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Diagnosing faults is crucial for ensuring the safety and reliability of medium-voltage direct current (MVDC) systems. In this study, we propose a bidirectional long short-term memory (Bi-LSTM)-based fault diagnosis scheme for the accurate classification of faults occurring in MVDC systems. First, to ensure stability in case a fault occurs, we modeled an MVDC system that included a resistor-based fault current limiter (R-FCL) and a direct current circuit breaker (DCCB). A discrete wavelet transform (DWT) extracted the transient voltages and currents measured using DC lines and AC grids in the frequency–time domain. Based on the digital signal normalized by the DWT, using the measurement data, the Bi-LSTM algorithm was used to classify and learn the types and locations of faults, such as DC line (PTP, P-PTG, and N-PTG) and internal inverter faults. The effectiveness of the proposed fault diagnosis scheme was validated through comparative analysis within the four-terminal MVDC system, demonstrating superior accuracy and a faster diagnosis time compared to those of the existing schemes that utilize other AI algorithms, such as the CNN and LSTM. According to the test results, the proposed fault diagnosis scheme detects MVDC faults and shows a high recognition accuracy of 97.7%. Additionally, when applying the Bi-LSTM-based fault diagnosis scheme, it was confirmed that not only the training diagnosis time (TraDT) but also the average diagnosis time (AvgDT) were 0.03 ms and 0.05 ms faster than LSTM and CNN, respectively. The results validate the superior fault clarification and fast diagnosis performance of the proposed scheme over those of the other methods. [ABSTRACT FROM AUTHOR]

Copyright of Educational Academic Research is the property of Ataturk University Coordinatorship of Scientific Journals and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We experimentally demonstrate the broadband and highly efficient inversion of the rotation direction of the terahertz circular polarization achieved by a dynamic metasurface with vanadium dioxide ( VO 2 ). This metasurface converts linear polarization into circular polarization. The rotational direction of the output circular polarization can be reversed based on the VO 2 phase transition. The VO 2 state can be dynamically switched by injecting direct current into an on-chip circuit. To improve the terahertz-wave utilization efficiency, the metasurface is operated at an incident angle of 45°, thereby eliminating the beam splitter typically used to separate the outgoing wave from the incident wave at normal incidence. To achieve broadband operation, we employ a dispersion-cancelation strategy that cancels the dispersive phase responses between orthogonal linear polarizations. This strategy was previously developed for static metasurfaces; we have applied it to the design of dynamic metasurfaces. At a center frequency of 0.99 THz, the experimental evaluation demonstrated helicity switching with conversion efficiencies of 92% and 87% for the insulating and metallic states of VO 2 , respectively. Dispersion cancelation is simultaneously achieved for the insulating and metallic states of VO 2 , resulting in a relative bandwidth of 0.26, which is 3.2 times broader than that of a previously developed efficient dynamic metasurface. [ABSTRACT FROM AUTHOR]

In response to the digital transformation in education, this study explores the efficacy of virtual reality (VR) video games in teaching direct current electrical circuits at a public university in Colombia. Using a mixed-method action research approach, this study aimed to design, implement, and evaluate a VR-based educational strategy to enhance undergraduate learning experiences. The methodology integrated VR into the curriculum, facilitating a comparison of this innovative approach with traditional teaching methods. The results indicate that the VR strategy significantly improved students' comprehension of electrical circuits and increased engagement, demonstrating the utility of immersive technologies in educational settings. Challenges such as the need for technological integration and curriculum adaptation were also identified. This study concludes that VR video games can effectively augment electrical engineering education, offering a model for incorporating advanced digital tools into higher education curricula. This approach aligns with ongoing trends in digital transformation, suggesting significant potential for broad applications across various educational contexts. [ABSTRACT FROM AUTHOR]

With the deep penetration of renewable energy and power electronic equipment, the overcurrent protection of an intelligent miniature circuit breaker faces new challenges. The electronic controller of an intelligent miniature circuit breaker is typically powered by the bus current rather than the phase voltage to ensure a robust overcurrent protection response under all conditions, including severe short-circuit faults. So, the performance of the current transformer serving as an energy harvesting unit and the corresponding direct current to direct current convention circuit is one of the critical issues due to the limited volume of an intelligent miniature circuit breaker. In this research, a finite element model of a current transformer for an intelligent miniature circuit breaker is constructed by COMSOL to evaluate the impact of the core material, the core size, and the number of coil turns on the energy harvesting capability of the current transformer. Meanwhile, the relationship between the output of the power supply and its design parameters is investigated by circuit simulation. As a result, a novel type of current transformer is proposed based on well-designed parameters. Finally, experimental tests have been conducted to verify the hysteresis characteristics, output characteristics, and energy harvesting effect. The results demonstrate that the hysteresis properties of the transformer align with the simulation results. The power supply can work with a minimum current of 8 amperes, which is 23.08% better than before. [ABSTRACT FROM AUTHOR]

