A generic topology for electrical energy storage systems

Inhalt:
This paper presents an energy storage system which is aimed for energy recuperation of electrical drives. The topology is based on a combination of a multilevel converter (MLC) and a bidirectional boost converter (BBC). The MLC enables the application of low voltage energy storage components; thus super- or ultracapacitors with arbitrary voltage rating can be utilized. The BBC is applied to limit the MLC current when energy is stored in the cells and also allows to supply the output voltage almost independently on the state of charge of the ultracapacitors. Due to its generic structure, the topology can be adapted to different voltage, power, and energy levels. The paper highlights the benefits and potential drawbacks of the topology, details the design of the MLC, and presents the modulation for the MLC converter stage. The theoretical results are validated on a prototype employing 10 cells with 50F/5.4V each (i.e. 2Wh in total). The system is designed to deliver a power of 500W for 5s to an 48V voltage bus. The system’s efficiency for an entire store-release cycle is 80.1% at a volume of 1.05dm3.