Definition and Experimental Validation of a Simplified Model for a Microgrid Thermal Network and its Integration into Energy Management Systems

The present paper aims at defining a simplified but effective model of a thermal network that links the thermal power generation with the resulting temperature time profile in a heated or refrigerated environment. For this purpose, an equivalent electric circuit is proposed together with an experimental procedure to evaluate its input parameters. The paper also highlights the simplicity of implementation of the proposed model into a microgrid Energy Management System. This allows the optimal operation of the thermal network to be achieved on the basis of available data (desired temperature profile) instead of a less realistic basis (such as the desired thermal power profile). The validation of the proposed model is performed on the Savona Campus Smart Polygeneration Microgrid (SPM) with the following steps: (i) identification of the parameters involved in the equivalent circuit (performed by minimizing the difference between the temperature profile, as calculated with the proposed model, and the measured one in a set of training days); (ii) test of the model accuracy on a set of testing days (comparing the measured temperature profiles with the calculated ones); (iii) implementation of the model into an Energy Management System in order to optimize the thermal generation starting from a desired temperature hourly profile

Energy management in hybrid systems coupling PV and electrical storage

In this contribution the possible benefits of the integration of a storage system (ST) and a photovoltaic power plant (PV) are investigated by means of a Heuristic Rules System (HRS), used both for the determination of the optimal size of the components and for the power production scheduling. The HRS takes into account the well-known electrical constraints and aims at satisfying the electrical demand following a priority order (PV, ST, main grid). Experimental results in the case of four possible scenarios are presented and discussed

Electrical-Loss Analysis of Power-Split Hybrid Electric Vehicles

The growing development of hybrid electric vehicles (HEVs) has seen the spread of architectures with transmission based on planetary gear train, realized thanks to two electric machines. This architecture, by continuously regulating the transmission ratio, allows the internal combustion engine (ICE) to work in optimal conditions. On the one hand, the average ICE efficiency is increased thanks to better loading situations, while, on the other hand, electrical losses are introduced due to the power circulation between the two electrical machines mentioned above. The aim of this study is then to accurately evaluate electrical losses and the average ICE efficiency in various operating conditions and over different road missions. The models used in this study are presented for both the Continuously Variable Transmission (CVT) architecture and the Discontinuously Variable Transmission (DVT) architecture. In addition, efficiency maps of the main components are shown. Finally, the simulation results are presented to point out strengths and weaknesses of the CVT architecture

Implementation of primary frequency regulation on fully rated wind turbine generators

© 2017 IEEE. The increased integration of wind generation via high power converters imposses numerous gauntlet to the management and control of modern power systems. One of them is caused by the decoupling effect between the power sources from the AC grid. It negatively impacts the system frequency response of modern power systems. This paper proposes a controller to enable the primary frequency regulation on fully rated wind turbine generators. The proposed controller is designed to enable primary frequency response mimiquing the classical syncrhonous generator controles. It includes a droop control and an other to enable the inertia response. Simulations on a test system are used to examine the frequency response provided by the prioposed strategy. The most important contributions of this paper is to demonstrate there is an actual limit value of the synthetic inertia gain that can be used in the controllers and that it is dependent on the system frequency noise

Do Wind Turbines Amplify the Effects of Lightning Strikes A Full-Maxwell Modelling Approach

Wind turbines (WTs) can be seriously damaged by lightning strikes and they can be struck by a significant number of flashes. This should be taken into account when the WT lightning protection system is designed. Moreover, WTs represent a path for the lightning current that can modify the well-known effects of the lightning discharge in terms of radiated electromagnetic fields, which are a source of damage and interference for nearby structures and systems. In this paper, a WT struck by a lightning discharge is analyzed with a full-wave modelling approach, taking into account the details of the WT and its interactions with the lightning channel. The effects of first and subsequent return strokes are analyzed as well as that of the rotation angle of the struck blade. Results show that the lightning current along the WT is mainly affected by the ground reflection and by the reflection between the struck blade and the channel. The computed electromagnetic fields show that, for subsequent return strokes, the presence of a WT almost doubles their magnitude with respect to a lightning striking the ground. Such enhancement is emphasized when the inclined struck blade is considere

A simple strategy to optimally design and manage a photovoltaic plant integrated with a storage system for different applications

The main goal of the present paper is that of proposing a methodology for the optimal sizing of a Photovoltaic (PV) unit and a Storage (ST) device, basing on data concerning typical load and PV production profiles. To achieve this result, a set of simple requirements to manage the charging/discharging of the storage is firstly proposed. Then, the overall cost of the whole system is deduced as a function of two variables (PV and ST sizes) and minimized in order to find the optimal sizing of the system. Finally, an economic analysis is presented to determine whether or not the investment is profitable

Approximate characterization of large Photovoltaic power plants at the Point of Interconnection

The aim of the present article is that of proposing a calculation procedure to assess electric quantities at the Point of Interconnection (POI) of large PhotoVoltaic (PV) power plants on the basis of rated data and main design elements of the plant itself. The quantities of inters are active and reactive power available at the POI in order to extrapolate the power plant capability starting from the capabilities of PWM inverters. The procedure also allows evaluating the POI voltage variations, an important element due to the increasing requirements for renewable generation units to participate in voltage regulation. The main interest in such a methodology lays in its simplicity of application, that allows avoiding the usage of dedicated software for load flow calculations, and flexibility, that makes it suitable for the support of the bidding and pre-design phase of large photovoltaic power plants

A two frame feedback linearization scheme for the control of fully rated wind generating units

The present paper proposes an innovative control scheme for a fully rated wind generating unit equipped with a permanent magnet synchronous generator. The main objective of this control strategy is that of allowing a decoupled and dynamically performing control of active power (by the MPPT curve) and reactive power at the point of interconnection to the grid. Moreover, the control will be able to integrate frequency supporting logics, such as synthetic inertial control and active power curtailment. The control synthesis is fully detailed and validated by means of dedicated simulations in comparison with the traditional control scheme for this type of wind generators

Nova aplicação do azul de tripano para superfície ocular: redefinindo corantes vitais

Different applications of trypan blue (TB) for intraocular surgery have been reported, with very high levels of safety and efficacy. We describe the use of TB as an alternative vital dye for staining the ocular surface to assess the integrity of superficial cell layers of the cornea and the surface environment. This facilitates the diagnosis of various ocular surface disorders, including screening for dry eye disease (DED) among refractive and cataract patients. TB staining properties are different from fluorescein and both are stable in a solution, so that a double staining technique is introduced.Diferentes aplicações do azul de tripano (AT) foram descritas para cirurgia intraocular, com elevados patamares de eficácia e segurança. Neste relato, é descrito a aplicação do AT como corante vital para superfíce ocular, de modo a estudar a integridade das células da superfície corneana e conjuntival na superfície ocular. Tal abordagem permite um diagnóstico mais sensível de desordens da superfície ocular, destacando-se disfunção lacrimal ou síndrome do olho seco. O AT tem propriedades distintas da fluoresceína, com a qual se mantém estável em solução permitindo a técnica de coloração dupla que é introduzida.Instituto de Olhos Renato AmbrósioCorneal Tomography and Biomechanics Study GroupDoheny Eye InstitutePrice Vision GroupUniversidade Federal de São Paulo (UNIFESP)UNIFESPSciEL