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Energies, Volume 15, Issue 24 (December-2 2022) – 397 articles

Cover Story (view full-size image): The National Observatory of Athens in Greece, contributing to the energy transition of the small islands of the Aegean Sea, is planning the energy autonomy for the island of Antikythera. With the European Climate Change Observatory called PANGEA as a springboard, a series of scenarios for the installation of solar power plants were studied. The ultimate goal is, together with the research activity of PANGEA, to drastically reduce the average cost of electricity production, which is currently the highest in the European Union. View this paper
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Review
Evaluation Metrics for Wind Power Forecasts: A Comprehensive Review and Statistical Analysis of Errors
Energies 2022, 15(24), 9657; https://doi.org/10.3390/en15249657 - 19 Dec 2022
Viewed by 697
Abstract
Power generation forecasts for wind farms, especially with a short-term horizon, have been extensively researched due to the growing share of wind farms in total power generation. Detailed forecasts are necessary for the optimization of power systems of various sizes. This review and [...] Read more.
Power generation forecasts for wind farms, especially with a short-term horizon, have been extensively researched due to the growing share of wind farms in total power generation. Detailed forecasts are necessary for the optimization of power systems of various sizes. This review and analytical paper is largely focused on a statistical analysis of forecasting errors based on more than one hundred papers on wind generation forecasts. Factors affecting the magnitude of forecasting errors are presented and discussed. Normalized root mean squared error (nRMSE) and normalized mean absolute error (nMAE) have been selected as the main error metrics considered here. A new and unique error dispersion factor (EDF) is proposed, being the ratio of nRMSE to nMAE. The variability of EDF depending on selected factors (size of wind farm, forecasting horizons, and class of forecasting method) has been examined. This is unique and original research, a novelty in studies on errors of power generation forecasts in wind farms. In addition, extensive quantitative and qualitative analyses have been conducted to assess the magnitude of forecasting error depending on selected factors (such as forecasting horizon, wind farm size, and a class of the forecasting method). Based on these analyses and a review of more than one hundred papers, a unique set of recommendations on the preferred content of papers addressing wind farm generation forecasts has been developed. These recommendations would make it possible to conduct very precise benchmarking meta-analyses of forecasting studies described in research papers and to develop valuable general conclusions concerning the analyzed phenomena. Full article
(This article belongs to the Special Issue Intelligent Forecasting and Optimization in Electrical Power Systems)
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Article
Agnostic Battery Management System Capacity Estimation for Electric Vehicles
Energies 2022, 15(24), 9656; https://doi.org/10.3390/en15249656 - 19 Dec 2022
Viewed by 822
Abstract
Battery degradation is a main concern for electric vehicle (EV) users, and a reliable capacity estimation is of major importance. Every EV battery management system (BMS) provides a variety of information, including measured current and voltage, and estimated capacity of the battery. However, [...] Read more.
Battery degradation is a main concern for electric vehicle (EV) users, and a reliable capacity estimation is of major importance. Every EV battery management system (BMS) provides a variety of information, including measured current and voltage, and estimated capacity of the battery. However, these estimations are not transparent and are manufacturer-specific, although measurement accuracy is unknown. This article uses extensive measurements from six diverse EVs to compare and assess capacity estimation with three different methods: (1) reading capacity estimation from the BMS through the central area network (CAN)-bus, (2) using an empirical capacity estimation (ECE) method with external current measurements, and (3) using the same method with measurements coming from the BMS. We show that the use of BMS current measurements provides consistent capacity estimation (a difference of approximately 1%) and can circumvent the need for costly experimental equipment and DC chargers. This data can simplify the ECE method only by using an on-board diagnostics port (OBDII) reader and an AC charger, as the car measures the current directly at the battery terminals. Full article
(This article belongs to the Special Issue Smart Electric Vehicle Charging Approaches for Demand Response)
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Article
New Energy Power System Static Security and Stability Region Calculation Research Based on IPSO-RLS Hybrid Algorithm
Energies 2022, 15(24), 9655; https://doi.org/10.3390/en15249655 - 19 Dec 2022
Viewed by 429
Abstract
With the rapid expansion of new energy in China, the large-scale grid connection of new energy is increasing, and the operating safety of the new energy power system is being put to the test. The static security and stability region (SSSR) with hyper-plane [...] Read more.
With the rapid expansion of new energy in China, the large-scale grid connection of new energy is increasing, and the operating safety of the new energy power system is being put to the test. The static security and stability region (SSSR) with hyper-plane expression is an effective instrument for situational awareness and the stability-constrained operation of power systems. This paper proposes a hybrid improved particle swarm optimization (IPSO) and recursive least square (RLS) approach for rapidly approximating the SSSR boundary. Initially, the operating point data in the high-dimensional nodal injection space is examined using the IPSO algorithm to find the key generators, equivalent search space, and crucial points, which have a relatively large impact on static stability. The RLS method is ultimately utilized to fit the SSSR border that best suits the crucial spots. Consequently, the adopted algorithm technique was used to rapidly approximate the SSSR border in power injection spaces. Finally, the suggested algorithm is confirmed by simulating three kinds of generators of the new energy 118 bus system using the DIgSILENT/Power Factory. As a result, this method accurately characterized the stability border of the new energy power system and created the visualization space of the SSSR. Using the SSSR, a rapid state analysis could be undertaken on a variety of parameters, such as security evaluation with diverse energy supply capacities. This study’s findings confirmed the accuracy and efficacy of the suggested modeling for the considered system and may thus give technical support for the new energy power system’s stability. Full article
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Article
Accurate State of Charge Estimation for Real-World Battery Systems Using a Novel Grid Search and Cross Validated Optimised LSTM Neural Network
Energies 2022, 15(24), 9654; https://doi.org/10.3390/en15249654 - 19 Dec 2022
Viewed by 377
Abstract
State of charge (SOC) is one of the most important parameters in battery management systems, and the accurate and stable estimation of battery SOC for real-world electric vehicles remains a great challenge. This paper proposes a long short-term memory network based on grid [...] Read more.
