Coordination between transmission and distribution system operators in the electricity sector: A conceptual framework

The increasing share of distributed energy resources in the distribution grid provides opportunities to use the resources for the overall benefit of both the Transmission System Operator (TSO) and the Distribution System Operator (DSO) to solve problems related to frequency control, congestion management, and voltage control. Consequently, coordination between system operators is needed to guarantee a safe, reliable, and cost-efficient use of flexibility-based services. This article presents five coordination schemes to enhance interaction between system operators. For each scheme, roles, responsibilities and market design are discussed. The advantages, disadvantages and feasibility of each coordination scheme are evaluated.