Search Results (2,383)

This study investigates the electro-thermal transient response of a photovoltaic–thermal (PV/T)–heat pump system under dynamic disturbances to optimize operational stability. A dynamic model integrating a PV/T collector and a heat pump was developed by the transient heat current method, enabling high-fidelity simulations of step perturbations: solar irradiance reduction, compressor operation, condenser water flow rate variations, and thermal storage tank volume changes. This study highlights the thermal storage tank’s critical role. For V_tank = 2 m³, water tank volume significantly suppresses the water tank and PV/T collector temperature fluctuations caused by solar irradiance reduction. PV/T collector temperature fluctuation suppression improved by 46.7%. For the PV/T heat pump system in this study, the water tank volume was selected between 1 and 1.5 m³ to optimize the balance of thermal inertia and cost. Despite PV cell electrical efficiency gains from PV cell temperature reductions caused by solar irradiance reduction, power recovery remains limited. Compressor dynamic performance exhibits asymmetry: the hot water temperature drop caused by speed reduction exceeds the rise from speed increase. Load fluctuations reveal heightened risk: load reduction triggers a hot water 7.6 °C decline versus a 2.2 °C gain under equivalent load increases. Meanwhile, water flow rate variation in condenser identifies electro-thermal time lags (100 s thermal and 50 s electrical stabilization), necessitating predictive compressor control to prevent temperature and compressor operation oscillations caused by system condition changes. These findings advance hybrid renewable systems by resolving transient coupling mechanisms and enhancing operational resilience, offering actionable strategies for PV/T–heat pump deployment in building energy applications. Full article

Phase-shifting transformers (PST) are widely used to control power flows. However, conventional designs can vary only the phase angle, leaving the voltage magnitude unaffected or requiring structurally complex devices. This study proposes a compact PST topology that realizes simultaneous, decoupled control of both voltage magnitude and phase angle through two coordinated sets of windings. Closed-form equations are derived to link the phase-shifting and voltage regulation windings turn ratios to any target magnitude ratio and phase-shift angle, providing a unified design framework that guarantees the full practical operating range. Steady-state tests verify that the device can change the phase or adjust the magnitude independently without cross-coupling. Dynamic tests demonstrate that, when a tap command is issued, the line currents and active power converge to new set-points within a few fundamental periods and with minimal oscillation. Furthermore, the PST’s application to loop closing operations in 220 kV networks is investigated, where simulation results show it can suppress loop closing currents by over 90% under adverse voltage mismatch conditions. These results confirm that the proposed PST offers a fast, economical alternative to Flexible AC Transmission Systems (FACTS) equipment for real-time power flow balancing, renewable integration and inter-area exchange in modern transmission networks. Full article

Hydraulic motors are increasingly pivotal in high-power drive systems for heavy-duty vehicles and industrial machinery due to their high power density. Radial piston hydraulic motors are commonly employed in heavy-load applications, while digital hydraulic motors have surfaced as a potential substitute for traditional hydraulic motors. Yet challenges such as torque pulsation and inefficient flow distribution persist in traditional designs. To improve performance and reliability, this paper proposed a digital radial piston hydraulic motor using several switching valves to distribute hydraulic oil, along with a comprehensive strategy to mitigate flow pulsation and enhance hydraulic transmission efficiency in digital hydraulic motors. The inherent torque pulsation characteristics are systematically investigated, revealing their dependence on valve actuation patterns and load dynamics. A novel torque pulsation mitigation design is introduced. Then, valve modeling and efficiency evaluation are developed; the phase-correction-based flow distribution method is conducted by optimizing valve sequencing; and simulations and experiments are carried out to demonstrate the feasibility. In conclusion, insights have been drawn to direct the design and control of radial piston digital hydraulic motors. This paper presents a potential solution for heavy-duty traction applications. Full article