State of charge (SOC) is one of the most important parameters in battery management systems, and the accurate and stable estimation of battery SOC for real-world electric vehicles remains a great challenge. This paper proposes a long short-term memory network based on grid search and cross-validation optimisation to estimate the SOC of real-world battery systems. The real-world electric vehicle data are divided into parking charging, travel charging, and finish charging cases. Meanwhile, the parameters associated with the SOC estimation under each operating condition are extracted by the Pearson correlation analysis. Moreover, the hyperparameters of the long short-term memory network are optimised by grid search and cross-validation to improve the accuracy of the model estimation. Moreover, the gaussian noise algorithm is used for data augmentation to improve the accuracy and robustness of SOC estimation under the working conditions of the small dataset. The results indicate that the absolute error of SOC estimation is within 4% for the small dataset and within 2% for the large dataset. More importantly, the robustness and effectiveness of the proposed method are validated based on operational data from three different real-world electric vehicles, and the mean square error of SOC estimation does not exceed 0.006. This paper aims to provide guidance for the SOC estimation of real-world electric vehicles. Full article
(This article belongs to the Topic Battery Design and Management)
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Review
Utilization of Ashes from Biomass Combustion
Energies 2022, 15(24), 9653; https://doi.org/10.3390/en15249653 - 19 Dec 2022
Viewed by 528
Abstract
Biomass is one of the most important sources of renewable energy in the energy industry. It is assumed that by 2050 the global energy deposit could be covered in 33–50% of biomass combustion. As with conventional fuels, the combustion of biomass produces combustion [...] Read more.
Biomass is one of the most important sources of renewable energy in the energy industry. It is assumed that by 2050 the global energy deposit could be covered in 33–50% of biomass combustion. As with conventional fuels, the combustion of biomass produces combustion by-products, such as fly ash. Therefore, along with the growing interest in the use of biomass as a source of energy, the production of ash as a combustion by-product increases every year. It is estimated that approximately 476 million tons of ashes per year can be produced from biomass combustion. For example, the calorific value of dry wood mass tends to be between 18.5 MJ × kg−1 and 19.5 MJ × kg−1, while the ash content resulting from thermal treatment of wood is from 0.4 to 3.9% of dry fuel mass. However, biomass ash is a waste that is particularly difficult to characterize due to the large variability of the chemical composition depending on the biomass and combustion technology. In addition, this waste is, on the one hand, a valuable fertilizer component, as it contains significant amounts of nutrients, e.g., calcium (Ca), potassium (K) and microelements, but on the other hand, it may contain toxic compounds harmful to the environment, including heavy metals and substances formed as a result of combustion, such as polycyclic aromatic hydrocarbons (PAHs) or volatile organic compounds (VOCs). PAHs and VOCs are formed mainly in the processes of incomplete combustion of coal and wood in low-power boilers, with unstable operating conditions. However, it is important to remember that before the fly ash is used in various industries (e.g., zeolite synthesis, recovery of rare earth metals or plastic production) as an additive to building materials or fertilizers for cultivation, a number of analyses are to be conducted so that the by-products of combustion could be used to allow the by-product of combustion to be used. It is important to conduct tests for the content of heavy metals, chlorides, sulphates, microelements and macroelements, grain and phase composition and organic compounds. If such ash is characterized by low pollution levels, it should be used in agriculture and reclamation of degraded land and not directed to landfills where it loses its valuable properties. The purpose of this review is to present the properties of ashes generated as a result of biomass combustion in Poland and the world, to discuss factors influencing changes in its composition and to present the possibilities of their reuse in the environment and in various branches of industry. Full article
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Article
Studies on Methane Gas Hydrate Formation Kinetics Enhanced by Isopentane and Sodium Dodecyl Sulfate Promoters for Seawater Desalination
Energies 2022, 15(24), 9652; https://doi.org/10.3390/en15249652 - 19 Dec 2022
Viewed by 386
Abstract
Methane hydrate applications in gas storage and desalination have attracted increasing attention in recent years. In the present work, the effect of isopentane (IP), sodium dodecyl sulfate (SDS), and IP/SDS blends as promoters on methane hydrate formation kinetics, in terms of the pressure–temperature [...] Read more.
Methane hydrate applications in gas storage and desalination have attracted increasing attention in recent years. In the present work, the effect of isopentane (IP), sodium dodecyl sulfate (SDS), and IP/SDS blends as promoters on methane hydrate formation kinetics, in terms of the pressure–temperature (P-T) profile, gas uptake, hydrate induction time (HIT), and water-to-hydrate conversion ratio (WHCR), were studied for distilled water and seawater samples with an IP/water sample ratio of 3:10 (by volume) and an SDS/water sample ratio of 1:1000 (by mass). Each solution was tested in a stirred tank at 600 rpm at a temperature and pressure of 2 °C and 5.2–5.3 MPa. In the case of methane hydrate formation in distilled water, the highest WHCR attained was 9.97% without additives, and 45.71% and 72.28% for SDS and isopentane additives, respectively. However, when using seawater at a salinity of 3.9%, the highest WHCR attained was 2.26% without additives and 9.89% and 18.03% for SDS and IP promoters, respectively, indicating the inhibiting effect of salinity on hydrate formation. However, the HIT was longer for seawater hydrate formation, with an average of 13.1 min compared to 9.90 min for methane hydrate formation. Isopentane enhances the HIT for methane hydrate formation in seawater by 2.23 times compared to SDS. For methane hydrate formation in seawater, the presence of IP shortened the HIT by 15.6 min compared to the seawater sample without promoters. Additionally, a synergistic effect was observed when IP and SDS were combined and used in methane hydrate formation in distilled water and seawater systems. The positive effect of IP on methane hydrate formation is possibly due to the binary hydrate formation mechanism, which improves the hydrate formation thermodynamic and kinetic parameters. Full article
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Article
Commutation Behavior and Stray Inductance Analysis of a FC-3L-BDC Phase-Leg PEBB
by , , , , and
Energies 2022, 15(24), 9651; https://doi.org/10.3390/en15249651 - 19 Dec 2022
Viewed by 508
Abstract
The bidirectional dc-dc converter is a critical component for extending the use of renewable energy and improving the efficiency of high-power electronic systems. This paper presents the analysis of the stray inductance of a commutation loop and the commutation behavior of IGBT devices [...] Read more.
