This is my master thesis "Optimal and Suboptimal control of SMES Devices for Power System Stability Enhancement." It includes the fallowing chapters 1.Chapter 1: Introduction 2.Chapter 2: System Modeling 3.Chapter 3: Control Design 4.Chapter 4: SMES Control for Single Machine Infinite Bus System 5.Chapter 5: Application to Multi-Machine System 6.Main Fortran Program of M. Sc. Thesis "Optimal and Suboptimal Control of SMES Devices for Power System Stability Enhancemen