Control of a Modular Multi-level Converter STATCOM for low voltage ride-through condition

This paper presents a simulation study on the implementation of the Single Star Flying Capacitor Converter Modular Multi-level Cascaded Converter (MMCC-SSFCC) as a STATCOM operating under voltage sag condition. This paper proposes a cluster balancing control, using a zero sequence voltage injection technique for the SSFCC-STATCOM operating either as a reactive compensator under Low Voltage Ride Through condition (LVRT) or unbalanced current compensator. This control strategy enables the STATCOM system to compensate for both positive sequence reactive and negative sequence currents. Not only does it compensate for the load demands, but also keep the module DC-link and flying capacitor voltages at their rated values.