Line-current control with a series thyristor-controlled reactance based on a superconducting coil for electric-energy systems

Abstract

This paper describes the experimentes carried out with a serires controlled reactance to be used for line-current control in an electric-power transmission line. The controlled reactance has been built with a superconducting coil that can be short-circuited by two inverse parallel thyristors. It is shown that, if the thyristors are fired at a variable angle every cycle, the effective series impedance of the device can be varied continuosly as a function of the firing angle. A single-phase prototype has been built for closed-loop current control in an a.c. circuit. Conventional thyristors and firing circuits have been used for the prototype and no weitching-off control is necessary. The same technology is frequently used in electric energy systems. The controller has been fully implemented using a digital signal processor (DSP) and a commercial real-time interface. This gives good flexibility to the controller design and test. The paper investigates experimental results for the steady state and the transient performance of the prototype.

This paper describes the experimentes carried out with a serires controlled reactance to be used for line-current control in an electric-power transmission line. The controlled reactance has been built with a superconducting coil that can be short-circuited by two inverse parallel thyristors. It is shown that, if the thyristors are fired at a variable angle every cycle, the effective series impedance of the device can be varied continuosly as a function of the firing angle. A single-phase prototype has been built for closed-loop current control in an a.c. circuit. Conventional thyristors and firing circuits have been used for the prototype and no weitching-off control is necessary. The same technology is frequently used in electric energy systems. The controller has been fully implemented using a digital signal processor (DSP) and a commercial real-time interface. This gives good flexibility to the controller design and test. The paper investigates experimental results for the steady state and the transient performance of the prototype.