A modified MPPT method with variable perturbation step for photovoltaic system

A novel MPPT method, which adjusts the perturbation step according to the work point of photovoltaic (PV) module, is proposed to reduce the power oscillation around MPP. There is the nonlinear relation between the output power of photovoltaic module with temperature and load. The perturbation step is constant in traditional perturbation and observation (P&O) MPPT method. There is serious power oscillation around MPP under the control of P&O method. 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, which shows the step around maximum power point (MPP) should become small enough to eliminate power oscillation. This paper proposes a simple variable perturbation step P&O method according to this conclusion. This method utilizes the relation of the output power and voltage of PV module as the judge of step changing. Simulation and experimental results show the proposed method has good stable and dynamic characteristics, which is applied in PV power generation system.