Hybrid Micro-Energy Harvesting System Based on Combined MPPT Method

Energy harvesting act as one of the promising techniques to provide sustainable energy for self-powered sensor nodes by converting environmental energy into electricity. Energy harvested from single micro-energy source suffers from low power density and vulnerable to environmental changes, while the hybrid energy harvesting system can supply energy sustainably. However, cumulative power from various energy sources leads to a challenge of low energy conversion efficiency. In this paper, a Combined Maximum Power Point Tracking (Com-MPPT) method for hybrid energy harvesting is designed to improve the overall harvesting efficiency. By analyzing output characteristic curves under different environmental states, a mathematic model for hybrid energy harvesting system is proposed. It is found that with the change of environmental factors, multiple power peaks exist with varying voltage on the load, where traditional MPPT method for single energy source is no longer applicable. Therefore, the proposed Com-MPPT algorithm based on Search skip and linear extrapolation proposed in this paper can quickly search for the global maximum power peak in the case of multiple power peaks in hybrid energy collection. Simulation and experimental results show that the proposed algorithm can track the global maximum power point rapidly under different environmental conditions, and the tracking time is more than 50% shorter than that of the improved particle swarm optimization and flower pollination algorithm.