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Publications

Publications by CPES

2014

Renewable Power Forecast to Scheduling of Thermal Units

Authors
Fonte, PM; Santos, B; Monteiro, C; Catalao, JPS; Barbosa, FM;

Publication
TECHNOLOGICAL INNOVATION FOR COLLECTIVE AWARENESS SYSTEMS

Abstract
In this work is discussed the importance of the renewable production forecast in an island environment. A probabilistic forecast based on kernel density estimators is proposed. The aggregation of these forecasts, allows the determination of thermal generation amount needed to schedule and operating a power grid of an island with high penetration of renewable generation. A case study based on electric system of S. Miguel Island is presented. The results show that the forecast techniques are an imperative tool help the grid management.

2014

Short-term forecasting model for aggregated regional hydropower generation

Authors
Monteiro, C; Ramirez Rosado, IJ; Alfredo Fernandez Jimenez, LA;

Publication
ENERGY CONVERSION AND MANAGEMENT

Abstract
This paper presents an original short-term forecasting model of the hourly electric power production for aggregated regional hydropower generation. The inputs of the model are previously recorded values of the aggregated hourly production of hydropower plants and hourly water precipitation forecasts using Numerical Weather Prediction tools, as well as other hourly data (load demand and wind generation). This model is composed of three modules; the first one gives the prediction of the "monthly" hourly power production of the hydropower plants; the second module gives the prediction of hourly power deviation values, which are added to that obtained by the first module to achieve the final forecast of the hourly hydropower generation; the third module allows a periodic adjustment of the prediction of the first module to improve its BIAS error. The model has been applied successfully to the real-life case study of the short-term forecasting of the aggregated hydropower generation in Spain and Portugal (Iberian Peninsula Power System), achieving satisfactory results for the next-day forecasts. The model can be valuable for agents involved in electricity markets and useful for power system operations.

2014

Coordinating Distributed Energy Resources During Microgrid Emergency Operation

Authors
Gouveia, C; Rua, D; Moreira, CL; Peças Lopes, JA;

Publication
Green Energy and Technology

Abstract
The development of the Smart Grid (SG) concept is the pathway for assuring flexible, reliable and efficient distribution networks while integrating high shares of Distributed Energy Resources (DER): renewable energy based generation, distributed storage and controllable loads such as Electric Vehicles (EV). Within the SG paradigm, the Microgrid (MG) can be regarded as a highly flexible and controllable Low Voltage (LV) cell, which is able to decentralize the distribution management and control system while providing additional controllability and observability. A network of controllers interconnected by a communication system ensures the management and control of the LV microgrid, enabling both interconnected and autonomous operation modes. This new distribution operation philosophy is in line with the SG paradigm, since it improves the security and reliability of the system, being able to tackle the technical challenges resulting from the large scale integration of DER and provide the adequate framework to fully integrate SG new players such as the EV. By exploiting the MG operational flexibility and controllability, this chapter aims to provide an extended overview on MG self-healing capabilities, namely on its ability of operating autonomously from the main grid and perform local service restoration. The MG hierarchical management and control structure is revisited and adapted in order to exploit the flexibility of SG new players, like the EV and flexible loads and integrate smart metering infrastructures. The implementation of the MG architecture and communication infrastructure in a laboratorial facility is also presented and used to validate the MG self-healing capabilities. © 2014, Springer Science+Business Media Singapore.

2014

Operation and Control of Multiterminal HVDC Grids for AC Fault Ride Through Compatibility

Authors
Moreira, CL; Silva, B;

Publication
2014 IEEE INTERNATIONAL ENERGY CONFERENCE (ENERGYCON 2014)

Abstract
A fully operational Multi-Terminal DC (MTDC) grid will play a strategic role for mainland AC systems interconnection and to integrate offshore wind farms. The importance of such infrastructure requires its compliance with Fault Ride Through (FRT) capability in case of mainland AC faults. In order to provide FRT capability in MTDC grids, communication-free advanced control functionalities exploiting a set of local control rules at the converter stations and wind turbines are identified. The proposed control functionalities are responsible for mitigating the DC voltage rise effect resulting from the reduction of active power injection into onshore AC systems during grid faults. The proposed strategies envision a fast control of the wind turbine active power output as a function of the DC grid voltage rise and constitute alternative options in order to avoid the use of classical solutions based on the installation of chopper resistors in the MTDC grid. The feasibility and robustness of the proposed strategies are demonstrated and discussed in the paper while considering different circumstances.

2014

The growing state of distributed generation and microgrids in the Ibero-American region: A view from the RIGMEI network

Authors
Castilla, M; Mercado, P; Negroni, J; Gomes, M; Moreira, C; Sosa, J; De Souza, ACZ;

Publication
2014 IEEE PES Transmission and Distribution Conference and Exposition, PES T and D-LA 2014 - Conference Proceedings

Abstract
The Ibero-American Network of Distributed Generation and Intelligent Electrical Microgrids is a thematic network of the CYTED programme that performs cooperation activities between leading companies and research groups of the Ibero-American countries in the renewable energy area. This paper presents the results and conclusions of a study carried out recently by the network, which focused on the state of penetration of the distributed generation and the electrical microgrids in the Ibero-American countries that collaborate with the network. A list of these countries, together with the contact details of the main researchers, can be found in Apendix I. © 2014 IEEE.

2014

Twenties: Conclusions of a major R&D demonstration project on offshore DC grids

Authors
Despouys, O; Denis, AM; Cirio, D; Bell, K; Moreira, C; Liu, CC; Grieshaber, W; Dupraz, JP;

Publication
CIGRE Session 45 - 45th International Conference on Large High Voltage Electric Systems 2014

Abstract
European governments' targets for renewable energy by 2020 will lead to large offshore wind power integration in the existing Power System. High-Voltage Direct Current (HVDC) provides the most suitable technology to enable massive integration of offshore wind farms into AC onshore grids over long distances, with great control on transmitted power. More specifically, DC Grids (DCG) based on Voltage Source Converters (VSC) are being widely investigated to integrate multiple offshore wind farms dispersed over wide areas into AC onshore networks. For three and a half years, the « DC GRID » demo within the TWENTIES European project was focussed on a wide range of challenging issues related to the DC grid benefits for connecting offshore intermittent power: offshore DCGs economic assessment and likely layouts; DCG control and protection; ancillary services provided by such grids to the mainland AC network. This paper presents major achievements of the TWENTIES project in these domains. In addition, two major outcomes of the « DC GRID » demo are physical demonstrators. One of them is a low scale DCG mock-up, on which some of the above controls, as well as DC grid protection algorithms were successfully tested. Last, a highly innovative DC Circuit Breaker (DCCB) prototype was developed to overcome a strong technological barrier: this new equipment was successfully tested in presence of an independent expert to establish the qualification of this technology in the HV domain.

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