The bidirectional dc-dc converter is a critical component for extending the use of renewable energy and improving the efficiency of high-power electronic systems. This paper presents the analysis of the stray inductance of a commutation loop and the commutation behavior of IGBT devices in a flying capacitor three-level bidirectional DC-DC converter (FC-3L-BDC) phase-leg power electronic building block (PEBB). An FC-3L-BDC phase-leg PEBB was designed as an example, which can be used to build 400 kW to MW-grade light rail train chargers, battery energy storage interface converters, or metro regenerative braking energy recovery converters with a single PEBB or several PEBBs interleaved parallel. In order to optimize the stray inductance of commutation paths and realize snubberless operation, a five-layer laminated bus bar was carefully designed, and the stray inductance of the bus bar was extracted by three-dimensional finite element analysis simulation. To obtain higher accuracy, the stray inductances of IGBT devices and capacitors were extracted from the test instead of their datasheets. Then, the accuracy of the commutation loop stray inductance analysis method was verified by practical experiments. The impact of the stray inductance of the commutation loop on the commutation behavior of IGBT devices was analyzed, and the switching characteristics of IGBT devices were measured under maximum DC-link voltage and entire current rating range at the temperatures of −40 °C, 25 °C, and 150 °C, respectively, finding that neither the excessive turn-off overvoltage of IGBTs nor the snappy reverse recovery of FWDs was observed. Full article
(This article belongs to the Special Issue Recent Studies in Power Electronic Devices and Applications)
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Article
Decarbonizing the International Shipping and Aviation Sectors
Energies 2022, 15(24), 9650; https://doi.org/10.3390/en15249650 - 19 Dec 2022
Viewed by 529
Abstract
The Paris Agreement requires a drastic reduction of global carbon emissions towards the net zero transition by mid-century, based on the large-scale transformation of the global energy system and major emitting sectors. Aviation and shipping emissions are not on a trajectory consistent with [...] Read more.
The Paris Agreement requires a drastic reduction of global carbon emissions towards the net zero transition by mid-century, based on the large-scale transformation of the global energy system and major emitting sectors. Aviation and shipping emissions are not on a trajectory consistent with Paris goals, driven by rapid activity growth and the lack of commercial mitigation options, given the challenges for electrification of these sectors. Large-scale models used for mitigation analysis commonly do not capture the specificities and emission reduction options of international shipping and aviation, while bottom-up sectoral models do not represent their interlinkages with the entire system. Here, I use the global energy system model PROMETHEUS, enhanced with a detailed representation of the shipping and aviation sector, to explore transformation pathways for these sectors and their emission, activity, and energy mix impacts. The most promising alternative towards decarbonizing these sectors is the large-scale deployment of low-carbon fuels, including biofuels and synthetic clean fuels, accompanied by energy efficiency improvements. The analysis shows that ambitious climate policy would reduce the trade of fossil fuels and lower the activity and the mitigation effort of international shipping, indicating synergies between national climate action and international transport. Full article
(This article belongs to the Special Issue Flexibility Integration and Decarbonisation Pathways)
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Article
Sequence Impedance Modeling and Optimization of MMC-HVDC Considering DC Voltage Control and Voltage Feedforward Control
Energies 2022, 15(24), 9649; https://doi.org/10.3390/en15249649 - 19 Dec 2022
Viewed by 324
Abstract
The dynamic performance of the DC bus significantly influences the impedance characteristics of MMC and the system stability in a high-voltage direct current system. However, most of the existing MMC-HVDC system stability research simplifies the DC side as an ideal voltage source and [...] Read more.
The dynamic performance of the DC bus significantly influences the impedance characteristics of MMC and the system stability in a high-voltage direct current system. However, most of the existing MMC-HVDC system stability research simplifies the DC side as an ideal voltage source and ignores the impacts of voltage feedforward control, which affects the accuracy and practicability of stability analysis. In this paper, a sequence impedance model considering both DC voltage control and voltage feedforward control is developed, and the necessity of considering DC control and voltage feedforward control for MMC-HVDC stability analysis is illustrated. Then, the impact of control parameters on MMC-HVDC impedance is discussed, and the boundary conditions of control parameters are also derived. Finally, a method of control parameters design and impedance optimization for MMC-HVDC based on the stability boundary is proposed. Compared to the traditional optimization method, the system stability is further improved by the impedance optimization method proposed this paper. Full article
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Article
Relay Protection Setting Calculation System for Nuclear Power Plant Based on B/S Architecture and Cloud Computing
Energies 2022, 15(24), 9648; https://doi.org/10.3390/en15249648 - 19 Dec 2022
Viewed by 346
Abstract
Nuclear power plants have a complex structure and changeable operation mode, which induces low setting calculation efficiency. After analyzing the technology, architecture, and functional logic of a variety of relay protection setting calculation systems and combining the characteristics of the setting calculation of [...] Read more.
Nuclear power plants have a complex structure and changeable operation mode, which induces low setting calculation efficiency. After analyzing the technology, architecture, and functional logic of a variety of relay protection setting calculation systems and combining the characteristics of the setting calculation of nuclear power plants, the relay protection setting calculation system in nuclear power plants based on B/S architecture and cloud computing is studied in this paper. The system adopts three-tier B/S architecture, applies two key technologies, the cloud computing task distribution synchronization mechanism and the cloud component automatic assembly mechanism, and introduces a particle swarm optimization algorithm to provide technical support for nuclear power plant setting calculation; the running example of the nuclear power plant system fully proves the efficiency and reliability of the relay protection setting calculation system of the nuclear power plant, which has high practical value. Full article
(This article belongs to the Topic Power System Protection)
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Article
Relationship among Economic Growth, Energy Consumption, CO2 Emission, and Urbanization: An Econometric Perspective Analysis
Energies 2022, 15(24), 9647; https://doi.org/10.3390/en15249647 - 19 Dec 2022
Viewed by 365
Abstract
The key goal of this research was to figure out the short and long run relationship between environmental degradation caused by carbon dioxide (CO2) emissions and energy consumption, the level of GDP economic growth, and urbanization in the Visegrad Region countries [...] Read more.
