Time-Scale Modeling of Wind-Integrated Power Systems

This paper describes time-scale separation properties of dynamic models of wind-integrated power systems. We first derive a mathematical model for the dynamics of a power network consisting of synchronous generators, loads and a wind power plant modeled by a wind turbine and a controlled doubly-fed induction generator. We then aggregate this system into multiple coherent areas, and apply a linear transformation to represent the model in terms of slow and fast states. Using this transformed system we show that the ratio of the time constant associated with the swing states to that of the wind plant can be used to characterize conditions under which the slow time-scale of the power system changes with increasing wind penetration. We further demonstrate that these modal responses depend on the relative locations of the synchronous generators, the loads and the wind generator in the power system. We illustrate these observations through simulations of a two-area 8-bus power system and a five-area 68-bus power system.