it is concluded that the use of XLPE/ZnO 5 wt.% as the insulation and PVC/ZnO 5 wt.% as the jacket material increased the cable current capacity by 6.2% for a cable of 33 kV rating, 9.2% for 66 kV cable, and 15.7% for 220 kV cable when wet clay is used as backfill soil. From the calculations carried out it is found that the use of nano-composite dielectrics reduces the temperature of the cable components by significant values. For example, the core temperature of the 33 kV cable is reduced by 15.6°C, while for the 66 kV cable, the cable core temperature is decreased by 12.6°C, and for 220 kV the conductor temperature is reduced from 71.3°C to 58.3°C when each cable is loaded by its rating.
Evaluating transient behaviour of large-scale photovoltaic systems during lightning events using enhanced finite difference time domain method with variable cell size approach
(2024-06) Hetita, Ibrahim; Mansour, Diaa Eldin A.; Han, Yang; Yang, Ping; Wang, Congling; Darwish, Mohamed M.F.; Lehtonen, Matti; Zalhaf, Amr S.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Photovoltaic (PV) arrays are usually installed in open areas; hence, they are vulnerable to lightning strikes that can result in cell degradation, complete damage, service disruption, and increased maintenance costs. As a result, it is imperative to develop an effective and efficient lightning protection system by evaluating the transient behaviour of PV arrays during lightning events. The aim is to evaluate the transient analysis of large-scale PV systems when subjected to lightning strikes using the finite difference time domain (FDTD) technique. Transient overvoltages are calculated at various points within the mounting system. To optimise the FDTD method's execution time and make it more suitable for less powerful hardware, a variable cell size approach is employed. Specifically, larger cell dimensions are used in the earthing system and smaller cell dimensions are used in the mounting system. The FDTD method is utilised to calculate the temporal variation of transient overvoltages for large-scale PV systems under different scenarios, including variations in the striking point, soil resistivity, and the presence of a metal frame. Simulation results indicate that the highest transient overvoltages occur at the striking point, and these values increase with the presence of a PV metal frame as well as with higher soil resistivity. Furthermore, a comparison is performed between the overvoltage results obtained from the FDTD approach and the partial element equivalent circuit (PEEC) method at the four corner points of the mounting systems to demonstrate the superior accuracy of the FDTD method. Besides, a laboratory experiment is conducted on a small-scale PV system to validate the simulation results. The calculated overvoltages obtained from the FDTD and PEEC methods are compared with the measured values, yielding a mean absolute error of 5% and 11% for the FDTD and PEEC methods, respectively, thereby confirming the accuracy of the FDTD simulation model.
Influence of Mineral Oil-Based Nanofluids on the Temperature Distribution and Generated Heat Energy Inside Minimum Oil Circuit Breaker in Making Process
(2023-06-27) Karaman, Hesham S.; El Dein, Adel Z.; Mansour, Diaa Eldin A.; Lehtonen, Matti; Darwish, Mohamed M.F.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The enhancement of the thermal properties of insulating oils has positively reflected on the performance of the electrical equipment that contains these oils. Nanomaterial science plays an influential role in enhancing the different properties of liquids, especially insulating oils. Although a minimum oil circuit breaker (MOCB) is one of the oldest circuit breakers in the electrical network, improving the insulating oil properties develops its performance to overcome some of its troubles. In this paper, 66 kV MOCB is modeled by COMSOL Multiphysics software. The internal temperature and the internally generated heat energy inside the MOCB during the making process of its contacts are simulated at different positions of the movable contact. This simulation is introduced for different modified insulating oils (mineral oil and synthetic ester oil) with different types of nanoparticles at different concentrations (0.0, 0.0025, 0.005, and 0.01 wt%). From the obtained results, it is noticed that the thermal stress on the MOCB can be reduced by the use of high thermal conductivity insulating oils. Nano/insulating oils decrease internal temperature and generate heat energy inside the MOCB by about 17.5%. The corresponding physical mechanisms are clarified considering the thermophoresis effect.
