An improved reconstruction procedure for the correction of local magnification effects in three-dimensional atom-probe

A new 3DAP reconstruction procedure is proposed that accounts for the evaporation field of a secondary phase. It applies the existing cluster selection software to identify the atoms of the second phase and, subsequently, an iterative algorithm to homogenise the volume laterally. This Procedure, easily implementable on existing reconstruction software, has been applied successfully on simulated and real 3DAP analyses

Comment on "Atomic Scale Structure and Chemical Composition across Order-Disorder Interfaces"

Interfaces have long been known to be the key to many mechanical and electric properties. To nickel base superalloys which have perfect creep and fatigue properties and have been widely used as materials of turbine blades, interfaces determine the strengthening capacities in high temperature. By means of high resolution scanning transmission electron microscopy (HRSTEM) and 3D atom probe (3DAP) tomography, Srinivasan et al. proposed a new point that in nickel base superalloys there exist two different interfacial widths across the {\gamma}/{\gamma}' interface, one corresponding to an order-disorder transition, and the other to the composition transition. We argue about this conclusion in this comment

Best-Fit Ellipsoids of Atom-Probe Tomographic Data to Study Coalescence of Gamma Prime (L1_2) Precipitates in Ni-Al-Cr

An algorithm is presented to fit precipitates in atom probe tomographic data sets as equivalent ellipsoids. Unlike previous techniques, which measure only the radius of gyration, these ellipsoids retain the moments of inertia and principle axes of the original precipitate, preserving crystallographic orientational information. The algorithm is applied to study interconnected gamma prime precipitates (L1_2) in the Gamma-matrix (FCC) of a Ni-Al-Cr alloy. The precipitates are found to coagulate along -type directions.Comment: Accepted for publication in Scripta Materialia, added information about local magnification effect

Grid integration of wave energy & generic modelling of ocean devices for power system studies

The work presented in this thesis covers four major topics of research related to the grid integration of wave energy. More specifically, the grid impact of a wave farm on the power quality of its local network is investigated. Two estimation methods were developed regarding the flicker level Pst generated by a wave farm in relation to its rated power as well as in relation to the impedance angle ψk of the node in the grid to which it is connected. The electrical design of a typical wave farm design is also studied in terms of minimum rating for three types of costly pieces of equipment, namely the VAr compensator, the submarine cables and the overhead line. The power losses dissipated within the farm's electrical network are also evaluated. The feasibility of transforming a test site into a commercial site of greater rated power is investigated from the perspective of power quality and of cables and overhead line thermal loading. Finally, the generic modelling of ocean devices, referring here to both wave and tidal current devices, is investigated

GRID INTEGRATION OF WAVE AND TIDAL ENERGY

International audienceWave and tidal energy provide a renewable source of electricity. However, their inherent fluctuations may have a negative impact on the power quality of a local electrical network. Grid operators assess this impact through the use of dynamic models of the generation units, which are inserted into the overall power system model. Providing these models is a compulsory step for any power generator to procure a grid connection above a specified power capacity. Significant issues were encountered in the wind energy industry regarding the dynamic modelling of devices, among which were model numerical instability, poor dynamic model quality and model incompatibility. Considering the large diversity of device types in the emerging ocean energy industry, these problems are considered as a major barrier to the larger scale grid-integration of marine energy converters. Dynamic models must clearly demonstrate the compliance of the actual power generation device and array of devices to the grid code requirements for grid-connection to be allowed. A further barrier to grid connection of ocean energy devices is that existing grid codes – mainly written in the context of wind energy-may be irrelevant or inadequate for ocean energy devices. This paper presents an overview of these issues, and details a radically different approach to the dynamic modelling of ocean energy devices that will assist in overcoming the issues previously encountered in the development of wind turbine models. It also highlights the gaps and inadequacy regarding grid code requirements for ocean energy devices, and provides some recommendations for a new ocean energy grid code

GRID IMPACT OF A WAVE FARM ON ITS LOCAL NETWORK: ANALYSIS OF VOLTAGE AND FLICKER LEVELS

International audienceMost oscillating wave energy converters without significant amounts of energy storage capacity generate significant electrical power fluctuations in the range of seconds. Because of these fluctuations, a wave farm may have a negative impact on the power quality of the local grid to which it is connected. Hence, the impact of these devices on both distribution and transmission networks needs to be well understood, before large scale wave farms can be allowed to connect to the grid. This paper details a case study on the impact of a wave farm on the distribution grid around the national wave test site of Ireland. The electrical power output of the oscillating water column (OWC) wave energy converters was derived from experimental time series produced in the context of the FP7 project " CORES ". The results presented in this paper consider voltage fluctuation levels and flicker levels for a typical time series. Simulations were performed using DIgSILENT simulation tool " PowerFactory "

Decentralized Smart Charging of Large-Scale EVs using Adaptive Multi-Agent Multi-Armed Bandits

The drastic growth of electric vehicles and photovoltaics can introduce new challenges, such as electrical current congestion and voltage limit violations due to peak load demands. These issues can be mitigated by controlling the operation of electric vehicles i.e., smart charging. Centralized smart charging solutions have already been proposed in the literature. But such solutions may lack scalability and suffer from inherent drawbacks of centralization, such as a single point of failure, and data privacy concerns. Decentralization can help tackle these challenges. In this paper, a fully decentralized smart charging system is proposed using the philosophy of adaptive multi-agent systems. The proposed system utilizes multi-armed bandit learning to handle uncertainties in the system. The presented system is decentralized, scalable, real-time, model-free, and takes fairness among different players into account. A detailed case study is also presented for performance evaluation.Comment: CIRED 2023 International Conference & Exhibition on Electricity Distribution, Jun 2023, Rome, Ital

SEAGRID: A New Dynamic Modelling Tool for Power System Analysis of Ocean Energy Devices

International audienceAs the ocean energy industry approaches commercial readiness, there will be a greater focus on integration of ocean energy devices (OEDs) into the electrical power system network. Device developers will be required to provide dynamic models of their device for grid connection, and ensure their device operates within the limits laid out in the grid code. Project developers will need to assess the impact of different wavefarm configurations, ratings for the electrical equipment, power losses, and performance during a fault. Grid operators will require dynamic models to investigate the impact an OED will have on the grid and also for future grid planning studies. The SEAGRID dynamic modelling tool attempts to address each of these issues using its generic modelling approach. The SEAGRID model is capable of producing a scalable time domain power system dynamic model using empirical test data and component specifications, bypassing the need for a full hydrodynamic study of the device

Nanostructure and properties of a Cu-Cr composite processed by severe plastic deformation

A Cu-Cr composite was processed by severe plastic deformation to investigate the role of interphase boundaries on the grain size reduction mechanisms. The as-deformed material exhibits a grain size of only 20nm. This gives rise to a dramatic increase of the hardness. Some deformation induced Cu super saturated solid solutions were clearly exhibited and it is shown that they decrease the hardness. The formation of such supersaturated solid solution and their influence on the mechanical properties are discussed

Towards the optimal use of an existing MRE electrical network from an electrothermal perspective

International audienc