Impact analysis of wind power injection on time-scale separation of power system oscillations

In this work, we present an analytical relationship between the two time-scale behavior of coherent power system networks with increasing levels of wind penetration. We first derive a mathematical model coupling the electro-mechanical swing dynamics of the grid integrated with the dynamics of a doubly-fed induction machine via power flow. We then consider the system to be comprised of r coherent areas and apply a similarity transformation to explicitly show that the integrated system may exhibit a three time-scale behavior depending on the amount of wind power injection. This effect is illustrated using simulations of a model of the US Western Interconnection.