Investigation of soil resistivity impacts on the electrodes of grounding system subjected to lightning strikes
(2024-11) Gouda, Osama E.; El Dein, Adel Z.; Yassin, Sara; Lehtonen, Matti; Darwish, Mohamed M.F.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In this paper, the study of the homogeneous resistivity and two-layer soil influences on the performance of the electrodes of grounding systems subjected to lightning strikes is carried out considering soil ionization. The study is done on the behaviour of the ground electrodes while the resistivity of the soil is altered from small to high value in the case of homogeneous soil, while the study is obtained on two-layer soils in the case of diverse values of the reflection factor. In the suggested algorithm for two-layer soils, each layer has its resistivity and dielectric constant, where the dielectric constant and soil resistivity depend on the lightning frequency. The field resulting from lightning strikes, which causes soil ionization, has been studied, and the results have been used to understand the behaviour of ground rods under the influence of lightning strikes. The credibility of the results has been strengthened by comparing it with what others have obtained recently. The article's novelty can be summarized in the investigation of the performance of the electrodes of grounding grids that are installed in high soil resistivity of uniform and two-layer soils containing the impacts of soil ionization, lightning frequency, soil resistivity, and permittivity variations.
Mitigation of the Electric and Magnetic Fields of 500-kV Overhead Transmission Lines
(2022-03-24) Dein, Adel Z.El; Gouda, Osama E.; Lehtonen, Matti; Darwish, Mohamed M.F.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The electric and magnetic fields of overhead high voltage transmission lines are still a critical problem for new construction because of their biological effects on the human body. This issue has been a subject of scientific interest and public concern for the risk of the electric and magnetic fields on living organisms. Accordingly, the overhead transmission lines are considered a source of such this risk due to their high electric and magnetic fields in the populated areas. Because of the recent concerns that electric besides magnetic fields, generated by overhead transmission lines, electric power researchers have been trying to find effective methods for the mitigation of the electrical and magnetic fields to be in the range of acceptable limits. Researchers have been trying to find transmission line geometries that will reduce these electric and magnetic fields. Therefore, in this article two novel methods of reducing the electric and magnetic fields are discussed, one is to change the position of the center phase to optimize the delta configuration and the other is to use more than two shielding wires with calculating the currents in these wires. The obtained results of the two proposed methods are compared with the electric as well as magnetic fields, and the right-of-way values of the present conventional configuration. Additionally, this article presents a case study carried out on an Egyptian 500 kV high voltage overhead transmission line for the mitigation of magnetic and electric field intensities.
Mitigation of the electric field under EHVTL in limited space crowded with human activities
(2024-03-18) Gouda, Ossama E.; ELMashtoly, Mohamed H.; Lehtonen, Matti; Darwish, Mohamed M.F.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Workers in the activities under high-voltage lines are exposed to the influence of the electric field of these lines, which may cause, in some cases, death as a result of some serious accidents such as the collapse of the towers and the occurrence of line to ground faults. In some densely populated countries, people may live near the right-of-way (ROW) of extra high-voltage transmission lines (EHVTLs), which may cause, as a result of the high electric field, health problems, for this reason, some researchers have pointed out the possible relationship between exposure to electric and magnetic fields on the one hand and the appearance of some diseases, especially in children, on the other hand. The aim of this article is to suggest a way to reduce the electric field in the place where people are found by using metal grids at safe distances from the EHVTLs. In this article, the electric field is calculated in the event that these grids are isolated or grounded. A comparison between the electric field without the use of shielding grids and with using these grids when they are isolated and earthed is carried out. The effect of changing the location of the shielding grids on the electric field values is examined. It is illustrated from this study that the peak value of the electric field intensity is mitigated to be 16.66% of its value before shielding, which proved the method's effectiveness in lowering the intensity of the electric field. The effect of an isolated shielding grid is to shift the electric field curve to be more flat. The installation of the earthed grids beside and parallel to the lines has a significant influence on the mitigation of the electric field under the EHVTL.
