Low cost and efficient PWM charge controller for autonomous photovoltaic systems Controlador de carga PWM eficiente y de bajo costo para sistemas fotovoltaicos autónomos

Abstract

An off-grid Photovoltaic (PV) system consists of a solar panel, a battery, an electrical load, and a charge controller. Particularly, the charge controller has the purpose of protecting the battery from overcharging and low discharging, controlling the energy delivered from the panel to the battery, and from the battery to the load. In this work, we described the design and implementation of a charge controller using pulse width modulation (PWM), taking into consideration an analysis of cost-benefit relation to obtain the highest efficiency at a competitive price in the market. The power electronics of the charge controller use Metal–Oxide–Semiconductor Field–Effect– Transistors (MOSFET); the MOSFETs are activated through a PWM signal
transmitted by a PIC micro–controller that was programmed to change the duty cycle of the PWM signal according to the variables measured on the PV system such as solar panel voltage and the state of charge of the battery (SoC). The SoC is determined by the Ampere-hour counting method, measuring the electrical variables using voltage divisors and a Hall Effect current sensor; these devices send the information to the micro-controller. The charge controller was implemented using low cost components and reducing the number of sensor commonly used without affecting the operation of the circuit. Consequently, we developed a charge controller with an efficiency and price that competes with the current PWM controllers available in
the market.

Keywords: Charge controller, Hall Effect, Micro-controller, Off-grid PV Systems, Pulse Width Modulation