Multi-Time-Scale Electromagnetic Modeling of a Battery-Integrated Solid-State Transformer

With the increasing integration of the renewable energy sources into power systems, solid-state transformers (SST) has been widely studied for applications in hybrid AC/DC distribution systems. In recent years, the SSTs with the integration of battery energy storage units are receiving widely attention. The battery-integrated SST (BISST) are among the most popular candidates due to its power routing capability and flexibility. However, its electromagnetic transient (EMT) simulation suffers from heavy computation burden because of complicated battery dynamics and multiple power conversion stages. In this paper, a multi-time-scale fast simulation method for EMT modeling of BISST is proposed. A novel modular topology of BISST is proposed to integrate two DC systems and one AC system. Its EMT model is divided into three parts with different calculating speed with the proposed simulation method. The multi-time-scale partitions decouple the parallel circuit and the cascaded circuit. Hence, the matrix dimension of the BISST are remarkably decreased. In addition, the inner dynamics and the power conversion stage of the battery are decoupled to further simplify the model. Finally, the proposed modeling method is verified by simulation and control hardware-in-the-loop experimental test. With the comparison of one-time-scale model and detailed model the accuracy and calculation speed of the proposed method is validated.