This report studies the impact of renewable energy resource intermittency on the dynamical stability of power systems. Renewable resources in this study include solar and wind power. In order to capture the interaction between the intermittent variation in the power output of renewable resources and the controllers in the system, each simulation case runs for 1200 seconds. Furthermore, in addition to the dynamic models that are normally included in typical electromechanical simulations, slow controllers such as automatic under-load tap changers, automatic switchable shunt controllers, and over-excitation limiters are also modeled. User-defined dynamic models are developed for several components including Automatic Generation Controller (AGC), operator action for a peaking unit, and energy storage unit. This study uses three planning power flow cases with varying levels of load and generation. Moreover, three renewable variation scenarios are also considered, namely drops in solar and wind power, drops in solar power with pre-outage of a major line, and wind gusts. The effect of intermittency is studied by itself as well as together with contingencies that result in line outages near renewable farms. Lastly, this paper discusses the observations from these simulations, as well as the experience of setting up long-term simulations using a transient analysis program.
Keywords: Renewable Energy, Intermittency, Simulation, Dynamic Models.