Utilizing a coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) approach, this study constructs a comprehensive three-dimensional numerical model to simulate particle migration dynamics within rough artificial fractures subjected to the high-energy impact of water inrush. The model explicitly incorporates key governing factors, including intricate fracture wall geometry characterized by the joint roughness coefficient (JRC) and aperture variation, hydraulic pressure gradients representative of inrush events, and polydisperse sand particle sizes. Sophisticated simulations track the complete mobilization, subsequent acceleration, and sustained transport of sand particles driven by the powerful high-pressure flow. The results demonstrate that particle migration trajectories undergo a distinct three-phase kinetic evolution: initial acceleration, intermediate coordination, and final attenuation. This evolution is critically governed by the complex interplay of hydrodynamic shear stress exerted by the fluid flow, frictional resistance at the fracture walls, and dynamic interactions (collisions, contacts) between individual particles. Sensitivity analyses reveal that parameters like fracture roughness exert significant nonlinear control on transport efficiency, with an identified optimal JRC range (14–16) promoting the most effective particle transit. Hydraulic pressure and mean aperture size also exhibit strong, nonlinear regulatory influences. Particle transport manifests through characteristic collective migration patterns, including “overall bulk progression”, processes of “fragmentation followed by reaggregation”, and distinctive “center-stretch-edge-retention” formation. Simultaneously, specific behaviors for individual particles are categorized as navigating the “main shear channel”, experiencing “boundary-disturbance drift”, or becoming trapped as “wall-adhered obstructed” particles. Crucially, a robust multivariate regression model is formulated, integrating these key parameter effects, to quantitatively predict the critical migration time required for 80% of the total particle mass to transit the fracture. This investigation provides fundamental mechanistic insights into the particle–fluid dynamics underpinning hazardous water–sand inrush phenomena, offering valuable theoretical underpinnings for risk assessment and mitigation strategies in deep underground engineering operations. Full article

This paper addresses the challenge of renewable energy curtailment, which stems from the inherent uncertainty and volatility of wind and photovoltaic (PV) generation, by developing a robust model predictive control (RMPC)-based scheduling strategy for an integrated wind–PV–hydrogen storage multi-energy flow system. By building a “wind–PV–hydrogen storage–fuel cell” collaborative system, the time and space complementarity of wind and PV is used to stabilize fluctuations, and the electrolyzer–hydrogen production–gas storage tank–fuel cell chain is used to absorb surplus power. A multi-time scale state-space model (SSM) including power balance equation, equipment constraints, and opportunity constraints is established. The RMPC scheduling framework is designed, taking the wind–PV joint probability scene generated by Copula and improved K-means and SSM state variables as inputs, and the improved genetic algorithm is used to solve the min–max robust optimization problem to achieve closed-loop control. Validation using real-world data from Xinjiang demonstrates a 57.83% reduction in grid power fluctuations under extreme conditions and a 58.41% decrease in renewable curtailment rates, markedly enhancing the local system’s capacity to utilize wind and solar energy. Full article

Power electronics convert and control electrical power in applications ranging from electric motors to telecommunications and computing. Ongoing efforts to miniaturize these systems and boost power density demand advanced thermal management solutions to maintain optimal cooling and temperature control. Spray cooling offers an effective means of removing high heat fluxes and keeping power electronics within safe operating temperatures. This study presents an experimental investigation of flash spray cooling in a closed-loop system using R410A refrigerant. In particular, two nozzles with different spraying angles are used to study the effects of the distance between the spray nozzle and a heated flat surface, as well as the mass flow rate of the coolant. Results indicate that three key flow-pattern factors—surface coverage, impingement intensity, and liquid film dynamics—govern the heat transfer mechanisms and determine cooling efficiency. Flash spray cooling using refrigerants like R410A demonstrates strong potential as a high-performance thermal management strategy for next-generation power electronics. Full article

Three-level non-inverting buck–boost converters are promising for electric vehicle charging stations due to their wide voltage regulation capability and bidirectional power flow. However, the number of three-level operating states is four times that of two-level operating states, and the lack of a unified switching state selection mechanism leads to serious challenges in its application. To address these issues, a finite control set model predictive control (FCS-MPC) strategy is proposed, which can determine the optimal set and select the best switching state from the excessive number of states. Not only does the proposed method achieve fast regulation over a wide voltage range, but it also maintains the input- and output-side capacitor voltage balance simultaneously. A further key advantage is that the number of switching actions in adjacent cycles is minimized. Finally, a hardware-in-the-loop experimental platform is built, and the proposed control method can realize smooth transitions between multiple operation modes without the need for detecting modes. In addition, the state polling range and the number of switching actions are superior to conventional predictive control, which provides an effective solution for high-performance multilevel converter control in energy systems. Full article

This project presents the development of an open-source educational platform based on an automotive Electrically Excited Synchronous Machine (EESM) repurposed from a KIA Sportage mild-hybrid vehicle. The introduction provides an overview of hybrid drive systems and the primary configurations employed in automotive applications, including classifications based on power flow and the placement of electric motors. The focus is placed on the parallel hybrid configuration, where a belt-driven starter-generator assists the internal combustion engine (ICE). Due to the proprietary nature of the original control system, the unit was disassembled, and a custom control board was designed using a Texas Instruments C2000 Digital Signal Processor (DSP). The motor features a six-phase dual three-phase stator, offering improved torque smoothness, fault tolerance, and reduced current per phase. A compact Anisotropic Magneto Resistive (AMR) position sensor was implemented for position and speed measurements. Current sensing was achieved using both direct and magnetic field-based methods. The control algorithm was verified on a modified six-phase inverter under simulated vehicle conditions utilizing a dynamometer. Results confirmed reliable operation and validated the control approach. Future work will involve complete hardware testing with the new control board to finalize the platform as a flexible, open-source tool for research and education in hybrid drive technologies. Full article

