Multidirektionale Energieflusssteuerung eines Modularen Multilevel-Umrichters mit integrierten Batteriespeichern in elektrischen Netzen

Description

Battery energy storage systems will play a key role in the ongoing process of integration of renewable energy generation into the electrical grid. The transformation of energy between battery and electrical grid is realized by converters. Modular Multilevel Converters are a type of self-commutated converters and are primarily used in high voltage direct current applications.

This thesis presents the integration of batteries into the modules of a Modular Multilevel Converter in double-star configuration. Thereby, the features of modular built multilevel converters can be utilized and restrictions of currently used converter topologies for battery energy storage systems can be abolished. For such an integration a highly dynamic energy flow control between the electrical grid, the DC terminals and the converter modules is required. During the control design several approaches for classical loop control and modern state space control are compared. Based on an comprehensive model of the energy relations within a modular multilevel converter with integrated batteries, degrees of freedom for energy flow control are identified. Finally, a verification of the developed controllers is performed with a hardware setup in laboratory. Various grid conditions as well as different configurations of battery integration are investigated.