Analysis and Optimization of Current Injection Method for Mitigating the Current Ripple of MMC-BESS

Due to the inherent operational property, the modular multilevel converter battery energy storage system (MMC-BESS) exists battery current ripple issue, which will inevitably affect the battery life and increase the conduction loss. To address this issue, this article investigates the current injection method for mitigating the battery current ripple of MMC-BESS. To analyze the mechanism of current ripple in submodules, the current deviation optimization problem is converted into the energy deviation optimization problem. The effect of the reactor and the battery module is considered to obtain the accurate analytical expression of battery current and capacitor voltage deviation for optimizing the current injection value. Furthermore, the quantitative analysis of factors affecting the battery current ripple is conducted for parameter optimization. The experiment results verify the correctness of the proposed energy-based analysis method as well as the ability of the optimized current injection method to mitigate the battery current ripple.