A Bidirectional Three Phase Solid-State Transformer for Utility Interface of Energy Storage Devices

In this paper, a three phase bidirectional medium frequency solid-state transformer (SST) for utility interface of DC energy storage devices is discussed. The SST operates at medium frequency transformer isolation to reduce the weight and volume to meet the requirements of mobile battery energy storage in subsea operations. The proposed SST allows for seamless power flow in both directions (bidirectional) employing the concept of AC choppers to eliminate the need for an intermediate dc-link capacitor to transfer power. A modified synchronous current controller is used to control the amount and direction of power flow in the circuit, and the generation of current ripple is analyzed in this paper. A few simulations of the proposed bidirectional SST is implemented, and the results are discussed to verify that the proposed circuit is capable of realizing bidirectional power transmission.