Ultra-Small DC-Link Capacitor, GaN-Based Low Power AC Motor Drive for Low Cost Applications

In some motor drive applications, such as fans and pumps, high performance, in general, is not required and regeneration is not needed. These application areas are sensitive to price and therefore reduction of weight and volume is very beneficial. The size and cost of passive components have become one of main concerns in terms of cost, volume, and weight. In the past, researchers tried to reduce the number of semi-conductors switches since the cost of semi-conductor switches was more significant than that of passive components. However, in these days, reducing passive components such as inductors, transformers, and electrolytic capacitors is much more significant than to reduce active elements in terms of size and cost effectiveness. In addition, the lifespan of electrolytic capacitors is typically shorter than the other components in the drive systems. Reducing the dc bus capacitance offers the improved input current THD, resulting in reduced input filter requirements. The benefits of ultra-small dc link drives are summarized as below: a) Improvement of input current THD due to absence of huge capacitance b) Cheaper, smaller, and lighter due to reduction of passive components c) Higher reliability, if electrolytic capacitors are replaced with film capacitors. This thesis presents the design of an ultra-small DC link capacitor motor drive by utilizing wide band gap (WBG) based power electronics. It examines the benefits of eliminating the dc-choke in a motor drive and reducing the size of the dc-link capacitor while designing the motor drive using Gallium Nitride (GaN) power transistors. Real-time simulation is performed to verify the performance of the developed drive and the analysis. The system performance is further validated with experimental results using a hardware prototype of the motor drive built with GaN-based transistors.