Open AccessRobust nested loop control scheme for LCL‐filtered inverter‐based DG unit in grid‐connected and islanded modes
Author(s) -
Buduma Parusharamulu,
Panda Gayadhar
Publication year - 2018
Publication title -
iet renewable power generation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.005
H-Index - 76
eISSN - 1752-1424
pISSN - 1752-1416
DOI - 10.1049/iet-rpg.2017.0803
Subject(s) - control theory (sociology) , inner loop , microgrid , robustness (evolution) , grid , inverter , interfacing , linear quadratic regulator , robust control , controller (irrigation) , computer science , loop (graph theory) , distributed generation , control system , engineering , voltage , control engineering , control (management) , mathematics , renewable energy , biochemistry , chemistry , geometry , electrical engineering , combinatorics , artificial intelligence , gene , computer hardware , agronomy , biology
The grid feeding and grid forming inverters are important candidates in grid connected and islanded modes (IMs) of microgrid system, respectively. The grid feeding inverter supplies the preset power during grid‐connected mode and the grid forming inverter generates a reference voltage for other distributed generation (DG) interfacing inverters in IM. In such scenario, the proper control of these inverters is an utmost importance. Generally, a nested loop control strategy uses a conventional PI controller for the inner and outer loops of grid feeding and grid forming inverter, but it gives deteriorative performance under parameter uncertainty condition. This study proposes a robust nested loop control scheme with the mixed H ∞ / H 2 optimal controller in the outer voltage control loop and the robust linear quadratic regulator (LQR) state feedback controller in the inner current control loop for the smooth operation of the system in both modes. The simulation and experimental results of the DG unit with proposed control scheme demonstrate good stability and performance robustness under the parameter uncertainty. Also, superior transient and steady‐state performance are confirmed over the conventional controller.