Modularized multilevel flexible DC power transmission current converter starting method

The invention relates to a modularized multilevel flexible DC power transmission current converter starting method comprising the following steps that A. the DC side poles of all converter stations are connected, the submodules of all the stations are locked, and the AC switch of an active station is closed so as to enter an uncontrollable charging stage; B. after voltage of the submodules of all the converter stations is higher than respectively corresponding charging threshold voltage, a controllable voltage equalizing charging method is switched on by the converter stations respectively and a controllable charging stage is initiated, and the AC side soft starting resistor of the active station is removed simultaneously; and C. a closed-loop voltage equalizing charging method is respectively switched on by all the converter stations according to the voltage situation of the AC and DC sides, and when voltage of the submodules of the converter stations is rated and stable, the converter stations are unlocked respectively and enter the unlock operation stage. The closed-loop charging mode is additionally arranged after controllable charging so that removal number can be adjusted in real time according to current voltage of the submodules, voltage of the submodules can be stabilized at the rated value via closed-loop control, and thus electrical impact in unlock operation can be avoided.