Distributed OPF for PET-Based AC/DC Distribution Networks With Convex Relaxation and Linear Approximation

A power electronic transformer (PET) can flexibly regulate the power flow of a network and facilitate the integration of distributed energy resources via AC/DC networks. With the continuous expansion of the scale of multiregional interconnection networks, the traditional centralized optimization method faces great challenges. This paper proposes a distributed convex optimal power flow (OPF) model by leveraging the hierarchical structural characteristics of PET enabled AC/DC distribution networks. An analytical target cascading method is introduced to divide the centralized OPF problem into several subproblems that can make the subnetworks operate individually and coordinate with each other. The PET flexibility is also harnessed to reduce network power loss and voltage deviation. To improve the computational efficiency and algorithm convergence, the convex relaxation and linear approximation methods are proposed. This allows us to transform the original nonconvex nonlinear problem into a successive convex programming problem, which can be easily solved by an iterative solution algorithm. Simulation results verify the feasibility and efficiency of the proposed approach.