Voltage Balancing Control of Bidirectional Input-Series Output-Series Dual Active Bridge DC/DC Converters without Auxiliary Circuits

The application of input-series output-series (ISOS) connected dual active bridge (DAB) converters has advantages in bidirectional power transmission and isolation. However, their application makes it difficult to maintain the voltage balance. In this study, a voltage balancing control method for ISOS-connected DAB converters with no auxiliary circuits is proposed. The proposed control changes methods according to the amount of load. Furthermore, a hierarchized simple controller is proposed to connect a large number of DAB converters for transmission and isolation in high voltage DC (HVDC) systems. The simulation and experimental results indicate that the proposed method can balance the voltage in bidirectional power transmission between two DC grids with unequal voltages. © 2022 The Institute of Electrical Engineers of Japan.