1,721,121 research outputs found
Rethinking Ports as Multienergy Hubs: Managing cold ironing and hydrogen supply/bunkering
No full textModern ports are expected to play a key role in the transportation chain, being transformed into smart grids and smart energy hubs where electric energy needs predominate. Cold ironing (CI), also known as onshore power supply (OPS) or alternate marine power, is indeed one the most energy-demanding applications. The power demand of a berthed ship depends on its characteristics and may vary from hundreds of kW, for container ships, to tens of MW, in the case of cruise ships
An algorithm for real-time rainfall rate estimation by using polarimetric radar: RIME
No full textPolarimetric radars provide measurements that describe the shape and dimensions of hydrometeors and are unaffected by calibration, attenuation, and the presence of ice. These measurements can potentially lead to a more detailed description of hydrometeors and to an improvement in quantitative rainfall rate estimation. The authors present an algorithm that exploits polarimetric measures for rain-rate estimation and investigate its application in a real-time framework by using measurements from the C-band polarimetric radar at Monte Settepani in Savona, Italy. It is based on a flowchart decision tree that allows the use of the best rain-rate retrieval algorithm, depending on the value of polarimetric variables. The methodology was applied to a real- time framework for more than a year, and the results were presented for all the significant events observed during the test period. To evaluate the performance of the algorithm, a comparison was made with rain gauge observation from a dense regional network. The performances of the algorithm were compared with those obtained by standard operational Z–R formulations to evaluate the benefit of this approach for operational applications
A Cross-Current Compensation Control Scheme to Improve Voltage Regulation and Power Sharing in DC Shipboard Microgrids
No full textThe ability to maintain the power balance, and effectively share the demand power among the available generating units is one of the essential requirements of a dc shipboard microgrid. When multiple power sources participate in the voltage regulation of a common dc-bus, droop control is typically used and a steady-state error in the voltage cannot be avoided. This work investigates a distributed control strategy inspired by the cross-current compensation technique, originally developed for ac power plants, that allows to eliminate the steady-state voltage error while enforcing the current sharing. The sources participating in the voltage regulation are equipped with a cascading controller where the outer voltage control loop, fed with the compensated voltage measurement, generates the reference signal for the inner current control loop. Control equations are developed, and a set of real-time simulations is performed. Results show that the proposed control strategy is effective in eliminating the steady-state voltage error and ensuring current sharing. Moreover, the control strategy exhibits a fail-safe behavior that allows the system to remain stable even in the event of compensation failure
Investigating the Stability of a DC Shipboard Microgrid protected with Solid-State Circuit Breaker
No full textDC microgrids represent a valuable solution for the realization of shipboard power systems. However, protection of dc microgrid is challenging: the absence of zero crossing of dc currents and the fast response of new technologies of energy storage system such as supercapacitor and batteries introduce strict requirements on the circuit breaker performances, making the conventional electro-mechanical circuit breaker not suitable for these applications. For these reasons, the solid-state circuit breaker is one of the most promising solutions. However, this component requires the presence of a current-limiting inductor, for limitation of the maximum value of fault current, whose effect in the normal operation of the system has not been addressed in literature. This work aims to identify, through an analysis of the impedance ratio in the point of coupling and real-time simulations, the presence of a potential resonance in the dc-bus of a notional dc microgrid. Different study cases have been considered, varying the value of the inductive fault current limiter, demonstrating the need to further investigating this phenomenon
Quantitative Flood Forecasting on Small and Medium Size Basins: a Probabilistic Approach for Operational Purposes
No full textShort-Circuit DC Current Estimation of Hybrid Energy Storage Systems
No full textDC microgrids have become a valuable alternative to AC microgrids for industrial and shipboard power systems due to the DC nature of most energy storage systems, which are increasingly used in these applications. However, integrating this technology introduces new protection issues. The unidirectionality and the very high derivative of DC fault currents discharging from the capacitor are the main challenges arising from adopting DC technology. Therefore, this study focuses on the short-circuit response of energy storage systems and their power electronic converters. Several energy storage sources are modeled using manufacturers datasheets, and their short-circuit responses are analyzed. The short-circuit responses of each energy storage system are simulated and compared with an analytical method. A parametric study is then performed, varying selected parameters to examine their influence on the short-circuit response
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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