Design and Evaluation of a Control Scheme for the Hybrid Cascaded Converter in Grid Applications

Compared with the well-known modular multilevel cascaded converter with single-star bridge-cells (MMCC-SSBC), the hybrid cascaded converter (HCC) has the advantage of the lower component count of power transistors and dc capacitors. Thereby, this paper explores the HCC in grid applications and proposes a hierarchical control scheme, which allows the HCC to operate under unbalanced grid conditions and power imbalances among all cells. The HCC is further compared with the MMCC-SSBC under these unbalanced conditions to evaluate its performance. The laboratory test results are provided to verify the proposed control scheme and the comparison. The operational flexibility and reliability of the HCC are also discussed.