Modeling and Analysis of High-Frequency MMC Impedance Considering Different Control Modes and Voltage Feedforward

IEEE Access

卷:8

Yonghui Liu¹  Taiyuan Yin²  Bo Yue²  Pengkun Li³  Delin Zhao⁴  Yue Wang⁴  Jie Sun⁵  Xiaolei Wang⁵ 

[1] State Grid Economic and Technological Research Institute Company Ltd., Beijing, China;

[2] State Key Laboratory of Electrical Insulation and Power Equipment, Xi&x2019;

[3] Zhongyuan University of Technology, Zhengzhou, China;

[4] an Jiaotong University, Xi&x2019;

[5] an, China;

关键词: Modular multilevel converter (MMC);    voltage feedforward;    impedance model;    time delay;    high frequency;   

DOI  :  10.1109/ACCESS.2020.3042892

来源: DOAJ

【 摘 要 】

The sequence impedance of modular multilevel converters (MMC) is the premise to analyze the stability of MMC-based high voltage direct current (HVDC) system. However, few papers have modeled MMC impedance with comprehensive consideration of different control modes and voltage feedforward, the high-frequency impedance characteristics of the MMC have not been intensively studied, either. In fact, the voltage feedforward has an important influence on the high-frequency impedance characteristics of the MMC, which can not be ignored. This article proposes a sequence impedance for MMC considering complete control loops. Not only current inner-loop, circulating current control loop and phase-locked loop (PLL) are considered, but also different control modes including power control, DC voltage control and AC voltage control are considered. It is worth mentioning that especially the voltage feedforward and time delay are taken into account. Based on this impedance model, the characteristics of the MMC are thoroughly analyzed, and the analysis shows that the voltage feedforward and time delay will greatly affect the high-frequency characteristics, which will deeply affect the stability of the system. Meanwhile, the influences of PLL dynamics, outer-loop control, circulating current control and parameters of controller on the sequence impedance are also analyzed in detail.

【 授权许可】

Unknown