Considering that the low voltage and small capacity ratings of traditional distributed energy storage system cannot meet the increasing capacity of renewable energy

the battery energy storage system(BESS)based on cascaded H-bridge topology is presented to achieve high-voltage and large-capacity. Moreover

in order to make BESS connected to grid friendly

the virtual synchronous generator(VSG)is investigated. Firstly

the second-order equivalent model of synchronous generator(SG)is analyzed and the VSG control strategy for BESS is given combined with primary frequency and voltage regulation of SG. Besides

the small signal dynamic model in wideband of VSG is established to analyze the inherent power coupling problem and the effect of AC side impedance on VSG control

also

the relationship between control parameters of VSG and performance of BESS is analyzed by frequency domain model

which provide the basis of stability analysis and the design and optimization of key parameters of VSG. Simultaneously

aiming to the problem of state of charge(SOC)balancing for sub-module batteries

a method based on improved nearest level modulation(I-NLM)is proposed and the modulation principle and implementation process are given. Finally

the effectiveness of VSG control on BESS and equalization method for SOC are verified through computer simulation.