Impact of Phase Selection on Accuracy and Scalability in Calculating Distributed Energy Resources Hosting Capacity

TL;DR

This paper examines how phase selection assumptions affect the accuracy and computational efficiency of calculating hosting capacity and dynamic operating envelopes in distribution networks, highlighting the trade-offs between solution optimality and computational complexity.

Contribution

It introduces a Python-based tool implementing linearised optimal power flow and analyzes the impact of phase connection assumptions on calculation accuracy and computational time.

Findings

Mixed integer OPF yields highest objective function values.

Binary variables significantly increase computational time.

Differences in results can reach up to 14 MW in real-world networks.

Abstract

Hosting capacity (HC) and dynamic operating envelopes (DOEs), defined as dynamic, time-varying HC, are calculated using three-phase optimal power flow (OPF) formulations. Due to the computational complexity of such optimisation problems, HC and DOE are often calculated by introducing certain assumptions and approximations, including the linearised OPF formulation, which we implement in the Python-based tool ppOPF. Furthermore, we investigate how assumptions of the distributed energy resource (DER) connection phase impact the objective function value and computational time in calculating HC and DOE in distribution networks of different sizes. The results are not unambiguous and show that it is not possible to determine the optimal connection phase without introducing binary variables since, no matter the case study, the highest objective function values are calculated with mixed integer OPF formulations. The difference is especially visible in a real-world low-voltage network in which the difference between different scenarios is up to 14 MW in a single day. However, binary variables make the problem computationally complex and increase computational time to several hours in the DOE calculation, even when the optimality gap different from zero is set.