Power Distribution Strategy of Fourth-level Haar Wavelet for Hybrid Energy Storage Systems in Electric Vehicle

Focused on the attenuation of cycle life caused by high-frequency power requirements of Lithium-ion batteries for electric vehicles, this paper proposed a fourth-level Haar wavelet power distribution strategy based on the multi-port converter topology. Firstly, a multi-port DC/DC converter is designed to interface the Lithium-ion battery and ultracapacitor, which can be used to make a precise power distribution between the two energy sources. Then, a power distribution method based on fourth-level Haar wavelet transform is proposed. Finally, the effectiveness of the method is verified through experiments under the Highway Fuel Economy Test driving cycle. The experimental results show that the fourth-level Haar wavelet power distribution method can reduce the frequency of the high-frequency component to 1/16 of the original value and reduce the peak output power, which improved the cycle life of the energy storage systems effectively.