Transmission line dynamic impedance compensation system

Abstract

A series impedance compensation system for a set of transmission lines which are used for electrical power transmission, with these parallel lines being protected from the transient faults and dynamic subsynchronous oscillation problems. These problems can become aggravated by the introduction of capacitor banks which thus serve as only a partial solution to the disturbances of transient faults during conventional recovery modes of operation. The impedance compensation system is coupled in series to each transmission line to dynamically balance the inductor impedance on the transmission line, responsive to demand, by injecting a voltage component determined to be optimized substantially at quadrature leading or lagging phase angles (.+-.90.degree.) with respect to the transmission line voltage and current components. The impedance compensation system includes a circuit based solid-state switching power converter with self-commutating thyristor or GTO semiconductor switches connected in a parallel shunting arrangement with reverse poled or freewheeling diodes. This is done in order to provide either an absorptive component or a generated component of output pole voltage carrying a 90.degree. segment of the output current in each cycle, as this provides dynamic stability without fostering subsynchronous resonance.

Dependencies are inferred from the claim text.