A Decoupled Detailed Equivalent Model for Accelerated EMT-Type Offline and Real-Time Simulation of Three-Port DAB-MMC With BESS

Three-port dual-active-bridge modular multilevel converter (DAB-MMC) with battery energy storage system (BESS) enables efficient integration of high voltage DC (HVDC) grids and medium voltage DC (MVDC) networks. Electromagnetic transient (EMT)-type simulation is critical for the design, control, and prototyping of the DAB-MMC with BESS. This paper proposes a decoupled switching function-based detailed equivalent model (DEM) with combined implicit and explicit (ImEx) multi-step Backward Differentiation Formula (BDF) solver for accurate EMT simulation of DAB-MMC with BESS. The proposed DEM employs 2nd- or 3rd-order ImEx-BDF to enable circuit decoupling, thereby reducing node count, and producing a constant network nodal conductance matrix. The proposed model can accurately represent the dynamics of the converter system under deblocking and blocking modes. Furthermore, a switching interpolation technique is employed to ensure accurate compensation of intra-time-step switching events. To further accelerate the simulation of DAB-MMC, a hybrid-parallel EMT solver is implemented using central and graphic processing units (CPU-GPU). The accuracy of the proposed decoupled DEM is validated against a detailed model (DM) developed in Simulink/Simscape Electrical toolbox with a 1μs time step-size. The proposed hybrid CPU-GPU solver achieves 49-fold speedup compared to a CPU-only serial implementation, and a 59,229-fold speedup compared to the DM reference solution.