This study presents a semi-empirical approach to generalizing the acoustic radiation generated by serrated airfoil configurations, based on small-scale aerodynamic/acoustic experiments and functional regression techniques. In the context of passive noise reduction strategies, such as leading-edge and trailing-edge serrations, acoustic measurements are performed in a controlled subsonic wind tunnel environment. Sound pressure level (SPL) spectra and acoustic power metrics are acquired for various geometric configurations and flow conditions. These spectral data are then analyzed using regression-based modeling techniques—linear, quadratic, logarithmic, and exponential forms—to capture the dependence of acoustic emission on key geometric and flow-related variables (e.g., serration amplitude, wavelength, angle of attack), without relying explicitly on predefined nondimensional numbers. The resulting predictive models aim to describe SPL behavior across relevant frequency bands (e.g., broadband or 1/3 octave) and to extrapolate acoustic trends for configurations beyond those tested. The proposed methodology allows for the identification of compact functional relationships between configuration parameters and acoustic output, offering a practical tool for the preliminary design and optimization of low-noise serrated profiles. The findings are intended to support both physical understanding and engineering application, bridging experimental data and parametric acoustic modeling in aerodynamic noise control. Full article

The subject of this paper is how certain electrode array parameters affect the operating characteristics of electrohydrodynamic (EHD) propulsion systems. The focus is on how changes in the shapes and arrangements of electrodes, such as the diameter of the coronating conductor, effective electrode length and the spacing between electrodes, influence the formation and behaviour of the corona discharge and the resulting ion-induced airflow. A modular experimental setup was created to allow for a systematic study of each parameter in controlled atmospheric conditions using a high-voltage DC power supply. The study includes both the theoretical background and experimental methods, in order to explore the connections between the electric field distribution, ion mobility and propulsion force generation. By measuring the current, voltage and flow velocity, the impacts of design changes on the propulsion behaviour are examined. The findings help to improve the understanding of EHD propulsion mechanics and lay the groundwork for optimising electrode designs in future applications. This research supports the ongoing work to create compact, quiet and efficient propulsion technologies for use in lightweight aerial vehicles, precise fluid control and other engineering areas, where solid-state thrust systems have clear benefits over traditional methods. Full article

Smart monitoring of local electricity systems (LESs) with sources based on renewable energy resources (RESs) from the point of view of the requirements of the functions of an intelligent system are hardware and software systems that can solve the tasks of both analysis (optimization) and synthesis (design, planning, control). The article considers the following: a functional scheme of smart monitoring of LESs, describing its main components and scope of application; an assessment of the state of the processes and the state of the equipment of generators and loads; dynamic pricing and a dynamic assessment of the state of use of primary fuel and/or current costs of generators; economic efficiency of generator operation and loads; an assessment of environmental acceptability, in particular, the volume of CO₂ emissions; provides demand-side management, managing maximum energy consumption; a forecast of system development; an assessment of mutual flows of electricity; system resistance to disturbances; a forecast of metrological indicators, potential opportunities for generating RESs (wind power plants, solar power plants, etc.); an assessment of current costs; the state of electromagnetic compatibility of system elements and operation of electricity storage devices; and ensures work on local electricity markets. The application of smart monitoring in the formation of tariffs on local energy markets for transactive energy systems is shown by conducting a combined comprehensive assessment of the energy produced by each individual power source with graphs of the dependence of costs on the generated power. Algorithms for the comprehensive assessment of the cost of electricity production in a transactive system for calculating planned costs are developed, and the calculation of the cost of production per 1 kW is also presented. A visualization of the results of applying this algorithm is presented. Full article

Islanded DC microgrids face challenges in voltage stability and communication overhead due to renewable energy variability. A novel enhanced distributed coordinated control framework, based on adaptive event-triggered mechanisms, is developed for the efficient management of multiple hybrid energy storage systems (HESSs) in islanded DC microgrids (MGs). We propose a hierarchical distributed control framework integrating ANN-based controllers and adaptive event-triggered mechanisms to dynamically regulate power flow and minimise communication. This system utilises a hierarchical coordinated control method (HCCM) with primary virtual resistance droop control integrated with state-of-charge (SoC) management and secondary control for voltage regulation and proportional current distribution through optimised communication networks. The integration of artificial neural network (ANN)-based controllers alongside traditional PI control leads to an improvement in system responsiveness. The control approach dynamically adjusts the trigger parameters to minimise communication overhead with tight voltage regulation. An extensive simulation using MATLAB/Simulink shows how the system can effectively manage variability in renewable energy sources and maintain stable voltage profiles with precise power distribution and minimal bus voltage fluctuations. Simulations confirm enhanced voltage regulation (±0.5% deviation), proportional current sharing (98% accuracy), and 60% communication reduction under load transients (outcomes). Full article

