Shooting method based modular multilevel converter initialization for electromagnetic transient analysis

This paper presents an accurate and efficient initialization strategy for modular multilevel converters (MMCs) based on the shooting method, a numerical technique aimed at deriving the periodic steady-state operating condition of any circuit. This technique is compatible with MMC models of different levels of detail and whose control scheme may include modulation strategies and capacitor voltage balancing algorithms. Electromagnetic transient simulations of the NORDIC32 power system modified by adding a high-voltage direct current link with 128-level MMCs prove that the proposed initialization strategy allows starting simulations close to steady-state, thereby significantly limiting initialization transients and their corresponding extra CPU time.