Study On The Control Strategy Of Dynamic Stabilizer For Subsynchronous Resonance Mitigation

As the long-distance and large-capacity transmission is more popular inmodern power system, series compensated equipment is often used to keepsystem stability and utilize finite resource more economically and efficiently.However, torsional interaction between the series compensated transmissionnetwork and the turbine-generator shaft system may lead to subsynchronousresonance (SSR) problems, which should be well understood and taken intoaccount when series compensation is designed. SSR conditions may limit thedegree of compensation needed for better performance of the power system.The use of dynamic stabilizer may alleviate such restriction. Presently,dynamic stabilizer is in its stage of research and development in demosticJinjie plant project. The improved dynamic phasor model, control strategy andthe optimum design methods are focused in the thesis. The main work is asfollows:(1) The improved dynamic phasor model of dynamic stabilizer isproposed with dynamic phasor method. The improved model is more accuratefor subsynchronous resonance study because the dead-zone characteristic ofthyristors is considered.(2)The independent modal control strategy of dynamic stabilizer isdesigned. It can mitigate multi-mode SSR simultaneously and has strong anti-disturbance ability to the velocity measurement noise. Moreover, itsphase compensation and gain can be calculated individually.(3)The optimal design method of dynamic stabilizer based onPSCAD/EMTDC simulation method is proposed. Dynamic stabilizer of theelectromagnetic transient simulation model in the power electronic circuit isadopted to avoid the difficulties in modeling dynamic stabilizer. In addition, apractical optimal design method of independent modal control strategies isdeveloped utilizing the multi-run component in PSCAD/EMTDC. During thesimulation and optimization, just the computer is involved whithout manualintervention.(4)The SSR problems in JinJie power plant series compensatedtransmission system are studied. The independent modal controller whichadaptes to a variety of operation modes is designed and its effectivenesseshave been proved by the time-domain simulation results. Finally, thesensitivity of the generator parameters, line parameters, and system equivalentparameters are examined by eigenvalue analysis methods.The achievements of this thesis have academic value and certain actualengineering significance on mitigating SSR in series compensatedtransmission project in our country.