Towards Distributed OPF using ALADIN

TL;DR

This paper explores the application of the ALADIN method to distributed AC Optimal Power Flow problems, demonstrating faster convergence than ADMM but with higher communication costs, and proposes variants to optimize performance.

Contribution

It introduces ALADIN for distributed AC OPF, showing quadratic convergence and proposing variants to balance communication and convergence speed.

Findings

ALADIN outperforms ADMM in convergence speed.

ALADIN achieves quadratic local convergence.

Proposed variants reduce communication while maintaining convergence.

Abstract

The present paper discusses the application of the recently proposed Augmented Lagrangian Alternating Direction Inexact Newton (ALADIN) method to non-convex AC Optimal Power Flow Problems (OPF) in a distributed fashion. In contrast to the often used Alternating Direction of Multipliers Method (ADMM), ALADIN guarantees locally quadratic convergence for AC OPF. Numerical results for 5 to 300 bus test cases indicate that ALADIN is able to outperform ADMM and to reduce the number of iterations by about one order of magnitude. We compare ALADIN to numerical results for ADMM documented in the literature. The improved convergence speed comes at the cost of increasing the communication effort per iteration. Therefore, we propose a variant of ALADIN that uses inexact Hessians to reduce communication. Additionally, we provide a detailed comparison of these ALADIN variants to ADMM from an algorithmic and communication perspective. Moreover, we prove that ALADIN converges locally at quadratic rate even for the relevant case of suboptimally solved local NLPs.