Secondary Frequency Regulation From Aggregated Distributed Photovoltaics: A Dynamic Flexibility Aggregation Approach

To fully utilize the potential of massive small-scale distributed photovoltaics (DPVs) for secondary frequency regulation (SFR), this article introduces a hierarchical coordination framework that incorporates the dynamic response characteristic (DRC) of DPV to automatic generation control (AGC) signals, thereby reflecting the dynamic flexibility of the aggregated DPVs (ADPVs). First, a reserved power feasible range is derived for scheduling the power reserve control (PRC) scheme considering the uncertainty in PV generation and the de-loaded margin base constraint. Second, a two-stage multi-cluster DRC aggregation method that considers the impact of the PRC scheme is developed to describe the equivalent DRC of the ADPVs. Last, the article constructs an integrated cost function (ICF) that reveals the interdependencies between SFR capacity, equivalent DRC and regulation cost, which enables the decoupled scheduling of the SFR indices and the PRC scheme. An event-triggered duty factor reassignment mechanism is further proposed to improve the reliability of SFR service deployment in case of unexpected events. Simulation results indicate that the framework is an efficient approach for quantifying, trading and realizing the dynamic flexibility of the ADPVs.