Modal analysis of power systems with doubly fed induction generators

This article is concerned with the impact of large scale wind farms utilising doubly fed induction generators on the stability of a conventional power system. Inspection of the eigenstructure of the system provides a foundation for assessment of the impact, which is then quantified by means of detailed numerical simulations. Simplified state-space models are used to describe the dynamics of generators in a very simple system, whose network is described by algebraic relations. A third order model is derived for a doubly fed induction generator. Mathematical models are used to identify the behavioural patterns of the system when it is subject to disturbances. Eigenvalue analysis reveals certain interesting properties of the system when it is subject to small disturbances. Numerical simulations show that the addition to a power system of doubly fed induction generators, such as those found in wind farms, improves the response of the system to small disturbances, but can have an adverse impact after larger disturbances.