A discrete-time model of thyristor controlled series compensators

The current trend in power systems is to use power electronic devices to enhance both system stability and power transfer limits. A recent point of interest is the use of thyristor control devices in series compensation of AC transmission lines. In this paper a linearized, discrete-time model of a thyristor controlled series compensated line is presented. The samples for these discrete models are obtained at the peaks of the capacitor voltage of the series compensator. Since these peaks are broad rather than sharp spikes they are quite good indicators of variations in the fundamental component. During transients this will result in variation from uniform sampling. However, the system degenerates to a uniform sampled system in the steady state and thus all the standard tools for the analysis of the standard discrete-time model can be applied. The model developed is validated through digital computer simulation studies.