Adaptive Fractional Open Circuit Voltage Method for Maximum Power Point Tracking in a Photovoltaic Panel.

The output power of a Photovoltaic (PV) panel changes with solar insolation and temperature. Also the P-V (Power-Voltage) and I-V (Current-Voltage) characteristics of a PV cell is highly non-linear. Hence the maximum output power from the PV panel is achieved at a particular voltage (VMPP) and current (IMPP). To improve the overall efficiency, it is important to keep the PV panel to work at Maximum Power Point (MPP). This paper presents an Adaptive Fractional Open Circuit Voltage (AFOCV) method to track the MPP. It does not require the PV panel characteristics to be known in advance. In the proposed circuit, the fraction (k) is estimated adaptively i.e. k is estimated once and then used for a certain period of time to determine the MPP. Again after sometime a new k (that might change due to change in solar insolation) is estimated. In the proposed circuit, for different values of k the output power from the PV panel is calculated and the power levels at two consecutive points on the PV panel is compared. When the MPP is reached that value of k is locked in the fractional voltage generator block and all other blocks are turned off so as to reduce the power consumption. The proposed circuit is designed in a 180 nm CMOS process