Power Distribution Strategy Based on Low-Pass Filter Controller with a Variable Time Constant in Hybrid Energy Storage Systems

A critical issue in a hybrid energy storage system (HESS) is the control strategy, especially the power distribution between the individual energy storage devices. In this paper, the power distribution strategy based on the low-pass filter (LPF) controller with a variable time constant is introduced. The adjustable range of the variable time constant is determined by the spectrum analysis of the imbalanced power in a stand-alone household-prosumer system. In addition, the variation of the time constant is based on the feedback of the state of charge (SoC) of the supercapacitor (SC). The simulation results show that the power distribution strategy keeps the SoC of the SC in a moderate range and utilizes the SC more properly. A scaled-down experimental setup is built to verify the effectiveness of the power distribution strategy and the simulation results. Therefore, the proposed power distribution strategy ensures the effective operation of the HESS, avoids the unnecessary enlarging of the SC, and achieves cost reduction.