Universal Decoupled Equivalent Circuit Models of Solid-State Transformer for Accelerated EMT‐Type Simulation

Multilevel Multimodule Solid-State Transformer (SST) is emerging as a key technology interfacing MVAC and LVAC systems via chainlink AC-DC converter and Dual Active Bridge (DAB) DC-DC converters. The SST has the advantages of high modularity, bidirectional power transfer, galvanic isolation, and high-frequency power conversion. Fast control prototyping of the SST requires numerically efficient and accurate equivalent circuit models for Electromagnetic Transient (EMT) simulation. This paper proposes universal decoupled equivalent circuit models using switching function to simplify the power converter circuits. Various types of power converters including full-bridge converter, DAB DC-DC converter, and three-phase 3-level converters can be universally modeled by the proposed equivalent circuits in both deblocking and blocking modes. The use of switching function and DC-link decoupling strategy in equivalent circuit models achieves constant G-matrix and significantly reduced node number in the EMT solution. A switching interpolation technique is proposed for the SST to accurately represent switching events when a large simulation time step is used. Case studies have demonstrated that the proposed equivalent circuit models significantly improve the numerical efficiency, compared to the conventional detailed model and variable G-matrix detailed equivalent model.