A current-based fuzzy controller for MPPT of grid-connected PV systems: Fid-Bau Portal

A current-based fuzzy controller for MPPT of grid-connected PV systems

Rahmani, Bijan / Li, Weixing

The output voltage oscillations of a photovoltaic (PV) system in parallel with other challenging voltage sources such as batteries result in drastic power oscillations. So, it is much more attractive to employ a PV system as a current source rather than as a source of voltage alongside a battery. To this aim, the inductance current of the PV's DC–DC converter is controlled and forced to track the maximum power point (MPP) reference, acting as a source of current. Then, the load voltage, and the DC–DC converter output voltage would be the same as the battery voltage. For this purpose, the paper proposes a two-level current-based maximum power point tracking (MPPT) algorithm. The proposed high-level algorithm contains two loops, namely, a set-point calculation loop and a fine-tuning loop. Based on an offline calculation using the PV's short circuit current, the set-point loop first estimates the PV's maximum power point. Second, the fine-tuning loop tracks the exact value of the PV's maximum power point, using the perturbation and observation (P&O) method. Further, a low-level fuzzy-based controller is proposed to force the continuous current (i.e., inductance current) of PV's DC–DC converter to track the generated reference of the high-level controller with no oscillation. The low-level fuzzy-based controller is proposed instead of the conventional proportional integral (PI) controller that does not work with minimal errors, since inserting one unstable pole into the PV system's transfer function. Matlab/Simulink simulations validate the effectiveness of the proposed MPPT algorithm.