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.