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:Introduction2) Chapter 2:System Modeling3) Chapter 3:Control Design4) Chapter 4:SMES Control for Single Machine Infinite Bus System5) Chapter 5: Application to Multi-Machine System6) Main Fortran Program of M. Sc. Thesis Optimal and Suboptimal Control of SMES Devices for Power System Stability Enhancement