Power swings damping improvement by control of UPFC and SMES based on direct Lyapunov method application

A new comprehensive approach is presented to improve the power swings damping of power systems. While the approach integrates the unified power flow controller (UPFC) and superconducting magnetic energy storage (SMES), employs direct Lyapunov method concept to determine the control scheme based on nonlinear power system model. It is shown that in transient states, SMES cooperates with the UPFC converters in active power exchange. Energy exchanging capability of SMES will reduce distribution of power oscillations among power system generators. Steady state control method is so obtained that UPFC fulfils its normal task in SMES presence. Decentralizing method is used to locally control the UPFC_SMES independent of state variables of synchronous generators which require wide area measurements. Also, PSCAD/EMTDC simulation results for a typical multi-area system are presented which demonstrate besides power swing damping improvement, first swing is considerably decreased.