Reactive Power Support Adequacy at the DSO/TSO Interface

Abstract

The exchange of reactive power at the interface between distribution and transmission systems gains significant importance with ongoing relocation of generators to lower voltage levels. To keep transmission systems operation secure and stable, distribution systems may need to be more flexible when exchanging power at the interface with the overlaying grid. A flexibility measure of this interface is proposed by this paper through introduction of flexibility coefficients. These coefficients are calculated by comparing DSO capability and TSO desirability surfaces. These surfaces describe the distribution system’s capability to provide flexible reactive power exchange and the transmission system’s needs to use these flexibilities. Since the surfaces can be calculated independently, the newly proposed method of flexibility assessment can be applied without substantial exchange of system information between DSO and TSO. The proposed concept is illustrated on the Nordic 32 system for a case of the connection of two differently behaving distribution systems.