Continuous Hydrothermal Flexibility Coordination Under Wind Power Uncertainty

This paper proposes a stochastic continuous-time optimization model for coordinating the operation of flexibility reserve in a hybrid hydro-thermal-wind power system. The proposed continuous-time model captures the sub-hourly uncertainty and variations of wind power and load, and accurately models and schedules the ramping flexibility of the hydrothermal system to match the uncertainty and variations of wind power and load. A simplified Northern European system is studied over a 30-hour period to examine the potential of using hydropower as a comprehensive flexibility provider. Norwegian hydropower is shown to be a significant source of flexibility used to mitigate wind power variations, especially during ramping constrained periods. The hydropower provides 73.5% of the balancing energy in the base case, which includes smoothing out longer wind power deviations as well as rapid ramping relief. The short-term implications of increasing the offshore wind power in the North Sea by 50% compared to 2020 was also studied in the Northern European test system. The increased wind power causes steeper ramping in the net load, which drives the hydropower to its full balancing potential to allow thermal units to operate within their ramping limits.