A Zero-Sequence Current-Based Cluster Energy Balancing Control in Single-Star Multilevel Converter With Zigzag Transformer

In a power system, when a fault occurs, a Static Synchronous Compensator (STATCOM) is often required to inject negative-sequence current to compensate for unbalanced conditions. In high-voltage applications, single-star multilevel converters are commonly used in STATCOM systems to efficiently interface with high-voltage levels. However, during unbalanced condition compensation, these circuits experience cluster energy imbalance, which must be addressed through the balancing control. The conventional cluster energy balancing method utilizes zero-sequence voltage to redistribute active power for system balance. Under severe unbalance, a large negative-sequence current must be injected to compensate grid or load asymmetry. In conventional single-star multilevel converters, the zero-sequence component of the cluster output voltage is then actively regulated to eliminate the resulting cluster…