I. Introduction
Due to its many operational advantages for high voltage and high power applications, the modular multilevel converter has become a choice solution for dc/ac conversion in HVDC applications [1]. The widely used MMC-HVDC models can be divided into three categories: 1) the electromagnetic transient (EMT) model [2], which is highly accurate but unsuitable for large-scale systems because of the long simulation time. 2) the phasor model [3], which is convenient for power-flow and parameter studies but neglects all of the dynamics. 3) the dynamic phasor model, which has flexible accuracy and simulation time for various applications [1].