Novel Battery-Supercapacitor Hybrid Energy Storage System for Wide Ambient Temperature Electric Vehicles Operation

Abstract

Electric vehicles (EVs) are gaining popularity in recent days to reduce the dependency on fossil fuels. Batteries are the main power source in EVs. However, the capacity of the battery degrades when it operates in low temperatures (< 0∘C). Hence, it is essential to maintain the battery temperature (> 0∘C) to operate at maximum capacity. Additionally, the battery alone is not suitable to supply the high transient power requirements of EVs. Thus, this paper proposes a novel integrated converter topology, which facilitates battery heating along with power transfer from the hybrid energy storage (battery and supercapacitors). The internal ac heating uses a resonant network for uniform heating of the battery cells in heating mode. The same inductor of the resonant network is also used for power transfer from hybrid energy storage during the driving mode. The Discrete Fourier Transform (DFT) based integrated inductor design ensures effective EV power sharing between battery and supercapacitors and reduces battery heating time. Thus, the proposed integrated converter reduces the number of converters stages, control complexity and overall cost. The detailed analysis and design are included along with the simulation and experiment results. The results show the uniform internal heating of the battery and efficient power transfer from/to the battery and supercapacitors. The experimentation is performed in a 1kW system considering the European driving cycle.