Considering the high consumption of the air compressors, a control system of screw compressor is designed and implemented to deal with energy saving and localization of mentioned compressor. In this paper the variable speed drive (VSD) control algorithm based on proportional-integral-derivative (PID) controller is optimized to decrease power consumption and more stable motor speed and outlet pressure. Automatic PI factors adjustment according to system behavior is goal of this control system. To show the validity of the proposed algorithm, we simulated P and I changes. The results of simulation and practical test on a GA111 Atlas Copco compressor were established which demonstrate that the proposed algorithm provides system stability improvement and as a consequence depreciation reduction and energy saving were achieved. پرونده مقاله