Minimization of Reactive Power Exchange at the DSO/TSO interface: Öland case

A rising penetration of renewable energy sources in electric power grids is both a challenge and an opportunity to utilize its potential to stabilize operation of future power systems. Bi-directional flows between distribution and transmission systems can cause significant problems with keeping the voltages and reactive power in grids within permissible levels. This paper addresses the problem of reactive power exchange between the distribution system of Öland and the mainland Swedish electricity grid. Wind turbine generators with the capacity that highly exceeds total demand in Öland, are used to minimize absolute reactive power exchanged at the point of connection. This is done by applying droop control functions for reactive support to the wind turbines. Results indicate that the controllability of the reactive power support from wind turbine generators can keep the reactive power flow minimized at the point of connection and simultaneously diminish the active power losses in the system. The analysis in this paper has been done using the PSS/E software.