simple control strategy for a pv battery system

Nowadays, energy storage systems, such as batteries, are spreading in many applications. Among the kinds of batteries, the lithium-ion technology is one of the most promising solutions. Considering the photovoltaic (PV) plants, it is very important to perform a correct sizing of the battery pack to both maximise the self-consumption and minimise the total costs. In general, PV plants need a dc–dc converter to maximise the electric power that can be extracted from PV panels and a dc–ac converter to connect them to the ac grid. The battery pack can be connected in three different ways: dc coupled and ac coupled using a dedicated converter or through a direct connection on the dc-link between the dc–dc and dc–ac converters. In the present study, the last solution, without any dedicated converters, is used and a simple control strategy to both maximise the power extracted from the PV panel and regulate the charging/discharging of the battery is proposed

From perfect to fractal transmission in spin chains

Perfect state transfer is possible in modulated spin chains, imperfections however are likely to corrupt the state transfer. We study the robustness of this quantum communication protocol in the presence of disorder both in the exchange couplings between the spins and in the local magnetic field. The degradation of the fidelity can be suitably expressed, as a function of the level of imperfection and the length of the chain, in a scaling form. In addition the time signal of fidelity becomes fractal. We further characterize the state transfer by analyzing the spectral properties of the Hamiltonian of the spin chain.Comment: 8 pages, 10 figures, published versio

Windowed PWM: a Configurable Modulation Scheme for Modular Multilevel Converter Based Traction Drives

This article introduces a modulation technique for modular multilevel converter (MMC) in variable speed traction drives for electrical transportation referred as windowed pulsewidth modulation (W-PWM). The windowed PWM (W-PWM) is derived by blending the principles of operation of conventional modulation schemes for MMC based on the nearest level control (NLC) and on PWM with the aim of combining their inherent strengths and offering a higher degree of flexibility. This can reduce switching losses compared to classical PWM schemes and lower the current harmonic distortion compared to NLC schemes. The window in which the PWM is applied can be seen as an additional degree of freedom that allows a dynamic optimization of the performance of the traction drive depending on its operating characteristics. The performance of the W-PWM technique is assessed in this article for several operating conditions and compared with conventional schemes based on NLC and on the phase opposition disposition PWM with both numerical simulation and experimental verification on a small-scale prototype. Results demonstrate the flexibility of the W-PWM and its potential for applications in electrical traction drives. © 1986-2012 IEEE.acceptedVersio

Strategies to optimize the use of marginal donors in liver transplantation.

Liver transplantation is the treatment of choice for end stage liver disease, but availability of liver grafts is still the main limitation to its wider use. Extended criteria donors (ECD) are considered not ideal for several reasons but their use has dramatically grown in the last decades in order to augment the donor liver pool. Due to improvement in surgical and medical strategies, results using grafts from these donors have become acceptable in terms of survival and complications; nevertheless a big debate still exists regarding their selection, discharge criteria and allocation policies. Many studies analyzed the use of these grafts from many points of view producing different or contradictory results so that accepted guidelines do not exist and the use of these grafts is still related to non-standardized policies changing from center to center. The aim of this review is to analyze every step of the donation-transplantation process emphasizing all those strategies, both clinical and experimental, that can optimize results using ECD

