UPFC USING MULTICONVERTER OPERATED BY PHASE-SHIFTED TRIANGLE CARRIER SPWM STRATEGY

The acronym UPFC covers Ggugyi's unified power flow controller and Aka gi and Fujita's unified power flow conditioner. This paper describes o ne method of meeting high megavoltampere specifications by using multi ple modules of two-level three-phase converter modules controlled by t he phase-shifted triangle carrier technique of the sinusoidal pulsewid th modulation (SPWM) strategy. Two conceptual designs are presented. T he first is the gate-turn-off (GTO)-SPWM-UPFC at the lowest switching rate, f(c)/f(m) = 3, to minimize GTO switching loss. The design is bas ed on applying the fundamentals of SPWM theory to overcome unbalances arising from sideband harmonic interferences. The second is the insula ted gate bipolar transistor (IGBT)-SPWM-UPFC, at f(c)/f(m) = 12 or hig her, which SPWM theory assures that direct paralleling of the modules is free of current unbalance. A laboratory UPFC based on six modules o f three-phase 5-kVA size IGBT converters operating at the baseline con dition of dual unity displacement factor at the sending end and the re ceiving end has been implemented.