Open AccessRobust tuning of transient droop gains based on Kharitonov's stability theorem in droop‐controlled microgrids
Author(s) -
Dehkordi Nima Mahdian,
Sadati Nasser,
Hamzeh Mohsen
Publication year - 2018
Publication title -
iet generation, transmission and distribution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.92
H-Index - 110
eISSN - 1751-8695
pISSN - 1751-8687
DOI - 10.1049/iet-gtd.2017.1767
Subject(s) - voltage droop , microgrid , control theory (sociology) , robustness (evolution) , transient (computer programming) , matlab , computer science , controller (irrigation) , inverter , robust control , engineering , voltage , control system , control (management) , voltage regulator , electrical engineering , artificial intelligence , operating system , agronomy , biochemistry , chemistry , biology , gene
This study addresses the robust stability analysis for an islanded microgrid with droop‐controlled inverter‐based distributed generators (DGs). Owing to large load changes, microgrid structure reconfiguration, and higher‐power demands, the low‐frequency (LF) dominant modes of a microgrid stir toward unstable zone and make the system more oscillatory or even unstable. In this study, a robust two‐degree‐of‐freedom (2DOF) decentralised droop controller, which is the combination of the conventional droop with a robust transient droop function, is utilised for each inverter‐based DG unit. Unlike conventional tuning of 2DOF droop controllers, a new design procedure is proposed to robustly determine the transient droop gains to effectively damp the LF oscillatory modes of the islanded microgrid irrespective of disturbances, equilibrium point variations, and uncertain parameters of a microgrid. To mitigate the LF power oscillations at different microgrid conditions, inspired by Kharitonov's stability theorem, a robust D‐stability analysis is performed to determine the specific ranges of the transient droop gains to provide a robustness margin for the disturbances, equilibrium point variations, and uncertain parameters of the islanded microgrid. Finally, digital time‐domain simulation studies are performed in MATLAB/SimPowerSystems software environment to verify the effectiveness of the proposed method.