Estimation and control of battery charging current for the asymmetrical Z-source topology in the HESS application

A new ultracapacitor-battery HESS based on bidirectional Z-Source topology is proposed in previous research for better energy and space utilization. By controlling the power of UCs and machine, the steady average battery current get controlled indirectly. However, for safety consideration, the dynamic performance of proposed HESS should be considered, so small signal model based on state-space average method is analyzed in this paper. Moreover, instantaneous current analysis for battery is studied in this paper as an extension for battery protection. Simulations and experiments are performed to verify the small signal model and the battery current estimation method.