Damping of power system oscillations by using unified Power Flow Controller with POD and PID controllers

The swift evolution on the area of power electronics has empowered the development of new equipment to be able to benefit more conveniently from the power systems. Power electronic equipment developed under the name of Flexible Alternating Current Transmission Systems (FACTS) is very much popular in last few years. Unified Power Flow Controller (UPFC) is the most popular and widely used FACTS device to control the power flow and to enhance the power system stability in the transmission line. This paper presents the model of a Unified Power Flow Controller which is controlled externally by a newly designed power system controller for the improvements of power system stability and damping effect of an on line power system with occurrence of fault. The proposed controller consist of Power oscillation damping controller and Proportional Integral Differential controller (POD & PID). The PID controller parameter has been optimized by Ziegler-Nichols tuning method. The simulation model is tested for both single-line to ground and three phase faults. A power system network is designed and simulated by using phasor simulated method and the network is examined in three steps; without UPFC, with UPFC but not externally controlled, power system with new proposed controller. The simulation result shows that without UPFC, the system parameters become unstable during faults. When UPFC is connected in the system, then system parameters become stable. Again, when the UPFC is externally controlled by the proposed controller, the power system parameters (P, Q, and V) become stable very rapidly. It has been observed that UPFC rating is only 15 MVA with controller and 100 MVA without controllers. So, UPFC is very effective to enhance the power system stability as well as to damp the power system oscillation.