PI Consensus-Based Integrated Distributed Control of MMC-MTDC Systems

This paper proposes a Proportional-Integral (PI) consensus-based integrated distributed control (IDC) for modular multilevel converter-based multi-terminal high-voltage direct current (MMC-MTDC) to regulate voltage and achieve power sharing. First, the paper analyzes the estimated voltage error of the conventional MTDC voltage observer under communication delay. To solve this problem, the paper proposes a novel voltage observer based on PI consensus to observe the global average voltage of MTDC. It improves the resilience of the voltage regulation controller to the communication delay. Then a distributed controller that integrates power sharing and voltage regulation is further proposed to reduce the amount of state information exchanged by the communication network. The power control converter exchanges the status information representing the voltage deviation with the adjacent converters, while the voltage control converter exchanges the status information representing the power status information and the power distribution difference with the adjacent converters. Moreover, a small-signal model is established and the influence of distributed controller on the dynamics of MMC-MTDC system is studied. Simulation cases are conducted to verify the effectiveness of the proposed IDC for MMC-MTDC system.