Search Results (1,017)

Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs) are emerging as the technology of choice for next-generation power conversion systems, offering switching speeds, on-state resistance, and power density unattainable with silicon or even silicon carbide (SiC) devices. However, the fast switching transients that make GaN attractive also make it a demanding source of electromagnetic interference (EMI), so credible electromagnetic compatibility (EMC) analysis requires an accurate functional device model. This paper addresses the functional electrothermal modeling of a commercial 650 V GaN HEMT (GS66504B) as a prerequisite to EMC validation. The manufacturer-supplied Level 3 SPICE model is evaluated against experimental static (I-V) and dynamic (C-V) measurements. Significant discrepancies motivate an optimization methodology in which an initial manual procedure is superseded by a fully automated pipeline coupling LTspice with a Genetic Algorithm in MATLAB R2025b. A forward/reverse and dual-temperature-segment strategy reduces the mean absolute relative error to below 7% (forward I-V) and 13% (reverse I-V) over 25–100 °C, while a dedicated two-stage C–V optimization reduces the reverse-transfer capacitance error from 95.4% to 2.89%. The resulting compact, unified, and fully validated model underpins the ongoing EMC validation phase, where it will be combined with extracted parasitic and cable models in a DC-DC converter topology. Full article

This paper presents the experimental validation of a high-frequency full-SiC railway auxiliary converter power module intended as a building block for modular multi-system railway auxiliary converters. The proposed architecture employs a unified SiC-based power conversion platform that integrates an active front-end single-phase PWM rectifier with a galvanically isolated high-frequency DC/DC stage operating at 90 kHz under zero-current switching (ZCS) conditions. Although the converter is designed for both AC and DC traction systems, this study focuses primarily on its operation under single-phase AC railway supply conditions, which are representative of practical applications. A hybrid bipolar–unipolar modulation strategy is used to reduce the RMS voltage stress on the input inductor while preserving controllability of the input current near the voltage zero-crossing regions. Special attention is given to operation under distorted railway supply voltages, which are common in real traction systems. The control structure combines a proportional–resonant (PR) current controller, harmonic compensators, feedforward voltage compensation, and MSOGI-based synchronization to ensure stable synchronization and low-input current distortion even under non-ideal conditions. Experimental validation was performed on a 10 kW laboratory prototype. The results demonstrate a peak efficiency of 98.4% and near-unity input power factor. Under heavily distorted supply conditions ${\mathrm{THD}}_{\mathrm{v}}>30\%$, the input current distortion remained below ${\mathrm{THD}}_{\mathrm{i}}=2.3\%$. Harmonic and STFT analyses confirmed the robustness of the proposed synchronization and current control structure. The obtained results indicate that the proposed high-frequency full-SiC converter topology is a promising solution for future modular railway auxiliary converters, offering high efficiency, reduced passive component volume, and high power density. Full-scale high-voltage validation under both AC and DC traction systems remains the subject of further work. Full article

The objective of the research presented in this paper was to develop methods for simulating the operating conditions of traction power supply systems (TPSSs) equipped with asynchronous generators (ASGs), which may be driven by wind or hydraulic turbines as prime movers, thereby significantly reducing train traction energy costs and lowering carbon monoxide emissions. Using phase-coordinate methods and the Fazonord AC-DC industrial software package, simulations were performed for a TPSS configuration comprising three traction substations (TSs) with ASGs connected to the 6 kV busbars. The results demonstrate that connecting the ASG reduces the maximum active power flow from the utility grid by 27%, decreases peak losses in the 220 kV primary supply line by 44%, and lowers voltage unbalance levels at the 220 kV busbars by 71–76%. Additionally, electromagnetic safety conditions along the 220 kV overhead lines feeding the substations are improved, and the temperature at the hottest points of the traction transformers is reduced. The developed ASG models, implemented using three controlled current sources, are universal and can be applied to TPSSs of various configurations and design layouts. Full article

