An adaptive control strategy for vsg based on energy storage capacity optimization of MMC-BESS

The energy storage unit is connected to the sub-module of the modular multilevel converter through the DC/DC link, which can effectively reduce the voltage-level requirements of the energy storage unit, and the energy storage capacity can be flexibly configured by changing the number of energy storage sub-modules. Virtual synchronous generator technology is applied to the top-level control strategy of the modular multilevel converter, which can effectively solve the defect that the system cannot perceive the frequency of the grid side. In addition, the adaptive parameter control of virtual synchronous generator can be realized by changing the moment of inertia J and damping coefficient D in real time according to the actual situation. On this basis, an improved adaptive algorithm is proposed in this paper. D is adjusted by active power deviation and active power change rate. J and D are selected by fast saturation function, and the range of parameters is reasonably limited to realize the optimization of energy storage capacity. Finally, the adaptive algorithm under frequency disturbance is modified to ensure its better transient performance. The simulation results show that the proposed adaptive algorithm can improve the dynamic performance of the system and reduce the energy storage capacity required by the system, which verifies the effectiveness of the proposed algorithm.