In this paper, Adaptive Neuro-Fuzzy Inference System (ANFIS) controlled Thyristor Capacitor Series Controller (TCSC) and Synchronous Series Compensator (SSSC) techniques were applied to improve voltage stability on the Nigerian 46 bus 330kV transmission grid power network. In order to obtain maximum result, (ANFIS) was created, trained and deployed to control the modeled SSSC and TCSC. The ANFIS controlled compensating devices are then integrated into the equivalent circuit of the test network for simulation and performance evaluation. The evaluation was done under three cases: base case situation, short circuit case and case of three phase fault in the network. For the base case; network without and with compensation recorded a voltage profile of 0.89pu and 1.04pu respectively, which is 16.85% improvement on voltage stability with respect to uncompensated network. In the case of short circuit in the system; network without compensation recorded a voltage profile of 0.66pu while the compensated network recorded a voltage profile of 0.85pu. This translates to an improvement of 28.73% on voltage stability with respect to uncompensated network. In the case of three phase fault on the system, a voltage profile of 0.53pu is recorded for network without compensation and 0.65pu for compensated network, which is a 22.5% improvement on voltage stability with respect to uncompensated network.