access icon free Low-voltage ride-through of a droop-based three-phase four-wire grid-connected microgrid

The ability of riding through the grid disturbances can increase the integration of microgrids into the distribution system. Consequently, a grid-connected microgrid should provide ancillary services such as low voltage ride-through (LVRT) capability and reactive power support to sustain the power system operations during abnormal grid conditions. The objective of this paper is to propose an LVRT scheme that improves the power quality of the entire microgrid. The developed method is implemented as the controller of the interface voltage-sourced converter (VSC) of a distributed energy resource and consists of primary and secondary control levels. The former includes the cascaded voltage and current control loops and the droop controller, while the latter controls the reactive power injection during the balanced/unbalanced voltage sags/swells. The proposed scheme is developed based on the independent control of each phase and does not require calculation of symmetrical components. Moreover, it can be employed in the VSC control systems with various reference frames and is effective for droop-based grid-connected microgrids with both single-phase and three-phase four-wire configurations. The proposed strategy is implemented using the hierarchical control system and preserves the plug and play capability. Several case studies are presented to verify the effectiveness of the proposed strategy.

Inspec keywords: power generation faults; hierarchical systems; power supply quality; voltage-source convertors; electric current control; power grids; distributed power generation; power generation control; reactive power control

Other keywords: balanced voltage sags; natural reference frame; reactive power; droop controller; unbalanced voltage sags; LVRT scheme; distributed energy resource; voltage-sourced converter; droop-based three-phase four-wire grid-connected microgrid; VSC control systems; current control loops; plug and play capability; benchmark low-voltage microgrid network; single-phase four-wire configurations; three-phase four-wire configurations; hierarchical control system; grid disturbances; secondary control levels; power system operations; ancillary services; unbalanced voltage swells; independent control ability; primary control levels; low-voltage ride-through scheme; power quality; cascaded voltage control loops; distribution system; balanced voltage swells

Subjects: Power convertors and power supplies to apparatus; Power and energy control; Current control; Multivariable control systems; Power supply quality and harmonics; Control of electric power systems; Power system control; Distributed power generation

http://iet.metastore.ingenta.com/content/journals/10.1049/iet-gtd.2017.1306
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