Parallel Electromagnetic Transient Simulation Method for MMC-based SST Based on Diakoptics

With the rapid development of renewable energy generation and the distribution network, the dc network has become a hotspot in research and engineering. In the dc network, the power electronic transformer (PET, also known as solid-state transformer, SST) is the crucial interface device. To achieve better characteristics, the SST based on modular-multilevel-converter (MMC) is proposed. The cascade modulization and high switch efficiency of MMC-SST bring challenges to its electromagnetic (EMT) simulation. The numerous submodules increase the order of the node admittance matrix, requiring more computation resources; the high switch frequency requires a smaller time step, decreasing the calculation speed. To deal with these problems, this paper proposes a parallel EMT simulation method based on the diakoptics. This method achieves parallelized calculation at the system level and submodule level by tearing the whole system into subsystems and applying the compact EMTP method. The proposed method is verified in MATLAB and an FPGA-based real-time simulation platform.