On flatness-based control for series-connected VSC for voltage dip mitigation

The grid connected series converter is a custom power device that is mainly used for mitigation of voltage sags. In this paper a novel direct flatness-based control (FBC) in cascade configuration, constituted by an outer voltage and an inner current controller, is presented. It can absorb and inject active and reactive power into the grid. Simulation model includes the practical limitation of voltage source converter output voltage and computational delay. Then, the simulations results for the FBC under balanced voltage dips are presented and compared with traditional proportional integral controller. Finally, the sensitivity analysis of the FBC for grid frequency, phase angle jump and inaccurate knowledge of system parameters are presented.