Voltage Profile Correction in Distribution Grids Combining Single- and Two-level Controllers

A real-time control scheme is proposed to correct undesired voltages in distribution networks by adjusting the reactive powers produced by Dispersed Generation Units (DGUs). This is performed at two levels: locally, in DGU controllers, and centrally by a supervisory controller acting on some of the DGUs only. The centralized, discrete controller solves a multi-time-step constrained optimization inspired of Model Predictive Control. Unacceptable voltage deviations are partially but rapidly corrected by the local controls. Further but slower corrections are applied by the upper level, taking advantage of the coordination between DGUs. This hybrid control is of practical interest where the deployment of the upper level control is not feasible or affordable over all DGUs. The proposed method effectiveness is demonstrated on a 75-bus test system.