Abstract: The frequent occurrence of voltage instability in a modern power system is alarming and thus, has been of a great concern to power system utilities. Presented in this paper is a new performance index which is based on the power flow solutions for voltage stability assessment of a power system. First, the voltage deviation with respect to reactive power load variation at each load bus is found. Thereafter, the performance voltage bus index for each load bus is computed. An improved modal analysis technique (IMAT) is also suggested in this paper. This technique only made use of a submatrix of the full Jacobian matrix for voltage stability analysis. Comparison of the proposed methods is done with the existing voltage stability indices and the conventional modal analysis technique (CMAT). The effectiveness of all the approaches presented is tested on both Western system coordinating Council (WSCC) 9-bus and IEEE 30 bus test systems. Results obtained show that the proposed techniques can serve as alternative tool to other conventional techniques for voltage stability assessment in a power system and can be of tremendous benefits by the system operators in the planning and operation of a power system.