A coordinated DC voltage control strategy for cascaded solid state transformer with star configuration

Authors: ZHENDONG JI, YICHAO SUN, CHENG JIN, JIANHUA WANG, JIANFENG ZHAO

Abstract: Cascaded solid-state transformer (SST) can be directly connected to the high-voltage distribution grid, and it has broad applications in the future smart grid, traction locomotive, and renewable energy integration. However, the reliability of the cascaded SST is seriously influenced by the DC voltage and power imbalance issues with this configuration. This paper presents a coordinated DC voltage control strategy for cascaded SST with star configuration, in which the average DC voltage and the balancing DC voltage are controlled separately without current sensors in dual active bridge (DAB) modules. This strategy not only reduces the cost and the complexity of the control system but also realizes the unbalanced reactive compensation to some extent. Simulation and experimental results verify the feasibility and validity of the proposed method

Keywords: Star configuration, cascaded solid state transformer, dual active bridge, DC voltage balancing, imbalance reactive compensation

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