Control of a combined GTO/IGBT drive system for low torque ripple in a large permanent magnet synchronous motor

A control method is developed for a drive system, built of a parallel interconnection of a high-power GTO and a low-power fast-switching IGBT, feeding a large permanent magnet synchronous motor (PMSM) where torque ripple attenuation is a primary concern. The GTO is the main power supply and the IGBT is used for attenuating the current ripple due to the GTOs low switching frequency. The proposed controller combines a hierarchical, passivity-based dynamic feedback compensator, guaranteeing global exponential stability, as a well as a space vector PWM (SVM) strategy, that prevents stray, zero-sequence currents. The prevention of substantial stray currents between inverters is essential for the successful implementation of the proposed topology and is addressed by the combination of the master-slave compensator structure with the matching SVM strategy.