Research On Damping SSO Of Power System Using Facts Technology

With the further implementation of west-to-east power transmission project, building a strong state power grid with high voltage power grid as the backbone and the coordinating development at all levels, It requires the power system can transmit electric energy with large capacity and long distance, so series capacitor compensation and HVDC transmission system are widely used in power transmission system. Though it will bring huge economic benefits, but also threatens the safety operation of power system, and causes Subsynchronous Oscillation(SSO) bring a serious threat in rotor shaft of large turbo-generator and power system.SSO is part of instable oscillation in the system, and it is caused by a special kind of mechanical-electric coupling effect in power system.Severe mechanical-electric coupling effect may directly cause rotor shaft of large turbo-generator severely destroyed, cause a major accident, and endanger the safe operation of power system. Therefore research on damping SSO in power system has high practical value.This paper uses flexible and rapid adjustment ability of thyristor controlled series capacitor, static var compensator and other FACTS devices, is based on electromagnetic transient simulation software PSCAD/EMTDC and numerical calculation software MATLAB, researchs IEEE first benchmark model by test signal method and time domain simulation method, and selects the appropriate control strategy, in order to damp subsynchronous oscillation in power system.Basic frequency impedance characteristic and subsynchronous frequency impedance of thyristor controlled series capacitor are researched, and the optimal main circuit characteristic parameter-K of thyristor controlled series capacitor is proposed. The electrical damping characteristic, torsional vibration of turbine generator shafts and TCSC capacitor voltage are studied in different triggering angles by test signal method and time domain simulation method when thyristor controlled series capacitor working on capacitive vernier operation. Results of simulation show that thyristor controlled series capacitor can damp the SSO to some extent. It is concluded that subsynchronous frequency positive resistance can weaken and ease the SSO but can’t completely eliminate the SSO, and subsynchronous frequency reactance can damp the SSO in certain triggering angles when thyristor controlled series capacitor working on capacitive vernier operation.Static var compensator structure, Mathematical model, the basic principles of static var compensator damping SSO and control system model are studied, and Subsynchronous Damping Controller(SSDC)is designed according to mechanism of static var compensator damping SSO.Electrical damping characteristic analysis and time domain simulation analysis are studied based on IEEE first benchmark model when static var compensator is paralleled in generator bus bar, the booster transformer secondary side bus, the point of the transmission line and the end of the transmission line in respectively; Results of simulation show that different installation locations of static var compensator have an affect on damping SSO, even can bring about SSO.