AC-DC Power Systems Optimization with Droop Control Smooth Approximation

TL;DR

This paper introduces a smooth approximation method for droop control in ac-dc power systems, enabling more accurate and efficient optimization and simulation by transforming nonsmooth control characteristics into differentiable functions.

Contribution

The authors develop a novel smooth approximation technique for droop control, allowing integration into power system optimization problems with improved accuracy and computational efficiency.

Findings

Enhanced accuracy in power sharing and voltage regulation.

Significant computational efficiency over existing methods.

Improved system efficiency in ac-dc power system optimization.

Abstract

This paper addresses the challenges of embedding common droop control characteristics in ac-dc power system steady-state simulation and optimization problems. We propose a smooth approximation methodology to construct differentiable functions that encode the attributes of piecewise linear droop control with saturation. We transform the nonsmooth droop curves into smooth nonlinear equality constraints, solvable with Newton methods and interior point solvers. These constraints are then added to power flow, optimal power flow, and security-constrained optimal power flow problems in ac-dc power systems. The results demonstrate significant improvements in accuracy in terms of power sharing response, voltage regulation, and system efficiency, while outperforming existing mixed-integer formulations in computational efficiency.