Capability and limitations of DFIG based wind turbines concerning negative sequence control

Modern wind turbine systems based on doubly-fed induction generator (DFIG) technology offer negative sequence control capability during grid faults or unsymmetrical system operation. This paper deals especially with the effects of current and voltage limitation of a typically rated converter system design based on positive sequence control requirements. At first a short summary of the most common alternative negative sequence control objectives is given. Then the corresponding rotor side converter (RSC) control algorithms are described. This is followed by typical characteristics of current capabilities as well as voltage constraints. Finally detailed calculations regarding control possibilities and limitations in the positive and negative sequence are shown.