COORDINATED DAMPING CONTROL DESIGN WITH STATCOM & PSS

Abstract

Modern power systems are characterized by extensive interconnections of different grids and more dependence on control for maximum utilization of available energy. The disturbance at one part of the system affects other parts due to interconnection. Maintenance of stability becomes a necessary part in modem power system. Under this stressed condition, low-frequency oscillation modes have been observed when power systems are interconnected by weak tie lines. Basically these low frequency oscillations are categorized as local mode and interarea mode of oscillations. In the early days, excitation control is used as one of the remedy for stabilization of these low frequency oscillations. Later, Power System Stabilizer (PSS) were developed which provides additional damping to these low frequency oscillations. But PSS is effective for local mode of oscillations. Now in the last one and half decades, Flexible AC Transmission System (FACTS) devoices are used for improvement of system damping towards interarea mode oscillations Robust optimum coordinated design of power system stabilizers (PSSs) and STATCOM damping controller (SDC) for power system stability enhancement is thoroughly investigated in this work. The design problem is considered as an optimization problem where different evolutionary techniques like GA, Biogeography based optimization(BBO) and Binary coded Biogeography Based optimization(BCBBO) are used for the simultaneous tuning of five parameters of each PSS and SDC installed in the multi machine system. An Eigen value-based objective function incorporating multi operating conditions on electromechanical modes is considered. The effectiveness of the proposed PSS is tested for 10-machine, 39-bus New England Power System under different loading conditions and disturbances. The eigenvalue analysis and the nonlinear simulation results show the effectiveness of the proposed damping controller to damp out the local as well as the interarea modes and enhance greatly the system stability over a wide range of loading conditions and system configurations. Also the convergence of the proposed optimization technique (BCBBO) is compared with GA and BBO.