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Robust tuning of transient droop gains based on kharitonov's stability theorem in droopcontrolled microgrids

Mahdian Dehkordi, N ; Sharif University of Technology

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  1. Type of Document: Article
  2. DOI: 10.1049/iet-gtd.2017.1767
  3. Abstract:
  4. 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. © The Institution of Engineering and Technology 2018
  5. Keywords:
  6. Degrees of freedom (mechanics) ; Electric inverters ; MATLAB ; Stability ; Uncertainty analysis ; Digital time-domain simulations ; Inverter-based distributed generators ; Microgrid structures ; Robust d-stability analysis ; Robust stability analysis ; Software environments ; Two-degree of freedom ; Uncertain parameters ; Time domain analysis
  7. Source: IET Generation, Transmission and Distribution ; Volume 12, Issue 14 , 2018 , Pages 3495-3501 ; 17518687 (ISSN)
  8. URL: https://ieeexplore.ieee.org/document/8425869