Decoupled Detailed Equivalent Model for Parallel and Multi-Rate EMT-Type Simulation of Modular Multilevel Converter With Battery Energy Storage

Modular multilevel converters (MMCs) integrated with battery energy storage systems (BESS) enable efficient utilization of renewable energy resources such as wind and photovoltaic, while enhancing reliability and scalability of high-voltage direct current systems. This paper proposes a decoupled detailed equivalent model (D-DEM) for BESS-integrated MMC for electromagnetic transient (EMT) simulation. The proposed model can accurately represent the dynamics of the converter under deblocking and blocking modes. To efficiently utilize available hardware resources, a multi-rate simulation technique is adopted to simulate the MMC subsystems with different time steps. Additionally, switching interpolation technique is proposed to accurately compensate for the intra-time-step switching events of the MMC multi-valves. To further accelerate the EMT simulation of MMC, a hybrid parallel computing EMT solver is implemented, using both central and graphical processing units (CPU-GPU). The accuracy of the proposed D-DEM is validated against a detailed model (DM) using Simulink/Simscape Electrical toolbox with 1 µs time step. The simulation efficiency of the proposed D-DEM is faster than the conventional DEM model by a factor of 2.81 with CPU-only implementation for the MMC with 400 submodules per arm. Furthermore, the proposed hybrid CPU-GPU solver achieves 79-fold faster than the CPU-only sequential implementation.