Distributed OPF Algorithm for System-Level Control of Active Multi-Terminal DC Distribution Grids

Abstract

This paper presents a distributed optimal power flow (OPF) algorithm for the system-level control of multi-terminal DC (MTDC) distribution grids with distributed energy resources (DER). At each control period, the algorithm updates the nominal voltage and power set-points of the DER-interfacing converters, which operate according to active network management (ANM) concepts. To achieve this, the OPF problem, in its nodal formulation, includes power dispatch strategies for diverse DER according to their technical characteristics, which change during the system operation. This multi-objective OPF-for-ANM problem is solved by distributed control units (DCUs) according to the distributed algorithm for the alternating direction method of multipliers (ADMM). All DCUs have identical roles in the distributed control structure and thus the distributed OPF-for-ANM algorithm is highly modular. Simulation results in different IEEE standard systems and various scenarios demonstrate that the algorithm is fast and scalable, irrespective of the number and location of integrated DER, as well as the operating condition of the system. The convergence speed of the algorithm is analysed considering the computation and communication time needed for its execution. The online application in a computers cluster demonstrates the fast execution of the developed algorithm in a physically-distributed implementation. Through the proposed OPF-for-ANM algorithm, the system-level control can dispatch fast diverse DER in different coordination approaches in a distributed manner.

Keywords

• Distributed control
• power system control
• DC-DC converters
• optimisation methods
• distributed power generation
• energy resources