Flow regimes study within the Strait of Gibraltar using a high-performance numerical model

A three-dimensional sigma coordinate free-surface high-performance model is used to investigate the flow regimes within the Strait of Gibraltar. High performances are achieved through a directive-based, MPI-like, parallelization of the code, obtained using SMS tool. The model makes use of a coastal-following, curvilinear orthogonal grid, that includes the Gulf of Cadiz and the Alboran Sea, reaching very high resolution in the Strait. Four experiments with different initial salinity conditions representing the present and possible future climate conditions over the Mediterranean basin have been performed. Model results, analysed by means of the three-layer composite Froude number theory, have shown two different possible regimes within the strait; for the present climate condition the strait is subjected to a sub-maximal regimewhilefor possible future climate conditions a maximal regime can be reached

A new coupling solution for G3-PLC employment in MV smart grids

This paper proposes a new coupling solution for transmitting narrowband multicarrier power line communication (PLC) signals over medium voltage (MV) power lines. The proposed system is based on an innovative PLC coupling principle, patented by the authors, which exploits the capacitive divider embedded in voltage detecting systems (VDS) already installed inside the MV switchboard. Thus, no dedicated couplers have to be installed and no switchboard modifications or energy interruptions are needed. This allows a significant cost reduction of MV PLC implementation. A first prototype of the proposed coupling system was presented in previous papers: it had a 15 kHz bandwidth useful to couple single carrier PSK modulated PLC signals with a center frequency from 50–200 kHz. In this paper, a new prototype is developed with a larger bandwidth, up to 164 kHz, thus allowing to couple multicarrier G3-PLC signals using orthogonal frequency division multiplexing (OFDM) digital modulation. This modulation ensures a more robust communication even in harsh power line channels. In the paper, the new coupling system design is described in detail. A new procedure is presented for tuning the coupling system parameters at first installation in a generic MV switchboard. Finally, laboratory and in-field experimental test results are reported and discussed. The coupling performances are evaluated measuring the throughput and success rate in the case of both 18 and 36 subcarriers, in one of the different tone masks standardized for the FCC-above CENELEC band (that is, from 154.6875–487.5 kHz). The experimental results show an efficient behavior of the proposed coupler allowing a two-way communication of G3-PLC OFDM signals on MV networks

Sensitivity of the Mediterranean circulation to horizontal space-time–dependent tracer diffusivity field in a OGCM

The sensitivity of the Mediterranean circulation to the variability of the horizontal mixing is investigated using a Bryan-Cox–type general circulation model (OGCM). Attention is focused on a parameterisation of mixing previously developed in the context of two-dimensional turbulence, that is for the first time implemented in a OGCM. This parameterisation is suitable for velocity fields characterised by the presence of geostrophic coherent structures, and it is a direct application of the well-known Taylor’s dispersion relation. Theoretical and experimental justifications of the parameterisation are discussed and results from four numerical experiments, with different tracer mixing schemes, are presented. In particular, it is shown that the proposed diffusivity parameterisation improves the tracers transport due to large eddy dynamics and, ensuring a more correct salt budget in the North western part of the basin, contributes to maintain a realistic vertical stratification and winter deep convection in long climatic integrations

Video semantic content analysis framework based on ontology combined MPEG-7

The rapid increase in the available amount of video data is creating a growing demand for efficient methods for understanding and managing it at the semantic level. New multimedia standard, MPEG-7, provides the rich functionalities to enable the generation of audiovisual descriptions and is expressed solely in XML Schema which provides little support for expressing semantic knowledge. In this paper, a video semantic content analysis framework based on ontology combined MPEG-7 is presented. Domain ontology is used to define high level semantic concepts and their relations in the context of the examined domain. MPEG-7 metadata terms of audiovisual descriptions and video content analysis algorithms are expressed in this ontology to enrich video semantic analysis. OWL is used for the ontology description. Rules in Description Logic are defined to describe how low-level features and algorithms for video analysis should be applied according to different perception content. Temporal Description Logic is used to describe the semantic events, and a reasoning algorithm is proposed for events detection. The proposed framework is demonstrated in sports video domain and shows promising results

Incremental heuristic approach for meter placement in radial distribution systems

