Power flow control with controllable reactive series elements

The basic features of controllable reactive series elements (CRSE) (i.e. controllable series compensation (CSC) and static synchronous series compensators (SSSC)) for power system load flow control are presented. Mathematical models of CRSE, including a simplified transmission system model, have been developed. Based on this, the CRSE impact on a longitudinal transmission system was studied. The physical background of the basic differences between a CSC and an SSSC in terms of power flow control has been presented. According to theoretical considerations, from the point of view of power flow control capability, SSSC is superior to CSC, especially at low transmission angles. Therefore SSSC seems to be suitable in situations where power flow needs to be controlled in short lines or in light-load conditions.