Improved secondary control for optimal total harmonic distortion compensation of parallel connected DGs in islanded microgrids

• Main Authors: Mohammad Hadi Andishgar, Eskandar Gholipour, Rahmat-Allah Hooshmand
• Format: Article
• Language: English
• Published: Wiley 2018-12-01
• Series: IET Smart Grid
• Subjects: quality control; power generation control; invertors; power distribution control; power supply quality; harmonic distortion; power distribution faults; distributed power generation; voltage control; SLB; distributed generators; compensating efforts; local buses; DG terminals; THD limitation; compensation portion; multilevel voltage quality control; multibus islanded microgrids; parallel DGs; DGs peak current limitation; microgrid parameters; control structure; improved secondary control; optimal total harmonic distortion compensation; parallel connected DGs; voltage quality requirements; bus-bars; two-layer hierarchical control; different buses; parallel-connected inverters; secondary layer; THD compensation; sensitive load bus
• Online Access: https://digital-library.theiet.org/content/journals/10.1049/iet-stg.2018.0093

This study proposes a two-layer hierarchical control to actualize optimal total harmonic distortion (THD) compensation in different buses of parallel-connected inverters in islanded microgrids which had not been studied so far. The proposed secondary layer is used to realize THD compensation of sensitive load bus (SLB) and make distributed generators (DGs) distribute the compensating efforts between them according to their rated capacity. It is noteworthy that improving THD at the SLB can lead to an increase in THD at local buses and/or DG terminals. Although the THD limitations of these buses are not as strict as the THD limitation of SLB, it is necessary to control them within their allowed range. This important problem is not well studied in the literature. A novel complementary part is designed and added to the secondary control to tune the compensation portion of each DG while the THD limitations in DG terminals and local buses are considered. The proposed method actualizes a multi-level voltage quality control in multi-bus islanded microgrids with parallel DGs through a simple yet effective solution. Furthermore, considering the DGs peak current limitation is added to the controller and a method for calculating this peak value is proposed.