A reliable and cost-effective mechanical direct current circuit breaker (DCCB) is a promising solution for DC interruption. However, the typical mechanical DCCB has difficulty in interrupting a rated current, because the high oscillating current superimposed on the rated current generates a steep current slope at current zero-crossing (CZC) points, which makes it difficult for the vacuum interrupter to extinguish the arc. The objective of this paper is to present a novel DCCB topology with a gradually increasing counter-current. It utilizes a full-controlled converter, a semi-controlled full bridge, and an LC oscillation branch to generate a gradually increasing counter-current, which is superimposed on any fault current and generates a smooth current slope at CZC points. The proposed DCCB topology is modeled with PSCAD, and the current slope and the initial transient interruption voltage (ITIV) at CZC are analyzed and compared with the typical mechanical DCCB. The results indicate that the current slope at CZC decreases by 57–84% in full-range current interruptions, and the ITIV can be reduced by the same extent. Additionally, the performance of the proposed DCCB is evaluated in a four-terminal HVDC system. A cost and performance comparison is conducted among the main topologies. The obtained results show that the proposed DCCB is a reliable solution for the multi-terminal HVDC system. [ABSTRACT FROM AUTHOR]

This article discusses the challenges and advancements in the protection of smart grids that integrate renewable energy sources. The increasing integration of renewable power into electric grids aims to reduce carbon emissions and dependence on fossil fuels. However, this integration poses challenges for electrical protection due to changes in fault current levels and flow direction. The article highlights the need for advanced protection schemes for the modern grid, including adaptive protection, high-impedance fault detection, protection of active distribution networks, protection of microgrids, and the application of artificial intelligence. The article also provides a summary of the contributions made in this field of research. [Extracted from the article]

The cathode sheath (CS) formation of the direct current air circuit breaker is simulated by a fluid model, and the influence of metal vapor concentration between the contacts after liquid metal bridge rupture is considered. The CS conductivity increases with the increasing concentration of copper vapor. The copper vapor concentration increases from 5% to 95%, and the thickness of the positive space charge layer and ionization layer increases from 22.3 and 49.1 μ m to 51.8 and 81.7 μ m , respectively. Increasing the CS conductivity is beneficial for the motion of arc roots in a certain range. [ABSTRACT FROM AUTHOR]

The integration of modular multilevel converters (MMCs) with high voltage direct current (HVDC) transmission systems is an efficient method for transporting electricity from distant renewable energy sources to demand centres. However, MMC-HVDC systems face reliability challenges during DC overcurrent faults, often caused by component failures that can lead to HVDC network shutdowns. Consequently, a reliable fault location approach is crucial for grid protection and restoration, aiding in fault isolation and alternate power flow identification. Conventional fault location methods struggle with manual protective threshold setting, susceptibility to fault resistance and noise, and the need for communication channels, resulting in signal delays. In multi-terminal HVDC networks, fault location becomes even more complex due to poor selectivity and sensitivity in traditional schemes. This study proposes a robust fault location approach based on bidirectional long short-term memory (bi-LSTM). The method offers a simplified decision-making model with low computational requirements, utilizing fault features from one end of the network, eliminating the need for a communication channel. Remarkably, this approach achieves high fault location accuracy, even with varying fault types, resistances, and noise levels, as demonstrated by an MSE of 0.006 and a percentage error below 1% in simulations conducted using a real-time simulator with MATLAB/Simulink. [ABSTRACT FROM AUTHOR]

The direct current circuit breaker (DCCB) is extensively employed in DC microgrid applications to protect the network during faults. However, numerous DC converters are combined in parallel to form a DC microgrid, which creates a large network inductance. The grid stores energy during regular operation, which repels instantaneous current breaking, and this stored energy needs to be eliminated after current breaking. Conventional topologies use different energy absorption methods to dissipate the stored energy after breaking the current. In this paper, an efficient bidirectional DC circuit breaker (EBDCCB) topology is introduced to extract and reuse this energy instead of dissipating it. The proposed topology has bidirectional power flow capability to meet the requirements of DC microgrid applications as energy storage devices are frequently utilized. Furthermore, EBDCCB shows drastically improved performance in terms of current breaking time, voltage stress, regenerated average current, and energy recovery efficiency compared to the conventional DCCB topology. The mathematical modeling and sizing of the components used in the proposed EBDCCB are elaborately analyzed, and detailed performance testing is presented along with extensive PSIM software simulation. Additionally, an experimental investigation is conducted on a laboratory-scale 48 V/1 A prototype. [ABSTRACT FROM AUTHOR]

Reliable and economic protection of DC grids against fault currents is the main challenge for the development of voltage source converter-based DC grids. Application of fault current limiters (FCLs) can limit the rapid increase of fault current and reduce the DC circuit breaker (DCCB) requirements to isolate the fault. This article reports a bidirectional solid-state FCL (BSSFCL) to protect the DC lines against DC short circuit fault. In addition, it can limit fault current in both directions. The circuit and principle operating of the proposed BSSFCL are presented. Then, the current limiting performance of the proposed BSSFCL is analyzed and its parameter design requirements are presented. Finally, the performance of the proposed BSFFCL is compared with that of the RL-current limiting circuit (RL-CLC), mutual inductance-type FCL (MIFCL), and restive mutual-inductance solid-state FCL (RMI-SSFCL). The numerical analysis and simulations were done using the PSCAD/EMTDC software. It was found that, the BSSFCL could effectively enhance the breaking capability of DCCBs. Moreover, it outperforms the RL-CLC, MIFCL, RMI-SSFCL in terms of the fault current limiting, the fault clearing time and metal oxide arrester (MOA) energy absorption of DCCBs. [ABSTRACT FROM AUTHOR]

