Power engineers are currently facing challenges to increase the power transfer capabilities of existing transmission system. Flexible AC Transmission system (FACTS) controllers can balance the power flow and thereby use the existing power system network most efficiently. Because of their fast response, FACTS controllers can also improve the stability of an electrical power system by helping critically disturbed generators to give away the excess energy gained through the acceleration during fault. Thyristor controlled series compensator (TCSC) is an important device in FACTS family, and is widely recognized as an effective and economical means to solve the power system stability problem. TCSC is used as series compensator in transmission system. In the present work a TCSC controller is designed and tested over a single machine infinite bus (SMIB) as well as a multi-machine power system. Detailed simulation studies are carried out with MATLAB/SIMULINK environment and the effect of the TCSC parameter variations over the system stability is studied.
Stator Flux Orientation Control Scheme (SFOCS) has limitations that its performance is mainly influenced by the tuning of parameters, the Proportional-Integral (PI) controller could not compensate system variations very efficiently. To overcome the drawbacks of PI controller the Fuzzy Logic Controllers (FLCs) are modelled. This paper presents the fuzzy logic based control strategy for the variable speed wind turbine generator by using Doubly Fed Induction Generator (DFIG). The mathematical model for DFIG is developed in synchronous reference frame by using SFOCS for current and voltage control and is discretized in time domain. Based on this model the artificial intelligence based FLCs are designed and implemented so as to improve the performance and efficiency of the system. This control scheme not only enhances the dynamic performance but also maintains almost unity power factor to the grid. In order to explore the robustness of the FLC and conventional PI controller, simulations are carried out for rapid variation of wind speed, and different disturbances generated in the system. The simulation results show that the proposed fuzzy logic based control strategies have better power control, faster oscillation damping, more accurate regulation, considerably reduced settling time and has fewer ripples in comparison with conventional PI controller. In the proposed SFOCS, the PI controllers are replaced with FLCs, to improve the performance and efficiency of the system. The system performance is analyzed for real and reactive power control in SFOCS for the effectiveness of synchronization with the grid.