Adaptive Split-Frequency Quantitative Power Allocation for Hybrid Energy Storage Systems

As the two classical power allocation methods in battery-supercapacitor hybrid energy storage systems, split-frequency methods and power-level methods have been developed separately for many years. In this paper, we made an attempt to integrate the advantages of the two methods, and proposed an adaptive frequency-split based quantitative power allocation strategy. First, an adaptive power pre-allocation is quantitatively determined according to the state of charge (SoC) of batteries and supercapacitors. Then, a windowed FFT based power spectrum calculation algorithm is designed to derive the power level corresponding to each sampling frequency. By mapping the pre-allocated power to the power spectrum, the split frequency is adaptively computed. Finally, the power allocation is implemented through a low pass filter (LPF) with the derived split-frequency. Extensive experiments verify that the proposed method provides an improved performance in suppressing the DC bus voltage fluctuations and protecting batteries when compared with existing methods.