Abstract:

To address the intermittent and unstable issues of high-proportion new energy grid connection and enhance its utilization efficiency,the grid-forming energy storage system based on vanadium redox flow batteries (VRFB) is focused on.The research employs a multi-physics field-coupled VRFB hybrid model to simulate its dynamic operation characteristics comprehensively.Based on this,a flexible charge and discharge control strategy based on the outer loop of the DC bus voltage is designed,and the virtual synchronous generator (VSG) control technology is integrated to achieve precise control of VRFB’s charge and discharge.The effectiveness of the strategy is verified through modeling and simulation in MATLAB/Simulink.The results indicate that this strategy can stabilize the output terminal voltage during long-term discharge and performs outstandingly in photovoltaic/VRFB grid-connected operation,frequency and voltage regulation,and maintaining the stability of the DC bus voltage,which can validate the application potential of VRFB in the field of grid-forming energy storage.

Key words: vanadium redox flow battery (VRFB), grid-forming energy storage, hybrid modeling, lexible charging and discharging, virtual synchronous generator (VSG)