A new technique for fault diagnosis in transformer insulating oil based on infrared spectroscopy measurements
(2024-04) Darwish, Mohamed M.F.; Hassan, Mohamed H.A.; Abdel-Gawad, Nagat M.K.; Lehtonen, Matti; Mansour, Diaa Eldin A.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Condition monitoring of the insulating system within power transformers has a massive importance according to the electrical utilities. Dissolved gas analysis (DGA) is frequently used for this purpose. However, DGA lacks the necessary level of accuracy to identify all equipment faults, particularly in their initial stages of degradation. Also, it does not have the capability for real-time monitoring and relies on manual sampling and laboratory testing, causing potential delays in fault identification. Additionally, the interpretation of DGA data necessitates specialised expertise, which may pose difficulties for smaller entities that have limited access to resources. Therefore, the contribution of this research is to use infrared spectroscopy measurements as a new effective technique substituting the DGA method for fault diagnosis in insulating oil. The inception faults that were considered in this study were the electrical fault (discharges of high energy) and the thermal fault (300°C < Temperature <700°C). Regarding that, two test cells were crafted especially for serving the simulation processes inside the laboratory for both types of inception faults. Subsequently, six samples of pure paraffinic mineral oil were taken to be degraded in the laboratory. Following that, all of them besides another sample that were not subjected to any kind of faults were taken to be examined by Fourier transform infrared (FTIR) spectroscopy to obtain an overview of the oil's behaviour in each fault case. After that, the FTIR analysis was initially verified utilising the DGA method. Then, for further affirmation, the dielectric dissipation factor (DDF) for all samples was measured. In the final analysis, the verification tests provide experimental evidence about the outperformance of this new optical technique in detecting the transformer's inception faults in addition to proving its potential for being a superior alternative to the well-known traditional diagnostic techniques.
A Novel Polyester Varnish Nanocomposites for Electrical Machines with Improved Thermal and Dielectric Properties Using Functionalized TiO2 Nanoparticles
(2023-10) Ahmed, Hanaa M.; Abdel-Gawad, Nagat M.K.; Afifi, Waleed A.; Mansour, Diaa Eldin A.; Lehtonen, Matti; Darwish, Mohamed M.F.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Recently, there has been a growing interest in polymer insulating materials that incorporate nanoscale inorganic additives, as they have shown significantly improved dielectric, thermal, and mechanical properties, making them highly suitable for application in high-voltage insulating materials for electrical machines. This study aims to improve the dielectric and thermal properties of a commercial polyester varnish by incorporating different concentrations of titanium dioxide nanoparticles (TiO2) with proper surface functionalization. Permafil 9637 dipping varnish is the varnish used for this investigation, and vinyl silane is the coupling agent used in the surface functionalization of TiO2 nanoparticles. First, nanoparticles are characterized through Fourier transform infrared spectroscopy to validate the success of their surface functionalization. Then, varnish nanocomposites are characterized through field emission scanning electron microscopy to validate the dispersion and morphology of nanoparticles within the varnish matrix. Following characterization, varnish nanocomposites are evaluated for thermal and dielectric properties. Regarding thermal properties, the thermal conductivity of the prepared nanocomposites is assessed. Regarding dielectric properties, both permittivity and dielectric losses are evaluated over a wide frequency range, starting from 20 Hz up to 2 MHz. Moreover, the AC breakdown voltage is measured for varnish nanocomposites, and the obtained data are incorporated into a finite element method to obtain the dielectric breakdown strength. Finally, the physical mechanisms behind the obtained results are discussed, considering the role of nanoparticle loading and surface functionalization.
