The distributed control can effectively reduce the operation and communication pressure of the main controller and also is easy to enhance the ability of expansion and hot swap. Due to a lot of disadvantages such as the large amount of communication and calculation and complicated setting in modular multilevel energy storage converter (MM-ESC)

a distributed control system architecture is proposed to reduce communication and calculation. The state of charge (SOC) droop control strategy for the control system is also discussed. The distributed control system consists of a central control unit and several submodule control units. The central control unit performs power decoupling control and sends modulated information to the submodule control units

while the submodule control units perform SOC droop control according to local information. The power difference characteristics of intra-phase and inter-phase are analyzed

and the droop coefficients are respectively set to achieve energy balance between batteries. The theory and control method are verified by a five-level MM-ESC simulation system and an experiment platform. The results show that the communication and calculation in the proposed control system are smaller than the existing control system

which can meet operation requirements.