Innovation IGCT main drives

The paper introduces the new IGCT drives which feature three-level NPC full regenerative power converters-the initial 3300 V product is rated up to 10 MVA. The drives utilize IGCT devices-new hard driven GTOs achieving unprecedented switching performance and effective PWM carrier frequencies up to 1 kHz. The converters use diodes formulated for soft recovery and efficient clamp snubbers to allow commutation of up to 4000 A. Under development is a 6600 V drive employing series connected IGCT elements to achieve up to a 20 MVA rating. These high performance drives, targeted at heavy-duty rolling mill applications, employ a DSP based three-level space vector modulation algorithm with active charge balance neutral point control. The drive system includes a high bandwidth feed forward synchronous motor control algorithm achieving unprecedented torque performance at these power levels. The PWM load converter is capable of achieving output frequencies up to 75 Hz. A mill resonance compensation algorithm has been developed to take advantage of the available torque response for mill stand control. The IGCT PWM source converter technology eliminates the need for the expensive VAr compensation and harmonic filtering required by cycloconverter main drives. The source converter controls feature synchronous reference frame current regulators that maintain a nominal unity power factor grid interface. The controls offer the opportunity to fix mill power quality issues by adding features such as VAr compensation, harmonic optimization, active damping of grid resonances, and flicker control.