Reliability of the multilevel inverters (MLIs) is one of the most important concerns in industrial applications, mainly due to the semiconductor devices. Whenever a fault occurs in one of the switches of the inverter, it leads to abnormal conditions and can also cause serious damage to the equipment connected to the multilevel inverter. In this paper, a recently proposed nine-level Packed-E-Cell (PEC) multilevel inverter topology is investigated for its fault-tolerant capability and improved reliability. The analysis is carried out for a reduced device multilevel inverter topology that, due to a lack of redundant states, cannot tolerate switch failures. The fault-tolerant (FT) topology provides additional redundant states in the switching sequence of the existing topology. The work in this paper presents Packed-E-Cell MLI modified for fault tolerance against single-switch open-circuit faults. The modified FT topology inherently achieves self-voltage balance in the DC-link capacitors. N... [more]

The Korean government is committed to advance the country’s energy transition to greener energy by increasing the share of renewable electricity to 20 percent by 2030 and to 30−35 percent by 2040. Achieving these goals will necessitate flexibility in energy markets as well as innovative business models and technological solutions. Peer-to-peer (P2P) electricity trading platforms (ETPs) are rapidly gaining traction, as they enable the integration of distributed energy sources into power systems. This study explores whether South Koreans are willing to participate in a hypothetical P2P ETP, which allows prosumers (who both consume and produce electricity) to trade electricity surpluses with their neighbours or with KEPCO (Korea Electric Power Corporation). We employ a choice experiment (CE) to examine respondent heterogeneous preferences and their willingness to pay (WTP) for a hypothetical P2P ETP in South Korea. Our findings indicate that two-thirds of total respondents in our CE are i... [more]

This work aims to investigate the effect of process temperature and catalyst content by pyrolysis and thermal catalytic cracking of (organic matter + paper) fraction from municipal household solid waste (MHSW) on the yields of reaction products (bio-oil, bio-char, H2O, and gas), acid value, chemical composition of bio-oils, and characterization of bio-chars in laboratory scale. The collecting sectors of MHSW in the municipality of Belém-Pará-Brazil were chosen based on geographic and socio-economic database. The MHSW collected and transported to the segregation area. The gravimetric analysis of MHSW was carried out and the fractions (Paper, Cardboard, Tetra Pack, Hard Plastic, Soft Plastic, Metal, Glass, Organic Matter, and Inert) were separated. The selected organic matter and paper were submitted to pre-treatment of crushing, drying, and sieving. The experiments carried out at 400, 450, and 475 °C and 1.0 atmosphere, and at 475 °C and 1.0 atmosphere, using 5.0, 10.0, and 15.0% (wt.)... [more]

Hydroelectric power plants (HEPPs) are renewable energy power plants with the highest installed power in the world. The control systems are responsible for stopping the relevant unit safely in case of any malfunction while ensuring the desired operating point. Conventional control systems detect anomalies at certain limits or predefined threshold values by evaluating analog signals regardless of differences caused by operating conditions. In this study, using real data from a large hydro unit (>150 MW), a normal behavior model of a hydraulic governor’s oil circulation in an operational HEPP is created using several machine learning methods and historical data obtained from the HEPP’s SCADA system. Model outputs resulted in up to 96.45% success of prediction with less than 1% absolute deviation from actual measurements and an R2 score of 0.985 with the random forest regression method. This novel approach makes the model outputs far more appropriate to use as an active threshold value ch... [more]

Aiming to design a generator with high reliability, high efficiency, and especially a constant output voltage over a wide speed range for hybrid electric vehicles (HEVs), this paper proposes a novel topology of a hybrid excitation doubly salient generator with separate windings (HEDSGSW). The topology herein utilizes a hybrid excitation type of PMs and DC windings to generate parallel magnetic circuits. In addition, PMs are embedded in the magnetic bridge to insulate the excitation windings with armature windings. This design can achieve compactness, efficiency, and especially constant output capability over a wide speed range. The geometry and flux regulation principles, including magnetic flux circuits, are elaborated. After comparing three power generation modes, the most suitable mode, namely, the doubly salient generation 2 (DSG2) mode, is confirmed to ensure a stable voltage output performance. Then, considering the non-uniformity effect of the stator and rotor slots, the no-load... [more]

