The invention relates to a modularized multi-
level converter optimization control method actively using a 
second harmonic generation loop current, and belongs to the technical field of high-
voltage high-capacity power electronic converter control. The method comprises the following steps: dynamically calculating alternating-current and direct-current reference voltages of a modularized multi-
level converter according to a command sent by an upper-level controller; calculating an initial 
second harmonic generation loop current according to each parameter of an 
alternating current obtained according to real-time measurement; using reversion of the initial 
second harmonic generation loop current as a control target, and dynamically calculating the second 
harmonic generation loop current target value of the modularized multi-
level converter; then overlaying a second 
harmonic generation reference 
voltage needing to be injected obtained according to dq decoupling control calculation to obtained alternating-current and direct-current reference voltages so as to obtain a bridge-arm reference 
voltage, carrying out pulse modulation and direct-current 
capacitor voltage balance control, and generating a pulse 
signal to carry out optimization control. According to the method, the direct-current 
capacitor voltage fluctuation can be greatly reduced, the optimization for the cost and volume of the modularized multi-level converter is effectively realized, and the method is particularly applicable to high-voltage large-capacity application occasions.