With the high proportion of new energy connected to power grid

multi-machine parallel coordinated control of energy storage inverter has become a key problem. Virtual synchronous generator(VSG) algorithm can provide damping

inertial support and stable voltage frequency for grid-forming energy storage system. However

the parallel synchronization

stability

state of charge(SOC) of each stack and impedance of each line should be considered in the coordinated control of parallel operation of multiple energy storage inverters. To solve this problem

a parallel mathematical model of energy storage inverter is established

the methods of reactive power allocation considering virtual impedance and active power allocation considering SOC are analyzed

and an improved VSG control strategy combining self-adaptive virtual impedance and SOC equalization is proposed.Finally

a model is built on the MATLAB/Simulink simulation platform

and the coordination control of each energy storage inverter is analyzed under the discharge condition with the all vanadium redox flow battery pack as the energy storage system. The validity of the improved VSG control strategy is verified

and the problem of over-discharge caused by voltage drop

reactive power and SOC difference caused by impedance difference is solved effectively

the utilization efficiency of the battery and the energy storage inverter is improved

and the life loss of the battery is reduced.