Dependable dynamic capacity provision of wind-storage plants

Although wind energy is volatile, the output of a wind-storage plant is partially dispatchable, making it a promising paradigm on the generation side. A grid-friendly wind-storage plant ought to be able to continuously output the desired power over a certain period of time. This paper proposes a dependable dynamic capacity provision scheme of a wind-storage plant over a daily horizon. It stipulates a minimum number of periods during which the committed capacity must be fulfilled and a maximum mismatch during the remaining periods when the desired power output is not achievable. In the general case, the day-ahead piecewise constant capacity provision results in a two-stage stochastic program formulated as a mixed-integer linear program. Specifically, for constant capacity provision, a decomposition algorithm is developed to determine the global optimal solution, and the complexity grows linearly with the number of scenarios. Given the committed capacity trajectory, the real-time operation problem is modeled as a four-state stochastic dynamic program. The discrete state-action values are derived recursively via the principle of optimality. Real-time dispatch actions are generated by using the action-value tabular leveraging inexact ultra-short-term forecasts. Numerical tests over one year demonstrate that the proposed method successfully fulfills reliable operation on 355 days and achieve an optimality gap of 9.47% compared with the ex-post optimum, which is comparable to model predictive control using exact 2–3-hour-ahead wind power forecasts.