How does the incremental conductance (INC) maximum power point tracking (MPPT) algorithm adapt its operation under rapidly changing irradiance conditions compared to the perturb and observe (P&O) method?

The incremental conductance (INC) and perturb and observe (P&O) methods are both Maximum Power Point Tracking (MPPT) algorithms used in solar inverters to extract the maximum power from a PV array. The P&O method works by periodically perturbing (slightly changing) the voltage or current of the PV array and observing the resulting change in power. If the power increases, the algorithm continues to perturb in the same direction; if the power decreases, it reverses the direction. However, under rapidly changing irradiance conditions, the P&O method can be misled. For example, if the irradiance increases during a perturbation, the algorithm might incorrectly conclude that the perturbation caused the power increase, even if the actual maximum power point (MPP) is in the opposite direction. This can lead to oscillations around the MPP or even tracking in the wrong direction, resulting in reduced energy harvest. The INC method, on the other hand, uses the incremental conductance (dI/dV) and instantaneous conductance (I/V) of the PV array to determine the location of the MPP. The algorithm calculates dI/dV and I/V and compares them. At the MPP, dI/dV is equal to -I/V. If dI/dV is greater than -I/V, the algorithm knows that it is to the left of the MPP on the I-V curve and needs to increase the voltage. Conversely, if dI/dV is less than -I/V, it is to the right and needs to decrease the voltage. Under rapidly changing irradiance, the INC method can more accurately track the MPP because it directly calculates the relationship between voltage and current changes, rather than relying on observing the power change after a perturbation. This reduces the risk of being misled by irradiance fluctuations and enables faster and more stable tracking of the MPP.