SPEAKER: Shivang, Electrical and Computer Engineering Department, UIUC
TITLE: "Switched Brushless Doubly-Fed Reluctance Machines for Wide-Speed Range Applications"
Turboelectric propulsion systems are considered as a critical enabler to reach low-carbon emission in the aircraft industry. Unlike hybrid-electric and all-electric systems, these systems do not use batteries for propulsive energy during any phase of flight. Since batteries with high power capacity and specific power required for commercial aircraft are unlikely to be developed within the next decade, turboelectric systems constitute the only feasible and practical option at this point of time. Several motors are available for driving the distributed propeller fans and, among these, brushless, doubly-fed reluctance machines (BDFRM) are seen as appropriate, primarily because of their use of partially rated power converters, brushless operations and low rotor losses. A conventional BDFRM drive architecture is capable to operate within a limited speed range similar to wind turbines, with the specified partially rated power electronics interface. This presentation discusses the switched drive architecture with a reconfigured stator excitation on-the-fly to allow a wide-speed range operation required for applications such as aircraft propulsion systems, with benefits of fractionally rated power electronics kept fully intact.
SPEAKER: Margaret Blackwell, Electrical and Computer Engineering Department, UIUC
TITLE: "Dynamic Level Selection for Full Range ZVS in Flying Capacitor Multi-Level Converters"
This talk presents a control technique for flying capacitor multi-level (FCML) converters to achieve zero-voltage switching (ZVS) across the full range of duty cycles for applications to high power density and high efficiency power converters. Earlier work made use of variable frequency control to enable ZVS at specific duty cycles in FCML converters, but without the ability to allow ZVS across the full range. The proposed technique uses dynamic level selection and variable frequency control to increase inductor current ripple at duty cycle ranges under which ZVS was previously unattainable. An experimental 5-level FCML prototype has been built using GaN devices on a single-sided PCB to incorporate this control technique. We demonstrate both 4 – and 5 – level operations with ZVS at duty cycles that are not possible with 5 – level operations alone, as well as a dynamic level transition with active capacitor voltage balancing.