Multi-period Two-stage Stochastic DER Aggregation for Power Flexibility Reserve

The high penetration of distributed energy resources (DERs) and the development of the energy internet bring a huge opportunity for distribution system. Although the individual DER capacity and visibility are small, aggregating various DERs can provide more flexibility for distribution system operation. This paper proposes a multi-period two-stage DER aggregation method for different types DERs considering the operating cost minimization. In the day-ahead stage, an aggregator determines the expected power trajectory of the aggregated DERs for energy trading and the optimal interval of flexibility reserve, which are in turn submitted to the distribution system operator (DSO). During the day, with the DSO dispatch signal, the aggregator re-optimizes the scheduling of the aggregated DERs to realize the power adjustment. To handle uncertainty, a stochastic optimization method with conditional value-at-risk is adopted, aiming to achieve the trade-off between power flexibility and operating cost reduction. The proposed method is compared with the conventional method which maximizes the flexibility reserve interval. The simulation results show that the proposed method can achieve a lower operating cost with only 0.6% infeasibility rate, verifying its high efficiency.