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Modeling of Noncatalytic Gas–Solid Reactions with a Coupled CFD-DEM-USCM Method: A Case Study on Adsorption of Ammonia
No full textInternational audienceThis study presents a novel approach for modeling the noncatalytic gas–solid reaction of adsorption of ammonia by metal ammine complexes. A coupled computational fluid dynamics–discrete element method–unreacted shrinking core model (CFD-DEM-USCM) is developed to simulate the behavior of an ammonia storage reactor. The model integrates both mesoscale gas dynamics and microscale particle interactions, allowing for a comprehensive analysis of the adsorption process. Validation of the model against experimental data demonstrated its accuracy in predicting the conversion. It was shown that the effective gas diffusivity of gas inside the particles greatly affects the overall conversion as well as the mean temperature of the particles and gas. Higher diffusion rates enhance mass transfer, resulting in higher temperatures for both particles and gas. The change in particle size during the absorption of ammonia was investigated, and its influence on the reactor void fraction was studied. Inspecting the change in the imposed pressure of the gas at the diffuser and reactor wall temperature indicated that increasing the pressure or decreasing the wall temperature enhances the conversion in the reactor. Estimating the force distribution among particles and between particles and the reactor wall indicated that increasing the particle size with conversion increases both forces. This study provides insight into efficient ammonia storage solutions, contributing to advancements in selective catalytic reduction technology for vehicle emissions control
Exploring lignins as bio-based stabilizers for advanced water-in-water emulsion design
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Enhanced Current-Limiting Strategy of Grid-Forming Converter Considering Grid-forming Capability
No full textInternational audienceRecently, Grid-forming (GFM) converters have gained significant attention for their ability to enhance power system stability during disturbances. However, conventional current-limiting strategies lack sufficient consideration for preserving GFM capability under current-limited conditions. To address this issue, this paper proposes a novel current-limiting strategy that simultaneously ensures accurate current limitation and preserves GFM capability. The proposed method minimizes deviations in the converter terminal voltage by incorporating a PCC voltage-based current-limiting condition in real time. This approach allows the GFM converter to preserve its natural response-driven GFM capability to the greatest extent possible within a given current limit. Experimental results validate the superior performance of the proposed method compared to existing methods
Protection design for pole-to-pole faults in DC networks
No full textInternational audienceFault protection is one of the primary challenges impeding the widespread adoption of DC and hybrid AC/DC grids. A structured planning process for protection systems is necessary with regard to standardization. In this paper, a novel three-step protection system design process is proposed building upon the CENELEC (CLC/TS 50654-1) approach. The proposed planning process is separated into concept, system and component level. On concept level, the operational modes "continued operation", "temporary stop" and "permanent stop" according to CENELEC are used to define desired system behaviour in the event of a fault. On system level, protective action sequences are defined to realize the system behaviour defined on concept level. Finally on component level, protective devices are dimensioned and tripping thresholds are determined
DC-DC converter with low components voltage stress and reduced conduction losses by branches parallel connection
No full textInternational audienceThis paper presents modular DC-DC bidirectional converter, which is characterized by reduced voltage and current stress of components as well as increased frequency of current ripple. The converter is dedicated to work with a high voltage step-down ratio, because the output current is divided among many switches, reducing their resistive losses. In addition, the synchronous branches of the system conduct the in parallel connection. The converter can be implemented from discrete components or halfbridge modules, which can simplify its design. Concept of the converter, its modular design, basic waveforms and efficiency results are demonstrated. Basic experimental results are presented as well. The advantages resulting from the multi-division input voltage and the parallel operation of transistors branches are discussed
Numerically Stable Implementation of Active Power Decoupling Control Strategies
No full textInternational audienceIn active power decoupling (APD), image ambiguity in functions like "sqrt" and "atan2" can destabilize capacitor voltage control, leading to glitches. This paper proposes a phase unwrapping technique (PUT) that stabilizes angle computation, eliminating glitches from atan2-induced image ambiguity. Simulations results recreate and eliminate atan2-induced glitches using the proposed PUT
Generalized algorithm for determining the control functions of an AC voltage compensator with a bipolar AC/AC converter
No full textInternational audiencePower quality problems in the low voltage distribution grid are related to the development of prosumer electricity generators (especially PV) and the network's inadequacy to new distributed energy sources with significant nominal power. The main problem is related to the increase in voltage above the normative values and its asymmetry. In the scientific literature, one can find many articles describing this problem and methods of its solution based on the use of power electronics systems, energy storage, transformer tap changers or appropriate management of energy demand and production. The paper presents a generalized procedure for determining the control functions of transistors in an AC voltage compensator with a bipolar AC/AC converter. The obtained mathematical relations allow determining the control functions for the amplitude or phase asymmetry of input voltages. The correctness of the determined relations was verified in simulation studies
Development of a 1MW Multi-Channel Fast Charging Station based on Solid State Transformer
No full textInternational audienceThis paper presents a novel solid-state transformer-based fast charging infrastructure for electric vehicles (EVs) with direct medium voltage connectivity. The proposed system integrates multiple charging ports, enabling simultaneous power delivery to several EVs while maintaining independent control. By eliminating the conventional low-frequency transformer and associated power conversion stages, this configuration achieves significant footprint reduction and enhanced costeffectiveness compared to traditional lowvoltage systems. The operating principles and control algorithms are thoroughly validated through experimental results, demonstrating rated power operation and successful successful interconnected operation with commercial EVs
Analysis of a high gain step-up converter 48V/1kV for piezoelectric driving application
No full textInternational audiencePiezoelectric actuators have been widely used in low-power applications to improve size and performance. However, a high-voltage is required to drive these actuators. This paper considers a three-switching-state step-up DC-DC topology able to drive multiple actuators at 1kV , used for hydraulic application. The topology analysis, design and experimental results are shown in this paper. The prototype shows off an efficiency higher than 94.5% on the whole power range (20 -200W )