Design and application of LED driver with isolated CUK converter for 10W is realized in this paper especially for automotive purposes. The advantage of isolated CUK topology from conventional CUK topology is to have electrical isolation with supply and load and providing same polarity output. Besides, power LED models including constant voltage and exponential model are obtained and employed in simulation study. Furthermore, maximum current limitation of power LED is provided via dsPIC30f4011 microcontroller. Also, power switch is operated by 100 kHz switching frequency, and connection of the power LED driver to the source provided by LC with parallel damping filter, whose noise reduction shown by application as well. Thanks to the experimental set up and simulations, proving the desired results provided by the converter is shown by the measurement of LED currentvoltage, input voltage-current. Simulation results also verifies application. Moreover, it is shown that exponential power LED model provides more accurate results than constant voltage model. [ABSTRACT FROM AUTHOR]

A 3D-printed multicoupled piston-type cylindrical triboelectric nanogenerator (MPC-TENG) that utilizes contact-separation and lateral-sliding operational modes to harvest rotational motion and convert it into electricity was proposed. The electrical performances of the fabricated four similar piston-type cylindrical TENGs (PC-TENGs) were systematically investigated. TENGs in general produce electricity in an alternating-signal form which may not be used to directly power electronic devices. Therefore, all the individual PC-TENGs were connected with a simple external filter circuit to obtain direct current (DC) electrical output, and further, they were parallelly connected to increase the overall electrical output from the MPC-TENG. The MPC-TENG consists of four PC-TENGs and produces a DC electrical output of ~40 V and ~12.5 μA at 380 rpm. Furthermore, the MPC-TENG was attached to wind cups to harvest wind energy and a Pilton wheel to harvest hydrokinetic energy, respectively. The harvested energy was stored in energy storage devices to power various small-scale electronic gadgets. Furthermore, a real-time self-sustaining alarm combined with the MPC-TENG was demonstrated to detect unauthorized human/wild animal entry into a protected region. This work also shows that the DC electrical signals from the proposed MPC-TENG can be further increased by combining more PC-TENG devices. [ABSTRACT FROM AUTHOR]

The intermittent access of renewable energy sources leads to a significant increase in fault short‐circuit currents in power grid. DC superconducting fault current limiters (SFCL) can limit short‐circuit currents in flexible DC transmission systems, which work in combination with direct current circuit breaker (DCCBs) to protect the grid system effectively. However, for the parameter design of DC superconducting fault current limiter (DCSFCL), it is difficult to balance the economics of the device and its adaptability to different fault situations. In this paper, a cross‐mapping design methodology for the DCSFCL is proposed and applied in the Nan'ao flexible DC transmission project, China. A cross‐mapping method is designed combining the critical parameters of DCSFCL and the system parameters. A three‐terminal simulation model of the flexible DC transmission system is constructed through MATLAB/Simulink and the design process of DCSFCL parameters is introduced. A cyclic calculation approach is proposed for the design of DCSFCL parameters through three fault conditions of the power system. Meanwhile, impact current short‐circuits test and artificial ground short‐circuit test were conducted on the prototype. Test results show that the designed DCSFCL meets the requirements of practical applications. [ABSTRACT FROM AUTHOR]

This work introduces a novel approach for enhancing the performance of a triboelectric generator (TEG) by using a solid–liquid interface-treated foam (SLITF) as its active layer, combined with two metal contacts of different work functions. SLITF is made by absorbing water into a cellulose foam, which enables charges generated by friction energy during the sliding motion to be separated and transferred through the conductive path formed by the hydrogen-bonded network of water molecules. Unlike traditional TEGs, the SLITF-TEG demonstrates an impressive current density of 3.57 A/m2 and can harvest electric power up to 0.174 W/m2 with an induced voltage of approximately 0.55 V. The device generates a direct current in the external circuit, eliminating the limitations of low current density and alternating current found in traditional TEGs. By connecting six-unit cells of SLITF-TEG in series and parallel, the peak voltage and current can be increased up to 3.2 V and 12.5 mA, respectively. Furthermore, the SLITF-TEG has the potential to serve as a self-powered vibration sensor with high accuracy (R2 = 0.99). The findings demonstrate the significant potential of the SLITF-TEG approach for efficiently harvesting low-frequency mechanical energy from the natural environment, with broad implications for a range of applications. [ABSTRACT FROM AUTHOR]

