Oscillation suppression strategy for modular multi-level converter grid-connected system based on virtual damping in modulation link

Modular multilevel converters (MMC) are widely used in power systems. However, relevant studies and reports show that MMC connected with the grid may cause oscillation problems. When the bridge arm resistance is large enough, the operating conditions will be stable because of overdamping in the system. According to this idea, a virtual damping strategy is proposed, which is equivalent to increasing the resistance of the bridge arm without any actual power loss. Meanwhile, from the perspective of the impedance-based analysis method, it is explained that this virtual damping control strategy can improve the stability margin of the system to realize the suppression of oscillation. In order to verify the effectiveness of the control method, the MMC simulation model is established under Matlab/Simulink. The simulation results show that the proposed virtual damping control can effectively suppress the MMC oscillation problem.