Search Results (1,721)

This study investigates the impact of Time-of-Use (TOU) scheduling and battery energy storage systems (BESS) on voltage stability in a typical Malaysian medium-voltage distribution network with high photovoltaic (PV) system penetration. The analyzed network comprises 110 nodes connected via eight feeders to a pair of 132/11 kV, 15 MVA transformers, supplying a total load of 20.006 MVA. Each node is integrated with a 100 kW PV system, enabling up to 100% PV penetration scenarios. A hybrid mitigation strategy combining TOU-based load shifting and BESS was implemented to address voltage violations occurring, particularly during low-load night hours. Dynamic simulations using DIgSILENT PowerFactory were conducted under worst-case (no load and peak load) conditions. The novelty of this research is the use of real rural network data to validate a hybrid BESS–TOU strategy, supported by detailed sensitivity analysis across PV penetration levels. This provides practical voltage stabilization insights not shown in earlier studies. Results show that at 100% PV penetration, TOU or BESS alone are insufficient to fully mitigate voltage drops. However, a hybrid application of 0.4 MWh BESS with 20% TOU load shifting eliminates voltage violations across all nodes, raising the minimum voltage from 0.924 p.u. to 0.951 p.u. while reducing active power losses and grid dependency. A sensitivity analysis further reveals that a 60% PV penetration can be supported reliably using only 0.4 MWh of BESS and 10% TOU. Beyond this, hybrid mitigation becomes essential to maintain stability. The proposed solution demonstrates a scalable approach to enable large-scale PV integration in dense rural grids and addresses the specific operational characteristics of Malaysian networks, which differ from commonly studied IEEE test systems. This work fills a critical research gap by using real local data to propose and validate practical voltage mitigation strategies. Full article

This paper presents a low-cost 1-bit phased array operating at 17 GHz (Ku band) with an enhanced scanning gain at the largest deflection angle to extend the beam coverage for ground target detection. The phased array is designed using 16 (2 × 8) radiation-phase reconfigurable dipoles and a fixed-phase feeding network, achieving 1-bit beam steering via a direct current (DC) bias voltage of ±5 V. Measurement results demonstrate a peak gain of 9.2 dBi at a deflection angle of ±37°, with a 3 dB beamwidth of 94° across the scanning plane. Compared with conventional phased array radars with equivalent peak gains, the proposed design achieves a 16% increase in the detection range at the largest deflection angle. Full article

In this study, we propose a bidirectional chemical sensor platform based on a reconfigurable ion-sensitive field-effect transistor (R-ISFET) architecture. The device incorporates Ni-silicide Schottky barrier source/drain (S/D) contacts, enabling ambipolar conduction and bidirectional turn-on behavior for both p-type and n-type configurations. Channel polarity is dynamically controlled via the program gate (PG), while the control gate (CG) suppresses leakage current, enhancing operational stability and energy efficiency. A dual-control-gate (DCG) structure enhances capacitive coupling, enabling sensitivity beyond the Nernst limit without external amplification. The extended-gate (EG) architecture physically separates the transistor and sensing regions, improving durability and long-term reliability. Electrical characteristics were evaluated through transfer and output curves, and carrier transport mechanisms were analyzed using band diagrams. Sensor performance—including sensitivity, hysteresis, and drift—was assessed under various pH conditions and external noise up to 5 V_pp (i.e., peak-to-peak voltage). The n-type configuration exhibited high mobility and fast response, while the p-type configuration demonstrated excellent noise immunity and low drift. Both modes showed consistent sensitivity trends, confirming the feasibility of complementary sensing. These results indicate that the proposed R-ISFET sensor enables selective mode switching for high sensitivity and robust operation, offering strong potential for next-generation biosensing and chemical detection. Full article

To address the limitations of low detection efficiency and poor spatial resolution of traditional cable insulation diagnosis methods, a novel cable insulation diagnosis method based on impedance spectroscopy has been proposed. An impedance spectroscopy analysis model of the frequency response of high-voltage single-core cables under different aging conditions has been established. The initial classification of insulation condition is achieved based on the impedance phase deviation between the test cable and the reference cable. Under localized aging conditions, the impedance phase spectroscopy is more than twice as sensitive to dielectric changes as the amplitude spectroscopy. Leveraging this advantage, a multi-parameter diagnostic framework is developed that integrates key spectral features such as the first phase angle zero-crossing frequency, initial phase, and resonance peak amplitude. The proposed method enables quantitative estimation of aging severity, spatial extent, and location. This technique offers a non-invasive, high-resolution solution for advanced cable health diagnostics and provides a foundation for practical deployment of power system asset management. Full article

