The Mechanism Research on Dual Impedance Solutions of TCSC

TCSC dual solution phenomenon is demonstrated by both digital simulation and dynamic experiment. Phasor diagram analysis of TCSC shows that even though quality factor remaining constant, the phase difference between capacitor voltage and line current decreases with the increasing of thyristor conduction current, which incurs the decrease of reactor current´s amplitude and width. Further, the thyristor conduction block is pointed out to be the mechanism of TCSC dual solution phenomenon. Reactor branch current and equivalent quality factor determine the degree of block. Both amplitude and width of the current are blocked when thyristor triggering synchronized by line current. Only amplitude is blocked synchronized by capacitor voltage. This explains why impedance dual solution phenomenon is easy to occur in the mode of line current synchronization.