Validation of a Modular Multilevel Converter with additionally integrated Energy Storage for Grid-supportive Operation

Abstract

For the successful energy transition, the Modular Multilevel Converter (MMC) serves as an attractive solution for HVDC power transmission. Within this paper, the partial integration of additional energy storage elements into the underlying structure of the converter is presented. By extending a certain proportion of the submodules to form energy storage modules, the resulting Energy-Storage MMC is capable of storing or releasing an additional portion of its rated power on the AC-side without the need to adjust the DC power flow. The design of this topology and the necessary modifications for the control structure are studied. The property of storing or releasing additional power during normal operation enables the converter to provide grid-supportive functions. The ES-MMC concept is validated by conducting appropriate dynamic simulations in MATLAB® Simulink®. For this purpose, its participation in the frequency containment process and in power oscillation damping is examined in the Kundur two-area test system.