Research on Adaptive Sliding-Mode Control Strategy for Modular Multilevel Converters

The Modular Multilevel Converter (MMC) has attracted considerable research attention due to its low switching losses, reduced current distortion, and ease of expansion and maintenance. However, most studies focus on steady-state control, with limited attention to AC grid current overshoot during startup. To enhance dynamic performance and prevent potential circuit damage or overcurrent isolation in the distribution network, this paper proposes an Adaptive Sliding-Mode Control (ASMC) strategy. A mathematical model of the MMC is established, and its normal operation is analyzed, including DC-side current components. To mitigate current overshoot, an adaptive reaching law based on target error is introduced. A 5-level MMC system is simulated in Simulink, and results show that the proposed method effectively suppresses current overshoot, improves response speed, and reduces chattering compared to conventional sliding-mode control.