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Publicações

Publicações por CPES

2016

Optimization of the Variable Speed Pump Storage Participation in Frequency Restoration Reserve Market

Autores
Filipe, JM; Moreira, CL; Bessa, RJ; Silva, BA;

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

Abstract
Several countries have a significant installed capacity of large-scale reversible hydro power plants. This large-scale storage technology comes with high investments costs, hence the constant search for methods to increase and diversify the sources of revenue. Traditional fixed speed pump storage units typically operate in the day-ahead market to perform price arbitrage and, in specific cases, provide downward replacement reserve (RR). Variable speed pump storage can not only participate in RR but also contribute to frequency restoration reserve (FRR), given their ability to control its operating point in pumping mode. This work proposes a strategy to manage the water resource and maximize the power plant revenue by participating in the day ahead market but also providing ancillary services. Moreover, a model to correctly allocate the water resource throughout the year is presented, as well as an evaluation module to calculate the real revenue of the system.

2016

Communication-free control solution for the provision of frequency regulation services in HVDC grids: Numerical simulation and experimental validation in a reduced scale platform

Autores
Moreira, CL; Gouveia, JR; Rodrigues, J; Silva, B; Peças Lopes, JA;

Publicação
CIGRE Session 46

Abstract
The development of future HVDC grids for transnational interconnections and offshore wind farms development should be compliant with specific requirements regarding frequency support and inertia emulation. Therefore, this paper presents the development of communication-free control solutions capable of dealing with these control requirements. The proposed solution exploit a coordinated control approach between offshore wind turbines and VSC-HVDC converter stations based on the DC grid voltage modulation. The effectiveness of the proposed control solutions are demonstrated to be of utmost importance for improving future grids frequency regulation capabilities. Recognizing that numerical simulations provide valuable knowledge regarding HVDC grids operation and control, this paper introduces a further step encompassing the development of a reduced scale laboratorial prototype of a DC grid making possible the demonstration of key frequency control functionalities. Following the theoretical/conceptual background that is demonstrated through numerical simulation, laboratorial tests were then performed in order to test and demonstrate the performance and effectiveness of the proposed control mechanisms that future HVDC grids will provide to frequency control in mainland AC grids.

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%.

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