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Publicações

Publicações por CPES

2016

Hierarchical control scheme for droop controlled parallel: Three phase voltage source inverters in low voltage AC microgrid

Autores
Margoum, E; Krami, N; Seca, L; Moreira, C;

Publicação
International Review of Automatic Control

Abstract
The hierarchical control scheme for three phase parallel connected voltage source inverters (VSI), forming a low voltage AC MicroGrid (MG)is presented and analyzed in this paper. The proposed control scheme consists of two controllers, a local controller and a centralized controller. The local controller consists of inner control loops that are composed by a voltage and current proportional resonant controllers with selective harmonics compensation, and the power sharing controller that includes the droop control and the virtual output impedance loops in order to share properly the active and reactive power between the connected VSIs. In this system, the centralized controller is designed to restore the magnitude and the frequency deviations of the AC bus voltage produced by the power sharing controller. Simulation results for three parallel connected VSIs forming a low voltage AC MG that operates in islanded mode are provided to show the effectiveness of the proposed control scheme. Active and reactive power are properly shared as well as good harmonics compensation is achieved when both linear and non-linear loads are connected to the load bus.

2016

Energy storage management for grid operation purposes

Autores
Santos, RJ; Andre, R; Bessa, R; Gouveia, C; Araujo, A; Guerra, F; Damásio, J; Bravo, G; Sumaili, J;

Publicação
IET Conference Publications

Abstract
The Horizon 2020 Storage ENabled SustaInable energy for BuiLdings and communitiEs (SENSIBLE) project is currently looking at the integration of small-scale storage technologies in buildings and distribution networks. In the demonstration site of the SENSIBLE project, EDP has already installed an experimental storage system supplying a university campus in MV. It was mainly designed to increase service quality to the university by providing backup power in the event of MV grid failure, but it can also control voltage profile and conduct peakshaving. In parallel, small-scale storage is being also installed at the LV level by SENSIBLE. For these new grid assets, the SENSIBLE project is implementing a use case for centralized control approach that guarantees a coordinated operation of MV and LV storage. Furthermore, adding a MV switchgear, the resulting system will be able to isolate from the main grid thus effectively working as a microgrid with MV and LV Storage, PV generation and residential/commercial loads. This paper presents an overview of the technologies and software that will enable new grid support functions from small-scale storage.

2016

On-line quantile regression in the RKHS (Reproducing Kernel Hilbert Space) for operational probabilistic forecasting of wind power

Autores
Gallego Castillo, C; Bessa, R; Cavalcante, L; Lopez Garcia, O;

Publicação
ENERGY

Abstract
Wind power probabilistic forecast is being used as input in several decision-making problems, such as stochastic unit commitment, operating reserve setting and electricity market bidding. This work introduces a new on-line quantile regression model based on the Reproducing Kernel Hilbert Space (RKHS) framework. Its application to the field of wind power forecasting involves a discussion on the choice of the bias term of the quantile models, and the consideration of the operational framework in order to mimic real conditions. Benchmark against linear and splines quantile regression models was performed for a real case study during a 18 months period. Model parameter selection was based on k-fold cross-validation. Results showed a noticeable improvement in terms of calibration, a key criterion for the wind power industry. Modest improvements in terms of Continuous Ranked Probability Score (CRPS) were also observed for prediction horizons between 6 and 20 h ahead.

2016

Probabilistic Forecasting of Day-ahead Electricity Prices for the Iberian Electricity Market

Autores
Moreira, R; Bessa, R; Gama, J;

Publicação
2016 13TH INTERNATIONAL CONFERENCE ON THE EUROPEAN ENERGY MARKET (EEM)

Abstract
With the liberalization of the electricity markets, price forecasting has become crucial for the decision-making process of market agents. The unique features of electricity price, such as non-stationary, non-linearity and high volatility make this a very difficult task. For this reason, rather than a simple point forecast, market participants are more interested in a probabilistic forecast that is essential to estimate the uncertainty involved in the price. By focusing on this issue, the aim of this paper is to analyze the impact of external factors in the electricity price and present a methodology for probabilistic forecasting of day-ahead electricity prices from the Iberian electricity market. The models are built using regression techniques and aim to obtain, for each hour, the quantiles of 5% to 95% by steps of 5%.

2016

SENSIBLE project: Évora demonstrator enabling energy storage and energy management creating value for grid and customers

Autores
Mendes, G; Gouveia, C; Guerra, F; Ferreira, A; Murphy O'connor, C; Rocha, L; Bessa, R; Albuquerque, S;

Publicação
IET Conference Publications

Abstract
This paper aims to discuss both the ICT and grid architectures of the Évora Demonstrator under the project SENSIBLE. The demonstrator is focused on testing grid management functions under normal and emergency operation in a rural low voltage grid, taking advantage of electrochemical, electromechanical and thermal storage technologies as well as renewable energy sources (photovoltaics) that will be deployed at both distribution grid and at clients' electrical installation. In addition, the community engagement strategy is presented since it is crucial for the full implementation of the project.

2016

Wind Power Probabilistic Forecast in the Reproducing Kernel Hilbert Space

Autores
Gallego Castillo, C; Cuerva Tejero, A; Bessa, RJ; Cavalcante, L;

Publicação
2016 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC)

Abstract
Wind power probabilistic forecast is a key input in decision-making problems under risk, such as stochastic unit commitment, operating reserve setting and electricity market bidding. While the majority of the probabilistic forecasting methods are based on quantile regression, the associated limitations call for new approaches. This paper described a new quantile regression model based on the Reproducing Kernel Hilbert Space (RKHS) framework. In particular, two versions of the model, off-line and on-line, were implemented and tested for a real wind farm. Results showed the superiority of the on-line approach in terms of performance, robustness and computational cost. Additionally, it was observed that, in the presence of correlated data, the optimal on-line learning may cause unreliable modelling. Potential solutions to this effect are also described and implemented in the paper.

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