Subsynchronous Frequency Impedance Characteristic Of TCSC And Influences Upon Subsynchronous Resonance

The application of Flexible AC Transmission System (FACTS) is quite promising in power systems. It becomes one of the research emphases in recent years. The Thyristor Controlled Series Compensation (TCSC) is an important member of FACTS family. It possesses the superexcellent capability, enhancing the transmission faculty of lines and improving system stability, with simpler configuration, cheaper cost. Thereby, it is of great value to investigate the theory and operation of TCSC.Subsynchronous resonance (SSR) is a quite hazardous state easily encountered in power systems. If the numerical value line resonance frequency plus some shaft connatural frequency of generator is equal to operation frequency, it brings about coupling resonance between generator and system, which maybe results in shaft rupture of synchronous generators.With TCSC established as studying object, this dissertation prosecutes a detailed analysis and puts forward its impedance model from time domain and frequency domain, rectifying some expressions in nowaday research articles. It is firstly brought forward the concept of impropriety upon series- voltage-source model and develops comparatively abundant demonstration, providing some available conclusions and interpretations at the same time. Then the different behaviors between fixed series capacitor and TCSC are compared aiming at SSR, when they are individually applied to typical Model of IEEE Second Benchmark on Subsynchronous Resonance.Investigations start with the practical state subsection models. The basal wave impedance expression of TCSC is deduced and established in time domain. Afterwards, a frequency impedance method is proposed in this dissertation. Deeper analyses are carried through to gain impedance characters due to model established previously, so as to obtain K principle of L and C during design. The theory of Complex-moment-coefficient method is provided due to SSR, and the relationship between Complex-moment-coefficient D(m) and Subsynchronous frequency is alsoillustrated. Finally, the different behaviors between fixed series capacitor and TCSC are presented through simulation, and the results show TCSC's positive effect on SSR. In the end, this dissertation attempts to provide reasonable interpretation from the view of TCSC impedance mechanism.