The analytical model of modular multilevel converter based on the harmonic balance theory

Abstract

This paper proposes an analytical model for the modular multilevel converter (MMC) based on the theory of harmonic balance, which removes the iteration process for traditional models. The proposed model considers dynamic harmonic interactions between the modulation of converters and passive elements in the MMC. By transferring the equations into frequency-domain as complex Fourier series, a steady-state harmonic model is created with singular coefficients matrix. Then, through the elimination of all DC components in dynamic model, the singular coefficient matrix can be derived to nonsingular one, and the order of it can be reduced. Finally, the typical open-loop analytical model with DC neutral grounded MMC is derived aim, and the time-domain simulations is used to validate the effectiveness of proposed model. The proposed model can be used to accelerate the simulation and analyze the influence of parameters to guide the design of MMC.

Keywords

• Modular multilevel converter
• Analytical model
• Harmonic balance theory
• Internal harmonic interaction