Chaos and voltage collapse are qualitative behaviors in power systems that exist due to lack of reactive power in critical loading. These phenomena are deeply explored using both detailed and approximate models in this paper. The ANFIS-based CC-SVC with an additional PID-loop was proposed to control these problems and to improve transient response of the detailed model. The main function of the PID-loop was to increase the minimum voltage and to decrease the settling time at transient response. The ANFIS-based method was chosen because its computational complexity was more efficient than Mamdani fuzzy logic controller. Therefore the convergence of training processes was more rapidly achieved by the ANFIS-based method. The load voltage was held to the setting value by adjusting the SVC susceptance properly. From the experimental results, the PID-loop was an effective controller which achieved good simulation result for the reactive load, the minimum voltage increased and the settling time decreased at the values of j0.12pu, 0.9435pu and 7.01s, respectively.