Disclosed in the present invention is a
state of charge (SOC) balancing method for an
energy storage MMC based on
capacitor voltage correction, comprising the following steps: acquiring important parameters such as the SOCs of
energy storage units and current directions of bridge arms in an
energy storage MMC; calculating SOC average values of phase units, of the bridge arms, and of three phases of energy storage units; calculating the inter-phase SOC imbalance degree, the inter-bridge arm SOC imbalance degree, and the inter-submodule SOC imbalance degree, obtaining an inter-phase power deviation, an inter-bridge arm power deviation, and an inter-submodule
voltage deviation by means of a proportional controller, and calculating a submodule energy storage power reference value and submodule corrected
capacitor voltages; calculating the
duty cycle of a switching device in a bidirectional DC /
DC converter; and sorting the submodule corrected
capacitor voltages, and on the basis of the charging / discharging state of submodule capacitors, determining submodules to be connected. The present invention can realize SOC balancing of energy storage MMCs, and reduces the number of bidirectional DC /
DC converter controllers, thereby improving the SOC balancing efficiency and the capacity
utilization rate of energy storage units.