Maximum power point tracking for low power photovoltaic solar panels

A maximum power point tracker unit is developed for the optimum coupling of photovoltaic panels (PVP) to the batteries and load through a controlled DC-DC power converter (chopper). The system consists of three main units: (i) the photovoltaic panels that convert solar power to electricity; (ii) a chopper which couples the power of PVP to the load or batteries at a constant voltage; and (iii) maximum power point (MPP) computing unit that determines the set point of the chopper to keep the panel voltage at a maximum power transfer (MPT) condition. The tracking of the MPP for low power PVP (50 W-1 kW) is feasible only when the power consumption of the tracking unit is lower than the increase of the output power that they provide. The developed and tested circuit consumes only 40 mW, and therefore is suitable even for low power applications down to 50 W. The tracking unit performs MPP computation periodically through analog computing stages. The computation mode requires 20 mA from the /spl plusmn/5 V source for a 50 ms period. In the control and sleep mode, the consumption falls down to 4 mA. The developed unit regulates the panel output voltage at its optimum value in the control mode. The modes are switched by a timing circuit. The sleep mode is initiated when maximum PVP output power of the existent illumination level drops to a preset value, which cannot balance the losses of the chopper and the consumption of the MPP tracker unit.