Nanoparticles are useful in improving the efficiency of convective heat transfer. The current study addresses this gap by making use of an analogy between Al2O3 and γ-Al2O3 nanoparticles in various base fluids across a stretched sheet conjunction with f. Base fluids include ethylene glycol and water. We address, for the first time, the stagnation-point flow of a boundary layer of γ-Al2O3 nanofluid over a stretched sheet with slip boundary condition. Al2O3 nanofluids employ Brinkman viscosity and Maxwell’s thermal conductivity models with thermal radiations, whereas γ-Al2O3 nanofluids use viscosity and thermal conductivity models generated from experimental data. For the boundary layer, the motion equation was solved numerically using the fourth-order Runge−Kutta method and the shooting approach. Plots of the velocity profile, temperature profile, skin friction coefficient and reduced Nusselt number are shown. Simultaneous exposure of the identical nanoparticles to water and ethylene gl... [more]

The proposed anthraquinone-bromate cell combines the advantages of anthraquinone-bromine redox flow batteries and novel hybrid hydrogen-bromate flow batteries. The anthraquinone-2,7-disulfonic acid is of interest as a promising organic negolyte due its high solubility, rapid kinetics of electrode reactions and suitable redox potentials combined with a high chemical stability during redox reactions. Lithium or sodium bromates as posolytes provide an anomalously high discharge current density of order ~A cm−2 due to a novel autocatalytic mechanism. Combining these two systems, we developed a single cell of novel anthraquinone-bromate flow battery, which showed a power density of 1.08 W cm−2, energy density of 16.1 W h L−1 and energy efficiency of 72% after 10 charge−discharge cycles.

Online monitoring of Partial Discharges (PDs) in rotating electrical machines is an useful tool for machine prognosis, as it presents reduced costs compared to intrusive inspections and is associated with relevant problems. Although this monitoring method has been developed for almost 50 years, the recent advancements in processes automation and signal processing techniques allow improvements that are still being studied by academic and industrial researchers. To analyze the current context of PDs monitoring, this article presents a literature review based on concepts of PDs in rotating machines, data acquisition techniques, state-of-the art commercial equipment, and recent methodologies for detection and pattern recognition of PDs. The challenges identified in the literature that motivate the development of more reliable and robust PD monitoring systems are presented and discussed.

A novel approach has been proposed for improving the performance of lithium-sulfur batteries (LSBs) with a carbon-based material as an interlayer between the cathode and separator. With this method, the cross-over of lithium polysulfides (LiPS) to the anode is suppressed, increasing reutilization of the sulfur cathode. In this study, activated carbons (ACs) were prepared using coffee waste as a carbon source and potassium hydroxide (KOH) as an activation agent at various reaction temperatures ranging from 500 to 800 °C. With the rise in heating temperature, the specific surface areas, micro-surface areas, and micro-pore volumes of the AC samples gradually increased. In particular, the AC sample prepared at 800 °C and used as a functional separator for LSB exhibited improved capacity and cycling performance while suppressing the LiPS shuttle effect.

