3.3 MPPT Routine

The firmware incorporates an active MPPT algorithm that is used to operate the converter at the most efficient voltage and current for the panel. The output of a solar panel follows an I/V curve, as shown in Figure 3-1.

Figure 3-1. Solar Cell I-V Curve in Varying Sunlight

The maximum power point (MPP) is where the product of current and voltage is maximized (the rising blue line in the graph). This operating point will continuously shift with changes in illumination intensity, panel temperature, sun angle, shadowing/shading, etc. There are several possible MPPT algorithms that can be incorporated into this design, including Perturb and Observe (P&O), incremental conductance and constant voltage. The P&O algorithm is currently implemented in this design.