On Highlighting the Merits of Gas-to-Liquid Transformer Oil Under Accelerated Thermal Aging and Faults: Electrical and Physio- Chemical Properties
(2024) Badawi, Mohamed; Ibrahim, Shimaa A.; Mansour, Diaa Eldin A.; Ward, Sayed A.; El-Faraskoury, Adel A.; Ghali, Mohsen; Mahmoud, Karar; Lehtonen, Matti; Darwish, Mohamed M.F.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Mineral (MO) oil has long been utilized as a dielectric and cooling medium in high-voltage power transformers due to its low cost and availability. Recently, there has been a great trend toward the use of gas-to-liquid (GTL) oil due to its purity, chemical consistency, and better performance than conventional oils. This study aims to investigate the normal and abnormal thermal impacts on GTL and MO oil types. In this regard, this paper presents two parts. Firstly, it studies a comprehensive evaluation of the aging characteristics under normal conditions of GTL oil in comparison to conventional MO. Aged oil samples were obtained using a laboratory-based accelerated aging test, for simulating the thermal stress during the transformer's operation. Hence, the two oil types are subjected to different aging durations (i.e., 3, 6, and 10 days). These aged and fresh samples were tested for AC breakdown voltage, dielectric dissipation factor, permittivity, and resistivity as electrical testing. Additionally, as chemical and physical testing, moisture and acidity are measured for fresh and aged samples of two of these oil types. Besides, optical spectroscopy measurements have been used for insulating oil assessment; these kinds of measurements point out the existence of overall aging byproducts, including sludge formation, which can negatively impact the oil properties including physio-chemical and electrical properties. The used optical techniques include Ultraviolet-visible absorption and photoluminescence tests. Secondly, thermal faults impact as abnormal conditions is generally evaluated through dissolved gas analysis as a chemical test, where it is utilized to measure the gas concentrations for the two oils under abnormal conditions test after the thermal heating test. This study concluded that the electrical and physio-chemical properties of GTL oil with aging have superior results compared to MO oil.
An optimal network constraint-based joint expansion planning model for modern distribution networks with multi-types intermittent RERs
(2022-07) Zhou, Siyu; Han, Yang; Yang, Ping; Mahmoud, Karar; Lehtonen, Matti; Darwish, Mohamed M.F.; Zalhaf, Amr S.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Currently, distribution systems are continuously evolving towards modern and flexible structures while integrating promising renewable energy resources (RERs). In this regard, an optimal network constraint-based expansion planning model combined with an optimal integration framework of intermittent RERs is proposed in this work to improve the topological flexibility in modern distribution networks (DNs). Specifically, the best investment locations and times of substations, lines, and RER-based distributed generations (DGs) are jointly taken into consideration. Additionally, the uncertainty-based multiple scenarios are modeled by probability distribution functions to strengthen the robustness and reliability of DNs influenced by the stochastic of renewable energy and load behavior. The novel network constraint is combined with three levels, where the first level introduces the graph theory to guarantee the radiality topology of modern DNs. In the second level of the network constraint, graph theory and fictitious load theory are collaboratively applied to ensure that each subsystem has a reserve connection interconnected to other subsystems. The third level is modifying the conventional fictitious load theory to ensure each subsystem is linked with at least one DG. The proposed planning model is driven by the minimum present value of total cost, including investment cost of branches, DGs, and substations, cost of substations operation, the electricity purchasing cost of substations and DGs, power losses cost, and environmental penalty cost of conventional generators. Numerical results are presented to verify that a more flexible and resilient topology of the DN system is obtained, and criteria evaluation is introduced to validate its higher performance with respect to existing procedures from power supplied quality, environmental burden, and supplied flexibility three aspects.
