Coordinated two-stage volt/var management in distribution networks

•Network-wide control combining feeder and substation controllers is presented.•The approach features reactive power-flow heuristics and optimal substation control.•The approach minimises losses and voltage deviations in constrained systems.•A comparative analysis of the proposed and existing approaches is conducted.

This paper investigates daily volt/var control in distribution networks using feeder capacitors as well as substation capacitors paired with on-load tap changers. A two-stage coordinated approach is proposed. Firstly, the feeder capacitor dispatch schedule is determined based on reactive power heuristics. Then, an optimisation model is applied to determine the dispatch schedule of the substation devices taking into account the control actions of the feeder capacitors. The reference voltage of the substation secondary bus and the tap position limits of transformers are modified such that the model adapts to varying load conditions. The optimisation model is solved with a modified particle swarm optimisation algorithm. The proposed method is compared with conventional volt/var control strategies using a 14-bus system and its effectiveness is further illustrated on a 69-bus system. It is demonstrated that the proposed approach performs better than the conventional strategies in terms of voltage deviation and energy loss minimisation.