Coordinated voltage control scheme for Flemish LV distribution grids utilizing OLTC transformers and D-STATCOM´s

The incorporation of on-load tap changers (OLTC) in secondary distribution transformers has been proposed as alternative technology to prevent the violation of the voltage statutory limits in Flemish LV distribution grids. Under high penetration levels of distributed generation (DG), this device can partly eliminate those violations increasing the voltage unbalances when independent tap-changing control per phase is applied. The paper describes a coordinative scheme for the regulation of positive and negative sequence voltages utilizing OLTC transformers and distributed static synchronous compensator (DSTATCOM) devices. From the results, it was concluded that the proposed scheme can fully remediate the over-voltage violations via active power control and decrease the voltage unbalances considerably via reactive power management.