Embedded SSSC in series capacitor compensation and in voltage source converter station

This thesis shows that series capacitive compensation of transmission lines by a combination of Static Synchronous Series Compensator (SSSC) and dielectric capacitors lowers the cost of series compensation. The SSSC has two functions: (1) to provide some series capacitive reactance compensation; (2) to damp out incipient unstable Subsynchronous Resonance (SSR) modes. Digital simulation using HYPERSIM shows that for an overall capacitive depth of compensation of 0.7 pu, the SSSC component is only about 1/3 of the capacitive Mvar. Based on the transient stability limit, the transmissibility of the line is increased by a factor of 2.23 for a depth of compensation of 0.7.; A second objective of this thesis is to extend the application of the SSSC concept. This application is found in HVDC, where there is no synchronizing power. In the family of Voltage-Source Converter (VSC) HVDC, it is possible to embed the control of the SSSC in the converter station so that there is enhanced synchronizing power. The effectiveness of the synchronizing power (together with damping power) is demonstrated through digital simulations of a turbine-generator system which is connected to a VSC-HVDC Station.; The thesis shows that the SSSC has two modes of operation: (1) the constant reactance mode, in which the SSSC voltage is proportional to the line current, and (2) the constant quadrature voltage mode, in which the SSSC voltage is a constant quadrature voltage independent of the line current. A comparison between the two modes shows that the constant reactance mode provides higher synchronizing power and has a higher transient stability limit.; Eigenvalue analysis and digital simulations are the methodologies used.