Silver oxide–aluminum (AgO-Al) batteries are widely used as power sources for underwater vehicles, where direct current/direct current (DC/DC) converters play a critical role in supplying low-voltage loads. Accurate reliability assessment of DC/DC converters is essential for ensuring successful missions. Existing studies rarely consider the constraints between key performance parameters, as well as the load-dependent characteristics of measurement errors, limiting their applicability to DC/DC converters. To address these issues, a probabilistic model describing the relationship between operating load and measurement error is proposed, with particular emphasis on the load-dependent stochastic characteristics of measurement errors. Based on this relationship, load-dependent stochastic models for both the power-on and power-off voltages are developed by jointly considering unit-to-unit variability and random measurement errors. The model parameters are estimated by maximum likelihood estimation. A failure criterion incorporating the operational constraints between the power-on and power-off voltages is established according to the practical requirements of DC/DC converters. A reliability assessment method considering the dependence between the power-on and power-off voltages is provided according to the practical requirements. Based on test data, the results show that the Kolmogorov–Smirnov statistic of the proposed method is at least 86% lower than the compared methods, indicating a more accurate reliability assessment. Full article

PV-supplied DC microgrids (PV-DCMGs) are well suited to powering many off-grid applications. Droop control is an effective approach for managing sources in microgrids because it improves system reliability and scalability. However, conventional droop control may not satisfy the requirements of PV-DCMGs, in which loads must connect and disconnect dynamically according to solar-power availability. This paper proposes a droop-based method for operating multiple loads in a PV-DCMG. The line voltage serves as a signal for allocating power among the loads and determining their connection status. A key requirement is a smooth line-voltage transient to preserve stability and avoid unnecessary load connection or disconnection. The paper presents the control logic and procedures for sizing the bus capacitance to achieve effective and stable operation. It also analyzes the effects of key non-idealities in the DC-microgrid model and proposes mitigation methods. Simulation and experimental results demonstrate the effectiveness of the proposed control logic and component-sizing procedures for managing the available power in a PV-DCMG. Full article

This paper presents an energy-management and state-of-charge (SoC) balancing scheme, denoted OEMSS, for a DC microgrid comprising photovoltaic generation, a fuel-cell source, two energy storage systems (ESSs), and six household loads. A demand-driven power-allocation layer first determines whether generation is sufficient, ESS support is required, or priority-based load scheduling must be activated. A supervisory balancing layer then allocates the fleet charging or discharging request by using a capacity-weighted average SoC and separate mode-dependent correction laws. The balancing command is dimensionally expressed as an energy-capacity deviation divided by the control interval and is projected onto the SoC and power limits. A Python simulation driven by recorded generation profiles is used to evaluate four seasonal operating conditions. In the tested equal-capacity case, the maximum inter-ESS SoC deviation is reduced from 18% to 4.8%, synchronization is reached within approximately 2 to 4 h, and simulated over-discharge events are avoided. The reported increase from 45% to approximately 70% is interpreted as a 25-percentage-point increase in the ESS storage contribution rate, rather than an increase in conversion efficiency. During shortage intervals, the retained priority demand is supplied, whereas satisfaction of the original uncurtailed demand is not claimed. A discrete-time Lyapunov analysis gives the nominal convergence condition $0<{\gamma }_b<2$, and the online implementation has $\mathcal{O}(J+K+H)$ time complexity. The study provides simulation evidence for a simple coordinated allocation rule; hardware performance, battery-life extension, converter-level stability, and global optimality remain to be established. Full article

