Generic Dynamically Reconfigurable Battery With Integrated Auxiliary Output and Balancing Capability
Nima Tashakor, Jan Kacetl, Jingyang Fang, Zhongxi Li, Stefan M. Goetz
Abstract
Modular multilevel converters and cascaded H-bridge converters are established concepts in ultrahigh-voltage systems. In combination with batteries, these circuits allow dynamically changing the series/parallel configuration of the battery modules, also known as reconfigurable batteries. A large body of research discusses applications of such systems in grid-storage and electromobility with a single load, such as an electric drive. However, most studies neglect the presence of auxiliary loads, which require additional voltage levels and isolation from the high-voltage battery. This article proposes a decoupling method that can fork a second (galvanically isolated) output off a reconfigurable dc battery without negatively affecting the main output by exploiting the many control degrees of freedom in the modular circuit. The proposed system provides a nonisolated port for the dc link of the motor-drive inverter(s), while generating an additional isolated output at another voltage for auxiliaries. The auxiliary output benefits from the interleaving effect, which increases the operating frequency of the transformer and reduces the filter size. The solution does not require additional active switches for the auxiliary port and can operate with a wide range of voltages. The integrated auxiliary circuit can also balance the modules during idling and charge/discharge cycles. Both simulation and experiments validate the analysis.