Error Accumulation using Linearized Models for Aggregating Flexibility in Distribution Systems

TL;DR

This paper analyzes linear models for flexibility aggregation in distribution systems, revealing that line loss errors tend to accumulate over time and at the point of common coupling, especially without negative losses.

Contribution

It provides a comprehensive theoretical and simulation-based evaluation of linear AC and DC power flow models for flexibility aggregation, highlighting their limitations in loss estimation.

Findings

Line losses are generally underestimated by linear models.

Loss errors accumulate over time and at the point of common coupling.

Linear models' assumptions impact accuracy in flexibility aggregation.

Abstract

This paper investigates flexibility aggregation approaches based on linear models. We begin by examining the theoretical foundations of linear AC power flow, two variants of so-called DC power flow, and the LinDistFlow model, along with their underlying assumptions. The discussion covers key system details, including network topology, voltage constraints, and line losses. Simulations are conducted on the KIT Campus Nord network with real demand and solar data. Results show that, in the absence of negative losses, line losses are generally underestimated by linear models. Furthermore, line losses errors tend to accumulate both at the point of common coupling (PCC) and over extended time horizons.