This study develops and experimentally validates a battery-coupled wind–photovoltaic power model for auxiliary electrical supply in small-vessel systems. The prototype integrates a 395 W CS6R-395MS monocrystalline photovoltaic module (CSI Solar Co., Ltd., Suzhou, Jiangsu, China), a 200 W FA200W horizontal-axis wind turbine (VEVOR, Rancho Cucamonga, CA, USA), maximum power point tracking (MPPT) power-conditioning stages, a 24 V/28 Ah AGM VRLA battery bank composed of four BAT212120086 batteries (Victron Energy B.V., Almere, The Netherlands), a 24 V DC bus, and a Phoenix 24/500 pure sine-wave inverter (Victron Energy B.V., Almere, The Netherlands), targeting non-propulsion navigation, communication, and lighting loads on a 5.7 m length overall (LOA) vessel. Field-acquired irradiance, cell temperature, incidence angle, PV voltage, wind speed, and rotor-speed data were used as time-dependent model inputs and compared with synchronized active-power measurements. Across the full 15–24 September 2025 experimental campaign, the maximum absolute relative error remained below 2.69%, while the aggregate statistical validation indices were ME = −0.1041 W, MAE = 0.3988 W, RMSE = 0.4931 W, and MAPE = 0.5946%. For the representative cloud-adverse case study conducted on 21 September 2025, the measured hybrid generation reached $E_{\mathrm{h}\mathrm{y}\mathrm{b}}=611.3 \mathrm{W}\mathrm{h}$ over 8.28 h, corresponding to $C_{\mathrm{R}\mathrm{E}\mathrm{S}}=102.1\%$ of the selected $E_{\mathrm{l}\mathrm{o}\mathrm{a}\mathrm{d}}=599 \mathrm{W}\mathrm{h}/\mathrm{d}\mathrm{a}\mathrm{y}$ auxiliary-load profile and to $C_{\mathrm{h}\mathrm{y}\mathrm{b}+\mathrm{b}\mathrm{a}\mathrm{t}}=158.1\%$ when the usable battery reserve at 50% depth of discharge (DOD) was included. Full article

In medium-voltage DC distribution systems (MVDC-DSs), feeder congestion may occur when multiple converter terminals sharing the same AC feeder experience fast source–load variations. Limited communication further challenges real-time converter coordination and secure system operation. To address these issues, this paper has proposed an adaptive online management strategy for multi-terminal feeder congestion in MVDC-DSs under limited communication. First, the economic operation objective and practical system constraints are formulated within a distributed optimization framework, where feeder congestion limits, voltage security, and load supply requirements are explicitly incorporated. Then, an adaptive online regulation mechanism is embedded into local converter controllers, enabling converter power to be coordinated in real time using only neighboring information. In this way, feeder congestion can be mitigated while reliable load supply and economic operation are maintained. Simulation studies and hardware-in-the-loop experimental results demonstrate the effectiveness, scalability, and real-time applicability of the proposed strategy under dynamic operating conditions. Full article

Reliability assessment of EMU onboard power supply boards is constrained by scarce field failure data and the intrusive nature of component-level degradation monitoring. Moreover, conventional linear degradation models may inadequately characterize the non-monotonic fluctuations and time-varying degradation rates of board-level health indicators. To address these limitations, this study proposes a mechanism-informed reliability assessment method using output ripple voltage as a non-invasive degradation indicator. A thermally accelerated degradation test was conducted on power supply boards used in video-monitoring servers, and a stable-baseline output-ripple relative-increment indicator was constructed to mitigate the effects of the initial burn-in process and sample-to-sample baseline differences. A nonlinear Wiener process with a power-law time scale was then developed to characterize the non-monotonic evolution, stochastic fluctuations, and time-varying degradation rate of the output ripple. Arrhenius-based lifetime extrapolation and time-censored MTBF analysis were subsequently performed. Compared with the linear and quadratic-drift Wiener processes, the proposed model achieved the largest maximized log-likelihood and the lowest AIC and BIC values; both information criteria were 22.56 lower than the corresponding values of the quadratic-drift model. Using an activation energy of 0.7 eV, the thermal acceleration factor was 41.19. Under the baseline scenario threshold of 150 mV, the predicted MTTF, R₉₀ lifetime, and R₅₀ lifetime were 16.20, 7.77, and 13.92 equivalent operating years, respectively, while the point estimate of the functional-failure-based time-censored MTBF was 43.45 years. The proposed method provides a non-invasive reliability assessment framework for condition monitoring, early warning, and preventive maintenance of EMU onboard power supply boards when failure data are scarce. Full article

