Dynamic modelling of thyristor-based static switching circuits with application to power systems

This work details a systematic approach to the modelling of thyristor-based static switching circuits typical of power systems. Such circuits are difficult to analyze on two counts: (1) the order of the circuit changes with thyristor transitions and (2) the uncontrolled state dependent turn-off associated with thyristors. These difficulties are overcome by a convenient linearization. The linearization permits the synthesis of linear, time-invariant (LTI) state-space models of thyristor-based static switching circuits for small-signal dynamic analysis. LTI models are synthesized for three conventional thyristor-based static switching circuits which find application in power systems: namely the Thyristor Controlled Series Capacitor (TCSC), the High Voltage direct current (HVdc) converter, and the Static VAr Compensator (SVC). The developed LTI models are valid in the vicinity of the frequency at which the system is linearized. Such models are suited to the study of the system small-signal dynamics by computation of the eigenvalues in the vicinity of the system frequency and to controller synthesis by standard linear techniques.; Relevant applications to power systems analysis are presented, namely (1) the application of time-domain linearization to the computation of HVdc converter harmonics, (2) the prediction of resonance in a single-phase rectifier interacting with a power system and (3) linearized dynamic analysis of a TCSC compensated generator/transmission system by eigenvalue analysis.