Analysis of a reactive power exchange between distribution and transmission grids

In this paper a novel co-simulation is developed, to study the dynamic exchange of reactive power from a distribution grid to the transmission grid. This exchange is performed under a regulatory scheme. In particular, a distribution grid optimizer signals to the transmission grid the available reactive power interval at the distribution/transmission nodes every 15 minutes. A transmission grid optimizer uses this information to compute a reactive power set point, to stabilize the voltage in the transmission grid. The distribution grid optimizer receives this set point and translates it into settings for transformers and renewable generators. This strategy is tested on a running grid simulation, with the tools working in parallel. It is shown that the voltage in the transmission grid can be improved, but at the cost of power losses in the distribution grid and renewable generators.