Universitat Ramón Llull. Barcelona (Spain)
April 12th, 2024
Summary:
I nsufficient attention has been dedicated to the study of stability in unbalanced power systems
within the existing literature. Given the significance of this scenario, particularly in
distribution systems featuring distributed generation, this thesis revisits modal analysis techniques
for stability assessment in power systems, and explains how to tackle unbalanced power
systems with voltage-dependent loads and constant-power loads. The procedure is described
in detail and applied to a low-voltage (LV) simple case study with Grid-Forming and Grid-
Following electronic power converters, along with three different Phase-Locked-Loop models,
and unbalanced loads, to investigate potential interactions among these components. The results
are then compared with those obtained with the popular impedance-based method. While
the latter is easier to implement using simulation or field data, the former requires a comprehensive
understanding of the system’s attributes, but gives a better insight into the problem. Since
both methods are based on a small-signal perturbation of the system, they provide identical
results, but they discern different information. To delve deeper into the subject, an extended
second case study is introduced: an LV CIGRE distribution system. This study employs a
comprehensive Simulink model of the microgrid, incorporating electronic power converters, to
derive and analyze the results.
Citation:
S.J. Yagüe (2024), Stability analysis of unbalanced microgrids with grid-forming and grid-following electronic power converters. Universitat Ramón Llull. Barcelona (Spain).
