Use of a reluctance stepper motor for solar tracking based on a programmable logic array (PLA) controller

The tracking of solar cell panels in solar-generation systems has improved their overall efficiency to a great extent. The methods used previously wer e either active or passive. In order to ensure a relatively small position resolution for the panel axis, the DC motors ordinarily used for active sol ar tracking need a complicated gear system. In this work, a 8/6 four-phase, reluctance stepper motor (RSM) controlled by a programmable logic array (P LA) is used. The angular position resolution for the RSM is 7.5 degrees. Th is resolution is guaranteed due to locking of the RSM at each step through a power converter fed from a 220 V DC supply. The control circuit for the p ower converter consists of an Erasable Electronic Programmable Read Only Me mory (EEPROM) and a PLA chip. The control circuit is fed from two separate sensing cells which determine the movement to the next angular position. Th e application of this tracker is essential for stand-alone systems in remot e areas. Its use may result in improving the solar energy generation by a c onsiderable factor. The control system is a completely closed loop system w ithout any human interference. (C) 2001 Elsevier Science Ltd. All rights re served.