Early wind turbines used for performing mechanical work (pumping, grinding and cutting)

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Abstract-An analytical averaged equivalent circuit model is derived revealing how dominant loss mechanisms vary with converter operating point in a PWM converter. The model is based on the operational characteristics of power diodes and IGBTs. Laboratory experiments support the derived model and confirm that IGBT current tailing and diode reverse-recovery are indeed the most critical losses in a PWM converter. These losses are more significant at light load, hence reducing the energy capture of converters used in wind generation.

The NREL Variable-Speed Test bed turbine has been used to examine the performance and controllability of a variable-speed, variable-pitch turbine.Control strategies that eliminate drive-train torque fluctuations in high winds have been published before and example data are given here. The energy capture of a variablespeed wind turbine depends in part on its ability to successfully operate at the peak of the Cp-A curve. The losses associated with the inability of the rotor to stay exactly on top of the curve at all have been found and quantified. New control strategies for improving energy capture in moderate winds are also proposed. The potential exists to improve overall energy capture by 5% or more.

No abstract