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 were either active or passive. In order to ensure a relatively small position resolution for the panel axis, the DC motors ordinarily used for active solar tracking need a complicated gear system. In this work, a 8/6 four-phase, reluctance stepper motor (RSM) controlled by a programmable logic array (PLA) is used. The angular position resolution for the RSM is 7.5 degrees. This 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 power converter consists of an Erasable Electronic Programmable Read Only Memory (EEPROM) and a PLA chip. The control circuit is fed from two separate sensing cells which determine the movement to the next angular position. The application of this tracker is essential for stand-alone systems in remote areas. Its use may result in improving the solar energy generation by a considerable factor. The control system is a completely closed loop system without any human interference. (C) 2001 Elsevier Science Ltd. All rights reserved.