Transient stability enhancement of steam turbine-based power plant by using improved bridge fault current limiter

This paper presents a new bridge Fault Current Limiter (FCL) used for the improvement of the transient stability of steam turbine-based power plants. The proposed FCL is operated by an innovative, accurate adaptive control algorithm with low computational complexity. This algorithm limits the fault currents to the desired values defined by the system's operator. Additional important advantages of the proposed FCL compared to recently published bridge-type FCLs are the prevention of power losses and harmonic distortion during normal operation and the need for only one current sensor for proper operation. The proposed FCL is compared with a Series Dynamic Breaking Resistor (SDBR) and a conventional bridge FCL with a bypassed resistor. This comparison was conducted by using a power system comprised of a 600MVA steam turbine-driven synchronous generator, a 600MVA step-up transformer, a 200 kW/10kVAR load, and the electric grid. The simulation results show that during the fault operation period the proposed FCL provided the best transient stability of the generator's stator currents and voltages, the active and reactive powers, and the torque. The FCL operation was also validated with an experimental setup for different values of limit currents and duty cycles.