Minimum harmonics PWM control for a self-commutated SVC

To maintain voltage stability in electric power systems, self-commutated static VAr compensators (self-commutated SVCs) employing high power gate turn-off thyristors (GTOs) have been developed. This paper presents a lower harmonic two-pulse PWM control technique which can decrease the harmonics in output voltage by selecting switching angles. Because of the lower GTO switching frequency, high efficiency power converters can be obtained. The decreased harmonics by the proposed PWM control were confirmed by numerical analysis and experiments using small-scale equipment. The technique has been applied to a 50 MVA self-commutated SVC which has been installed in the Shinshinano substation of Tokyo Electric Power Company, and field testing of this equipment is now in progress.<>