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Publications

Publications by CPES

2015

A new electricity market design for power systems with large share of hydro: Improving flexibility and ensuring efficiency and security in the Brazilian case

Authors
Calabria, FA; Saraiva, JT; Rocha, AP;

Publication
2015 IEEE EINDHOVEN POWERTECH

Abstract
This paper discusses some problems related with the current Brazilian electricity market, brings out some dilemmas that should be examined in order to implement a more market oriented approach, and proposes a new market design to overcome these issues. The proposed market design is based on the concept of energy right accounts as virtual reservoirs and aims at enhancing the flexibility to enable market participants to comply with their contracts, while still ensuring the efficient use of the energy resources and maintaining the current security supply level. In addition, in order to simulate the behavior of the market participants in this new framework, an Agent-Based Model - ABM where agents use reinforcement Q-Learning is developed for the study case. The results show that this new market design is suitable to be applied to hydrothermal systems having a large share of hydros.

2015

Development and implementation of Portuguese smart distribution system

Authors
Gouveia, C; Rua, D; Soares, FJ; Moreira, C; Matos, PG; Pecas Lopes, JAP;

Publication
ELECTRIC POWER SYSTEMS RESEARCH

Abstract
The consolidation of smart grids is inevitably related with the development and actual implementation of different functionalities envisioned for future electric grids. This paper presents the major implementations of smart grid projects in Portugal, which resulted from a close collaboration between academia and industry. An overview of the entire development process is presented culminating with the real implementation of the developed concepts. The architectures and functional models are presented as the initial step in defining the management and control functionalities for future smart distribution networks. The intermediate step consists in validating the advances introduced by smart grids. Simulation tools are emphasized considering both electrical and communications aspects. Finally, a laboratory infrastructure implemented to be used as a real test bed and a pilot deployed in a large city are presented in the end. The associated learning has provided relevant information for future developments.

2015

Electric vehicles contribution for frequency control with inertial emulation

Authors
Rocha Almeida, PMR; Soares, FJ; Pecas Lopes, JAP;

Publication
ELECTRIC POWER SYSTEMS RESEARCH

Abstract
This work proposes a novel primary frequency control technique with electric vehicles (EV), the combination of inertial emulation and droop control, for isolated systems. Being EV dispersed along the grids, the impacts of possible delayed actions are assessed. Islanded systems have reduced inertia and so load/generation imbalance situations may lead to large frequency deviations. Therefore, this paper focuses essentially on the EV contribution for primary reserves provision, in order to allow a safe integration of further intermittent Renewable Energy Sources (RES). An avant-garde generation dispatch was adopted for the test system used in this work, fully reliant on RES, mainly conventional hydro units and some wind generation. The studied disturbances include a rapid shortfall on wind power production and a sequence of consecutive events caused by the variability of the wind resource in an ordinary situation.

2015

IMICV fault analysis method with multiple PV grid-connected inverters for distribution systems

Authors
Moura, AP; Lopes, JAP; de Moura, AAF; Sumaili, J; Moreira, CL;

Publication
ELECTRIC POWER SYSTEMS RESEARCH

Abstract
A novel faults analysis method with multiple PV grid-connected inverters for distribution systems is proposed. The aforesaid proposed method Inverter Matrix Impedance Current Vector (IMICV) employs symmetrical components combined with a matrix denominated of Inverter Matrix Impedance and with a vector denominated Impedance-Current Vector which are formed by inspection. This matrix and this vector are used to solve a linear system of equations where the following post-fault variables are: current in substation, the voltage at the fault point and voltages in the PV grid-connected nodes. A comparison of results obtained using the new method with the results of the professional software ANAFAS validates the method proposed. Computer simulations show that the proposed method for classical shunt faults analysis is efficient, accurate and easy to program.

2015

Sequence networks to the calculation of two-simultaneous faults at the same location

Authors
Moura, AP; Pecas Lopes, JAP; de Moura, AAF;

Publication
INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS

Abstract
The system of symmetrical components (012-system) can be used to simulate symmetrical and asymmetrical operation of power systems. However, the classical literature of Power Systems Analysis does not present one equivalent circuit in 012-system to two-simultaneous faults where there are a single-line-to-ground fault and a bolted line-to-line fault. This paper presents the equations and the new equivalent circuit mentioned. In addition, we present a comparison of results between the proposed approach and the output of the commercial software ANAFAS, which validates the methodology. We find evidence that the new equivalent circuit developed can substitute the equivalent circuits used to calculate a single line-to-ground fault and a bolted line-to-line fault.

2015

KEY OBSTACLES TO WIND ENERGY DEVELOPMENT: A STUDY WITH THE TOP 10 COUNTRIES IN NEWLY INSTALLED CAPACITY

Authors
Farkat Diogenes, JRF; Bordalo da Costa, DMB; Pecas Lopes, JAP; Barbosa Pereira Queiroz, FCBP; Queiroz, JV;

Publication
PROCEEDINGS OF THE 2ND INTERNATIONAL CONFERENCE ON ENERGY & ENVIRONMENT: BRINGING TOGETHER ENGINEERING AND ECONOMICS

Abstract
This article identifies and classifies the key obstacles to wind energy development, in order to better understand these barriers and provide guidelines to help public managers to develop and share new energy policies. The methodology used was a case study with documentary research, carried out through an analysis of the Global Wind Report - Annual Market Update, 2009 to 2013, published by Global Wind Energy Council - GWEC. The results showed a significant occurrence of technological and operational obstacles, especially concerning electricity grids. The results lead to the conclusion that the biggest issue for wind energy development is concentrated in technological and operational obstacles, especially concerning the management of transmission networks. In addition, the results indicate the possibility of countries, with common obstacles, to improve their energy policies in partnership, or share their successful expertises.

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