The key goal of this research was to figure out the short and long run relationship between environmental degradation caused by carbon dioxide (CO2) emissions and energy consumption, the level of GDP economic growth, and urbanization in the Visegrad Region countries (V4). The study used data from the years 1996–2020. In the methodological area, ARDL bound test, and ARDL and ECM models were used to determine the directions and strength of interdependence. The results show that in the case of some V4 countries (Poland, Slovakia, and Hungary), changes in the urbanization rate affect CO2 emissions. Moreover, it was confirmed that the phenomenon of urbanization influences the enhanced energy consumption in the studied countries. In the case of individual countries, these relationships were varied, both unidirectional and bidirectional. Their nature was also varied—there were both long and short-term relationships. These findings suggest that the V4 countries should increase renewable and ecological energy sources. It is also recommended to enhancement energy savings in the areas of both individual and industrial consumption by promoting low-emission solutions. This should be done while considering changes in urbanization. Full article
(This article belongs to the Topic Energy Economics and Sustainable Development)
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Review
Electromagnetic Surveys for Petroleum Exploration: Challenges and Prospects
Energies 2022, 15(24), 9646; https://doi.org/10.3390/en15249646 - 19 Dec 2022
Viewed by 335
Abstract
Transient electromagnetic (TEM) surveys constitute an important element in exploration projects and can be successfully used in the search for oil and gas. Different modifications of the method include shallow (sTEM), 2D, 3D, and 4D (time-lapse) soundings. TEM data allow for solving a [...] Read more.
Transient electromagnetic (TEM) surveys constitute an important element in exploration projects and can be successfully used in the search for oil and gas. Different modifications of the method include shallow (sTEM), 2D, 3D, and 4D (time-lapse) soundings. TEM data allow for solving a large scope of problems for estimating resources and reserves of hydrocarbons, discriminating reservoir rocks, detecting tectonic features, and characterizing drilling conditions. TEM surveys are applicable at all stages, from initial prospecting to production, and are especially efficient when combined with seismic surveys. Each stage has its specific objectives: estimation of net pay thickness, porosity, and fluid type during prospecting, optimization of well placement and prediction of drilling conditions in exploration, and monitoring of flooding during production. Electromagnetic soundings resolve permafrost features well and thus have a high potentiality for exploration in the Arctic petroleum province. At the first reconnaissance stage of regional prospecting in East Siberia, electromagnetic and seismic data were used jointly to map the junction of the Aldan basin (part of the Aldan-Maya foredeep) with the eastern slope of the Aldan uplift and to constrain the limits of Neoproterozoic sediments. The TEM-based images revealed reservoir rocks in the Upper and Middle Neoproterozoic strata. TEM data have implications for the amount of in-place oil and gas resources in prospects, leads, and plays (Russian categories D1–3) at the prospecting and exploration stages and contingent recoverable reserves (C2) during exploration (latest stage). The contribution of the TEM survey to oil and gas evaluation is quantified via economic variables, such as the value of information (VOI) and expected monetary value (EMV). Full article
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Review
Review of Energy Deposition for High-Speed Flow Control
Energies 2022, 15(24), 9645; https://doi.org/10.3390/en15249645 - 19 Dec 2022
Viewed by 419
Abstract
Energy deposition for flow and flight control has received significant interest in the past several decades due to its potential application to high-speed flow and flight control. This paper reviews recent progress and recommends future research. Full article
(This article belongs to the Special Issue Supersonic Flow Control Using Energy Deposition)
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Article
A Study on a Design Considering the Transient State of a Line-Start Permanent Magnet Synchronous Motor Satisfying the Requirements of the IE4 Efficiency Class
Energies 2022, 15(24), 9644; https://doi.org/10.3390/en15249644 - 19 Dec 2022
Viewed by 418
Abstract
In this paper, the transient state analysis of a Line-Start Permanent Magnet Synchronous Motor (LSPMSM) and the optimum design for high efficiency were studied. In the case of an LSPMSM, aluminum bars and permanent magnets are inserted in the rotor. Since it has [...] Read more.
In this paper, the transient state analysis of a Line-Start Permanent Magnet Synchronous Motor (LSPMSM) and the optimum design for high efficiency were studied. In the case of an LSPMSM, aluminum bars and permanent magnets are inserted in the rotor. Since it has aluminum bars, it can be directly started on-line without closed-loop control at the time of starting, like an induction motor. Furthermore, once driven, it rotates at a synchronous speed due to the permanent magnets in the steady state. Theoretically, since the rotor bars have no induced current, copper loss does not occur in the rotor bars. Further, because of the inserted permanent magnets, an LSPMSM has a higher power density than an induction motor with the same output power. However, since it is driven directly on-line, the transient state is longer than that of a synchronous motor driven by an inverter. Therefore, it is important to analyze the characteristics of the transient state depending on the rotor shape in the LSPMSM design. In this study, an LSPMSM that has the same outer diameter of a 7.5 kW IE3 efficiency class induction motor currently used for the industry was designed. The optimal design of the motor was designed using Finite-Element Analysis (FEA) and Design of Experiment (D.O.E). In the design process, the velocity ripple was minimized in the transient state, and the steady state was quickly reached. Finally, the efficiency of the motor satisfies the requirements of the IE4 efficiency class, an efficiency standard described in IEC 60034-30, which is an international standard. Full article
(This article belongs to the Special Issue Regulations and Advances in High Performance Electric Motor and Drive)
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Article
Memory Effect: How the Initial Structure of Nanoparticles Affects the Performance of De-Alloyed PtCu Electrocatalysts?
Energies 2022, 15(24), 9643; https://doi.org/10.3390/en15249643 - 19 Dec 2022
Viewed by 369
Abstract
An important feature of this research is the investigation of the de-alloyed catalysts based on the nanoparticles with a simple structure (alloy) and a complex structure (gradient). The resulting samples exhibit the 2–4 times higher mass activity in the ORR compared with the [...] Read more.
