针对模块化多电平换流器（modular multilevel converter，MMC）出现动态负载、参数失配和单相短路接地故障，造成稳态功率脉动、电流谐波过大问题，提出了一种电流环改进无模型滑模控制方法（improved model-free sliding mode control，IMFSMC）。首先，基于MMC系统数学模型，构建了参数失配时的模型补偿超局部模型。其次，提出一种时变增益自适应滑模趋近律设计电流环滑模无模型反馈控制器；同时设计一种模型补偿改进线性扩张状态观测器（model-compensated improved linearly extended state observer，MCILESO）估计超局部模型中未知扰动并补偿至滑模反馈控制器，并使用Lyapunov函数和赫尔维兹定理证明了控制器和观测器的稳定性。最后，基于MATLAB仿真及RTLAB半实物平台与PI控制以及传统无模型滑模控制对比，其结果表明所提方法能极大提高MMC系统在动态负载、参数失配和单相短路接地下的动稳态性能；降低MMC系统模型依赖度，增加系统鲁棒性和抗扰能力。

A current loop improved model-free sliding mode control (IMFSMC) method is proposed to address the issues of steady-state power ripple and excessive current harmonics caused by dynamic loads, parameter mismatches, and single-phase short-circuit grounding faults in modular multilevel converters (MMC). Firstly, based on the mathematical model of MMC system, a model compensation hyperlocal model is constructed for parameter mismatch. Secondly, a time-varying gain adaptive sliding mode approach law is proposed to design a current loop sliding mode model-free feedback controller. Simultaneously, a model compensated improved linearly extended state observer (MCILESO) is designed to estimate unknown disturbances in the hyperlocal model and compensate them to the sliding mode feedback controller. The stability of the controller and observer is proved using Lyapunov function and Hurwitz theorem. Finally, based on MATLAB simulation and RTLAB semi physical platform, compared with PI control and traditional model-free sliding mode control, the results show that the proposed method can greatly improve the dynamic and steady-state performance of MMC systems under dynamic loads, parameter mismatches, and single-phase short-circuit grounding. Reduce the model dependency of MMC system, increase system robustness and anti-interference ability.