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

Abstract

Cascaded solid-state transformer (SST) can be directly connected to the high-voltage distribution grid, andit 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 thisconfiguration. 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 dualactive bridge (DAB) modules. This strategy not only reduces the cost and the complexity of the control system but alsorealizes the unbalanced reactive compensation to some extent. Simulation and experimental results verify the feasibilityand validity of the proposed method.