A Two-stage Efficient Model of Modular Multilevel Converter for Electromagnetic Transient Simulation

For modular multilevel converter, large number of switching elements introduce challenges to electromagnetic transient simulations. In order to improve the simulation efficiency, this paper proposes a two-stage modeling method of the MMC converter. The converter is represented as an extended state-space equation, which is more suitable for circulating current and control strategy studies. Then, the capacitor voltage of each submodule is updated on the second stage, which is based on each arm current adopting the backward Euler algorithm. Further, a fast simulation algorithm involving MMC converters is developed. It reduces the computational costs compared with the detailed model in PSCAD and provides accurate representation of MMC in both steady and transient states. Simulation results validate the accuracy and numerical performance of the proposed model with FSA algorithm.