This paper presents an improvement of the tuning process of the holistic control published by the authors in previous research to achieve a seamless transition among three operation mode changes and load transients. The proposed tuning approach reveals an improvement in the energy consumption of the Battery Energy Storage System (BESS) during all operation mode transients compared to the holistic control. For this aim, the system addressed is a BESS with the capability to ride through three operation modes of interest: the grid-connected mode as an inverter, the grid-connected mode as a rectifier, and the islanded operation mode. The LCL filter design by using the Butterworth polynomial approach is presented in more detail, and its smooth inherent transient response is preserved when the tuning of the controller gains is carried out by using the same polynomial approach but now including the integral action within the Butterworth polynomial. To reveal the reduction in energy consumptio... [more]

The paper evaluates particulate matter emissions and exhaust gas components from retrofitted engines of non-road vehicles measured under actual operating conditions. The content is divided into three main parts: formation of guidelines, production of the filter and emission tests. The obtained results clearly indicate excess PM and PN emissions from the engine under actual operating conditions when compared to the limits outlined in the type approval standards. Moreover, it was observed that the actual conditions are reflected to a very small extent at the points included in the stationary homologation test cycle. Based on these observations, the authors decided to modify the stationary test cycle. The measured exhaust gas compositions and their mass flow rates were used to create the geometry of the newly developed filter. The paper contains detailed results of the relative specific exhaust emissions of particulate matter and gaseous components at individual engine operating points. T... [more]

A low-performance fuel cell significantly hinders the application and commercialization of fuel cell technology. Computational fluid dynamics modeling could predict and evaluate the performance of a proton exchange membrane fuel cell (PEMFC) with less time consumption and cost-effectiveness. PEMFC performance is influenced by the distribution of reactants, water, heat, and current density. An uneven distribution of reactants leads to the localization of current density that produces heat and water, which are the by-products of the reaction to be concentrated at the location. The simplification of model geometry can affect performance prediction. Numerical investigations are commonly validated with experimental results to validate the method’s accuracy. Poor prediction of PEMFC results has not been discussed. Thus, this study aims to predict the effect of geometry modeling on fuel cell performance. Two contrasting 3D model dimensions, particularly single-channel and small-scale seven-ch... [more]

Energy harvesters serve as continuous and long-lasting sources of energy that can be integrated into wearable and implantable sensors and biomedical devices. This review paper presents the current progress, the challenges, the advantages, the disadvantages and the future trends of energy harvesters which can harvest energy from various sources from the human body. The most used types of energy are chemical; thermal and biomechanical and each group is represented by several nano-generators. Chemical energy can be harvested with a help of microbial and enzymatic biofuel cells, thermal energy is collected via thermal and pyroelectric nano-generators, biomechanical energy can be scavenged with piezoelectric and triboelectric materials, electromagnetic and electrostatic generators and photovoltaic effect allows scavenging of light energy. Their operating principles, power ratings, features, materials, and designs are presented. There are different ways of extracting the maximum energy and c... [more]

A tri-generation system combining cooling, heating, and power generation can contribute to increased system efficiency and thereby reduce greenhouse gas emissions. This study proposed a novel concept using 100-kW polymer electrolyte membrane fuel cells (PEMFCs) as the basis for a tri-generation system with an integrated heat pump and adsorption chiller for greenhouse use. Three configurations of heat pump loop were designed to recover the waste heat from PEMFCs and used either for direct heating or cooling power generation in adsorption cooling. Analyses were carried out in terms of primary energy rate (PER) and exergy efficiencies. Of those investigated, the layout with a heat pump and internal heat exchanger demonstrated the best performance, with PERs of the cooling and heating modes at 0.94 and 0.78, respectively. Additionally, the exergy analysis revealed that the exergies are mostly destroyed at the expansion valve and evaporator due to differences in pressure and temperature. Th... [more]

Oil has historically been the most significant primary energy source for our daily lives and business activities. However, recent skyrocketing oil prices have been one of the greatest concerns among policymakers, business executives, and the general public due to their impacts on daily necessities, including food, clothing, and automobile transportation. As a result, fast-rising inflation on the global scale is attributed to mounting oil prices. Even though many countries have made a conscious effort to tame oil prices and the subsequent inflation, their efforts are often in vain due to some uncontrollable situations. These situations include the ongoing war between Ukraine and Russia, where Russia began weaponizing its oil resources and limiting oil supplies to its neighboring European countries. Faced with the current energy crisis, a growing number of policymakers and business executives have attempted to develop energy-induced risk mitigation strategies. With this in mind, the prim... [more]

