Constant Voltage Battery Charger Energized from an MPPT Photovoltaic System

Maximum power point tracking (MPPT) enables extracting the maximum power that a photovoltaic panel is capable of delivering regardless of the change in solar irradiance or ambient temperature throughout the day, maximizing its efficiency; it is carried out by means of the control of a DC-DC converter to modify the voltage delivered to the load, such that the variation in the current keeps the power constant. In this work it is designed and simulated an MPPT with an SEPIC converter whose pulse width control signal is determined by the Perturb & Observe (P&O) algorithm to identify the voltage that produces the maximum power, it is available at the output of a BUCK converter controlled by a PID that enables energizing loads with constant voltage despite of the variations produced by the P&O algorithm. The will be energized from a 30 W panel and will charge 9 V batteries at a constant charge voltage, that are commonly used in the robotics club of the Universidad Politécnica Salesiana, located in Quito, Ecuador. Matlab/Simulink is used for simulation considering scenarios of variable irradiance levels and also load variations. The results show a good transient response of the SEPIC converter with the MPPT control to extract the maximum power, moreover the PID c ontroller enables attenuating the ripple obtaining a constant output with a ripple of 2.5%, and does not generate overshoot.