Monitoring Array Output Current and Voltage in Stand Alone Photovoltaics Systems With Pulse Width Modulated Charge Regulators

Abstract

Pulse width modulated (PWM) charge regulators are frequently used in stand alone photovoltaic (SAPV) systems. Once the battery has reached the regulating voltage, these electronic devices provide current and voltage pulses to regulate the charge current to the battery. This kind of signals implies rapid variation in the variables and may provide, when being monitored, and if some special considerations are not taken into account, an erroneous measurement of the array output current, the array output voltage and the current to storage. Moreover, this inappropriate monitoring will affect not only to these monitored variables but also may spread over the array output power and most of the derived parameters, providing a mistaken system performance analysis from monitored data. In this way, this paper focus on the different issues that can arise when monitoring the parameters mentioned above in SAPV systems with PWM charge regulators. A comparative study of the two types of sensors (shunt and halleffect transducer) that can be used to capture either the array output current or the current to storage will be developed. Moreover, it is intended to provide easy monitoring procedures to collect the array output and voltage, the current to storage and the array output power as these variables are the more sensitive to the use of PWM charge regulators. These monitoring requirements may be appropriate under field conditions and may become costeffective. The solutions given here intends to avoid the complex monitoring system and the high computational cost that may require a simultaneous sampling mode at a relative high sampling frequency to obtain an appropriate monitoring for the modulated signals in SAPV systems with PWM charge regulators.