Responses of the AC and DC global electric circuits (GECs) to the large eruption of the Hunga Tonga‐Hunga Ha'apai (HT‐HH) volcano on 15 January 2022 are discussed. The AC‐related investigation is based on Schumann resonance (SR) measurements from six stations on four continents. The DC‐related investigation utilizes atmospheric electric field (potential gradient, PG) measurements from six recording stations in Europe and the USA. According to data from the GLD360 and WWLLN lightning detection networks, the peak lightning stroke rate, 83/s, was dominated by negative polarity lightning, but the distributions of positive and negative lightning discharges in latitude and longitude around the volcano differed. A global intensification of SR is apparent in connection with the enhanced lightning activity caused by the eruption. SR data‐based results confirm that the lightning activity in the eruption dominated the naturally occurring global activity for a period of about 1 hr. The highly localized increase in lightning activity over HT‐HH was a unique point source of SR excitation. PG measurements suggest that impulse‐like charging of the DC GEC, by ∼15%, via negative cloud‐to‐ground lightning strokes took place twice during the eruption. A time constant of 7 or 8 min has been inferred for near‐surface PG changes due to these enhancements. This could be the first direct measurement of the time constant of the GEC near the Earth's surface, as well as the first observation of the direct charging of the DC GEC by a unique atmospheric electrified source. Plain Language Summary: The eruption of the undersea volcano near Tonga on 15 January 2022 caused dramatic changes to both the AC and DC global electric circuits in association with the extremely intensive volcanic lightning activity, which was evaluated using data from global lightning detection networks. During the evolution over almost 2 hr of the lightning from the volcanic cloud, episodes of predominantly positive and negative polarity lightning alternated. As time progressed after the first explosion of the volcano at 4:16 UTC, lightning stroke locations formed rings of varying radius up to ∼150 km around the vent. A connection between the dynamics of the eruption and the varying lightning activity is plausible. For AC circuit investigations, Schumann resonances at six stations on four continents were found to be considerably stronger than usual during the lightning generated by the volcano. Measurements of the vertical electric field, otherwise termed the potential gradient, just above the Earth's surface suggest that the DC circuit was charged impulsively twice during this extended event. The time constant of the DC global circuit was inferred from these measurements to be between 7 and 8 min. This is believed to be the first direct measurement of that time constant. Key Points: Lightning in the eruption dominates the naturally occurring global lightning activity for a period of at least 1 hrCharging of the direct current global electric circuit (GEC) by volcanic electrical activity is suggested by the observationsRelaxation time of electric field changes in the GEC has been inferred to be 7 or 8 min near the Earth's surface [ABSTRACT FROM AUTHOR]

In order to ensure the reliable interruption of high voltage direct current circuit breaker (HVDC CB), the breaking test of HVDC CB plays an important role in its performance verification. In this paper, the interruption process of the HVDC CB is analyzed, and the equivalent requirements for the breaking test of HVDC CB are summarized. In the breaking test of high voltage and high current, the transient interruption voltage (TIV) duration is short, which leads to insufficient voltage stress. A new synthetic test circuit for testing the interruption performance of HVDC CBs is proposed, which can solve the problem of insufficient TIV duration caused by insufficient test capacity. Subsequently, the working principle of the test circuit is introduced in detail and the design method of the circuit parameters is given. The short‐circuit current breaking test simulation of HVDC CB is carried out. The simulation results fit most well with the results of actual test cases, which verifies the universality of this test method. Finally, a test platform is built to verify the principle of the test circuit. TIV rose to 2.5 kV compared to the predetermined system voltage of 1.67 kV during the test, which means that the key stress provided by the test circuit can meet the expected requirements. [ABSTRACT FROM AUTHOR]

The main aim of this study is the development of a fast and secure charging system for electric vehicles. Recently, many different charging methods have been introduced. The main charging methods are the induction charging method and the conduction charging method. In this paper, the conduction charging method is employed. With regard to the conduction method, there are three levels of charging. At level 1, there is single-phase charging, while both single-phase and three-phase charging occur at level 2. Lastly, at level 3, a three-phase AC charging method, DC conduction charging method, and AC/DC conduction charging method is focused. The level 3 charging method is the main focus of this paper. Toward this end, a 12-diode rectifier or 12-pulse rectifier with a firing angle of zero degrees having two bridges is used for AC to DC conversion, while a SEPIC converter is used for DC-to-DC conversion. The design presented in this paper was simulated and verified using MATLAB/Simulink, and the results show that the Total Harmonic Distortion (THD) of the input current was reduced, and that overall efficiency was improved. [ABSTRACT FROM AUTHOR]

The hybrid modular multilevel converter (MMC) consisting of half-bridge submodules (HBSMs) and full-bridge submodules (FBSMs) is a promising solution for overhead lines high-voltage direct current systems (HVDC) due to the advantages of direct current short circuit fault ride-through (DC-FRT) capability. This paper proposes an improved phase-disposition pulse width modulation (PDPWM) method for the hybrid modular multilevel converter. The number of carriers can be reduced from 3N (N is the number of submodules in each arm) to 6. The theoretical harmonic analysis of the improved PDPWM method for hybrid MMC is performed by using double Fourier integral analysis. The influence of three carrier displacement angles between HBSMs and FBSMs in the upper and lower arms on harmonic characteristics is investigated. The output voltage harmonics minimization PDPWM scheme and circulating current harmonics cancellation PDPWM scheme can be achieved by selecting the optimum carrier displacement angles, respectively. The proposed method for hybrid MMC is verified by the simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a modern method for approaching the electrical circuits using the MATLAB-SIMULINK package programs. The simple series circuits which are switched on a DC voltage at the initial moment are presented below. We can determine the current variation forms and the reactive elements voltage, by using this virtual medium. Each presented case contains an analytical presentation of the problem, but it also contains electrical diagrams of electrical parameters. The diagrams were obtained by different methods which use this programs package. [ABSTRACT FROM AUTHOR]

