Abstract: When the modular multilevel converter (an MMC) system is connected to a low inertia AC system, the MMC control system may interact with the generator control system, resulting in low frequency oscillations of the system. First, a detailed small-signal model of the MMC system connected to the generator is established and compared with the electromagnetic transient model in PSCAD/EMTDC to verify the accuracy of the small-signal model. Then, the influence of the AC system inertia on the system stability is studied, the dominant low-frequency mode of the system is identified, and the factors influencing the dominant low-frequency modes are analyzed. After that, the interaction between generator and MMC control parameters is studied by calculating the feasible region of control parameters. By analyzing the transmission path of frequency disturbance signal of the system, two main interaction paths between generator and MMC connected to the low-inertia AC system are revealed: the interaction path between the generator governor system and MMC control system and the interaction path between the generator excitation system and MMC control system. Finally, electromagnetic transient simulation verifies the correctness of the theoretical analysis.