Harmonic Stability Analysis of Microgrids with Converter-Interfaced Distributed Energy Resources, Part II: Case Studies

TL;DR

This paper presents a detailed harmonic stability assessment method for power systems with converter-interfaced distributed energy resources, using eigenvalue analysis and case studies to identify potential harmonic instabilities.

Contribution

It extends the harmonic stability analysis to include grid-forming and grid-following CIDERs with detailed eigenvalue classification and sensitivity analysis, validated through simulations.

Findings

Harmonic eigenvalues can indicate system stability or instability.

The method accurately detects harmonic instability in a benchmark system.

Eigenvalue sensitivity analysis reveals control parameter impacts.

Abstract

In Part I of this paper a method for the Harmonic Stability Assessment (HSA) of power systems with a high share of Converter-Interfaced Distributed Energy Resources (CIDERs) was proposed. Specifically, the Harmonic State-Space (HSS) model of a generic power system is derived through combination of the components HSS models. The HSS models of CIDERs and grid are based on Linear Time-Periodic (LTP) models, capable of representing the coupling between different harmonics. In Part II, the HSA of a grid-forming, and two grid-following CIDERs (i.e., ex- and including the DC-side modelling) is performed. More precisely, the classification of the eigenvalues, the impact of the maximum harmonic order on the locations of the eigenvalues, and the sensitivity curves of the eigenvalues w.r.t. to control parameters are provided. These analyses allow to study the physical meaning and origin of the CIDERs eigenvalues. Additionally, the HSA is performed for a representative example system derived from the CIGRE low-voltage benchmark system. A case of harmonic instability is identified through the system eigenvalues, and validated with Time-Domain Simulations (TDS) in Simulink. It is demonstrated that, as opposed to stability analyses based on Linear Time-Invariant (LTI) models, the HSA is suitable for the detection of harmonic instability.