Small-signal impedance modelling of type-III wind turbine

Impedance-based small signal analysis is a useful tool to examine resonance between type-III wind turbines and the grid, but no accurate and complete model of the turbine has been presented for the frequency range that covers from a few Hz to a few kHz. Existing models either ignore the effects of the converters or do not model such effects correctly. This paper presents positive- and negative-sequence impedance models of the turbine with and without phase-lock loop (PLL). This paper also gives an overview on the modelling approach taken to model the machine with PLL dynamics. Finally, the models are validated with impedance sweeps using real-time simulation.