Sliding Mode Circulating Current Control of Modular Multilevel Converter

Modular multilevel converter (MMC) are extensively used in medium and high-voltage (HV) operations, except controlling circulating current is a major challenge. This can lead to increased device ratings, submodule (SM) power losses, and voltage ripple in SM capacitor. This article presents a Sliding Mode Control (SMC) approach to decrease the circulating current in MMCs. The abc–dq reference frame is applied to simplify the control procedure. The proposed methodology successfully tackles the second order harmonic in the circulating current, reducing the Total Harmonic Distortion (THD) of the arm current from 41% to 5.7%. Additionally, there is a 90% reduction in circulating current. The suggested approach is validated through simulations in MATLAB/SIMULINK and compared with several standard approaches, demonstrating its effectiveness.