This study investigates the thermal response and surface modification of low-carbon manganese-alloyed 20GL steel during electrolytic plasma hardening. The objective was to evaluate the feasibility of surface hardening 20GL steel—traditionally considered difficult to quench—by combining high-rate surface heating with rapid cooling in an electrolyte medium. To achieve this, a transient two-dimensional heat conduction model was developed to simulate temperature evolution in the steel sample under three voltage regimes. The model accounted for dynamic thermal properties and non-linear boundary conditions, focusing on temperature gradients across the thickness. Experimental temperature measurements were obtained using a K-type thermocouple embedded at a depth of 2 mm, with corrections for sensor inertia based on exponential response behavior. A comparison between simulation and experiment was conducted, focusing on peak temperatures, heating and cooling rates, and the effective thermal penetration depth. Microhardness profiling and metallographic examination confirmed surface strengthening and structural refinement, which intensified with increasing voltage. Importantly, the study identified a critical cooling rate threshold of approximately 50 °C/s required to initiate martensitic transformation in 20GL steel. These findings provide a foundation for future optimization of quenching strategies for low-carbon steels by offering insight into the interplay between thermal fluxes, surface kinetics, and process parameters. Full article

This paper presents a practical framework for the design and real-time implementation of a Power Management System (PMS) for microgrids based on Supervisory Control Theory (SCT) for discrete-event systems. A detailed step-by-step methodology is provided, which covers the entire process from defining discrete events, modeling microgrid components, synthesizing supervisory controllers, and realizing them in MATLAB (R2024b) Stateflow. This methodology is applied to a case study, where a decentralized supervisor controller is designed for a microgrid containing a Battery Energy Storage System (BESS), a generator set (Genset), a wind and a solar generation system, critical loads, and noncritical loads. Unlike previous works based on SCT, the proposed PMS addresses the following functionalities: $\left(i\right)$ grid-connected and islanded operation; $\left(ii\right)$ peak shaving; $\left(iii\right)$ voltage support; $\left(iv\right)$ load shedding. Finally, a CHIL testing is employed to validate the synthesized SCT-based PMS. Full article

Cumulative inhibition of voltage-gated Na⁺ channel current (I_Na) caused by high-frequency depolarization plays a critical role in regulating electrical activity in excitable cells. As discussed in this review paper, exposure to certain small-molecule modulators can perturb I_Na during high-frequency stimulation, influencing the extent of cumulative inhibition and electrical excitability in excitable cells. Carbamazepine differentially suppressed transient or peak (I_Na(T)) and late (I_Na(L)) components of I_Na. Moreover, the cumulative inhibition of I_Na(T) during pulse-train stimulation at 40 Hz was enhanced by lacosamide. GV-58 was noted to exert stimulatory effect on I_Na(T) and I_Na(L). This stimulated I_Na was not countered by ω-conotoxin MVIID but was effectively reversed by ranolazine. GV-58′s exposure can slow down I_Na inactivation elicited during pulse-train stimulation. Lacosamide directly inhibited I_Na magnitude as well as promoted this cumulative inhibition of I_Na during pulse-train stimuli. Mirogabalin depressed I_Na magnitude as well as modulated frequency dependence of the current. Phenobarbital can directly modulate both the magnitude and frequency dependence of ionic currents, including I_Na. Previous investigations have shown that exposure to small-molecule modulators can perturb I_Na under conditions of high-frequency stimulation. This ionic mechanism plays a crucial role in modulating membrane excitability, hereby supporting the validity of these findings. Full article

