The incremental conductivity method is based on the operating characteristics of photovoltaic components and identifies the maximum power point (MPP) by measuring and comparing the increments of current and voltage. The basic principle is as follows:
Current and voltage relationship: On the photovoltaic characteristic curve, the current and voltage changes at the MPP have a certain relationship. When the operating point is close to MPP, the change in current (I) and voltage (V) can be expressed by the following formula:
If (\frac{dP}{dV} = 0), then MPP is reached.
If (\frac{dP}{dV} > 0), you need to increase the voltage to get more power (the operating point is to the left of the MPP).
If (\frac{dP}{dV} < 0), the voltage needs to be reduced to reduce power loss (the operating point is to the right of the MPP).
Calculating derivatives: Using the definition of derivatives, one can obtain:
( \frac{dP}{dV} = I + V \cdot \frac{dI}{dV} )
Thus, if (\Delta I) and (\Delta V) are the changes in current and voltage, respectively, the incremental conductance rule consists in comparing the two:
( \Delta I / \Delta V = -I / V )
By analyzing the symbol of the derivative, you can determine whether the operating point needs to be adjusted.
Control strategy: By constantly measuring changes in current and voltage, the controller will adjust the working voltage of the photovoltaic system in real time to ensure that it approaches or remains at the maximum power point.