Abstract
There are two unbalanced conditions for cascaded converter in Renewable Energy Source (RES) system. One is from the different output power of RES in bridge cells, and the other is grid voltage unbalanced fault. This paper presents a flexible voltage control technique of Modular Multilevel Cascaded Converter with single-delta bridge cells (MMCC-SDBC) in the RES system for maintaining the stable operation under the unbalanced conditions. Moreover, the comparison of the fault ride through capability between MMCC with Single Star Bridge Cells (MMCC-SSBC) and MMCC-SDBC is addressed in this paper. The laboratory test results are given to verify the proposed method and the analysis.