What is Maximum Power Point Tracking (MPPT) & how does it work?

Every solar module has its own I-V curve. The I-V curve expresses the relationship between current and voltage and is affected by both irradiance and temperature.

As power is the product of current x voltage the I-V curve can be used to determine the power of the module for any given parameter. There is a single point on the I-V curve where power is at a maximum, this is consistently on the knee of the I-V curve and is termed the maximum power point.

As the solar module will produce its optimum power output at this point it figures that the voltage & current parameters if configured to the values required for MPP are the optimum values for the module to be operating at.

As previously mentioned the irradiance and temperature affect the I-V curve, therefore under cloud shading for example or temperature increases the I-V curve will reduce in size thus the maximum power point will also shift accordingly. As this is happening constantly in real time the purpose of maximum power point tracking is to consistently monitor the I-V curve to ascertain the maximum power point and attempt to keep the modules operating at their maximum efficiency under varying conditions.

Various methods are used to track the maximum power point, using a differentiation algorithm for example on the actual power curve the point at which maximum occurs is at a 0 gradient as the power curve increases from 0W, flattens at maximum power to a 0 gradient before decreasing again to 0W. Therefore using differentiation the power electronics can iterate to find the maximum point and then stabilise the voltage parameter at this level. In practise the MPPT is constantly tracking and adjusting these parameters to maintain optimum output and thus keep the system at optimum efficiency.