Stochastic estimation of PQ powers at the interface between distribution and transport grids

The insertion of stochastic renewable energies in distribution grids generates important voltage fluctuations and reactive power exchange between distribution grids and transmission grids. These variations need to comply with European grid codes. The control strategy involves the actuation of the On Load Tap Changer and Capacitor Banks tap position, and the reactive powers of the DGs. This paper focuses on the stochastic estimation of the powers at the interface and the influence of the Capacitor Bank tap position. The main results are that, using a simplified stochastic model of the grid, one can obtain the distribution of the powers, and select, on a daily basis, the tap position which minimizes the level of the prescribed PQ diagram violation risk. This study paves the way for a volt-var stochastic optimization of the distribution grid.