Power Flow Solution Methods for Combined Transmission and Distribution Systems
Abstract
High distributed PV penetration makes the distribution systems more active and increases their impact on the upstream transmission grid. To facilitate the studies on this area, this paper proposes a power flow (PF) model and formulation of combined transmission and distribution (T&D) power systems. The formulation is based on the physical coupling of transmission and distribution grids. The unbalanced nature of distribution feeders and voltage regulators are modeled so that the resulting PF balance equations in distribution systems are similar to
those in the interconnected transmission system. The formulated
nonlinear PF equations are solved using the proposed unified
and sequential methods. Both methods are verified and compared
with each other using several combined T&D power systems. A
multi-period PF simulation is also included to demonstrate the
capability of the proposed formulation and solution methods in
capturing the influences of high distributed PV penetration on
transmission level.