Distributed multi-sensor network for real time monitoring of illumination states for a reconfigurable solar photovoltaic array

Abstract

In a solar photovoltaic (SPV) array [mxn] the solar modules are connected in series and parallel to achieve desired power output. The SPV array performance depends on different parameters such as incident insolation, temperature, array layout, shading etc. Shading due to cloud cover results in Non-Uniform Illumination (NUI STATES- BRIGHT, GREY and DARK). Mismatch in currents and voltages of the modules due to change in one or more parameters leads to loss in output power. Hence real time monitoring of current (I, di/dt) for each solar module and bypass diode in the SPV array is necessary. In addition temperature sensors are required to monitor open-circuit voltage (Voc) fluctuations. Previously, we have demonstrated optimization of an SPV array in BRIGHT and DARK state [1]. However in field testing we have observed an intermediate GREY state as well. The power output can be depressed in a string having multiple state modules in series. In this paper we have proposed a reconfiguration strategy whereby modules are categorized into BRIGHT, GREY, and DARK illumination states. Based on this strategy it has been demonstrated that a reconfigured SPV array will yield maximum power at the highest operating voltage.