Abstract:The paper proposes a method of extended state observer based passivity-based sliding mode control （ESOPBSMC） to enhance the control performance of grid-connected modular multilevel converters （MMC） under grid-side fault and other disturbance conditions. This approach injects passive damping from an energy perspective and introduces a sliding mode acceleration system to ensure asymptotic stability and expedite system convergence. Subsequently，it employs an extended state observer （ESO） to observe and compensate for disturbances，thereby enhancing the system’s active suppression capability against disturbances. Simulation results demonstrate that compared to traditional proportional-integral（PI）control and passivity-based sliding mode control（PBSMC），the proposed method exhibits faster current tracking speed，stronger robustness，and better circulating current suppression effects.