DC side ripple cancellation in a cascaded multi-level topology for automotive applications

Cascaded H-Bridge converters are an attractive topology for automotive applications due to the potential improvements in motor efficiency and the system modularity they offer. Isolated voltage sources are required in this structure and one approach to providing these is use of the Dual Active Bridge converter. Regardless of the number of phases in the load, each element in the cascade supplies a single phase, and hence must supply the associated twice output frequency ripple component. The presented control methodologies effectively transfer these twice output frequency ripple components back to the primary side of the Dual Active Bridge converters, where in the case of a balanced multi-phase load, cancellation occurs. This results in both a smaller input and output capacitor requirement for the Dual Active Bridge Converter while ensuring the ripple current is not sourced from the battery in this application. Simulation results for two methodologies are presented, along with experimental results.