Doubly-fed full-controlled induction wind generator for optimal power utilisation

Abstract

Abslroct:Doubly-fed induction generators are used mainly for wind energy conversion in MW power plants. They have a rotor inverter and a front-end converter while the stator is linked directly to the grid. If a dc bus bar is available, a double feeding can occur about inverter. This paper describes a doubly-led fullcontrolled induction wind generator which offers high flexibility of stator side control to ensure minimal losses as well as optimal power utilisation. The equation of the optimal loss reglme is derived while simulation results show improvements in the eniciency power extraction. The special wind converter system has been investigated at a glance of installed off-shore MWgenerators, where a dc-transmission is advantageous because of the avoided reactive power. The precalculated improvements behave 6% at most in the winddriven range. Some investigations with the operating characteristic in winddriven and constant power modes are presented and discussed.

Transient Characteristics of Two Wind Turbine Generator Systems Having Two Types of Control Methods

“…Region [2]: Region in which the wind speed ranged from the cut-in wind speed to the level of the generator speed reaching the synchronous speed ( N = 1000 rpm). Region [3]: Region in which the generator speed ranged from the synchronous speed ( N = 1000 rpm) to the nominal rated power. Until the wind speed reached the cut-in wind speed (Region [1]), the wind speed on the nacelle remained at 3 m/s or less on average, which was the level when the generator speed fluctuated from 700 to 900 rpm.…”

“…When the wind speed increased, the change in the IGBT frequency showed the reverse response to the up/down of the generator speed (4) . Figure 4 shows the transient change in various electrical parameters, including the active power and current, and the wind speed on the meteorological mast and the nacelle, as well as the change in the generator speed and IGBT frequency over time when the output power suddenly increased by approximately 200 kW to reach Region [3], from approximately 100 kW (Region [2]). …”

“…In Region [3], on the other hand, where the generator speed exceeded the synchronous speed of 1000 rpm, the generator speed reached approximately 1100 rpm and a comparatively excessive frequency of approximately 5 Hz was supplied to the Region 【3】 20 grid-connected through the IGBT in order to retain a power frequency of 50 Hz. At this point, the change in the IGBT frequency corresponded to the change in the generator speed (4) over time.…”

“…5 indicates with diagrams the average power curve in relation to the generator speed and the IGBT frequency. In these diagrams, the loci of the transient change in various electrical parameters, with the output power starting from P = 0 kW (in transition from Region [1] to Region [2]) in the aforementioned case, and in this case, with the output power suddenly increasing by approximately 200 kW from 100 kW (in transition from Region [2] to Region [3]), are also described.…”

Sub-Synchronous Range of Operation for a Wind Driven Double-Fed Induction Generator

“…Most, if not all, of the published papers on the subject analyze the performance of DFIG using the d-q axes theory [3][4][5][6][7]. However, in this paper another approach is used which is the power flow approach.…”