J. Antunes Ferreira

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The objective of this paper is to review direct-drive and geared generator systems and to identify suitable generator concepts for direct-drive wind turbines. The comparison of different generator systems in literature is discussed with the criteria based on the energy yield, cost, and weight. Different promising permanent-magnet (PM) machines proposed in(More)
At a workshop held on the Aeolian Islands in Sicily during May 2004 a group of academic and industry engineers from all over the world discussed the medium- and long-term future of power electronics and its applications in specific areas. The following main issues were identified and discussed: The demand is not for power electronic solutions but for system(More)
First, an electromechanical converter with two mechanical ports and one electrical port (consisting of two concentric machines and two inverters) is considered. This converter works as a continuously variable transmission between the mechanical ports and may, e.g., replace the clutch, gearbox, generator, and starter motor in a motor vehicle. The working(More)
Aerospace systems require high power density as well as high availability. An integrated permanent magnet machine and drive has been considered. System integration aids achieving high power density in aerospace applications whereas fault tolerance increases availability, mostly by increasing system phase count. This increase in the number of system phases(More)
The objective of this paper is to assess 10 MW directdrive permanent-magnet (DDPM) generator systems with different control strategies namely pitch control and active speed stall control. In the active speed stall control concept, there is no pitch mechanism, and the rotor speed is actively controlled by the generator to control the output power. The active(More)
The risk of the duration of a project exceeding a certain limit has been studied since the early papers proposing the PERT method but no results are available relating the statistical distribution of the total duration with the morphological features of the network. In this paper, a set of indicators is proposed to describe the morphology of the project(More)
An increasing number of distributed generation (DG) units is being connected to the distribution network. This introduces a large number of power electronic converters. Due to the output capacitance of these and other converters there is a risk on harmonics, badly damped transients and so on. In this paper it has been investigated whether the DG unit(More)
This paper proposes the use of a three-phase four-leg (3P4L) converter in combination with an LCL filter for the inverter stage of a solid state transformer (SST). This configuration gives full control over the line-to-line, as well as the line-to-neutral voltage and currents, while providing exceptional harmonics mitigation. A procedure to calculate the(More)
First, an electromechanical converter with two mechanical ports and one electrical port (consisting of two concentric machines and two inverters) is considered. This converter works as a continuously variable transmission between the mechanical ports and may, for example, replace the clutch, gearbox, generator, and starter motor in a motor vehicle. The(More)