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Due to the double fed induction generatorpsilas (DFIG) advantage of controlling active and reactive power independently and partial power converter, DFIG is becoming a popular type of wind power generation system. Nowadays, the grid code demands that the wind power generator possesses the ability of riding through the grid voltage sags, only when the grid voltage drops below the specific curve, the...
Direct-drive wind power system was increasing attention due to its inherent high efficiency. By eliminating the need of a gearbox between the wind turbine and generator, direct-drive wind power systems are less expensive and also require less maintenance. With numerous advantages, the direct drive, grid-connected permanent magnet synchronous generator (PMSG) generation system represents one important...
In parallel converters applications, direct parallel topology was respected because of the advantages of small size, low cost, simple structure and easy to extend. However, the coupling effects maybe exist because the parallel converters are connected by non-isolated mode. In this paper the average model was proposed in the rotating coordinate system. As the entire system is a symmetric structure,...
Low voltage ride through (LVRT) capability is required by new power system operating codes, then voltage sag generator (VSG) is generally used to simulate different voltage sag faults. The work principles of transformer and bidirectional switches based VSG and full-power converter based VSG are explained and discussed, the former can choose relay, thyristor or IGBT as bidirectional switches, and the...
Direct-drive wind power generator has been receiving increasing attention due to their inherent efficiency. By eliminating the need for a gearbox between the wind turbine and generator, these systems are less expensive and also require less maintenance. This paper outlined a procedure of adapting a small, standard, readily available PM synchronous machine for direct coupling to a small wind turbine...
With the direct-drive wind power system, full-power converter technology has been developed and applied. However, most of wind generators operate at rated voltage of 690 V in wind field at present while direct-drive power system needs the full-scale power converter. For the high-power output, power devices must support higher current. Before the breakthrough of the present level of the current rating,...
In this paper, modeling of parallel three-phase converters is first presented. Then definition of the circulating currents of paralleled converters and the circulating-current-generating mechanism are clearly explained. Thus, based on this definition, an averaged model of the circulating current is proposed. It is seen from this model that the circulating current consists of mainly the zero-sequence...
Direct-drive wind power system needs a full-scale power converter to transmit the variable frequency electrical power to the grid. In order to improve the low voltage ride through (LVRT) capability, the grid-connected inverter (GCI) should work at a unity, a leading or a lagging power factor. Traditional control methods are complicated and output waveform is distorted by dead time. This paper introduces...
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