Variable-Speed Wind Turbines with Doubly-Fed Induction Generators Part IV: Uninterrupted Operation Features at Grid Faults with Converter Control Coordination

Abstract

A model of variable-speed wind turbines equipped with doubly-fed induction generators (DFIG) and controlled by partial-load frequency converters described in [1,2] is applied in power stability investigations. A technical feature of uninterrupted operation at grid disturbances of large wind farms with such variable-speed wind turbines is suggested and discussed. This technical feature is based on fast re-start of the rotor converter, which blocks at grid faults. The main reactive power control is organised by the rotor converter [3]. The new part is that reactive power is controlled by the grid-side converter when the rotor converter blocks. Possible discrepancies between the results reached with the detailed representation of the frequency converter and the representation where only the rotor converter is regarded are notified and explained. The converter representation details influence on the machine current transients modelled at grid disturbances and also on damping characteristics of torsional shaft oscillations.