Managing cascade transformers equipped with on-load tap changers in bidirectional power flow environment

Existing voltage control schemes of cascade on-load tap changers (OLTCs) have been developed considering unidirectional power flow. However, in recent years, integration of distributed generation such as solar and wind power to the grid has created possibility for bidirectional power flow resulting in inefficiency of previous voltage control methods of cascade OLTCs. In this paper, an effective method for managing cascade OLTCs in bidirectional power flow environment is presented. Tracking the active and reactive power changes in both MV and LV networks, the developed method is able to detect the cause of voltage variation i.e. MV or LV network. Accordingly, it enables the system operator to order tap actions at accurate voltage level which decreases unnecessary tap actions and improves the voltage quality at costumer points. The proposed voltage control method is tested in different network scenarios.