Real-time low/high-voltage ride-through capability improvement of micro-grid based on coordinated robust grid-following control

This paper proposes a coordinated control strategy to enhance the low/high-voltage ride-through (L/HVRT) capability of grid-tied micro-grids (MGs). The novel control scheme, which is based on grid-following concepts, contains two layers for each power source of MG. The former, known as the primary layer, has reverse-droop and non-linear robust sliding mode control. Furthermore, the secondary layer detects voltage perturbations based on L/HVRT curves. Then, the reactive power required for supporting the main grid is determined through the dynamic-voltage-support requirement of the grid codes. Finally, coordinated reactive power-sharing among the sources is performed based on the presented method and free capacity of the power sources. Several case studies are carried out to assess the effectiveness of the proposed control scheme, which points out that the aims of this study, such as compliance with the grid codes, sharing reactive power among the sources, tracking the reactive power precisely and feeding local loads, are achieved. The superiority of the presented strategy against its grid-forming counterparts is demonstrated in comparison tests for the studied grid-tied MG. Simulations are performed in an offline MATLAB/Simulink environment and then validated by experimental real-time results.