Dual-mode control and switching control strategy of microgrid for power battery formation and grading testing system

To address the stability issues of the microgrid system for power battery formation and grading testing systems in scenarios involving multiple parallel converters, this paper proposes a hybrid dual-mode control strategy combining grid-following and grid-forming modes to ensure stable operation of the microgrid system. However, the conventional switching between the two control strategies during the operation of the converter can lead to transient power and current surges, which may even affect the stable operation of the converter. Therefore, this paper studies the characteristics of grid-following and grid-forming control strategies. Based on the fact that both have the same type of output variables, a seamless switching control strategy based on the method of controller output state following is proposed, the switching time can be shortened by more than 1 s to the greatest extent possible. Furthermore, a seamless switching control strategy for grid-connected and islanded operation modes of the microgrid system is introduced. Finally, the effectiveness of the proposed method is verified using the Simulink simulation platform and a hardware-in-the-loop experimental simulation platform. The experimental results demonstrate the validity of the proposed approach.