An important feature of this research is the investigation of the de-alloyed catalysts based on the nanoparticles with a simple structure (alloy) and a complex structure (gradient). The resulting samples exhibit the 2–4 times higher mass activity in the ORR compared with the commercial Pt/C. The novelty of this study is due to the application of the express-electrochemical experiment to register the trend of changes in the ORR activity caused by rearranging the structure of bimetallic nanoparticles. The state-of-the-art protocol makes it possible to establish the dependence of properties of the de-alloyed catalysts on the nanoparticles’ structure obtained at the stage of the material’s synthesis. The study shows the possibility of determining the rate of the ongoing reorganization of bimetallic nanoparticles with different architectures. The PtCu/C electrocatalysts for proton-exchange membrane fuel cells presented in this work are commercially promising in terms of both the high functional characteristics and the production by facile one-pot methods. Full article
(This article belongs to the Special Issue Design and Application of Nanoporous Energy Materials)
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Article
Smart Contract Vulnerability Detection Model Based on Siamese Network (SCVSN): A Case Study of Reentrancy Vulnerability
Energies 2022, 15(24), 9642; https://doi.org/10.3390/en15249642 - 19 Dec 2022
Viewed by 493
Abstract
Blockchain technology is currently evolving rapidly, and smart contracts are the hallmark of the second generation of blockchains. Currently, smart contracts are gradually being used in power system networks to build a decentralized energy system. Security is very important to power systems and [...] Read more.
Blockchain technology is currently evolving rapidly, and smart contracts are the hallmark of the second generation of blockchains. Currently, smart contracts are gradually being used in power system networks to build a decentralized energy system. Security is very important to power systems and attacks launched against smart contract vulnerabilities occur frequently, seriously affecting the development of the smart contract ecosystem. Current smart contract vulnerability detection tools suffer from low correct rates and high false positive rates, which cannot meet current needs. Therefore, we propose a smart contract vulnerability detection system based on the Siamese network in this paper. We improved the original Siamese network model to perform smart contract vulnerability detection by comparing the similarity of two sub networks with the same structure and shared parameters. We also demonstrate, through extensive experiments, that the model has better vulnerability detection performance and lower false alarm rate compared with previous research results. Full article
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Article
Experimental Performance Evaluation of an Integrated, LCPV/T Membrane Distillation System for Electricity and Seawater Desalination
Energies 2022, 15(24), 9641; https://doi.org/10.3390/en15249641 - 19 Dec 2022
Viewed by 378
Abstract
In this paper, an integrated system based on low-concentrated photovoltaic/thermal (LCPV/T) technology and efficient vacuum membrane distillation (VMD) seawater desalination utilizing the energy of solar is established. Through a theoretical analysis and a series of experiments, this paper explores the temperature change of [...] Read more.
In this paper, an integrated system based on low-concentrated photovoltaic/thermal (LCPV/T) technology and efficient vacuum membrane distillation (VMD) seawater desalination utilizing the energy of solar is established. Through a theoretical analysis and a series of experiments, this paper explores the temperature change of a single VMD process, and the variation trend of single-day membrane flux with solar irradiation and temperature parameters. In addition, the changes in solar irradiation, temperatures of the integrated system, membrane flux, and thermoelectric properties in different seasons are also analyzed. A mathematical model was established to calculate the relationship between membrane flux and temperature difference. The experimental results show that the membrane flux of VMD is 2.73 L/(m2·h); the simulated seawater can achieve a desalination rate of 99.9%. After economic analysis, the operating incomes of the system under sunny weather conditions in different seasons were all positive. Full article
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Article
Study of the Technologies for Freeze Protection of Cooling Towers in the Solar System
Energies 2022, 15(24), 9640; https://doi.org/10.3390/en15249640 - 19 Dec 2022
Viewed by 418
Abstract
A cooling tower is an important guarantee for the proper operation of a solar system. To ensure proper operation of the system and to maintain high-efficiency points, the cooling tower must operate year-round. However, freezing is a common problem that degrades the performance [...] Read more.
A cooling tower is an important guarantee for the proper operation of a solar system. To ensure proper operation of the system and to maintain high-efficiency points, the cooling tower must operate year-round. However, freezing is a common problem that degrades the performance of cooling towers in winter. For example, the air inlet forms hanging ice, which clogs the air path, and the coil in closed cooling towers freezes and cracks, leading to water leakage in the internal circulation. This has become an intractable problem that affects the safety and performance of cooling systems in winter. To address this problem, three methods of freeze protection for cooling towers are studied: (a) the dry and wet mixing operation method—the method of selecting heat exchangers under dry operation at different environments and inlet water temperatures is presented. The numerical experiment shows that the dry and wet mixing operation method can effectively avoid ice hanging on the air inlet. (b) The engineering plastic capillary mats method—its freeze protection characteristics, thermal performance, and economics are studied, and the experiment result is that polyethylene (PE) can meet the demands of freeze protection. (c) The antifreeze fluid method—the cooling capacity of the closed cooling towers with different concentrations of glycol antifreeze fluid is numerically studied by analyzing the heat transfer coefficient ratio, the air volume ratio, the heat dissipation ratio, and the flow rate ratio. The addition of glycol will reduce the cooling capacity of the closed cooling tower. Full article
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Article
Economic and Low-Carbon-Oriented Distribution Network Planning Considering the Uncertainties of Photovoltaic Generation and Load Demand to Achieve Their Reliability
Energies 2022, 15(24), 9639; https://doi.org/10.3390/en15249639 - 19 Dec 2022
Viewed by 782
Abstract
The integration of renewable resources with distribution networks (DNs) is an effective way to reduce carbon emissions in energy systems. In this paper, an economic and low-carbon-oriented optimal planning solution for the integration of photovoltaic generation (PV) and an energy storage system (ESS) [...] Read more.
The integration of renewable resources with distribution networks (DNs) is an effective way to reduce carbon emissions in energy systems. In this paper, an economic and low-carbon-oriented optimal planning solution for the integration of photovoltaic generation (PV) and an energy storage system (ESS) in DNs is proposed. A convolutional neural network (CNN)-based prediction model is adopted to characterize the uncertainties of PV and load demand in advance. Then, taking the lowest total economic cost, the largest carbon emission reduction, and the highest system power supply reliability as the optimization objectives, the optimal distribution network planning model is constructed. The improved multi-objective particle swarm optimization (MOPSO) algorithm is used to solve the optimization model, and the effectiveness of the proposed solution is confirmed through a comparative case study on the IEEE-33 bus system. Simulation results show that the proposed solution can better maintain the balance between economic cost and carbon emissions in DNs. Full article
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Article
A HELIOS-Based Dynamic Salt Clean-Up Study Analysing the Effects of a Plutonium-Based Initial Core for iMAGINE
Energies 2022, 15(24), 9638; https://doi.org/10.3390/en15249638 - 19 Dec 2022
Viewed by 379
Abstract
Nuclear technologies have strong potential and a unique role to play in delivering reliable low carbon energy to enable a net-zero society for future generations. However, to assure the sustainability required for its long-term success, nuclear will need to deliver innovative solutions as [...] Read more.
