Effect of Battery Power on Capacitor Voltage Ripple Characteristics in Modular Multilevel Converter with Integrated Battery Energy Storage System

Abstract

Modular Multilevel Converter (MMC) with integrated Battery Energy Storage System (BESS), where the battery strings are connected to each Submodule (SM) through DC-DC converters, can transfer energy among the DC link, the AC grid, and the batteries. And this flexible structure is suitable to be applied in the microgrid and the wind power generation system, in which the BESS is needed to smooth energy fluctuations. However, compared with the common MMC, the Battery Manage System (BMS) which is used in BESS to balance the State of Charge (SOC) among batteries makes the capacitor voltage ripple of each Submodule different and complicated. The capacitor selection needs to take this into consideration. Some simulation results under different initial SOC situations derived from a Simulation model are given to evaluate the influence. And some corresponding conclusions and suggestions are obtained based on these simulation results.