What are Double Fed Induction Generators (DFIG)?
DFIG stands for Double Fed Induction Generators. They are most noticeably used in wind turbines for electricity production. Unlike a generator alternator, which generates electricity rotating at a nice constant 1500RPM. The wind is significantly less reliable. Maximise the amount of energy with DFIG. Consequently, this allows electricity generation from much lower rotational speeds.
Advantages of using DFIG
- Reduced inverter cost, because inverter rating is typically 25% of total system power, while the speed range of the ASG is ±33% around the synchronous speed.
- Secondly, reduced cost of the inverter filters and EMI filters. Filters rated for 0.25 p.u. total system power. Inverter harmonics represent a smaller fraction of total system harmonics.
- Above all, improved system efficiency. Approximately 2-3% obtained.
- Power-factor control likely implemented at lower costs. The DFIG system (four-quadrant converter and induction machine) operates similar to a synchronous generator. The converter has to provide only excitation energy.
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