Nuclear technologies have strong potential and a unique role to play in delivering reliable low carbon energy to enable a net-zero society for future generations. However, to assure the sustainability required for its long-term success, nuclear will need to deliver innovative solutions as proposed in iMAGINE. One of the most attractive features, but also a key challenge for the envisaged highly integrated nuclear energy system iMAGINE, is the need for a demand driven salt clean-up system based on the principles of reverse reprocessing. The work described provides an insight into the dynamic interplay between a potential salt clean-up system and reactor operation in a plutonium-started core in a dynamic approach. The results presented will help to optimise the parameters for the salt clean-up process as well as to understand the differences which appear between a core started with enriched uranium and plutonium as the fissile material. The integrated model is used to investigate the effects of the initial fissile material on core size, achievable burnup, and long-term operation. Different approaches are tested to achieve a higher burnup in the significantly smaller Pu-driven core. The effects of different clean-up system throughputs on the concentration of fission products in the reactor salt and its consequences are discussed for general molten salt reactor design. Finally, an investigation into how a plutonium loaded core could be used to provide fuel for future reactors through fuel salt splitting is presented, with the outcome that one Pu-started reactor of the same size as a uranium-started core could deliver fuel for 1.5 new cores due to enhanced breeding. The results provide an essential understanding for the progress of iMAGINE as well as the basis for inter-disciplinary work required for optimising iMAGINE. Full article
(This article belongs to the Section B4: Nuclear Energy)
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Article
Research on Vibration Characteristics of an Underground Powerhouse of Large Pumped-Storage Power Station
Energies 2022, 15(24), 9637; https://doi.org/10.3390/en15249637 - 19 Dec 2022
Viewed by 335
Abstract
With the rapid development of pumped storage, the vibration problems caused by the operation of power stations have become increasingly prominent. In this paper, a large-scale pumped-storage power station is taken as the research object, and a three-dimensional refined finite element model of [...] Read more.
With the rapid development of pumped storage, the vibration problems caused by the operation of power stations have become increasingly prominent. In this paper, a large-scale pumped-storage power station is taken as the research object, and a three-dimensional refined finite element model of the underground powerhouse including the surrounding rock mass is established. Based on the analysis of the vibration source of the powerhouse and the water diversion pipeline, the modal and dynamic response analysis of the underground powerhouse of the hydropower station is carried out, and the distribution law of the larger vibration displacement position is revealed. The calculation results show that under the premise that the vibration source is selected reasonably and the numerical model is accurate, the main frequency of the underground powerhouse structure can be obtained more accurately. After optimizing the design of the underground powerhouse based on the calculation results, the resonance problem of the underground powerhouse of the hydropower station can be avoided. The dynamic elastic modulus of the rock mass around the underground powerhouse has little influence on the mode shape of the powerhouse, but has a great influence on its fundamental frequency. When the dynamic elastic modulus of the rock mass increases by 50%, the fundamental frequency of the plant increases by about 29%. At the same time, the mode shape of each order of the underground powerhouse structure does not change much, mainly manifested as the vibration of the beam system structure, which is mainly caused by the stiffness of the beam system components being much smaller than the structural stiffness of the windshield, machine pier, and mass concrete around the volute. The research results can provide references for the design of underground powerhouses of large-scale pumped-storage power stations and the analysis of vibration problems. Full article
(This article belongs to the Section A: Sustainable Energy)
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Review
Possibilities of Using Whey Wastes in Agriculture: Case of Turkey
Energies 2022, 15(24), 9636; https://doi.org/10.3390/en15249636 - 19 Dec 2022
Viewed by 479
Abstract
Liquid wastes are generated during production in the milk and cheese industries. During cheese production, whey emerges as a liquid product. Researchers define waste as raw material instead of waste alone. Hence, there is no doubt that the use and management of waste [...] Read more.
Liquid wastes are generated during production in the milk and cheese industries. During cheese production, whey emerges as a liquid product. Researchers define waste as raw material instead of waste alone. Hence, there is no doubt that the use and management of waste will gain greater importance in the upcoming years. This study discusses the use of whey, which is food waste, in agriculture and the benefits derived from it in terms of energy value. Our research was based on the current literature and the amount of whey that emerged in the dairy industry. For this purpose, the existing literature was evaluated to determine how much waste was produced from whey. The total amount of whey waste in Turkey for 2021 was determined. Afterwards, the amount of potential energy was determined in evaluating these wastes. Turkey’s total amount of potential energy obtained from whey waste was calculated as 570.11 × 106 MJ, with 158.36 × 106 kWh as potential electrical energy. Moreover, it was calculated that a total of 158.36 × 106 kWh of electrical energy would meet the electrical energy of 688,548 families of four people for a month. It is also stated that this potential energy will be used in the field of equivalent electrical energy content and agriculture. It is a fact that cheese wastewater, rich in nutrients and organic matter, can be used in agriculture. Whey is used as animal feed in agricultural fertilization activities and the livestock sector. It has also been understood from the literature that it can also be used in biogas production. However, it should not be forgotten that whey released into rivers, water sources, or sewers threatens the environment due to its high protein content. Therefore, by increasing the number of similar studies on the subject, a wide range of wastes, such as whey, can be utilized in the most accurate manner. As a result, environmental protection, conservation of water resources, and energy conservation can be ensured by properly benefiting from whey waste. Considering that the world population will increase in the future, it is a fact that we will need a cleaner environment and more energy. It was concluded that greater importance should be given to waste management practices for a cleaner environment and energy saving. Full article
Article
Generator Fault Classification Method Based on Multi-Source Information Fusion Naive Bayes Classification Algorithm
Energies 2022, 15(24), 9635; https://doi.org/10.3390/en15249635 - 19 Dec 2022
Viewed by 320
Abstract
The existing motor fault classification methods mostly use sensors to detect a single fault feature, which makes it difficult to ensure high diagnostic accuracy. In this paper, a motor fault classification method based on multi-source information fusion Naive Bayes classification algorithm is proposed. [...] Read more.
