Influence Of Compensation Currents On Asymmetrical Voltage Condition Using Star Connected Modular Multilevel Cascaded Converter

This paper present reactive power control strategies for SSBC-MMCC under unbalanced grid voltage conditions. A new zero-sequence voltage expression is derived using positive and negative sequence voltage and current components. This improves the dynamic behaviour of the STATCOM dc capacitor voltage balancing particularly during asymmetric voltage fault conditions. The three reference current strategies of active power oscillatory elimination (APOE), reactive power oscillatory elimination (RPOE) and balanced positive sequence currents (BPSC) are compared with zero-sequence voltage and maximum current under asymmetric voltage conditions. The simulation and analytical results show that the RPOE requires the least zero-sequence voltage while BPSC injects symmetrical and minimal currents. Also, RPOE gives the best voltage improvement.