An Improved Repetitive Control for Circulating Current Restraining in MMC-MTDC
Abstract: The modular
multilevel converter (MMC) is widely used in many important application fields
such as high voltage DC transmission system. And the multi-terminal
architecture of it attracts many attentions. However, the circulating current
of MMC is an inherent problem which is mainly caused by the voltage mismatch
between arms and DC bus. In this paper, an advanced repetitive control method
is proposed. This method is based on the even-harmonic characteristic of the
circulating current and the potential feature of repetitive control that it has
an internal integration part. The pole diagram of the closed loop transform
function of the proposed control system proves the stability of the proposed
method. And according to the simulation results of a three-terminal MMC-MTDC
model in PSCAD/EMTDC, the improved repetitive control presents better
circulation repression ability and superior anti-interference capability by
comparing with traditional PI control method. Additionally, the simulation
results also indicate that the proposed repetitive controller can restrain the
fluctuation of SM voltage more effectively than PI control.
Keywords: Modular multilevel
converter (MMC), circulating current, multi-terminal direct current system (MTDC),
repetitive control
Author: Yahui Wang, Yijia Cao,
Yong Li, Chang Li
Journal Code: jptkomputergg170026
