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Publications

Publications by João Peças Lopes

2010

MICROGRIDS OPERATION AND CONTROL UNDER EMERGENCY CONDITIONS

Authors
Moreira, CL; Pecas Lopes, JAP;

Publication
INTELLIGENT AUTOMATION AND SOFT COMPUTING

Abstract
Under normal conditions, the MicroGrid operates interconnected with the upstream medium voltage network. However, scheduled or forced isolation can take place. In such conditions, the MicroGrid must have the ability to operate stably and autonomously, requiring the development of suitable control strategies in order to enable MicroGrid islanded operation. The MicroGrid power sources can also be exploited in order to locally promote a service restoration strategy following a general blackout. A sequence of actions for the black start procedure is also identified and it is expected to be an advantage for power system operation in terms of reliability as a result from the presence of very large amounts of dispersed generation in distribution grids.

2010

Identification of control and management strategies for LV unbalanced microgrids with plugged-in electric vehicles

Authors
Pecas Lopes, JAP; Polenz, SA; Moreira, CL; Cherkaoui, R;

Publication
ELECTRIC POWER SYSTEMS RESEARCH

Abstract
This paper addresses issues concerning the integration of single-phase charging devices for electric vehicles (EV) in low-voltage microgrids Fast release energy storage is a key issue for microgrid islanding operation. EV batteries provide an additional storage capacity, which can now be exploited in order to improve MG islanding Aiming to do so, different control strategies were developed and tested (1) a local control approach where no communication link is required and (2) a centralized charging control solution The local control approach is based on the measuring of EV terminal voltage and frequency in order to define the charging or discharging rates of the batteries The centralized control strategy allows balancing single-phase loads connected to the microgrid by adapting the charging rates of the EV storage devices. Simulation results show that EV batteries can actively contribute for voltage balancing and frequency control during islanding operating conditions

2007

A unit commitment and dispatch for a wind park considering wind power forecast

Authors
Moyano, CF; Lopes, JAP;

Publication
Renewable Energy and Power Quality Journal

Abstract
The present paper describes an optimization strategy, to be adopted at the wind park control level, especially for those with large power output, that allow to define the commitment of the wind turbines and their active and reactive set points following requests from the wind park dispatch centers, assuming that individual wind turbines short term wind power forecasts are known and are expressed as power availability. This approach was also developed with a concern on the minimization of the connection / disconnection of the individual wind generators, for a given time horizon, and takes also into account restrictions in the limits for reactive power generated at the wind turbines.

2010

Islanding Operation of Active Distribution Grids using an Agent-based Architecture

Authors
Issicaba, D; Gil, NJ; Pecas Lopes, JAP;

Publication
2010 IEEE PES CONFERENCE ON INNOVATIVE SMART GRID TECHNOLOGIES EUROPE (ISGT EUROPE)

Abstract
This paper presents a decentralized architecture for the islanding operation of distribution grids with large volume of distributed generation. This architecture involves the definition of network blocks which share the responsibility of frequency control. The control block abstraction was particularly designed to support the transition from regular grids to smart grids. In addition, the control schemes were developed using an agent-based paradigm. Hence, an agent-based simulation platform was implemented using libraries from the Java Agent Development Framework (JADE). The control schemes were evaluated using a test system with different sorts of distributed energy resources and modeled in the EUROSTAG environment. Simulation results show the effectiveness of the control architecture when different failure events are applied to the test system.

2011

Impact of Multi-Microgrid Communication Systems in Islanded Operation

Authors
Rua, D; Moura Pereira, LFM; Gil, N; Pecas Lopes, JAP;

Publication
2011 2ND IEEE PES INTERNATIONAL CONFERENCE AND EXHIBITION ON INNOVATIVE SMART GRID TECHNOLOGIES (ISGT EUROPE)

Abstract
This paper presents an impact analysis of communications in frequency and active power control in hierarchic multi-microgrid structures. Since communications can potentially introduce significant difficulties in the operation of electric power systems, particularly in the case of islanded multi-microgrids, an assessment is performed considering delays and losses that control information is likely to experience when traversing the communication infrastructure. Results show that the impact of communication difficulties under most simulated scenarios is reduced, whereas in more demanding scenarios the control structure can have a significant role in minimizing the impact of communication failures.

2011

Integration of Electric Vehicles in the Electric Power System

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

Publication
PROCEEDINGS OF THE IEEE

Abstract
This paper presents a conceptual framework to successfully integrate electric vehicles into electric power systems. The proposed framework covers two different domains: the grid technical operation and the electricity markets environment. All the players involved in both these processes, as well as their activities, are described in detail. Additionally, several simulations are presented in order to illustrate the potential impacts/benefits arising from the electric vehicles grid integration under the referred framework, comprising steady-state and dynamic behavior analysis.

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