Development of a control system for a high-performance self-commutated AC/DC converter

A self-commutated AC/DC converter composed of controlled turn-off devices to be applied to future system interconnection is described. The advantages of a control system for this type of converter are: (1) commutation does not fail when the system voltage is decreased or distorted by a power system fault; (2) it needs no equipment for reactive power supply, such as static capacitors or synchronous rotating condensers, when used in a low short-circuit capacity power system; and (3) it can independently control active power through DC lines and reactive power from each terminal. The proposed back-to-back (BTB) control system using the voltage margin method was verified with a simulator, and the results demonstrated the excellent features of the high-performance self-commutated converter.