On the effect of TCSC and TCSC-controller gain on bifurcations of subsynchronous resonance in power systems

The effect of thyristor-controlled series capacitor (TCSC) and its controller gain on bifurcations of subsynchronous resonance (SSR) in power system are studied. Single machine infinite bus (SMIB) power system is considered for the numerical investigations. The series compensation of the transmission line is done by either conventional variable series capacitor or TCSC. The effect of the dynamics of the damper windings is investigated. The results show that in all cases, the operating point of the system loses stability via Hopf bifurcation. Hopf bifurcation comes either in subcritical or supercritical type. Supercritical Hopf bifurcation is depicted when the dynamics of the damper windings are neglected and the line is compensated by conventional series capacitor. With the same compensation scheme i.e., conventional series capacitor, supercritical Hopf bifurcation is addressed when the dynamics of the damper windings are included. On the other hand, subcritical Hopf bifurcation is predicted when the compensation is carried out by TCSC for both cases of including and neglecting the dynamics of the damper windings. In case of supercritical Hopf bifurcation, the system routes to chaos via torus breakdown. Additionally, it is found that when the compensation is done by TCSC, the stable operating point region is enlarged. Moreover, the stable operating point region increases when the damper windings are neglected. The effect of the TCSC controller gain on the locations of the Hopf bifurcation has also been studied.