A novel MPPT method with variable perturbation step for photovoltaic system

The output power of photovoltaic (PV) power generation system is the nonlinear function of insolation, temperature and load, and thus the perturbation step of perturbation and observation (P&O) method should be regulated according to PV module working condition to improve the MPPT effect. P&O with fuzzy control, which can implement variable perturb step control, has good control effect, however this method is too complex for practical use. The relation of the perturbation step and the output power of PV module is analyzed that shows the step around maximum power point (MPP) should become small enough to eliminate power oscillation. This paper proposes a variable perturbation step P&O method according to this conclusion. This method utilizes the relation of the output power vs. voltage of PV module as the judge of step change. Simulation and experimental results show the proposed method has good stable and dynamic characteristics applied in PV power generation system.