Traditional MPPT methods are divided into open-loop and closed-loop MPPT methods according to the difference of judgment methods and criteria. In fact, the effects of changes in external temperature, light and load on the output characteristics of photovoltaic cells show some basic laws. For example, there is an approximate linear relationship between the maximum power point voltage of photovoltaic cells and the open circuit voltage of photovoltaic cells. Based on these laws , some open-loop MPPT control methods can be proposed, such as constant voltage tracking method, short-circuit current proportional coefficient method and interpolation calculation method.

The closed-loop MPPT method realizes MPPT through real-time measurement and closed-loop control of the output voltage and current value of photovoltaic cells. The most widely used self-optimization algorithm belongs to this category. Typical self-optimizing MPPT algorithms include Perturbation and Observation Method (P&O) and Incremental Conductance (INC).