Effects of the Reactive Power Injection on the Grid—The Rise of the Volt/var Interaction Chain

The major challenge to increase the decentralized generation share in distribution grids is the maintenance of the voltage within the limits. The inductive power injection is widely used as a remedial measure. The main aim of this paper is to study the effect of the reactive power injection (by what-ever means) on radial grid structures and their impact on the voltage of the higher voltage-level grids. Various studies have shown that, in addition to the major local effect on the voltage at the injection point, the injection of the reactive power on a feeder has a global effect, which cannot be neglected. The reactive power flow and the voltage on the higher voltage level grid are significantly affected. In addition, a random effect is introduced by the DGs which are connected through inverters (using wind or PVs). Although their operation is in accordance with the grid code, a volatile reactive power flow circulates on the grid. Finally, this study proposes the implementation of the “Volt/var secondary control” interaction chain in order to increase the distributed generation share at every distribution voltage level, be it medium or low voltage, and at the same time to guarantee a stable operation of the power grid. Features of Volt/var secondary control loops ensure a resilient behavior of the whole chain.