Design, Construction and Testing of a Voltage-based Maximum Power Point Tracker (VMPPT) for Small Satellite Power Supply

Design, Construction and Testing of a Voltage-based Maximum Power Point Tracker (VMPPT) for Small Satellite Power Supply

It is shown that at maximum power, the Photovoltaic (PV) voltage varies nonlinearily with temperature and isolation level, but is directly proportional to the PV cell open circuit voltage. The proportionality voltage-factor is fixed for a given PV generator regardless of temperature, isolation and panel configuration, but depends on cell material and manufacturing. This remarkable property is used to achieve temperature and insolation independent maximum power point tracking of satellite's solar cells with a simple and reliable technique. The open circuit voltage is continuously measured by a microcontroller and is used to estimate the maximum power operating point of the system. The Voltage-based Maximum Power Point Tracker (VMPPT) is demonstrated by construction and testing of a solar battery charger (using silicon solar cells, Ni-Cd batteries and a buck mode VMPPT), a solar water pump (using silicon solar cells, a PM DC Motor and a boost mode VMPPT) and resistive loads supplied by solar cells. Measured results are satisfactory and confirm the proposed technique. The advantage of this method as compared to the current-based MPPT are "simplicity" and "higher efficiency".