The Delta-Connected Cascaded H-Bridge Converter Application in Distributed Energy Resources and Fault Ride Through Capability Analysis

This paper presents a flexible dc voltage balancing control technique of the modular multilevel cascaded converter with single-delta bridge-cells (MMCC-SDBC) in the distributed energy resources (DERs) system for maintaining the stable operation under different unbalanced conditions. The unbalanced conditions, for example, the different output powers of the DERs in bridge cells, and the unbalanced grid faults are considered in the proposed method. In addition, the comparison of the fault ride through capability between MMCC with single-star bridge-cells and MMCC-SDBC is addressed. The laboratory test results are given to verify the proposed method and the analysis.