Two-Diode Model-Based Nonlinear MPPT Controller for PV Systems

The main objective of this contribution is to present a nonlinear maximum power point tracking (MPPT) controller for photovoltaic (PV) systems based on a two-diode model of a PV module. The proposed MPPT technique operates in conjunction with a Z-source dc-dc converter as an interface between a PV system and a load. The scheme of the proposed nonlinear MPPT controller consists of the design of a nonlinear MPPT algorithm and a nonlinear controller for the generation of duty cycle. The nonlinearity of the PV model as well as the power electronics converter is taken into account in the design of the MPPT controller. Since the PV model parameters vary depending not only on the values of the insolation and the temperature but also on the position of the operating point on the PV characteristics, an adaptation mechanism based on the two-diode PV model is proposed. Thus, these parameters are updated as per real atmospheric conditions. The effectiveness of the proposed method in transient regime as well as steady-state condition is investigated via MATLAB simulation. Furthermore, simulation results are compared with the conventional perturb and observe and incremental conductance methods. The simulation results highlight the capability of the proposed technique over these conventional methods in terms of an improved response in the transient state, an accurate tracking of MPP as well as a significant reduction in the oscillations around the MPP.