The evolution of modern power distribution systems into smart grids requires the development of dedicated state estimation (SE) algorithms for real-time identification of the overall system state variables. This paper proposes a strategy to evaluate the minimum number and best position of power injection meters in radial distribution systems for SE purposes. Measurement points are identified with the aim of reducing uncertainty in branch power flow estimations. An incremental heuristic meter placement (IHMP) approach is proposed to select the locations and total number of power measurements. The meter placement procedure was implemented for a backward/forward load flow algorithm proposed by the authors, which allows the evaluation of medium-voltage power flows starting from low-voltage load measurements. This allows the reduction of the overall costs of measurement equipment and setup. The IHMP method was tested in the real 25-bus medium-voltage (MV) radial distribution network of the Island of Ustica (Mediterranean Sea). The proposed method is useful both for finding the best measurement configuration in a new distribution network and also for implementing an incremental enhancement of an existing measurement configuration, reaching a good tradeoff between instrumentation costs and measurement uncertainty

Characterization of DC series arc faults in PV systems based on current low frequency spectral analysis

This work presents an experimental study focused on the characterization of series arc faults in direct current (DC) photovoltaic (PV) systems. The aim of the study is to identify some relevant characteristics of arcing current, which can be obtained by means of low frequency spectral analysis of current signal. On field tests have been carried out on a real PV system, in accordance with some tests requirements of UL 1699B Standard for protection devices against PV DC arc faults. Arcing and non-arcing current signals are acquired and compared and the behavior of a set of indicators proposed by authors is analyzed. Different measurement equipment have been used, in order to study the impact of both measurement transducers and data acquisition systems on proposed indicators effectiveness. Presented results show that the considered indicators are suitable for detecting the arc presence even with commercial devices normally used for smart metering applications

An interface protection system based on an embedded metrology system platform

The aim of this work is to present an interface protection system (IPS) for Distributed Generators (DG) and Energy Storage Systems (ESS). The new prototype of IPS guarantees standard protection requirements, in terms of both voltage and frequency measurement accuracies and trip times. Moreover, it has the additional functionalities of implementing a communication link between the Distribution System Operator (DSO) and the DG and ESS Inverter. The new IPS is based on a smart meter platform with an integrated power line communication modem. Moreover, it has also an integrated metrology section. Experimental tests will show how this last feature allows a significant reduction of the measurement data access time allowing an improvement of trip time accuracy

A Line Impedance Calculator Based on a G3 PLC Modem Platform

Power line communication (PLC) is one of the most today used technologies for both automatic meter reading and many other smart grid applications. In this framework, a characterization of the electrical network in the PLC frequency range is needed in terms of impedance measurement and received signal level. This can allow choosing the most suitable and less noisy frequency ranges for PLC transmission. Usually, these characterization measurements are performed with dedicated instrumentation and in the absence of mains voltage. This article wants to propose an alternative solution, which allows these kinds of measurements to be performed using electronic boards currently used as on-field applications, such as smart meters. To this aim, an innovative measurement tool is proposed, which does not need a specific characterization signal to be injected because it uses the preamble of a generic PLC transmission. Moreover, the impedance calculation is performed using an FFT analysis, which does not require high computational capabilities. These features allowed the proposed tool to be implemented using a G3-PLC transceiver, embedded in many commercial smart meters, and low-cost additional hardware. This article shows how the proposed system correctly measures the PLC impedance on CENELEC A, B, and FCC frequency ranges

Li-ion battery modeling and state of charge estimation method including the hysteresis effect

In this paper, a new approach to modeling the hysteresis phenomenon of the open circuit voltage (OCV) of lithium-ion batteries and estimating the battery state of charge (SoC) is presented. A characterization procedure is proposed to identify the battery model parameters, in particular, those related to the hysteresis phenomenon and the transition between charging and discharging conditions. A linearization method is used to obtain a suitable trade-off between the model accuracy and a low computational cost, in order to allow the implementation of SoC estimation on common hardware platforms. The proposed characterization procedure and the model effectiveness for SoC estimation are experimentally verified using a real grid-connected storage system. A mixed algorithm is adopted for SoC estimation, which takes into account both the traditional Coulomb counting method and the developed model. The experimental comparison with the traditional approach and the obtained results show the feasibility of the proposed approach for accurate SoC estimation, even in the presence of low-accuracy measurement transducers