Optimal scheduling of DG and EV parking lots simultaneously with demand response based on self-adjusted PSO and K-means clustering
(2022-10) Abo-Elyousr, Farag K.; Sharaf, Adel M.; Darwish, Mohamed M.F.; Lehtonen, Matti; Mahmoud, Karar
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Recently, the proliferation of distributed generation (DG) has been intensively increased in distribution systems worldwide. In distributed systems, DGs and utility-owned electric vehicle (EV) to grid aggregators have to be efficiently scaled for cost-effective network operation. Accordingly, with the penetration of power systems, demand response (DR) is considered an advanced step towards a smart grid. To cope with these advancements, this study aims to develop an innovative solution for the day-ahead sizing approach of energy storage systems of EVs parking lots and DGs in smart distribution systems complying with DR and minimizing the pertinent costs. The unique feature of the proposed approach is to allow interactive customers to participate effectively in power systems. To accurately solve this optimization model, two probabilistic self-adjusted modified particle swarm optimization (SAPSO) algorithms are developed and compared for minimizing the total operational costs addressing all constraints of the distribution system, DG units, and energy storage systems of EV parking lots. The K-means clustering and the Naive Bayes approach are utilized to determine the EVs that are ready to participate efficiently in the DR program. The obtained results on the IEEE-24 reliability test system are compared to the genetic algorithm and the conventional PSO to verify the effectiveness of the developed algorithms. The results show that the first SAPSO algorithm outperforms the algorithms in terms of minimizing the total running costs. The finding demonstrates that the proposed near-optimal day-ahead scheduling approach of DG units and EV energy storage systems in a simultaneous manner can effectively minimize the total operational costs subjected to generation constraints complying with DR.
Optimum estimation of series capacitors for enhancing distribution system performance via an improved hybrid optimization algorithm
(2023-06) Mohamed, Mohamed Abd El Hakeem; Abdelaziz, Almoataz Y.; Darwish, Mohamed M.F.; Lehtonen, Matti; Mahmoud, Karar
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
As the load on distribution networks grows, system operators and planners are constantly challenged with the issue of voltage regulation or enhancing the quality of supply to customers at the load end of lengthy distribution lines. This paper presents the optimum determination of series capacitor units in a distribution system to maximize energy-saving and enhance voltage levels. Interestingly, series capacitors can enhance the capability of transmission lines, reduce line losses, enhance the performance of buses with large induction motor loads and reduce voltage flicker. At the same time, the limitations of series compensation are taken into consideration while calculating its optimum values. To achieve the planning objective and optimal load flow objective, two strategies: The Improved Grey Wolf Optimization method (I-GWO) and Tabu Search (TS), are hybridized to get the benefit of their advantages. The I-GWO has a movement strategy called dimension learning-based hunting for enhancing the balance between global and local search and maintaining diversity. The proposed (I-GWO-TS) algorithm can solve mixed-integer programming to achieve the planning and the optimal load flow objectives. The proposed method can be applied to a real Egyptian distribution system that is heavily loaded, with poor voltage regulation, and also has high-power losses. The obtained results demonstrate the capability of the proposed approach to determine optimal series capacitors’ location and sizing for maximization of energy saving. Further, the proposed method improves the network performance regarding the voltage profile and power losses, although the limitations of including series compensation were considered in the distribution system.
Pollution Severity Monitoring of High Voltage Transmission Line Insulators Using Wireless Device Based on Leakage Current Bursts
(2022) Gouda, Osama E.; Darwish, Mohamed M.F.; Mahmoud, Karar; Lehtonen, Matti; Elkhodragy, Tamer M.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The present article describes a smart wireless online device for the severity monitoring of the contaminated insulators of high voltage transmission networks. Accordingly, the wireless developed monitor works by continuously sensing the magnitudes of the leakage current bursts and calculating its average root-mean-square (RMS) value for every second or minute as the monitor software is calibrated. Regarding, if the average of the leakage current RMS value is adjudicated by the monitor as corresponding to a probably significant scale of a power outage, the monitor transfers an alarm signal and sends a warning message to the maintenance crew members to take the action to wash the high voltage line insulators on time before the unexpected outage of the high voltage network has been occurring. The developed monitor contains the following main units: current transformer with burden resistor, Node MCU (ESP8266), solar power bank, cloud-based data storage, and smart device (Mobile or tablet). These units can be assembled to work without the need for a power source. The proposed monitor has many merits over the other monitoring devices; it enjoys little cost, easy of handling, and calibration. It has a high degree of safety, it is an online system, and its design is simple. The developed monitor is tested in the Laboratory using insulators with different pollution layers' conductivity and the findings show that the accuracy of the proposed monitor reached 91.66 % after carrying out 50 tests.
