MS student Nathan Brooks with advisor R. Pilawa-Podgurski

Figure 15: Schematic of ac-dc series-stacked buffer architecture

Single-phase ac-dc and dc-ac converters have fundamental power-processing limitations at twice the ac line frequency. The conventional solution for twice-line cycle energy storage utilizes a large dc link capacitor across the dc bus to buffer the instantaneous energy difference between the ac and dc side. This research involves employing high power density converters to actively buffer the twice-line energy across the dc bus. Higher overall buffer power density is achieved by switching at higher frequencies with GaN devices. The trade-off of active power decoupling compared to conventional passive methods is an overall higher power density of the system and lower voltage ripple on the dc bus.

Figure 16: Initial hardware prototype of the buffer converter

A series-stacked buffer architecture is proposed to supply the instantaneous twice-line current ripple required by the dc side of the ac-dc or dc-ac converter. A schematic is shown in Figure 15 for an ac-dc converter architecture. Figure 16 shows the initial hardware prototype of the buffer converter designed with the use of GaN switching devices. This research is supported by the Grainger Center for Electric Machinery and Electromechanics.