Yashar Hashemi - Sahand University of Technology
Rasool Kazemzadeh - Sahand University of Technology
Mohammad Reza Azizian - Sahand University of Technology
Ahmad Sadeghi - Sahand University of Technology

This paper describes a new UPFC controller design for damping power system oscillations focusing on inter-area modes. Proposed controller for power oscillation damping is a two-level controller that first level of control is derived from local signals and the second level of control is supplied from global signals as additional measuring information from suitable remote network locations, where oscillations are well observable. In order to damping local modes, the conventional PSS (CPSS) is used that choice of CPSSs location is based on modal analysis. Since uncoordinated proposed controller for UPFC and CPSSs may cause unwanted interactions, it is necessary to simultaneous coordinated tune the controller parameters. The problem of coordinated design is formulated as an optimization problem and particle swarm optimization (PSO) algorithm is employed to search for optimal parameters of controllers. A time delay introduced by remote signal transmission and processing in wide-area damping controller (WADC) may be harmful to system stability and may degrade system robustness. The investigation of delay-dependent stability of power system equipped with a WADC is carried out using lyapunov theory and model reduction technique. The effectiveness and robustness of the designed controllers are tested on a typical four-machine two-area benchmark power system.

Wide area damping controller (WADC), Unified power flow controller (UPFC), Power oscillation damping (POD), Two-level UPFC damping controller