Sub-module capacitor voltage balancing is an important prerequisite for the stable operation of modular multilevel converter(MMC). In order to solve the problems of heavy computation burden and high switching frequency of devices

a novel capacitor voltage balancing control method applicable for field programmable gate array(FPGA)is proposed from the perspective of practical engineering. Several sub-intervals are divided according to the fluctuation range of capacitor voltage during normal operation

and sub-modules are matched into the corresponding sub-intervals according to the capacitor voltage measured in real-time. On this basis

for the sub-modules with capacitor voltage near the rated value

the switching state at the last control period is considered when grouping

and the switching frequency is further reduced according to the principle of keeping the original switching state unchanged as much as possible. The proposed method is developed and implemented in ML605-FPGA board

and a hardware-in-the-loop real-time simulation system is built with the real-time digital simulator. The simulation results verify the feasibility and effectiveness of the method.