Electricity is a very important concept in learning Physics. Mastering this concept can make learning Physics meaningful and relatable to real life problems. However, literature indicates that students have poor conceptual understanding of concepts about electricity. The current research aims to improve Form 5 (aged 17 years) students' understanding of direct current circuits by using Concept Cartoons Worksheets. Concept Cartoons are A single-group pre-test/post-test investigation was carried out using seven Concept Cartoons Worksheets designed to address common conceptual misconceptions about direct current circuits with a total of 30 physics student participants. The seven Concept Cartoons were modified based on the Concept Inventory Test "Determining and Interpreting Resistive Electric Circuit Concepts Test (DIRECT). Concept Cartoons Worksheets were used to correct students' misconceptions about direct current circuits and to increase their level of conceptual understanding. The data collected were analysed quantitatively to obtain percentages, means, and t-test values. The descriptive statistics showed an increase in the level of student's conceptual understanding after the use of Concept Cartoons. The t-test analysis reported that the difference was significant. The results show that Malaysian students do havemisconceptions about electricity concepts. However, Concept Cartoons Worksheets are effective to overcome students' misconceptions about electrical concepts, specifically toward current circuits. Concept Cartoons are not only effective in overcoming misconceptions among students, they are also refreshing and unique because of the cartoons presented while relating to Physics concepts that are abstract. [ABSTRACT FROM AUTHOR]

In this paper, a performance evaluation of a developed Solar-Powered Vapor Absorption Refrigeration (VAR) System using the NH3-H2O solution as a working fluid is done. The cooling system has a total storage space of 0.038 m³ with the capacity to accommodate about 0.04 metric tonnes (40kg) of items, such as cool water and other drinks for human comfort, applicable in rural regions where electricity is unreliable or non-existent. A solar Photovoltaic (PV) panel of 300W, 40 W Direct Current (DC) heating element with a 20A solar controller was designed to power the developed cooling system. Measurements of important operational parameters such as the generator, ambient, evaporator, cabinet and condenser temperatures were studied and measured from the system. Performance evaluation of the system refrigerating capacity was determined in terms of its cooling performance (COP) and the system efficiency ratio (?) based on no load and on load conditions. The system, when tested, has COP of 0.1275 at an average cabinet temperature (Tr) of 9.0 °C against an average room temperature of 25.8 °C. Additionally, the system had an overall refrigerating efficiency ratio of 8.25. The performance test results revealed that the developed cooling system performed well in terms of temperature regulation for refrigeration purposes. [ABSTRACT FROM AUTHOR]

Despite the high performance of high-voltage direct current circuit breaker (CB) technology, its high cost restricts its further development. Thus, this article proposes a high-efficiency protection circuit for solid-state switches (SSs) that integrates semisoft switching and voltage limiting functions. The protection circuit also does not resonate with the system inductance which in turn does not affect the reclosing operation of the CB. The novel SS scheme reduces the cost and simplifies the layout of the SS. The special constraints for the parameter design of power electronics, gaps, and metal oxide varistors (MOVs) are proposed in this article for the first time, and a parameters design method that solves the transient power shock and voltage spike problems during the large current breaking process under multiple constraints is formed. Finally, an SS prototype is developed to verify the feasibility and the strong surge and turn-off ability of the novel SS and to test the robustness of the series-connected gapped-MOV circuits. [ABSTRACT FROM AUTHOR]

The current-limiting performance of the smoothing reactor is weak. The traditional saturated core-type fault current limiter (TFCL) is better, but will cause the dc circuit breaker (DCCB) to endure high overvoltage, energy absorption and also increase the current fall time. When DCCB recloses on the permanent fault, the whole dc system will face a harmful second shock that cannot be solved effectively by TFCL. To solve the above problems, a secondary active limiting fault current limiter (SAFCL) topology is proposed. It can reduce the DCCB overvoltage and energy absorption greatly. Meanwhile, it can store fault energy and uses it to active limit the current when the DCCB recloses on the permanent fault. The secondary active current limiting effect is better than the first and the DCCB breaking electric stress is lower than the first. First of all, the topology and principle of the SAFCL are introduced. The main electromagnet parameters are then analyzed. The performance of different FCLs are simulated comparatively to verify the superiority of the SAFCL. Final, the experiment is carried out, the comparison with simulations verifies the feasibility of the SAFCL. [ABSTRACT FROM AUTHOR]

Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An impedance measurement object with an H-shaped four-terminal equivalent substitution circuit is considered. An error analysis was performed for sensors whose non-informative supply resistances are of the same order or exceed the measured impedance. A new definition of four-terminal impedance has been proposed, namely four-terminal axial beshielded (FTABS) measuring object. Based on such new definition, the scheme of axial-bishielded bridges is proposed for precision measurement of temperature and electrolytic conductivity of liquids. Such bridges differ from the wellknown coaxial bridges since the former ones have an additional circuit for equipotential protection, which is located between the flow circuits of direct and reverse currents. [ABSTRACT FROM AUTHOR]

