MMC-HVDCsystem oscillation suppression control strategy based on state feedback decoupling control

Background: Subsynchronous oscillation (SSO) of wind farm integration through modular multi-level converter-based high voltage direct current (MMC-HVDC) transmission system puts forward high requirements for the robustness of MMC control strategy and parameters, which is the key problem to be solved in SSO suppression. This paper proposes a method to suppress the oscillation in wind farm integration through modular multi-level converter-based high voltage direct current (MMC-HVDC) transmission system. The proposed method is developed in two main steps. First, the mathematical model is established between the sequence impedance of wind farm integration through MMC-HVDC transmission system and their controller parameters, the influence of parameters on the sequence impedance characteristics is also studied. Second, the hierarchical control strategy is proposed and the MMC double closed-loop control system is established. The operating modes of MMC are considered in analyzing characteristics via the Fortescue approach, and exploit the hierarchical control to alleviate negative effects of transient data samples on the oscillation suppression. The influences of different system disturbances, the sensitivity of control parameters, and different MMC operating conditions are evaluated. The results verify the correctness of the MMC-HVDC mathematical model and the effectiveness of the modular design of the control strategy.