It is always crucial for power systems to be Voltage stable to ensure reliable and secure power to its customers. However, voltage stability of modern power systems is being challenged more and more as the structure of power systems is being changed. Voltage stability analysis techniques were introduced to understand about voltage stability problem and to take necessary precautions to prevent voltage collapse. There have been different techniques proposed in the literature and this paper compares some of these techniques. Finally, IEEE 9 bus systems is used to evaluate results for voltage stability using 6 different techniques described in this paper. A ranking of buses in IEEE 9 bus system is given using evaluation from each technique. The impact of action of under load tap changing transformer (ULTC) for voltage stability is also observed for the test system.