The primary function of hybrid direct current circuit breakers (HCBs) is to quickly interrupt fault currents to protect high-voltage direct current (HVDC) systems. To enhance the reliability and stability of HVDC systems, optimal design of HCBs is required to minimize the peak fault current, interruption time, and recovery time. Therefore, this study develops a multi-objective genetic algorithm (MOGA)-based optimization model to identify the optimal parameters for HCBs. The MOGA model consists of three objective functions that provide trade-offs among reductions in the peak fault current, the interruption time, and the recovery time. The proposed algorithm is verified with a novel HCB topology using inverse current injection techniques. The performance of the HCB topology with the optimal parameters is validated in the MATLAB/Simulink environment. In addition, a comparison study between the optimal design of an HCB using the proposed algorithm and a typical HCB model is presented in this study to show the effectiveness of the proposed optimization method. Our simulation results show that the optimal parameter design of HCBs significantly reduces the magnitude of the peak fault current and operating time, thus maintaining the safe and stable operation of the entire system. [ABSTRACT FROM AUTHOR]

It is necessary to elucidate the mechanism of atmospheric arc plasma movement and the variation in its physical properties for constructing an accurate virtual model while using digital twin technology to design a next‐generation direct current circuit breaker. In this study, the calculation setting for considering the thermal nonequilibrium effect on an electrode surface was established. Moreover, the thermal field theory was employed for simulating the cathode spot movement and a thermal nonequilibrium model was implemented for analyzing the triggering factor of the re‐strike phenomenon occurrence on the anode surface. It was found that heavy particles (ions and neutral particles) were transported forward by the cathode jet and not only caused an increment in the electrical conductivity on the anode surface, but also increased the electric field between the arc column and the anode surface. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Hybrid direct current circuit breakers (DCCBs) have become prominent because of their low on‐state power dissipation and small arc erosion compared with conventional semiconductor and mechanical circuit breakers (CBs). After a fault occurs in a DC circuit, the current commutates from the mechanical contacts to the semiconductor devices of the hybrid DCCB, and finally, the current is interrupted by the semiconductor devices. Thus, a low turn‐on voltage or a low on‐state resistance of the devices is needed to reduce the commutation time and power dissipation of the current interruption. This paper presents a comparison of DCCB performances metrics, such as the maximum interruption current, power dissipation, and junction temperature, using a silicon carbide metal‐oxide‐field‐effect transistor (SiC‐MOSFET) and silicon insulated‐gate‐bipolar transistor (Si‐IGBT) module. An interruption of 1.1 kA was achieved in 4.3 ms using the SiC‐MOSFET module of which rated current was 444 A. The junction temperature after the interruption was determined to be 275°C, which exceeded the maximum junction temperature of 175°C. In the case of the Si‐IGBT module of which rated current was 1110 A, the maximum interrupting current was limited to 900 A; however, the maximum junction temperature was 41°C. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The arc behavior during commutation of a pyro-breaker is the main determinant of performance evaluation. The pyro-breaker discussed in this article is an explosive-driven, extremely fast and non-linear Direct Current circuit breaker. It has been developed for the Quench Protection System (QPS) of superconducting fusion facilities, such as the China Fusion Engineering Test Reactor (CFETR). The feasibility of the Schavemaker differential equation is verified in a simplified 40 kA commutation simulation. The Commutation Section of the pyro-breaker will form multiple gaps after the operation, which causes multiple arc ignitions during the explosion. The influence of the gap quantity on the commutation performance of the pyro-breaker has not previously been studied. A more accurate simulation, which takes the multiple-arc formation into consideration, is proposed and verified under the current of 60 kA. The simulation model, which takes the numerical analysis of the driving mechanism into consideration, will be the designing basis for the pyro-breaker in further development and implementation. [ABSTRACT FROM AUTHOR]

A Gas tungsten arc welding (GTAW)-based additive manufacturing has a potential for manufacturing metallic parts with better dimensional accuracy and dense structure. This paper discusses the issues in the GTAW-based metal deposition process for the positive and negative polarity of the welding electrode in the direct current circuit. The effect of direct current electrode positive (DCEP) and direct current electrode negative (DCEN) polarity on GTAW-based metal deposition process has been discussed. The experimental study has been done with a constant voltage source of ESAB Caddy 2200i welding machine and the metal beads were deposited on the substrate plate of mild steel. The results of these experiments showed that the metal deposited using DCEN polarity has a better dimensional accuracy over DCEP polarity due to its stability in arc formation and proper transmission of heat. The experimental investigation showed that the DCEP polarity causes the deterioration of the tungsten electrode after a few trials. The work done in this paper will help to distinguish between the use of DCEP polarity and DCEN polarity in GTAW-based additive manufacturing process for depositing the metal with better dimensional accuracy and better surface finish. [ABSTRACT FROM AUTHOR]

This study employed a non-equivalent quasi-experimental pre-test/post-test control-group design to study the effect of the PhET simulation intervention on students’ engagement, satisfaction, and academic achievement in the learning of direct current electric circuit concepts among Bhutanese students. We analysed the pre- and post-test scores and perceptions of 57 ninth-grade students, divided into experimental group (EG, n = 29) and control group (CG, n = 28), from one high school in Paro District, Bhutan. The EG students were taught with the PhET simulation intervention, while the CG students were taught with the traditional chalk-talk method. The pre- and post-test scores were collected with the Electric Circuits Conceptual Evaluation (ECEE) inventory. Mean, standard deviation, a two-sample t-test, and multiple linear regression (MLR) were computed using R and RStudio. The t-test revealed a statistically significant difference in the mean post-test scores of CG and EG students. MLR analysis further confirmed that this difference was due to the PhET simulation intervention, ruling out the influence of other confounding variables. Additionally, an instrument called the PhET Engagement-Satisfaction Questionnaire was developed to assess EG students’ engagement level and satisfaction with the PhET simulation intervention. Confirmatory factor analysis and Cronbach’s alpha calculation confirmed its validity and reliability. Data from  the PhET Engagement-Satisfaction Questionnaire unveiled significant impact of the PhET simulation intervention on students’ engagement level and their overall satisfaction, reinforcing prior research. However, further research with a larger sample size, incorporating lesson observations, interviews, and our measurement tool, is necessary to ascertain whether the findings it yields align with the present study’s findings. [ABSTRACT FROM AUTHOR]

