Impact of Low-Frequency Ripple on Lifetime of Battery in MMC-based Battery Storage Systems

Modular multilevel converter (MMC)-based battery energy storage system (BESS) is a promising solution for grid-level battery energy storage to accelerate utilization and integration of intermittent renewable energy resources, i.e., solar and wind energy. When the battery units are directly integrated in submodules (SMs) without dc-dc interfaced converters, this configuration provides the highest system efficiency and lowest cost. However, the lifetime of battery will be affected by the low-frequency components contained in arm currents, which has not been investigated. This paper investigates impact of various low-frequency arm-current ripples on lifetime of Li-ion battery cells and evaluate the performance of battery charging and discharging in an MMC-BESS without dc-dc interfaced converters.