The existing motor fault classification methods mostly use sensors to detect a single fault feature, which makes it difficult to ensure high diagnostic accuracy. In this paper, a motor fault classification method based on multi-source information fusion Naive Bayes classification algorithm is proposed. Firstly, this paper introduces the concept and advantages of multi-source information fusion, as well as its problems of miscellaneous information and inconsistent data magnitude. For example, as this paper classifies the fault of generators, there are many physical quantities, such as voltage, current and temperature, which are not in the same dimension, therefore it is difficult to fuse. Then, aiming at the corresponding problems, this paper uses a PCA dimension reduction method to remove redundant information and reduce the dimension of multi-dimensional complex information. Aiming at the problem of unequal data magnitude, the interval mapping method is adopted to effectively solve the misjudgment caused by unequal data magnitude. After the initial multi-source information processing, the classical Naive Bayes classification algorithm is used for fault classification, and the algorithm diagnosis and verification are carried out according to the statistical fault data. Use of the algorithm increases accuracy to more than 97%. Full article
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Article
Energy, Exergy Efficiency and Thermal-Electrical Production Assessment for an Active Water Heating System Using Four PV/T Module Models
Energies 2022, 15(24), 9634; https://doi.org/10.3390/en15249634 - 19 Dec 2022
Viewed by 506
Abstract
In order to objectively reflect the energy utilization performance of an active water heating system (AWHS) using photovoltaic/thermal (PV/T) modules, this study proposes a new evaluation method based on energy efficiency, exergy efficiency and thermal-electrical output of a system in year-round weather conditions. [...] Read more.
In order to objectively reflect the energy utilization performance of an active water heating system (AWHS) using photovoltaic/thermal (PV/T) modules, this study proposes a new evaluation method based on energy efficiency, exergy efficiency and thermal-electrical output of a system in year-round weather conditions. Four samples of PV/T modules were surveyed to compare and evaluate the effectiveness of the system, called MD1, MD2, MD3 and MD4, respectively. The simulation program was developed to suit four types of PV/T modules and MATLAB was used as the programming language. The water flow through the four PV/T module samples and the hot water tank volume were investigated for the highest exergy efficiency of the system. The final results illustrate that in the weather conditions of Ho Chi Minh City, Vietnam, the system has the highest energy efficiency, exergy efficiency and thermal output when using MD1 with 57.85%, 15.67% and 2.93 kWh/m2/day, respectively, while the system has highest electrical output when using MD3 with 0.8 kWh/m2/day. In addition, under stable conditions ignoring heat loss, MD1 has the highest thermal efficiency with 54.85% and MD3 type has the highest electrical efficiency with 13.67%. Full article
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Article
Peer-to-Peer Trading for Energy-Saving Based on Reinforcement Learning
Energies 2022, 15(24), 9633; https://doi.org/10.3390/en15249633 - 19 Dec 2022
Viewed by 826
Abstract
This paper proposes a new peer-to-peer (P2P) energy trading method between energy sellers and consumers in a community based on multi-agent reinforcement learning (MARL). Each user of the community is treated as a smart agent who can choose the amount and the price [...] Read more.
This paper proposes a new peer-to-peer (P2P) energy trading method between energy sellers and consumers in a community based on multi-agent reinforcement learning (MARL). Each user of the community is treated as a smart agent who can choose the amount and the price of the electric energy to sell/buy. There are two aspects we need to examine: the profits for the individual user and the utility for the community. For a single user, we consider that they want to realise both a comfortable living environment to enhance happiness and satisfaction by adjusting usage loads and certain economic benefits by selling the surplus electric energy. Taking the whole community into account, we care about the balance between energy sellers and consumers so that the surplus electric energy can be locally absorbed and consumed within the community. To this end, MARL is applied to solve the problem, where the decision making of each user in the community not only focuses on their own interests but also takes into account the entire community’s welfare. The experimental results prove that our method is profitable both both the sellers and buyers in the community. Full article
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Article
The Influence of Particle Size and Hydrate Formation Path on the Geomechanical Behavior of Hydrate Bearing Sands
Energies 2022, 15(24), 9632; https://doi.org/10.3390/en15249632 - 19 Dec 2022
Viewed by 556
Abstract
Determining the geomechanical properties of hydrate-bearing sands (HBS), such as strength and stiffness, are critical for evaluating the potential for the economic and safe recovery of methane gas from HBS reservoirs. To date, results from numerous independent laboratory studies on synthesized HBS have [...] Read more.
Determining the geomechanical properties of hydrate-bearing sands (HBS), such as strength and stiffness, are critical for evaluating the potential for the economic and safe recovery of methane gas from HBS reservoirs. To date, results from numerous independent laboratory studies on synthesized HBS have shown that strength and stiffness are largely influenced by hydrate saturation, the method adopted for hydrate formation, and to a lesser extent, the confining stresses applied during testing. However, a significant scatter is observed in the data even when these conditions are similar. These include recent studies on natural HBS where sands with larger particle size distribution (PSD) exhibited higher strengths despite lower hydrate saturation. To investigate the impact of PSD, and the role that specific hydrate formation conditions might impose, on the strength and stiffness of HBS, a series of laboratory tests were carried out on sand specimens formed with different particle size distributions and utilizing different approaches for forming gas saturated HBS. The laboratory apparatus included a resonant column drive head to measure the small-strain stiffness of the specimen during hydrate formation, and subsequent drained compressional shearing to capture the stress-strain response of the HBS. Results indicate that the PSD significantly affects both the stiffness evolution (during hydrate formation) and peak strength at failure after formation compared to the effect of the methodology adopted for hydrate formation. These observations improve our understanding of the geomechanical behavior of laboratory-synthesized HBS and allow more robust relationships to be developed between them and natural HBS. This may aid in the development of economic and safe methane gas production methods to help realize the energy resource potential of HBS reservoirs. Full article
(This article belongs to the Special Issue Gas Hydrate Energy Technologies for Net-Zero Carbon Emissions)
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Article
Impact of a HVDC Link on the Reliability of the Bulk Nigerian Transmission Network
Energies 2022, 15(24), 9631; https://doi.org/10.3390/en15249631 - 19 Dec 2022
Viewed by 386
Abstract
Regular and reliable access to energy is critical to the foundations of a stable and growing economy. The Nigerian transmission network generates more electricity than is consumed but, due to unpredicted outages, customers are often left without electrical power for several hours during [...] Read more.