Modular multilevel converter (MMC) high-voltage direct current (HVdc) transmission is a promising method to integrate renewable energies. However, limiting the dc-link fault current and accelerating the fault-current clearance are critical issues for MMC-HVdc systems. In this article, we propose an air-core-transformer-based fault-current limiter (ACT-FCL) in cooperation with the dc circuit breaker to limit fault-current rising and decrease fault-clearing time. Compared with the conventional dc reactor, hybrid current-limiting circuit, current-commutation-based fault-current limiter (FCL), and magnetic coupling FCL, the ACT-FCL can increase the equivalent inductance during the dc fault stage to reduce the rising rate and peak of fault current. The ACT-FCL can also decrease the equivalent inductance during the fault-current-clearing stage to reduce the fault-clearing time. The simulations and laboratory experiments verify the effectiveness of the proposed ACT-FCL in the bidirectional HVdc systems. The ACT-FCL may be extended to more fields, such as dc microgrid and domestic dc transmission. [ABSTRACT FROM AUTHOR]

The traditional saturated core type fault current limiters (TFCLs) cause large energy absorption and high overvoltage in direct current circuit breakers (DCCBs). Energy absorbing FCLs (AFCLs) cause coils to bear the fault current for a long period and the fault energy absorption is slow. In order to solve the problems of TFCLs and AFCLs, a novel fast energy storage dc FCL (EFCL) topology is proposed in this article. The EFCL not only reduces the overvoltage and energy absorption of DCCBs but also quickly stores energy. First, the working principle and topology of the EFCL are proposed. The design requirements of the main electrical and core size parameters are then analyzed. Then, the key electrical parameters are optimized by electromagnetic circuit simulations. The economy is analyzed. Finally, the whole process simulation and FCL comparison simulation are carried out. The feasibility of the EFCL is verified by the comparison of simulation with experiment. [ABSTRACT FROM AUTHOR]

Scaling is one of the most important aspects and is considered for designing digital circuits. With the help of scaling techniques, it can integrate more features into the chip for optimization of actual circuit space. But the main drawback of this scaling is short channel effects. And also as the technology shrinks, the leakage power plays a crucial role compared to dynamic power consumption. To avoid leakage power, the proposed design technology is used for the optimization of power and for avoiding short channel effects. To further reduce power consumption, the CMOS technology is replaced with transmission gates in switched-capacitor converter circuits and GDI Technique while generating clock signals in the circuit for operations. [ABSTRACT FROM AUTHOR]

For realizing the widespread application of fast charging of electric vehicles, a direct current circuit breaker (DCCB) is required to interrupt a large charging current. For developing a next‐generation DCCB that can satisfy this requirement, a three‐dimensional electromagnetic thermal fluid simulation was developed to mimic the interruption process of the DCCB, and an artificial intelligence (AI) model was constructed for differentiating the simulation result. As a result, successful and failed interruption of the DCCB were both simulated, and the constructed AI model successfully differentiated the interruption result and located the extinguish timing of arc plasma in case of a successful interruption. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This article presents the electrical circuit, a description of the design, and results of measurements of the radiative watt–ampere and time characteristics of compact inexpensive emitters based on commercial laser diodes with wavelengths from 405 to 850 nm, which operate in the picosecond (70–180 ps) and nanosecond (0.69–1.2 ns) modes. The optical emitter includes a master crystal oscillator based on a microcontroller (frequencies of 76 Hz–20/80 MHz), a synchronization circuit, a low-voltage (9–12 V) subnanosecond electric pulse shaper that operates according to the method of double differentiation, a pump circuit with an adjustable direct current source, and a laser diode. The average light power at a frequency of 80 MHz varies in pico mode from 0.6 to 1.6 mW and in nano mode from 6 to 18 mW. The lasers are powered by a 220 V/12 V, 0.25 A serial power supply, with a power consumption of 3 W and a weight of 0.2 kg. [ABSTRACT FROM AUTHOR]

Proliferation of distributed energy resources (DERs) calls for a coordinated transmission and distribution (T&D) scheduling at the day‐ahead stage. The problem becomes more complicated dealing with the variability of stochastic parameters. Also, privacy and complexity are two barriers to the development of such coordinated platforms. This paper addresses these issues by introducing a hybrid centrally‐supported decentralized stochastic framework for the day‐ahead energy and reserve market with minimum complexity and the need for data‐sharing between system operators. The proposed model is able to calculate the bidirectional power exchange at the T&D interface and the separated costs, dispatches, and reserves of all market participants. The proposed model does not consider any priority for operators and increases the liquidity by facilitating participants' access to the market platform. Also, the second‐order cone programming (SOCP) formulation is used for calculating the AC power flow of distribution grids, and the model is validated and compared with other implementation strategies. The proposed model is implemented on a modified IEEE 24‐bus test system, and results show that the model can schedule resources for supplying energy and reserves in both transmission and distribution levels in an acceptable computation time. [ABSTRACT FROM AUTHOR]