Management of Road Infrastructure Safety

Road Infrastructure Safety Management (RISM) refers to a set of procedures that support a road authority in decision making related to the improvement of safety on a road network. Some of these procedures can be applied to existing infrastructure, thus enabling a reactive approach; and other procedures are used in early stages of a project's life-cycle allowing a proactive approach. The objective of this paper is to provide an overview of the most well-known procedures and present a series of recommendations for successful road infrastructure safety management. The work described in the paper was completed by the IRTAD sub-working group on Road Infrastructure Safety Management and presented in detail in the respective Report. The methodology followed on this purpose included the description of the most consolidated RISM procedures, the analysis of the use of RISM procedures worldwide and the identification of possible weaknesses and barriers to their implementation, the provision of good practice examples and the contribution to the scientific assessment of procedures. Specifically, the following RISM procedures were considered: Road Safety Impact Assessment (RIA), Efficiency Assessment Tools (EAT), Road Safety Audit (RSA), Network Operation (NO), Road Infrastructure Safety Performance Indicators (SPI), Network Safety Ranking (NSR), Road Assessment Programs (RAP), Road Safety Inspection (RSI), High Risk Sites (HRS) and In-depth Investigation. Each procedure was described along with tools and data needed for its implementation as well as relevant common practices worldwide. A synthesis summarizing the key information for each procedure was also drafted. Based on a survey on 23 IRTAD member countries from worldwide, the lack of resources or tools is the most commonly stated reason for not applying a RISM procedure. This has been frequently found mainly in European countries. Another common reason is the absence of recommendations/guidelines, especially for SPI, RAP, RSI and RSA. This highlights the importance of the presence of some legislation regulating the application of the procedures. Lack of data was found important mainly for SPI, HRS and EAT. Good practices of road infrastructure safety management have been explored in order to find solutions to the issues highlighted by the survey and provide examples about how these issues have been overcome in some countries. Specifically, issues related to data, legal framework, funding, knowledge, tools and dealing with more RISM procedures were addressed. Finally, nine key messages and six recommendations for better Road Infrastructure Safety Management were developed based on the conclusions made

Liquid Metals Heat-Pipe solution for hypersonic air-intake leading edge: Conceptual design, numerical analysis and verification

Embedded propulsion systems will allow future hypersonic aircraft to reach amazing levels of performance. However, their peculiar small-radius air-intake leading edges pose serious challenges from the aerothermodynamic, design, integration, and manufacturing standpoints. This paper discloses the methodology developed in the framework of the H2020 STRATOFLY project and specifically tailored to support the conceptual and preliminary design phases of future high-speed transportation systems. The methodology implements an incremental approach which includes multifidelity design, modelling and simulation techniques. The specific application to the MR3, a Mach 8 waverider configuration with an embedded dorsal mounted propulsive subsystem, is reported. Different alternative solutions have been thoroughly analysed, including five liquid metals as fluids (Mercury, Cesium, Potassium, Sodium and Lithium) and relative wick and case materials (Steel, Titanium, Nickel, Inconel® and Tungsten) and three leading-edges materials (CMC, Tungsten with low emissivity painting and Tungsten with high emissivity painting). The analysis of the heat transfer limits (the capillary, entrainment, viscosity, chocking and boiling limits) carried out for all five fluids and relative compatible materials, together with a more accurate FEM analysis, suggest the adoption of a Nickel- Potassium liquid metal heat pipe completely integrated in a platelet air-intake leading edge made of CMC material. Ultimately, the effectiveness of the adopted solution throughout all mission phases has been verified with a detailed numerical model, built upon an electrical analogy

Cooling system of STRATOFLY hypersonic vehicle: conceptual design, numerical analysis and verification

This paper describes the thermal design processes of STRATOFLY hypersonic vehicle cooling system showing either the methodology and the supporting FEM numerical simulations. It focuses on two different regions that are both subjected to severe overheating: air-intake leading edges and the combustion chamber. Final remarks on structure survivability are presented

Thermal Protection System preliminary design of STRATOFLY high-speed propelled vehicle

This paper discloses the methodology and the preliminary results achieved in the framework of the H2020 STRATOFLY Project on the design of the Thermal Protection System of the MR3 vehicle. The results of the aero-thermal assessment performed throughout the trajectory clearly indicate the air-intake leading edges as the most critical area, thus dedicated Thermal Protection System alternatives have been explored. Specifically, solutions coupling high-temperature materials (mainly CMC and tungsten with different emissivity paints) with Liquid Metals Heat Pipe arrangements are modelled. Eventually, the effectiveness of the designed solutions is verified with detailed numerical simulation. The design which includes the air-intake main structure made of CMC material and integrating Nickel - Potassium heat pipe results to be the most promising solution to withstand the high thermal loads experienced by STRATOFLY MR3 throughout its Mach 8 long-haul route