Maritime transport, responsible for over 90% of global trade, is a significant contributor to greenhouse gas emissions due to its reliance on fossil fuels. Achieving international decarbonization targets set by the International Maritime Organization and the European Green Deal requires not only advancements in vessel technologies but also the sustainable transformation of port infrastructures. In this context, this study examines current trends in shore-to-ship (STS) charging technologies as a key enabler of sustainable port electrification. It provides a comprehensive review of AC, DC, and hybrid charging architectures, along with recent developments in robotic and autonomous charging systems. The study also explores industrial standards and energy management strategies for smart port applications, and identifies renewable integration and grid interaction models as key directions for future research. Furthermore, the study proposes an Onshore Power Supply (OPS) Readiness Index (OPSRI), a multi-criteria assessment framework that evaluates ship types based on their operational, technical, infrastructural, and regulatory suitability for onshore power integration. The main contribution of this review lies in integrating international standards, robotic charging technologies, and ship-type-specific readiness assessment into a unified analytical framework. The results indicate that ferries and tugboats are highly suitable for OPS deployment, while long-haul cargo vessels face greater limitations under current conditions. Overall, the findings offer practical insights for port authorities, policymakers, and energy planners, highlighting key challenges and future directions toward smart, sustainable, and low-carbon port ecosystems. Full article

This article reviews the reactive magnetron sputtering of piezoelectric Aluminium Nitride (AlN) thin films, with a focus on process parameter optimisation and system-level deposition challenges. AlN is a leading material for MEMS and RF applications owing to its c-axis (002) orientation, high acoustic velocity, wide bandgap (∼6.2 eV), and CMOS compatibility. We review the influence of sputtering power, nitrogen flow ratio, substrate temperature, and target-to-substrate distance on crystallographic quality and document practical hardware challenges, including vacuum leakage, grounding faults, target erosion, and mass flow controller drift, that critically affect reproducibility but are systematically underreported in the literature. A perspective is provided on emerging application domains where optimised AlN films address current performance gaps, including next-generation RF/telecom systems towards 6G and Future Networks, harsh environment sensing and actuation, biomedical ultrasound, and IoT energy harvesting. The complementarity between AlN and Silicon Carbide (SiC) is discussed for high-temperature, high-power, and radiation-hard MEMS, where AlN/SiC heterostructures combine the piezoelectric activity of AlN with the mechanical and chemical robustness of SiC. It also incorporates a discussion of dopant- and heteroepitaxy-based AlN engineering, AlN deposition on a wider range of substrates, the role of seed and electrode underlayers, and pulsed-DC sputtering as a third power supply mode alongside RF and conventional DC. Full article

Various inverter applications such as electronic vehicles, renewable energy systems, and uninterrupted power supplies have been the motive behind the increasing focus on the DC-AC inverters field. Therefore, DC-AC inverters have been evolving with the recent topology being the Z-source inverters (ZSIs). Though the ZSI overcame most of the limitations faced by the previous topologies such as the Voltage-Source Inverters (VSIs) and Current-Source Inverters (CSIs), they had shortcomings such as the increase in switching devices’ voltage stress and hence the deterioration of power quality with the increase in the boost factor. As a result, several ZSI-based topologies have been proposed in the literature to further improve the performance of a ZSI. This paper also proposes a different Z-source inverter topology called the Shunt Capacitor-Boosted Z-Source Inverter (SCB-ZSI) which seeks to improve the boost factor and lower the voltage stress. This inverter strategically adds two shunt capacitors on the impedance network of a traditional Z-source inverter, hence the Shunt Capacitor-Boosted-ZSI. The SCB-ZSI was mathematically modeled and simulated on MATLAB Simulink R2024a version. The SCB-ZSI was found to have a high boost factor compared to the ZSI for the same input DC voltage and modulation index. The SCB-ZSI was also found to incur less switching voltage stress across the switching devices compared to the ZSI for the same input DC voltage and modulation index. The simulation test results showed that the selection of shunt capacitors of a ZSI at 1% of those of the original ZSI improves the boost factor by 56% and reduces the switch voltage stress ration by 40% on an SCB-ZSI for the same set of input parameters. Though the SCB-ZSI is one of the promising ZSI-based inverter topologies, more work still has to be done before they can be industrially applied, such as developing an algorithm to design the shunt capacitors. Full article

