Modeling Method of Submodule-Hybrid Modular Multilevel Converters for Fast Electromagnetic Transient Simulation

The two most representative fast electromagnetic transient models of the modular multilevel converter (MMC) are the averaged model and Thevenin equivalent model, but both of them have the problems of low computational efficiency and insufficient computational accuracy, respectively. To solve that, this paper develops a fast simulation method of the hybrid MMC with full-bridge submodules and half-bridge submodules (FHMMC) based on the bridge arm equivalence principle, deduces the equivalent circuit model of bridge arm under normal working state, blocked state and full state. A two-terminal MMC DC grid test system was built on the PSCAD/EMTDC platform, and its feasibility was verified by simulation. At the same time, the simulation waveforms and simulation time are compared between the Thevenin equivalent model and the proposed model, and the result indicates that the proposed model speeds up simulation while maintaining accuracy.