Analysis and design of an impedance source modular DC/DC converter for energy storage system

This paper proposes an improved modular multilevel DC/DC converter (MMDDC) suitable for DC energy storage system (ESS). The bidirectional quasi-Z source is introduced into the sub-module of MMDDC, which not only makes the input voltage improved, but also changes the energy conversion mode so that the system can store energy as buck conversion and release energy as boost conversion. Therefore, the system current can be strictly controlled, the overcurrent problem of the traditional MMDDC in the charging mode is solved, and the improved sub-module input voltage helps reduce the series of sub-modules, thereby simplifying the system design. Overall, the proposed converter has more advantages in DC energy storage system compares to traditional MMDDC.