A multiple PWM GTO line-side converter for unity power factor and reduced harmonics

A multiple PWM GTO line-side converter with low switching frequency has been developed for industrial uses needing both higher capacity and higher performance. The multiple converter is composed of two GTO converter units connected in parallel through an interphase reactor. The switching frequency of the GTO thyristors in the multiple converter can be reduced to a quarter of that in the single converter. It is verified by simulations and experiments with a 2750-kVA GTO converter and inverter system with a 500-Hz switching frequency that the system has 1) a unity power factor, 2) reduced harmonics, 3) bidirectional power flow, and 4) speed regulatory performance equal to that of an advanced cycloconverter drive system. Analogies between inverter control and converter control are also studied for the development of the converter control.