Decentralized Control Using Wireless Signal Communication for Solid-state Transformer with Cascaded Chopper Cell

This paper proposes a novel decentralized control method and controllers on cells, which communicate with the main controller using Bluetooth communication, for a medium voltage solid-state transformer (SST) with multiple chopper cells. SST requires a considerable number of signal lines between the main controller and each cell in order to communicate the amount of information such as detected DC voltage, current, fail, and commands. The proposed control system with wireless communication is effective in reducing the number of signal lines. Moreover, the proposed control method allows only low-speed communication and uses only a few parameters to be exchanged between the main controller and each cell controllers because the instantaneous values are not required for the control in the proposed method. The validity of the proposed method is demonstrated with a 3-kW prototype. From the experimented results, the input-current imbalance is reduced from 24.6 % to 5.46 %, where total harmonic distortion is less than 3%.