Control of wind turbine output power via a variable rotor resistance

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Title:	Control of wind turbine output power via a variable rotor resistance
Author:	Burnham, David James
Abstract:	Many utility-scale wind turbine generators use wound-rotor induction machines. By adding an external rotor resistance to the rotor circuit it is possible to control the wind turbine output power and, with proper control, maintain a constant power for wind speeds between rated and cut-out. The external resistance modifies the generator torque-speed curve and changes the angular velocity of the rotor, resulting in a greater power extraction from the wind. A number of control strategies can achieve this objective. These include controlling the rotor resistance to maintain a constant generator equivalent circuit, and control based on the aerodynamic torque. It is also possible to use a lookup table instead of a feedback controller. These options all have the same steady-state result as direct output power control, but differing transient performance. Computer simulations and hardware experiments are used to investigate and characterize the different control methods.
Department:	Electrical and Computer Engineering
Subject:	wind turbines wind power wound-rotor induction machines
URI:	http://hdl.handle.net/2152/ETD-UT-2009-05-105
Date:	2009-05