The main objective of this book was to introduce a new approach to the design of stable digital control systems which is achieved by using a global digital re-design method for converting an analog control system into a digital one is called plant input mapping (PIM).The main advantages of the new approach are the guaranteed closed-loop stability for almost all sampling periods, and the recovery of the continuous-time performance when the sampling period approaches zero. The result guarantees closed loop stability for all non-pathological sampling periods. On the other hand the major disadvantage of this algorithm is depending on plant model. In this thesis, the design some of digital controllers for power system stability which power system represented by single machine infinite bus system (SMIB) Such as Digital power system stabilizer, Digital Proportional-Integral controller, and Digital Proportional-Integral-Derivative controller.