Modeling and Control of a Modular Multilevel Converter-Based HVDC System Under Unbalanced Grid Conditions

作者：Guan, Minyuan^*; Xu, Zheng

来源：IEEE Transactions on Power Electronics, 2012, 27(12): 4858-4867.

DOI：10.1109/TPEL.2012.2192752

• High-voltage direct-current (HVDC) transmission
• modular multilevel converter (MMC)
• unbalanced operation
• voltage-sourced converter (VSC)-HVDC

The modular multilevel converter (MMC) is an emerging and attractive topology for the high-voltage direct-current (HVDC) transmission system. This paper presents a generalized mathematical model for MMC in HVDC applications under balanced and unbalanced grid conditions. The dynamics of the positive-, negative-, and zero-sequence components are derived from the model. Then, a dual current control scheme with positive-and negative-sequence current controllers is applied to MMC. The power controller to eliminate negative-sequence current components and the other one to eliminate double-line-frequency voltage ripple are compared. Moreover, a zero-sequence current controller is proposed in addition to the positive-and negative-sequence current controllers. Time-domain simulations on a 61-level MMC-HVDC test system are performed in the PSCAD/EMTDC software environment. The results demonstrate that the MMC-HVDC system with or without converter transformer is able to operate under unbalanced conditions by the use of the proposed control scheme.

• 出版日期2012-12
• 单位浙江大学