With the development of autopilot, the performance of intelligent vehicles is constrained by their inability to perceive blind and beyond visual range areas. Vehicle-to-infrastructure cooperative perception has become an effective method for achieving reliable and higher-level autonomous driving. A vehicle-to-infrastructure cooperative beyond visual range and non-blind area method, based on heterogeneous sensors, was proposed in this study. Firstly, a feature map receptive field enhancement module with spatial dilated convolution module (SDCM), based on spatial dilated convolution, was proposed and embedded into the YOLOv4 algorithm. The YOLOv4-SDCM algorithm with SDCM module achieved a 1.65% mAP improvement in multi-object detection performance with the BDD100K test set. Moreover, the backbone of CenterPoint was improved with the addition of self-calibrated convolutions, coordinate attention, and residual structure. The proposed Centerpoint-FE (Feature Enhancement) algorithm achieved... [more]

The capacity of photovoltaic solar power installations has been boosted last years by reaching a new record with 175 GWdc of newly installed solar power in 2021. To guarantee reliable performances of photovoltaic (PV) plants and maintain target requirements, faults have to be reliably detected and diagnosed. A method for an effective and reliable fault diagnosis of PV plants based on the behavioral model and performance analysis under the LabVIEW environment is presented in this paper. Specifically, the first phase of this study consists of the behavioral modeling of the PV array and the inverter in order to estimate the electricity production and analyze the performance of the 9.54 kWp Grid Connected PV System (GCPVS). Here, the results obtained from the empirical models were validated and calibrated by experimental data. Furthermore, a user interface for modeling and analyzing the performance of a PV system under LabVIEW has been designed. The second phase of this work is dedicated t... [more]

The efficiency of permanent magnet synchronous hub motors (PMSHM) used in light electric vehicles (EVs) is lower than that used in commercial EVs. Therefore, in this study a high-efficiency radial-flux outer-rotor PMSHM was designed for light EVs. The high-efficiency motor will contribute to the reduction of the power consumption demand from the batteries of EVs, the longer life of the batteries and the longer uninterrupted operation of the system. The optimization objectives, such as motor sizing, number of slots and poles, air gap length, material selection, stator winding structure, stator slot shape, magnet thickness, and cutting method for stator sheets were considered to ensure high efficiency and low cogging torque. In this study, three validation stages were followed; electromagnetic analyzes with FEM, analytical calculations, and finally experimental validation. First, the design parameters of the motor were determined based on the analyses results obtained using ANSYS Maxwell... [more]

Due to the simple structure and the possibility of manual production, coin cells enable fast and, compared to larger cell formats, an inexpensive examination option in battery research. The comparability and traceability of coin cell structures in literature are only feasible to a limited extent due to the lack of a standard in manual production. Since the findings from the literature are barely building up on each other and have not been repeated, a full factorial Design of Experiments (DoE) was performed to investigate the significance of earlier findings in terms of their influence on the reproducibility of the performance. The parameters studied were the anode-to-cathode ratio, the amount of electrolyte, the spring type and the separator count. To quantify the reproducibility of coin cell assembly, the number of functional cells (here: successful formation followed by 30 cycles) and the empirical coefficient of variation for the performance parameters discharge capacity, internal r... [more]

The power attenuation of internal combustion engines in high-altitude environments restricts the performance of unmanned aerial vehicles. Herein, a single-zone model of a hydrogen-doped high-efficiency hybrid cycle rotary engine that considers high-altitude environments was proposed. The indicated values for power, thermal efficiency, and specific fuel cost were used to evaluate the power performance, energy conversion efficiency, and economic performance of the engine, respectively. Then, the effects of adjusting the hydrogen fraction, ignition angle, and rotational speed on high-altitude performance were analyzed. The results showed that high-altitude environments prolonged combustion duration and reduced in-cylinder pressure, thereby causing power attenuation; however, increasing the hydrogen fraction can increase the indicated power. At an altitude of 6 km, the indicated power with a hydrogen fraction of 0.3 was approximately 20.7% higher than that obtained with pure gasoline. The... [more]

