Control of Energy Storage units to limit active power ramp-rates of renewable energy sources using non-ideal generation forecasts

This paper compares three different methods to limit the active power gradient of a renewable energy plant. The methods are based on the utilization of an Energy Storage System (ESS) to absorb and release power required in the case of fast power ramp-up or ramp-down, respectively. The paper presents analytical solutions for the required energy storage capacity in case of an ideal ramp event, using each of the three methods. The control methods are verified by simulations, using an active power time-series of a 6 MW wind farm. The novelty of this study lies in the inclusion of non-ideal power forecasts and evaluation of the control methods under varying forecast accuracies. The performance of the control methods when including a simple energy storage state controller was also studied. The controller prevents any drifts in the energy storage state.