Improvement of Power System Stability Using SFCL in Electric Power Grid under Voltage Unbalance conditions

This paper presents a novel approach to determine the power system stability using resistive superconducting fault current limiter (SFCL) of an electric power grid (EPG). In addition, the electric railway system has rapidly changing load characteristics in time. An unbalance is generated owing to the rapidly changing large single-phase loads. Subsequently, the unbalanced load causes an unbalanced transmission line. A voltage unbalance in the source influences the power equipment by causing a reduction in the power generation capacity of the generator and a decrease in the output of the other facil ities in the transmission line. In addition, many flexible ac transmission systems are applied to transmission lines to compensate for and control electric power. A voltage unbalance causes a control error in these systems. In addition, we analyzed the effects of the proposed method using transient simulations. The angular separation of the rotors of synchronous machines present in the power system is introduced. It is shown that the SFCL can have different impacts (positive and negative) in function of its location in the EPG when a fault occurs. To evaluate the effectiveness of the proposed method, the IEEE benchmarked four-machine two- area test system is used to carry out several case studies. The results show that the transient stability using SFCL combined with its optimal resistive value reduces the angular separation of the rotors that improves effectively the system stability during a fault. Index Terms—Damping performance, electric power grid, superconducting fault current limiter, transient stability .