Sequential Capacitor-Based Closed-Loop Precharge Control during the Single-Phase MMC Start-Up Process

Abstract

Modularity, flexible scalability, and high efficiency are some of the aspects that have paved the way toward the modular multilevel converter (MMC) being regarded as one of the most encouraging converter technologies for medium-/high-power applications; however, the precharging process of all the distributed submodules’ capacitors during the MMC’s start-up is considered to be a very challenging technical problem, which has been the center of attention since the emergence of the MMC back in 2002. In this paper, a new start-up method based on the sequential capacitors’ charging method is introduced for precharging the single-phase MMC from the DC grid while drastically reducing the charging (start-up) time. A detailed design algorithm for the proposed start-up method is presented. The findings of the simulation of the proposed method are provided to illustrate the capability of the suggested method.

Keywords

• start-up precharging process
• modular multilevel converter (MMC)
• precharging control scheme
• single-phase MMC start-up control
• sequential capacitors charging
• closed-loop precharging