POWER SWINGS DAMPING IMPROVEMENT BY UPFC AND SMES INTEGRATION BASED ON DIRECT LYAPUNOV METHOD CONTROL

A. Bidadfar, M. Abedi, and C.-C. Chu

Keywords

Direct Lyapunov method, power swings, UPFC, SMESNomenclatureδi, ωi i-th generator mechanical angle and velocityMi, Di i-th generator inertia and damping coefficientEqi i-th generator q-axis voltage behind transientreactancexdi, xqi i-th generator d- and q-axis synchronousreactances∗ Department of Electrical Engineering, Tafresh University,Tafresh, Iran; e-mail: B_ali59@yahoo.com∗∗ Department of Electrical Engineering, AmirKabir University,Tehran, Iran; e-mail: abedi@aut.ac.ir

Abstract

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 mag- netic 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. Considering the UPFC current injection model paves the way for controlling UPFC converters by Lyapunov direct method. 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 re- quire wide area measurements. Also, PSCAD/EMTDC simulation results for a typical multi-area system are presented which demon- strate besides power swing damping improvement, first swing is considerably decreased.

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