Regular and reliable access to energy is critical to the foundations of a stable and growing economy. The Nigerian transmission network generates more electricity than is consumed but, due to unpredicted outages, customers are often left without electrical power for several hours during the year. This paper aims to assess the present reliability indices of the Nigerian transmission network, and to determine the impact of HVDCs on system reliability. In the first part of this paper, the reliability of the Nigerian transmission system is quantified by building a model in DIgSILENT PowerFactory and carrying out a reliability study based on data provided by the Nigerian transmission-system operator. Both network indices and load-point indices are evaluated, and the weakest points in the network are identified. In the second part of the paper, an HVDC model is built and integrated into the existing network at the locations identified by the reliability study. A comparative study using two different HVDC connections is then carried out, to determine the critical impact of HVDC on system reliability. The reliability results indicate that the weakest points of the transmission system are the radial feeders, and the highest impact could be achieved by spanning an HVDC line between two busbars located at the two extremes of a radial feeder: Azura and Yola. Full article
(This article belongs to the Special Issue Power Systems Flexibility, Reliability, and Resilience)
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Review
Assessment of Reliability Indicators of Combined Systems of Offshore Wind Turbines and Wave Energy Converters
Energies 2022, 15(24), 9630; https://doi.org/10.3390/en15249630 - 19 Dec 2022
Cited by 1 | Viewed by 632
Abstract
Marine renewable sources can make a significant contribution to the development of electrical energy generation and can increase the power supply reliability of mineral complexes. The development of alternative energy sources is happening at a fast pace, and this is due to the [...] Read more.
Marine renewable sources can make a significant contribution to the development of electrical energy generation and can increase the power supply reliability of mineral complexes. The development of alternative energy sources is happening at a fast pace, and this is due to the improvement of technologies that allow for generating more energy and operating in more extreme conditions, with almost no negative effect on the environment. However, currently, renewable sources are not able to meet all the energy requirements of the platforms. Hence, a key point is to gradually introduce and develop new technologies. This article explores the advantages of combining power generation by wave converters and offshore wind turbines. It investigates the possibilities of improving the combined systems’ reliabilities through justification of their mutual topology and accounting for the shadow effect from the wave installations. Full article
(This article belongs to the Section A3: Wind, Wave and Tidal Energy)
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Article
The Application of a Multi-Criteria Decision-Making for Indication of Directions of the Development of Renewable Energy Sources in the Context of Energy Policy
Energies 2022, 15(24), 9629; https://doi.org/10.3390/en15249629 - 19 Dec 2022
Viewed by 596
Abstract
This paper presents the application of multi-criteria decision-making (MCDM) for evaluating what technologies using renewable energy sources (RES) for electricity production have the chance to develop in Poland under the current socio-economic conditions. First, the Analytical Hierarchy Process (AHP) method was used to [...] Read more.
This paper presents the application of multi-criteria decision-making (MCDM) for evaluating what technologies using renewable energy sources (RES) for electricity production have the chance to develop in Poland under the current socio-economic conditions. First, the Analytical Hierarchy Process (AHP) method was used to determine the weights of the optimization criteria. Five main criteria and 30 sub-criteria were identified. Next, the authors modified numerical taxonomy (NT) to rank eight RES technologies (such as onshore and offshore wind farms, photovoltaics, or biogas plants). The results show that offshore wind farms are the RES technology with the greatest development opportunities in Poland. The following three technologies: distributed photovoltaic energy, biogas plants, and biomass power plants, respectively, received a similar rating in the ranking. Hydropower and geothermal were the lowest-ranked technologies. The ranking, which is the result of multi-criteria analysis, in several respects, is significantly different from the directions of activities indicated in the state energy policy. Full article
(This article belongs to the Special Issue Sustainable Development, Energy Economics and Economic Analysis)
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Article
Sliding Mode Input Current Control of the Synchronous DC-DC Buck Converter for Electro-Mechanical Actuator Emulation in More Electric Aircrafts
Energies 2022, 15(24), 9628; https://doi.org/10.3390/en15249628 - 19 Dec 2022
Viewed by 375
Abstract
The main challenges of the input current control in synchronous DC-DC buck converters are the nonlinear model of the system, changes of the operating point in a wide range, and the need to use an input LC filter for current smoothing, which may [...] Read more.
The main challenges of the input current control in synchronous DC-DC buck converters are the nonlinear model of the system, changes of the operating point in a wide range, and the need to use an input LC filter for current smoothing, which may result in the instability of the closed-loop system. In this paper, a step-by-step approach is developed for the design and improvement of a PI-feedforward closed-loop controller. It is shown that a linear PI controller cannot stabilize the closed-loop system properly during wide changes in model parameters, e.g., an equivalent series resistance of the input filter. To cope with the stability issues, a fixed-frequency sliding mode controller (SMC) has been developed in this paper for the implementation of an electro-mechanical actuator (EMA) emulator. Moreover, a systematic approach is proposed for controller tuning and the selection of the SMC’s gains. To achieve high power efficiency, high-frequency GaN switches are used for the practical implementation of the DC-DC converter. Despite large changes in the load current, the designed nonlinear controller can track the input current reference satisfactorily. Steady-state and dynamic responses of the proposed SMC are compared with conventional linear controllers. Considering the Lyapunov stability theorem, it is proved that the designed SMC can stabilize the closed-loop system in the entire utilizable domain. The proposed nonlinear SMC controller enjoys a very simple control law. Hence, despite having very high switching and sampling frequencies, it can be easily implemented. The experimental response of the designed synchronous DC-DC buck converter is evaluated experimentally by implementing the control strategy in a TMS320F28335PGFA DSP from Texas Instrument. Moreover, the comprehensive comparison of the proposed SMC controller and a PI-feedforward controller proved the superior performance of the developed closed-loop system, in terms of the transient time response, robustness, and stability of the EMA emulator. Full article
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