Sun tracking by peak power positioning for photovoltaic concentrator arrays

Abstract

This paper details the design, development, and evaluation of a microcomputer-based solar tracking and control system (TACS) capable of maintaining the peak power position of a photovoltaic (PV) array by adjusting the load on the array for maximum efficiency and changing the position of the array relative to the sun. At large PV array system installations, inverters are used to convert the dc electrical output to ac for power grid compatibility. Adjustment of the inverter or load for maximum array output is one function performed by the tracking and control system. Another important function of the system is the tracking of the sun, often a necessity for concentrating arrays. The TACS also minimizes several other problems associated with conventional shadow-band sun trackers such as their susceptibility to dust and dirt that may cause drift in solar alignment. It also minimizes effects of structural warpage or sag to which large arrays may be subject during the day. Array positioning is controlled by a single-board computer used with a specially designed input/output board. An orderly method of stepped movements and the finding of new peak power points is implemented. This maximum power positioning concept was tested using a small two-axis tracking concentrator array. A real-time profile of the TACS activity was produced and the data analysis shows a deviation in maximum power of less than 1% during the day after accounting for other variations.