An adaptive sliding-mode control strategy for hybrid power sources of battery-supercapacitor with a boost converter

For the battery-supercapacitor (SC) hybrid power source (HPS) with a boost converter, the supercapacitor voltage (i.e. output voltage) might be unstable and the battery current (i.e. input current) fluctuation might be very high. To solve these problems, an adaptive sliding-mode control strategy is proposed. A dynamic model of the battery-SC HPS with the boost converter is established by combining the conventional averaged model of the boost converter and the characteristics of the SC. It is based on the model that an adaptive estimator is designed to estimate the related parameters, and adaptive rules are defined according Lyapunov function. Furthermore, a suitable sliding surface is selected and a duty ratio function is designed according to the selected sliding surface and the adaptive rules. Observe gains are also designed in accordance with the constant current/voltage control requirement in the HPS. An experimental platform is established. Experimental results show that the proposed strategy makes the system reach steady state quickly. A comparison with the PI control strategy in the conditions of both constant current control and constant voltage control shows that the strategy improves the transient time by 88.8% and 62.5%, respectively. It effectively eliminates the fluctuation of the output voltage and inductor current, and improves the safety and reliability of system when the SC voltage is lower.