Optimal Energy Storage Capacity Sizing Method Based on Power-Energy Characteristics of Curtailment and Deficit Events

With the increasing penetration of renewable energy represented by wind and photovoltaic (PV) power in the power grid, the fluctuation amplitude of the net load curve is growing significantly, and the regulation capability of thermal power units can hardly accommodate such large fluctuations. When the adjustable range fails to meet the net load fluctuations, power curtailment and deficit issues arise in the system. Deploying energy storage is a common method to addressing power curtailment and deficit. However, over-sizing the storage capacity leads to low utilization of the storage equipment, while under-sizing fails to effectively mitigate the curtailment and deficit issues. Addressing the insufficiency of regulation capacity in future power systems with high wind and solar penetration, this paper proposes an optimal energy storage capacity allocation method based on the characteristics of power curtailment and deficit. First, a characterization model for the regulation capacity of existing conventional power sources is constructed. Combined with the annual wind and PV output curves, the temporal distribution of annual curtailment and deficit events is quantified based on the existing regulation capacity. Second, an optimal energy storage capacity allocation method matching the power–energy characteristics of curtailment and shortage is developed to minimize storage investment and maximize the reduction in losses caused by curtailment and deficit. Finally, the proposed method is validated based on a full-cycle operation scenario of a provincial power grid. The results show that compared with traditional empirical sizing schemes, the proposed scheme increases the complete mitigation rate of curtailment and deficit events from 32.57% to 49.01%; compared with the extreme sizing scheme that completely covers the gaps, it avoids a massive investment of nearly 380 million RMB/year. In future scenarios with gradually increasing renewable energy penetration, both the optimal charge/discharge duration and the event mitigation rate derived by the proposed scheme increase steadily, demonstrating its significant guiding value for long-term planning.