This paper presents the design, construction, and experimental evaluation of a low-cost, portable solar tracking system for monitoring ultraviolet solar radiation in real time. It integrates a Raspberry Pi Zero 2W as the embedded control unit, an AS7331 spectral sensor to measure UVA, UVB, and UVC irradiance, two 270° servomotors to position the system toward the sun, an NEO-6M GPS module to geolocate the system, and a DS3231 real-time clock to synchronize the time. To enable autonomous outdoor operation, a multistage power supply architecture based on a solar panel, a rechargeable battery, and LM2596 and MP1584EN DC-DC regulators was implemented. The tracking algorithm uses astronomical equations to estimate the solar azimuth and elevation and updates the sensor orientation during daylight hours. This allows the UV sensor to remain approximately normal to the incoming solar radiation. Experimental tests were conducted in Arequipa, Peru. The recorded data included UVA, UVB, and UVC irradiance; sensor temperature; geographic coordinates; time; and solar angles. The measured UV profiles exhibited the anticipated diurnal behavior: maximum values around solar noon, higher UVA levels than UVB levels, and minimal UVC levels due to atmospheric absorption. We compared the radiometric response with reference information from EarthKit, PVGIS 5.3, SAMPA, and a Davis Vantage Pro 2 weather station. We evaluated the solar positioning performance against Stellarium, NOAA, and the NREL Solar Position Algorithm. Across the complete five-day validation at three daily evaluation times, the maximum percentage errors were 0.0584% for azimuth and 0.5059% for elevation relative to the NREL SPA, NOAA, and Stellarium reference calculations. The results demonstrate that the proposed system constitutes an embedded, portable, autonomous, and low-cost platform for in situ monitoring of solar ultraviolet radiation. Due to its modular architecture, georeferencing capability, time synchronization, and independent power supply, the prototype can be used as a mobile measurement unit or as part of a distributed network of UV stations at various locations in Arequipa. In this regard, the system enables multipoint measurement campaigns, complements fixed weather stations, validates solar models, and generates local experimental data for the spatial and temporal assessment of the solar UV resource under real-world field conditions. Full article

Single-use pyrotechnic and compressed-gas actuators currently meet industrial safety tasks that demand rapid response and high force. An integrated hydrogen production and combustion-driven actuation system is proposed as a clean and reusable alternative. Hydrogen is generated on demand inside the unit by water electrolysis. It is stored in a metal hydride module and burned with air under controlled conditions to drive a double-piston mechanism. A combined approach of modeling, such as thermodynamic analysis, ideal gas laws, and Engineering Equation Solver (EES) simulations, was used to predict the hydrogen demand and system performance. In addition, the combustion behavior and chamber pressure distribution were investigated using COMSOL Multiphysics. It was shown that hydrogen–air combustion allows for more stable and controllable operating conditions than hydrogen–oxygen combustion, while still satisfying the required in-cylinder pressure of about 350 bar. The designed proton exchange membrane (PEM) electrolyzer consumes about 221 W of power from a 24 V DC power source and produces 0.16 g of hydrogen in 135 s, which is sufficient for a high-force actuation stroke. Unlike conventional pyrotechnic cartridges and pneumatic and hydraulic actuators, the suggested system generates no solid combustion residues and does not require single-use consumables. It is reusable for many cycles, with water vapor as the main combustion product. Overall, the findings support hydrogen-powered actuation on demand as a viable and clean option for high-force safety tasks, ranging from closing emergency shut-off valves at oil and gas facilities to pressurizing fire protection and other safety systems, making it particularly attractive for remote facilities without a continuous grid power supply. Full article

This paper presents a single-sensor solution for the detection and monitoring of power supply voltage unbalances in AC/DC/AC converters. By analyzing the DC-link input current, it is demonstrated that characteristic current pulse deformations directly indicate the presence and severity of grid voltage imbalances. Based on these pulse profile variations, a novel diagnostic metric termed the Current Ripple Voltage Unbalance Factor (CRVUF) is derived. The proposed methodology was comprehensively evaluated and validated through both simulation studies and experimental testing. The presented approach offers a computationally efficient, non-invasive alternative to conventional monitoring systems, effectively reducing the number of required voltage sensors from three to a single current sensor. Full article