Development of MPPT Circuit for Low-Power Solar Energy Harvesting

Ng, Chee How (2016) Development of MPPT Circuit for Low-Power Solar Energy Harvesting. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Photovoltaic (PV) cells can convert solar irradiance from sunlight directly into electrical energy. Hence, PV cells are utilised as solar energy harvesters for low-power applications. The energy collected from solar energy harvesters could then be conditioned using DC-DC converter into a form that is suitable for charging of power bank. A MPPT circuit is needed for maximizing the energy extracted from the PV energy harvester by enabling the operating point of the PV cells to track the maximum power point. Different MPPT techniques are available based on their features such as the number of control variables involved, types of control strategies employed, types of circuitry used and costs. A mbed NXP LPC11U24 microcontroller is used to run selected MPPT algorithms (perturb and observe and incremental conductance). Current and voltage sensors are used to sense the operating current and voltage while the microcontroller performs the calculation to provide the duty cycle for the MOSFET in the converter to track maximum power point. Experiments were conducted to determine the tracking speed to reach MPPT, the amount of oscillation and the energy harvested with and without MPPT circuit. Incremental conductance is 15.3 % faster to reach the MPP and the oscillation is 42.86 % lesser than perturb and observe. The energy harvested from solar charger with MPPT has 36.27 % more than solar charger without MPPT. The final efficiency of prototype is 43.27 %.