Integrated power transmission and distribution systems

The penetration of on-site electricity generations through devices referred to as distributed energy resources (DERs) is reaching levels that cannot be neglected anymore. The negligence of detailed operations of DERs in the power distribution systems (DSs) can lead to extreme operational problems of the whole power grid. Such problems include high pressure on the power transmission system (TS) and reverse power flow from the DSs towards the TS, while the potential benefits from the DSs are also overlooked. In this chapter, through a careful and systematic analysis of the power system planning problems, we underline the necessity of developing methods that can tackle such problems and realize the potential profits by considering both the TS and DS in an coordinated mode. Furthermore, we introduce an integrated transmission and distribution system problem which minimizes the unit commitment costs of the TS and the distributed energy resource management costs of the DSs, respectively, while respecting the technical constraints of both systems. In our model, we consider both the combinatorial nature of unit commitment decisions and the AC power flow characteristics of the DS. We show that our integrated model achieves significant lower costs as compared to solving these problems separately. Finally we tighten the proposed mixed-integer linear programming formulation by adding valid inequalities for the problem. The computational results verified the efficiency of our proposed integrated model combined with the valid inequalities.