2011
Authors
Soares, FJ; Peças Lopes, JA; Rocha Almeida, PM; Moreira, CL; Seca, L;
Publication
17th Power Systems Computation Conference, PSCC 2011
Abstract
The uncertainties related to when and where electric vehicles will charge in the future requires the development of stochastic based approaches to identify the corresponding load scenarios. This paper describes a tool based on Monte Carlo techniques to be used for distribution grid planning, providing a characterization of possible grid operation conditions, regarding voltage profiles, branch loading, grid peak power and energy losses. A medium voltage network based on real data is used to illustrate the application of the developed methodology.
2010
Authors
Lopes, JAP; Almeida, PMR; Soares, FJ; Moreira, CL;
Publication
IFAC Proceedings Volumes (IFAC-PapersOnline)
Abstract
This paper presents a conceptual framework to enable a successful integration of Electric Vehicles (EV) into isolated power systems. The developed framework includes the management and control actions that might be implemented over EV in order to improve the system's resilience. Several dynamic stability simulations were performed, using a small isolated grid as a test system, in order to demonstrate the possible contributions EV may provide to fast power/frequency control, either as a highly flexible and controllable load and/or as an energy storage device.
2012
Authors
Silva, B; Moreira, CL; Seca, L; Phulpin, Y; Pecas Lopes, JAP;
Publication
IEEE TRANSACTIONS ON SUSTAINABLE ENERGY
Abstract
This paper addresses the problem of providing frequency control services, including inertia emulation and primary frequency control, from offshore wind farms connected through a multiterminal HVDC network. The proposed strategy consists of a cascading control mechanism based on dc voltage regulation at the onshore converters and frequency regulation at the offshore converters. The control scheme involves only local measurements and actions avoiding security and reliability issues of control structures based on remote information. The effectiveness of the proposed strategy is illustrated in a test system that consists of two nonsynchronous areas linked by a multiterminal HVDC grid where two offshore wind farms are also connected.
2006
Authors
Lopes, JAP; Moreira, CL; Madureira, AG;
Publication
IEEE TRANSACTIONS ON POWER SYSTEMS
Abstract
This paper describes and evaluates the feasibility of control strategies to be adopted for the operation of a microgrid when it becomes isolated. Normally, the microgrid operates in interconnected mode with the 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. An evaluation of the need of storage devices and load shedding strategies is included in this paper.
2007
Authors
Moreira, CL; Resende, FO; Lopes, JAP;
Publication
IEEE TRANSACTIONS ON POWER SYSTEMS
Abstract
Under normal operating conditions, a MicroGrid is interconnected with the medium voltage network; however, in order to deal with black start and islanded operation following a general blackout, an emergency operation mode must be envisaged. A sequence of actions and conditions to be checked during the restoration stage are identified and tested through numerical simulation. Voltage and frequency control approaches, inverter control modes, and the need of storage devices are addressed in this paper in order to ensure system stability, achieve robustness of operation, and not jeopardize power quality during service restoration in the low voltage area.
2010
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.
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