Design of a three-states charge controller for photovoltaic systems using fuzzy logic

This paper presents the design and simulation of a buck charge controller for lead-acid accumulators used in photovoltaic applications, based on fuzzy control techniques. The proposed design fully implements the three-stage algorithm: bulk, absorption, and flotation, which allows the battery to be accurately charged, ensuring its integrity and durability. The control system consists of two independent fuzzy controllers, the first regulates the current accurately in the bulk stage, while the second regulates the voltage in the absorption, and flotation stages; additionally, it has switching logic, which allows transitioning between the different stages of the algorithm. The system was designed and simulated in MATLAB; and the results show the correct functionality of the design by simulating the charge of 12 V accumulators with capacities from 60 to 120 Ah. Even though in the literature, there are similar works, very few use an algorithm with multiple stages completely, and that can be implemented directly in economic systems such as microcontrollers. This work can be taken as a reference in the design of charge controllers even different from those based on fuzzy logic, which represents an important didactic contribution.