Voltage Regulation Enhanced Hierarchical Coordinated Volt/Var and Volt/Watt Control for Active Distribution Networks With Soft Open Points

The integration of renewable energy sources (RESs) into active distribution networks (ADNs) is essential for reducing carbon emissions but often results in voltage fluctuations and violations. This paper proposes a hierarchical voltage control framework that effectively coordinates diverse controllable devices with various response times in an ADN. The framework comprises three stages: day-ahead scheduling of on-load tap changer (OLTC), intra-day optimization for droop slopes and references for droop controllers in Soft Open Points (SOPs) and distributed generators (DGs), and real-time local voltage regulation. Unlike existing approaches, the proposed approach analytically establishes voltage stability constraints and incorporates them into droop slope optimization for local controllers, mitigating voltage oscillation risks. Additionally, a novel deviation-aware optimization method is developed to calculate optimal voltage references. This method treats the deviations between fixed-point voltages and their references as uncertainties and accounts for their impacts on voltage security through chance-constrained programming. Simulation results demonstrate the effectiveness of the proposed framework in improving voltage regulation performance with guaranteed stability.