Aiming at the problems of low withstand voltage and poor RF performance of traditional HEMT devices, a new AlGaN/GaN high electron mobility transistor device with a π-gate (NπGS HEMT) is designed in this paper. The new structure incorporates a π-gate design along with a PN-junction field plate and an AlGaN back-barrier layer. The device is modeled and simulated in Silvaco TCAD 2015 software and compared with traditional t-gate HEMT devices. The results show that the NπGS HEMT has a significant improvement in various characteristics. The new structure has a higher peak transconductance of 336 mS·mm⁻¹, which is 13% higher than that of the traditional HEMT structure. In terms of output characteristics, the new structure has a higher saturation drain current of 0.188 A/mm. The new structure improves the RF performance of the device with a higher maximum cutoff frequency of about 839 GHz. The device also has a better performance in terms of voltage withstand, exhibiting a higher breakdown voltage of 1817 V. These results show that the proposed new structure could be useful for future research on high voltage withstand and high RF HEMT devices. Full article

In a power transformer short-circuit, transient current and magnetic flux interactions create strong electromagnetic forces that can deform windings and the core, risking failure. Accurate calculation of these forces during design is critical to prevent such outcomes. This paper employs two-dimensional (2D) and three-dimensional (3D) finite-element analysis (FEA) to model a 110 kV, 40 MVA three-phase transformer, calculating magnetic flux density, short-circuit current, and electromagnetic forces. The difference in force values at inner and outer core window positions, reaching up to 40%, is analyzed. The impact of physical winding displacement on axial forces is also studied. Simulation results, validated against analytical calculations, show peak short-circuit currents of 6963 A on the high-voltage (HV) winding and 70,411 A on the low-voltage (LV) winding. Average radial forces were 136 kN on the HV winding and 89 kN on the LV winding, while average axial forces were 8 kN on the HV and 9 kN on the LV. This agreement verifies the FEA models’ reliability. The results provide insights into winding behavior under severe faults and enhance transformer design reliability. Full article

Vertical GaN P-i-N diodes exhibit excellent high-voltage performance, fast switching speed, and low conduction losses, making them highly attractive for power applications. However, their breakdown voltage is severely constrained by electric field crowding at device edges. Using silvaco tcad (2019) tools, this work systematically evaluates multiple edge termination techniques, including deep-etched mesa, beveled mesa, and field-plate configurations with both vertical and inclined mesa structures. We present an optimized multi-drift-layer GaN P-i-N diode incorporating field-plate termination and analyze its electrical performance in detail. This study covers forward conduction characteristics including on-state voltage, on-resistance, and their temperature dependence, reverse breakdown behavior examining voltage capability and electric field distribution under different temperatures, and switching performance addressing both forward recovery phenomena, i.e., voltage overshoot and carrier injection dynamics, and reverse recovery characteristics including peak current and recovery time. The comprehensive analysis offers practical design guidelines for developing high-performance GaN power devices. Full article

The totem-pole bridgeless power factor correction (PFC) circuit based on the triangular current mode (TCM) in the front-end PFC of a switching power supply has the advantage of realizing zero-voltage switching (ZVS) in the full working range. However, the TCM control based on the critical conduction mode (CRM) further increases the inductance current ripple, and the traditional input voltage AC sampling circuit increases the circuit complexity and device cost. Therefore, this paper studies the corresponding improvement technology from two dimensions. Firstly, the coordinated interleaved parallel technology is employed to design the system’s overall control-improvement strategy. This approach not only achieves full working-range ZVS but also reduces both the inductor current ripple and power device stress. Simultaneously, an optimized input voltage sampling circuit is designed to accommodate varying voltage requirements of control chip pins. This circuit demonstrates strong synchronization in both voltage and phase sampling, and the structural characteristics of the optocoupler can also suppress electrical signal interference. Finally, a 600 W totem-pole bridgeless PFC prototype is developed. The experimental results demonstrate the effectiveness of the proposed improved method. The prototype efficiency peak reaches 97.3%. Full article

