Integrating Black Start Capabilities into Offshore Wind Farms by Grid-Forming Batteries

Power systems are currently experiencing a transition towards decarbonisation of electrical generation through large-scale deployment of renewable energy sources. These are gradually replacing conventional thermal power plants which today are the main providers of black start (BS) services. Consequently, in case of a total/partial blackout, conventional black-start resources are not ready for operation. Offshore wind farms (OWFs), with their large capacity and fast controllers, have potential as novel BS units. This new service introduces a need for a new design for wind power systems to be able to fulfil the black start requirements for non-traditional generation units. In this paper, challenges, and possible solutions in integrating BS services into OWFs will be presented. A first challenge is represented by the implementation of a BS unit. The BS unit should be capable of firstly forming the wind farm power island and withstanding transient phenomena due to energisation. There could be several different solutions, e.g., the integration of grid-forming converters in the wind farm design which could be battery energy storage systems (BESSs). In this paper, specific challenges are analysed using simulations on a wind farm equipped with a grid-forming BESS, and the proposed solutions discussed. It can be concluded that a hybrid system comprised of a BESS and an OWF, in combination with novel technologies such as grid-forming control, soft-charging, etc. represents a feasible proposal for being able to provide BS services with OWFs.Comment: 12 pages, 7 figures, journal (submitted to IET Renewable Power Generation

Offshore Wind Farm Black Start Service Integration:Review and Outlook of Ongoing Research

A review of the ongoing research on black start (BS) service integrated with offshore wind farms (OWFs) is presented in this paper. The overall goal is to firstly gain a better understanding of the BS capabilities required by modern power systems. Subsequently, the challenges faced by OWFs as novel BS service providers as well as an outlook on the ongoing research which may provide solutions to these are presented. OWFs have the potential to be a fast and environmentally friendly technology to provide BS services for power system restoration and, therefore, to ensure resiliency after blackouts. As a power electronic-based system, OWFs can be equipped with a self-starter in the system in order to perform BS. The self-start unit could be a synchronous generator (SG) or a power electronic unit such as a grid-forming (GFM) converter. Preliminary BS studies performed in PSCAD/EMTDC are presented in a simplified OWF system via an SG as the self-start unit. Consequently, technical challenges during the BS procedure in an OWF benchmark system are outlined via theoretical discussions and simulations results. This is useful to understand the threats to power electronics during BS. Finally, the most relevant GFM strategies in the state-of-the-art literature are presented and their application to OWF BS is discussed

A Poll Oriented Classifier for Affective Brain Computer Interfaces

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Bistable Clustering in Driven Granular Mixtures

The behavior of a bidisperse inelastic gas vertically shaken in a compartmentalized container is investigated using two different approaches: the first is a mean-field dynamical model, which treats the number of particles in the two compartments and the associated kinetic temperatures in a self-consistent fashion; the second is an event-driven numerical simulation. Both approaches reveal a non-stationary regime, which has no counterpart in the case of monodisperse granular gases. Specifically, when the mass difference between the two species exceeds a certain threshold the populations display a bistable behavior, with particles of each species switching back and forth between compartments. The reason for such an unexpected behavior is attributed to the interplay of kinetic energy non-equipartition due to inelasticity with the energy redistribution induced by collisions. The mean-field model and numerical simulation are found to agree qualitatively.Comment: 23 pages, 12 figure

A virtual system for postural stability assessment based on a TOF camera and a mirror

Postural stability is often compromised in many pathological states and decreases with age. In clinical practice, an objective tool for balance is fundamental. Recently, virtual tools, based on the use of depth cameras, have been presented. In this paper, a new virtual system for postural stability assessment was presented, involving the use of a Time of Flight camera (TOF) and of a mirror for the reduction of the occlusions errors by allowing the camera to see the hidden body surface. The validity of the tool was assessed through some experimental results. Data were also compared with those measured by a physical force platform and those calculated with another virtual stability assessment system, in order to highlight the error reduction while maintaining simplicity and low-cos