Precise transformer fault diagnosis via random forest model enhanced by synthetic minority over-sampling technique
(2023-07) Prasojo, Rahman Azis; Putra, Muhammad Akmal A.; Ekojono; Apriyani, Meyti Eka; Rahmanto, Anugrah Nur; Ghoneim, Sherif S.M.; Mahmoud, Karar; Lehtonen, Matti; Darwish, Mohamed M.F.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Power transformers are considered one of the power system's most critical and expensive assets. In this regard, it is vital to assess the fault within the power transformer considering numerous operational aspects. In the literature, dissolved gas analysis (DGA) is the routine in-service test for power transformers and one of the most important tests to ensure sufficient system reliability. Specifically, this test can detect dissolved gases in transformer oil which are then interpreted to detect the fault type of the transformer. Previous studies reported that the graphical Duval pentagon is one of the most accurate and consistent DGA interpretation techniques. However, it still has limitations on the complexity of the implementation in large amounts of data. To cover these issues, this study mitigates the limitation and complexity of implementing the graphical Duval Pentagon Method (DPM) in large amounts of data. To reach this goal, we develop a precise machine-learning-based fault identification model by employing the Random Forest algorithm with Synthetic minority over-sampling technique (SMOTE) preprocessing. The proposed Random Forest models with SMOTE perform satisfactorily in diagnosing faults for the evaluation dataset, with a total accuracy of 96.2% for DPM1 and 96.5% for DPM2. The proposed models were also compared to other machine learning algorithms, performing better both in classification accuracy and consistency due to uncertainty.
Proposed ANFIS Based Approach for Fault Tracking, Detection, Clearing and Rearrangement for Photovoltaic System
(2021-03-24) Bendary, Ahmed F.; Abdelaziz, Almoataz Y.; Ismail, Mohamed M.; Mahmoud, Karar; Lehtonen, Matti; Darwish, Mohamed M.F.
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In the last few decades, photovoltaics have contributed deeply to electric power networks due to their economic and technical benefits. Typically, photovoltaic systems are widely used and implemented in many fields like electric vehicles, homes, and satellites. One of the biggest problems that face the relatability and stability of the electrical power system is the loss of one of the photovoltaic modules. In other words, fault detection methods designed for photovoltaic systems are required to not only diagnose but also clear such undesirable faults to improve the reliability and efficiency of solar farms. Accordingly, the loss of any module leads to a decrease in the efficiency of the overall system. To avoid this issue, this paper proposes an optimum solution for fault finding, tracking, and clearing in an effective manner. Specifically, this proposed approach is done by developing one of the most promising techniques of artificial intelligence called the adaptive neuro-fuzzy inference system. The proposed fault detection approach is based on associating the actual measured values of current and voltage with respect to the trained historical values for this parameter while considering the ambient changes in conditions including irradiation and temperature. Two adaptive neuro-fuzzy inference system-based controllers are proposed: (1) the first one is utilized to detect the faulted string and (2) the other one is utilized for detecting the exact faulted group in the photovoltaic array. The utilized model was installed using a configuration of 4 x 4 photovoltaic arrays that are connected through several switches, besides four ammeters and four voltmeters. This study is implemented using MATLAB/Simulink and the simulation results are presented to show the validity of the proposed technique. The simulation results demonstrate the innovation of this study while proving the effective and high performance of the proposed adaptive neuro-fuzzy inference system-based approach in fault tracking, detection, clearing, and rearrangement for practical photovoltaic systems.