Silicon carbide (SiC) half-bridge power modules are widely utilized in new energy power generation, electric vehicles, and industrial power supplies. To address the research gap in collaborative validation between electro-thermal coupling models and process reliability, this paper proposes a closed-loop methodology of “design-simulation-process-validation”. This approach integrates in-depth electro-thermal simulation (LTspice XVII/COMSOL Multiphysics 6.3) with micro/nano-packaging processes (sintering/bonding). Firstly, a multifunctional double-pulse test board was designed for the dynamic characterization of SiC devices. LTspice simulations revealed the switching characteristics under an 800 V operating condition. Subsequently, a thermal simulation model was constructed in COMSOL to quantify the module junction temperature gradient (25 °C → 80 °C). Key process parameters affecting reliability were then quantified, including conductive adhesive sintering (S820-F680, 39.3 W/m·K), high-temperature baking at 175 °C, and aluminum wire bonding (15 mil wire diameter and 500 mW ultrasonic power/500 g bonding force). Finally, a double-pulse dynamic test platform was established to capture switching transient characteristics. Experimental results demonstrated the following: (1) The packaged module successfully passed the 800 V high-voltage validation. Measured drain current (4.62 A) exhibited an error of <0.65% compared to the simulated value (4.65 A). (2) The simulated junction temperature (80 °C) was significantly below the safety threshold (175 °C). (3) Microscopic examination using a Leica IVesta 3 microscope (55× magnification) confirmed the absence of voids at the sintering and bonding interfaces. (4) Frequency-dependent dynamic characterization revealed a 6 nH parasitic inductance via Ansys Q3D 2025 R1 simulation, with experimental validation at 8.3 nH through double-pulse testing. Thermal evaluations up to 200 kHz indicated 109 °C peak temperature (below 175 °C datasheet limit) and low switching losses. This work provides a critical process benchmark for the micro/nano-manufacturing of high-density SiC modules. Full article

Insulation materials are critical for the reliability and performance of electrical power systems, particularly in high-voltage rotating machines. While failures can arise from thermal, mechanical, or electrical stress, they predominantly manifest as electrical breakdowns. Prior research has primarily concentrated on aging in straight winding sections, despite evidence indicating that failures frequently occur in the bending regions of turn insulation. This study explores the influence of high-frequency pulsed electrical stress on the lifetime behavior of Type II insulation systems used in high-voltage rotating machines. Practical samples, designed with geometric configurations and technology akin to that in rotating machines, were tested under conditions characterized by voltage slew rates (dv/dt) exceeding 10 kV/μs, with variations in frequency and waveform shape. The findings reveal that the rate of electrical aging remains consistent across differing pulse widths, risetimes, and polarities, displaying a similar lifetime exponent. Nonetheless, insulation durability is markedly more compromised under pulsed conditions. At the identical times-to-failure, the sinusoidal waveform necessitated nearly twice the applied peak voltage as the bipolar pulse waveform. This finding clearly suggests that pulsed excitation exacerbates insulation degradation more effectively due to the sharp rise times and high (dv/dt) rates imposing substantial electrical stress on dielectric materials. Full article

Electric vehicles (EVs) offer a sustainable solution for reducing carbon emissions in the transportation sector. However, their increasing widespread adoption poses significant challenges for local distribution grids, many of which were not designed to accommodate the heightened and irregular power demands of EV charging. Components such as transformers and distribution networks may experience overload, voltage imbalances, and congestion—particularly during peak periods. While upgrading grid infrastructure is a potential solution, it is often costly and complex to implement. The unpredictable nature of EV charging behavior further complicates grid operations, as charging demand fluctuates throughout the day. Therefore, efficient integration into the grid—both for charging and potential discharging—is essential. This paper reviews recent studies on the impacts of high EV penetration on distribution grids and explores various strategies to enhance grid performance during peak demand. It also examines promising optimization methods aimed at mitigating negative effects, such as load shifting and smart charging, and compares their effectiveness across different grid parameters. Additionally, the paper discusses key challenges related to impact analysis and proposes approaches to improve them in order to achieve better overall grid performance. Full article

Bifacial photovoltaic technology is made up of solar cells with the ability to generate electrical power on both sides of the cell (front and rear), consequently, they generate more energy in the same area compared to conventional or monofacial solar cells. The present work deals with the calculation of the energy yield using bifacial solar cells under the specific environmental conditions of Tampico, Tamaulipas, Mexico. Two configurations were compared: (1) tilted, optimized in height and angle, oriented to the south, and (2) vertically optimized in height, oriented east–west. The results were also compared with a standard monofacial solar cell optimally tilted and oriented south. The experimental data were acquired using a current–voltage (I-V) curve tracer designed for this purpose. This study shows that the vertically optimized bifacial solar cell produces similar electrical power to the conventional monofacial solar cell, with the benefit of maximum production in peak hours (8:30 and 16:30). In contrast, in the case of the inclined bifacial solar cell, about 26% more in the production of electrical power was reached. These results guide similar studies in other places of the Mexican Republic and regions with similar latitudes and climate. Full article