Implementation of a P&O MPPT Algorithm in Low-Milliwatt-Scale Energy Harvesting Wireless Sensor Nodes

The Fractional Open-Circuit Voltage (FOCV) based Maximum Power Point Tracking (MPPT) method, typically used in low power energy harvesting circuits, is not truly dynamic and wastes harvestable energy in each MPPT cycle. Commercial-off-the-shelf (COTS) energy harvesting chips offer provision for externally setting the MPPT reference using more accurate and dynamic algorithms like Perturb-and-Observe (P&O), Incremental Conductance (INC) etc., but this can come at the cost of increased power consumption and sensing complexity. To address this issue, a simple low power implementation of the P&O method in an energy harvesting wireless sensor node (WSN) is presented in this paper. With only two additional analog load switches (SOT23 package), and no extra current or voltage sensor, the proposed method achieves dynamic MPPT with a power overhead of only eight microwatts.