In droop‐controlled DC microgrids, parasitic resistances of long conductive lines introduce additional terms for the power calculation and impact the power sharing accuracy. This paper proposed a comprehensive local control design for enhancing power sharing accuracy and restoring DC bus voltage while increasing stability performance in DC microgrids. A passive controller is used in the primary control to ensure the sufficient bandwidth of controller in case of frequent operation modes alteration and voltage deviation in the DC microgrid. A concept of Virtual Negative Line Resistance (VNLR) is used in the secondary control layer to compensate the real line resistance such that line resistance no longer degrades power sharing accuracy. The common DC bus voltage needs to be monitored in the proposed secondary controller. Simultaneously, the common DC bus voltage can be restored as the designed value. The monitored DC bus voltage signal is filtered by a designed low‐pass filter such that mid‐high frequency dynamics can be decoupled between secondary controls and primary controls. Then the entire local control scheme relaxes three Degrees of Freedom (DoF) which can be used for upper layer controls. Finally, the proposed control method has been experimentally validated in a 50 V DC microgrid laboratory testing system. [ABSTRACT FROM AUTHOR]

This paper presents the shunt compensation performance of quasi-Z-source inverter (QZSI) and back to back connected QZSIs (BB-QZSI) to address the power quality (PQ) issues in the three-phase three-wire power utility network (PUN). Generally, these PQ issues are poor voltage regulation, low power factor (PF), source current distortion, unbalanced voltage, etc. The proposed BBQZSI-based distribution static compensator (DSTATCOM) consists of two QZSIs with a common dc-link capacitor. Because the QZSI could achieve buck/boost conversion as well as DC to AC inversion in a single-stage and the back to back configuration decreases the system down time cost (if a fault occurs in one QZSI the other can continue the shunt compensation). Particularly, icos ϕ control algorithmcontrol algorithm is implemented to generate proper switching pulses for the switches of DSTATCOM. The effectiveness of the BB-QZSI is verified through simulation studies over QZSI using MATLAB/Simulink software satisfying the recommended grid code. [ABSTRACT FROM AUTHOR]

In this paper, a new structure is proposed for a boost dc-dc converter based on the voltagelift (VL) technique. The main advantages of the proposed converter are its lack of transformer, simple structure, free and low input current ripple, high voltage gain capability by using an input source, suitable voltage stress on semiconductors and lower output capacitance. Herein, the analysis of the proposed converter operating and its elements voltage and current relations in continuous conduction mode (CCM) and discontinuous conduction mode (DCM) are presented, and the voltage gain of each operating mode is individually calculated. Additionally, the critical inductance, current stress of switches, calculation of passive components' values and efficiency are analyzed. In addition, the proposed converter is compared with other studied boost converters in terms of ideal voltage gain in the CCM and the number of active and passive components, maximum voltage stress on semiconductors, and situation of input current ripples. The correctness of the theoretical concepts is examined from the experimental results using the laboratory prototype. [ABSTRACT FROM AUTHOR]

Concerning the poor immunity of DC line protection to fault resistance in the case of internal fault and its mal‐operation proneness in the case of external fault, a new pilot directional protection scheme for HVDC line in AC/DC hybrid system based on the polarity of inductive energy is proposed. First, by analysing the conducting state of converter at different time sections, the impedance characteristic equations of converter in different commutation failure scenes are derived. On this basis, by combining the impedance characteristics of other components in DC system, the fault component network of an AC/DC hybrid system consisting of inductive impedances is established. Then, according to the difference in the flowing direction of the inductive energy in the fault component networks of internal and external faults, a protection criterion for identifying internal and external faults is constructed. Finally, simulation tests in RT‐LAB verify that, the proposed method can accurately identify internal and external faults in different fault cases, unaffected by commutation failure and lightning interference and highly immune to the fault resistance. Besides, the proposed method does not involve real‐time interaction of synchronous information, thus it is simple and reliable. [ABSTRACT FROM AUTHOR]

There are two bias schemes, namely current-bias and voltage-bias, for the directly coupled readout circuit of direct current superconducting quantum interference device (dc SQUID). In order to find out the difference between two bias schemes, we present the theoretical analyses on their equivalent circuits, working point locations, and noise performances. The theoretical analysis and experimental validation prove that the voltage-bias scheme achieves a larger transfer coefficient and exhibits a better noise performance than the current-bias scheme in the reading of conventional dc SQUID. [ABSTRACT FROM AUTHOR]

Analysis of transient recovery voltage is essential to develop high-voltage direct current circuit breakers with active current injection technology. This study presents a theoretical analysis of the transient recovery voltage using the Laplace transform, thereafter the value of the transient recovery voltage obtained using this analytical equation is compared to measured reference values. It is found that the analytical transient recovery voltage is given by the sum of a linear function and a damped oscillation function. The amplitude of the damped oscillation is reduced by the resistance of post-arc plasma; therefore, it is necessary to consider the resistance owing to post-arc plasma to evaluate the transient recovery voltage accurately. [ABSTRACT FROM AUTHOR]