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 Enhancement"