Investigation of Self-Excited Induction Generators for Wind Turbine Applications

Research output: Contribution to conferencePaper


The use of squirrel-cage induction machines in wind generation is widely accepted as a generator of choice. The squirrel-cage induction machine is simple, reliable, cheap, lightweight, and requires very little maintenance. Generally, the induction generator is connected to the utility at constant frequency. With a constant frequency operation, the induction generator operates at practicallyconstant speed (small range of slip). The wind turbine operates in optimum efficiency only within a small range of wind speed variation. The variable-speed operation allows an increase in energy captured and reduces both the torque peaks in the drive train and the power fluctuations sent to the utility. In variable-speed operation, an induction generator needs an interface to convert thevariable frequency output of the generator to the fixed frequency at the utility. This interface can be simplified by using a self-excited generator because a simple diode bridge is required to perform the ac/dc conversion. The subsequent dc/ac conversion can be performed using different techniques. The use of a thyristor bridge is readily available for large power conversion and has a lowercost and higher reliability. The firing angle of the inverter bridge can be controlled to track the optimum power curve of the wind turbine. With only diodes and thyristors used in power conversion, the system can be scaled up to a very high voltage and high power applications. This paper analyzes the operation of such a system applied to a 1/3-hp self-excited induction generator. It includesthe simulations and tests performed for the different excitation configurations.
Original languageAmerican English
StatePublished - 2000
Event1999 IEEE-IAS Conference - Phoenix, Arizona
Duration: 3 Oct 19997 Oct 1999


Conference1999 IEEE-IAS Conference
CityPhoenix, Arizona

NREL Publication Number

  • NREL/CP-500-26713


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