A three-stage energy router with modified transformer and improved voltage balance strategy

Three-stage energy router is the most popular design scheme for energy router. Many high-frequency transformers exist in this structure but how to reduce their volume is a difficult problem. A modified high-frequency transformer structure is introduced in this paper which is beneficial to compression volume. Cascaded H-Bridge topology is usually served as a rectifier in the three-stage energy router. Due to the inherent problem of capacitor voltage balance among each module in this topology, the so called working mode exchange scheme is always employed to regulate capacitor voltages. However, the conventional exchange scheme brings a tremendous amount of computing and ignores the problem of extra device action times during the execution process which can increase switching losses. A modified working mode exchange strategy is presented in this paper. It can reduce the amount of computation and decrease extra device action times at the same time. The proposed strategy only changes the working mode for the largest voltage and smallest voltage module. It reduces the mode exchange frequency and then decreases the possibility of extra action times appearing. Finally, the validity of the modified transformer structure and improved strategy is confirmed by simulation results on a 2MW three-stage energy router.