SYNOPSIS:
MMC is a converter topology that acquires a significant and increasing role in a number of applications, such as HVDC. The current project thesis aims at enhancing the MMC Control for cases of AC Faults, with respect to the grid requirements for reactive current injection without violating the physical limitation of the converter. The following injection strategies are developed; Positive Sequence Injection, Mixed Sequence Injection with Balanced Power and Mixed Sequence Injection with Grid Compliance. The strategies show improvement in the support of the positive sequence voltage, decrease of the negative sequence and ripple minimization for active power. A current limitation method is furthermore developed, with priority to the reactive current injection for both positive and mixed sequence injection. These techniques are validated both in simulation and in experimental results, which are compared and discussed.