Three-Timescale Hierarchical Multi-Objective Volt/Var Control in Active Distribution Network With Inverters Droop Control

In response to the uncertainties and power quality degradation caused by the integration of numerous renewable energy resources (RESs) and the increasing adoption of plug-in electric vehicles (PEVs) in active distribution networks (ADNs), this paper proposes a three-timescale hierarchical volt/var control (VVC) model operating at 1 hour, 15 minutes, and 1 minute. The model aims to achieve effective coordination between centralized optimization and local control, considering the unique characteristics of different reactive power control devices. A three-stage optimization method is developed to solve the proposed three-timescale models; specifically, a three-step method is proposed to solve the one-hour look-ahead model for scheduling the tap position of the on-load tap changer (OLTC) and the number of switching groups for the shunt capacitors (SCs). For the 15-minute timescale, the voltage set-point of the inverter is optimized to minimize the voltage deviations of the pilot buses in typical scenarios, taking into account the uncertainties associated with RESs. For the 1-minute timescale, local measurement information is utilized, and a double-loop droop control method is adopted to track the voltage setting value provided by the 15-minute timescale model. This ensures the optimization of the system’s voltage level and the minimization of voltage fluctuations. The IEEE 33-bus and IEEE 123-bus distribution networks are employed to validate the proposed method and its ability to deal with uncertainties.