Large capacity high performance 3-level GTO inverter system for steel main rolling mill drives

This paper proposes a high performance 10 MVA 3-level GTO inverter system for steel main rolling mill drives, which consists of a three-level power converter, a three-level inverter and two series-connected DC-link capacitors with a neutral point. To realize this system, newly developed 6-inch 6 kV-6 kA GTOs have been applied first in the world. A novel regenerative snubber circuit topology is proposed to maximize power conversion efficiency of the system and to guarantee maximum turn-off current capability of 6 kA of GTOs implemented in the main circuit. By applying high power factor control of the power converter and high performance vector control of a synchronous motor, a high performance GTO inverter system has been realized. Experimental results using a 6000 kW synchronous motor demonstrate the availability of this inverter system for steel main rolling mill drives.