Co-ordinated Design of PSS and TCSC Damping Controllers in Multi-machine Power System using PSO

Abstract

Transmission networks of modern power systems are becoming increasingly stressed because of growing demand and restrictions on building new lines. One of the consequences of such a stressed system is the threat of losing stability following a disturbance. Transient stability improvement is essential for maintaining system security that is the incidence of a fault should not lead to tripping of generating unit due to loss of synchronism. Flexible ac transmission system (FACTS) devices are found to be every effective in stressing a transmission network for better utilization of its existing facilities without sacrificing the desired stability margin. Amongst the available FACTS devices for transient stability enhancement, the TCSC is the most versatile one and it is a series FACTS device which allows continuous changes of the transmission line impedance. It has great application and potential in accurately regulating the power flow on a transmission line, damping inter-area power oscillations and improving the transient stability. Power System Stabilizer (PSS) which detects changes in the generator output power and by controlling the excitation value it reduces the power swings in the system. This Report presents coordinated control tuning of PSS with TCSC. The design of proposed coordinated damping controller is formulated as an optimization problem and the controller gains are optimized instantaneously using particle swarm optimization (PSO). Here single machine infinite bus system and the multi-machine power system employed with PSS and TCSC is considered. The coordinated tuning among the damping controllers is performed on the non-linear power system dynamic model. Finally, the proposed coordinated controller performance is discussed with time domain simulations. Different loading conditions are employed on the test system to test the robustness of proposed coordinate controller and the simulation results are compared with four different control schemes.