Phase–amplitude model for doubly fed induction generators

The doubly fed induction generator (DFIG) is major type of wind turbine generator used in grid-connected wind farms. Practical models of DFIG have been built to study the influence of wind power generation on power system dynamics. However, most existing practical models of the DFIG are based on rectangular coordinates, in which frequency variation is neglected. In this paper, a phase–amplitude (P–A) model is proposed for a DFIG based on phase and amplitude of the internal voltage. The model structure is much like that of the synchronous generator, and the rotor voltage can manipulate both the amplitude and the phase of the internal voltage. Comparisons have been made between the new P–A model of the DFIG and the synchronous generator model, as well as the asynchronous motor model. The contributions of the new P–A model of the DFIG are discussed and it is demonstrated that the proposed model has better ability in describing power system dynamic phenomena such as voltage dynamics and structural dynamics in general. Simulation results and a field test validate these contributions.