The transport properties of biased type II superconductors are strongly influenced by external magnetic fields, which play a crucial role in optimizing the stability and performance of low-noise superconducting electronic devices. A major challenge is the stochastic behavior of Abrikosov vortices, which emerge in the mixed state and lead to energy dissipation through their nucleation, motion, and annihilation. Uncontrolled vortex dynamics can introduce electronic noise in low-power systems and trigger thermal breakdown in high-power applications. This study examines the effect of a perpendicular external magnetic field on vortex pinning in biased YBa₂Cu₃O_7-δ devices containing laser-written, rectangular-shaped, partially deoxygenated regions (δ ≈ 0.2). The results show that increasing the magnetic field amplitude induces an asymmetry in the concentration of vortices and antivortices, shifting the annihilation line toward a region of lower flux density and altering the flux pinning characteristics. Oxygen-deficient segments aligned parallel to the current flow act as barriers to vortex motion, enhancing the net pinning force by preventing vortex–antivortex pairs from reaching their annihilation zone. The current–voltage characteristics reveal periodic voltage steps corresponding to the onset and suppression of thermally activated flux flow and flux creep. These features indicate magnetic field–tunable transport behavior within a narrow range of temperatures from 0.94·T_c to 0.98·T_c, where T_c is the critical temperature of the superconductor. These findings offer new insights into the design of vortex-motion-controlled superconducting electronics that utilize engineered pinning structures. Full article

Micro-hydroelectric power plants play a fundamental role in microgrid systems and rural electrification projects based on non-conventional renewable energies, where the stability of the electricity supply and load variability are critical factors for efficient operation. This work focuses on analyzing the impact of electrical load variation on the performance of a 10 kW micro hydroelectric power plant equipped with a Pelton turbine coupled to an electric generator. The main objective is to characterize the behavior of the turbine–generator system under different operating conditions, evaluating the hydraulic performance of the turbine, the electrical performance of the generator, and the overall performance of the micro power plant. Key variables such as flow rate, pressure, shaft speed, mechanical torque, current, and electrical voltage are monitored, considering the effect of electrical consumption on each of them. The experimental methodology includes tests at different electrical loads connected to the generator, using the spear system, which allows the flow rate in the injector to be modulated. The results indicate that reducing the flow rate using the spear increases the torque on the shaft, as well as the electrical current and voltage, for the same energy demand. Likewise, it is observed that the electrical efficiency of the generator remains stable for shaft speeds above 400 rpm, while the overall efficiency of the turbine–generator improves by up to 25% at this same speed. However, a voltage drop of more than 8% is recorded when the electrical power consumption increases from 3 kW to 9 kW, which demonstrates the sensitivity of the system to load variations. This work provides a comprehensive view of the dynamic behavior of micro-hydraulic power plants under realistic operating conditions, proposing an experimental methodology that can be applied to the design, optimization, and control of small-scale hydroelectric systems. These results provide novel experimental evidence on how electrical load variations affect the global performance of P -based micro hydropower systems. Full article

In loop-powered 4–20 mA transmitter systems, sensors like temperature, pressure, flow, and gas sensors are chosen based on specific application requirements. These systems are widely adopted in high-precision measurement scenarios, including industrial automation, process control, and environmental monitoring. The transmitter requires a high-performance analog front end (AFE) for precise amplification and signal conditioning. This paper presents a low-noise instrumentation amplifier (IA) for high-precision transmitter front ends, featuring a Successive Approximation Register (SAR)-assisted offset calibration architecture. The proposed structure integrates a chopper current-feedback instrumentation amplifier (CFIA) with an automatic offset calibration loop (AOCL), significantly suppressing internal offset errors and enabling high-accuracy signal acquisition under stringent power and environmental temperature constraints. The designed amplifier provides four selectable gain settings, covering a range from ×32 to ×256. Fabricated in a 0.18 μm CMOS process, the CFIA operates at a 1.8 V supply voltage, consumes a static current of 182 μA, and achieves an input-referred noise as low as 20.28 nV/√Hz at 1 kHz, with a common-mode rejection ratio (CMRR) up to 122 dB and a power-supply rejection ratio (PSRR) up to 117 dB. Experimental results demonstrate that the proposed amplifier exhibits excellent performance in terms of input-referred noise, offset voltage, PSRR, and CMRR, making it well-suited for front-end detection in field instruments that require direct interfacing with measured media. Full article