In this paper, a new carrier phase-shift (CPS) modulation method based on switching the displacement angle (SDA) is proposed to compromise the harmonic content of the output voltage and the circulating current. It can be used in medium- and low-voltage applications where the AC-side voltage and DC-side current of the modular multilevel converter (MMC) are required to have low harmonic content simultaneously. In this proposed SDA-based CPS modulation, the carrier displacement angle of the MMC with N submodules in each arm is periodically switched between the values of 0 and π/N degrees, so that the harmonic content of the output voltage and the harmonic content of the circulating current will not be in extreme conditions, which occurs when the displacement angle is set to 0 or π/N degrees. The effectiveness of this method has been verified by simulation and experimental results.

Interoperability becomes a key issue for smart grid systems, as the interaction between diverse components needs to lead to a normal system operation. In this paper, we test interoperability issues with respect to home automation. In particular, interaction of a home energy management system (HEMS) is examined with an external actor for home/building remote control. We show the importance and the feasibility of remotely controlling domestic loads from outside the house premises, which can be crucial for energy saving operations, such as demand response. The Smart Grid Architecture Model (SGAM) is used, where the different actors are depicted. The interoperability testing methodology for smart grids, developed by our unit, is followed in order to design the necessary tests and execute them. For the experimental part, we develop an HEMS in our lab along with a Home Automation End Device (HAED), used to transform two normal plugs, and consequently, normal loads into smart ones, thus creat... [more]

Magnetic properties of hard magnets are currently attracting a great deal of attention. In the paper, the modified Harrison model was used to describe the saturating hysteresis loops of three praseodymium−dysprosium ribbons that differed in their chemical composition and processing conditions. Microstructural studies (TEM and diffraction patterns) were performed for the ribbons under consideration. The Harrison model incorporates a number of physically tangible concepts such as the anhysteretic curve, bifurcations, and bi-stability. The modification of the original approach consisted of adding an additional degree of freedom in the modeling by freeing the restraints present in the original version, in which both coercivity and remanence are functions of temperature only.

This work focused on the modelling of latent heat thermal energy storage systems. The mathematical modelling of a melting and solidification process has time-dependent boundary conditions because the interface between solid and liquid phases is a moving boundary. The heat transfer analysis needs the interface position over time to predict the temperature inside the liquid and the solid regions. This work started by solving the classical two-phase (one-dimensional) Stefan problem through a Matlab implementation of the analytical model. The same physical problem was numerically simulated using ANSYS FLUENT, and the good match of analytical and numerical results validated the numerical model, which was used for a more interesting problem: comparing three different latent heat TES configurations during the discharging process to evaluate the most efficient in terms of maximum average discharging power. The three axial heat conduction structures changed only for the fin shape (rectangular,... [more]

The quality of electrical energy is of particular importance for power engineering. This study presents an analysis of articles made in the Special Issue “Analysis and Experiments for Electric Power Quality”. As techniques and technology advance, electrical consumers and equipment become more sensitive to disturbances in the electrical network (in particular, low- and medium-voltage). It can lead to costly outages and lost production, which affect productivity. The analyzed articles present interesting technical studies made on industrial and nonindustrial consumers, of low- and medium-voltage, from the point of view of the quality of electricity. Voltage and current harmonics, voltage sags and swells, interruptions, unbalance, and low power factor will lead to higher electricity bills, overloading, and rapid aging of electrical networks and electric equipment. The power quality depends not only on the supplier but also on all consumers connected to the same power network; some can cau... [more]