Wang, Haoming | Search NASA

DOE OSTI2020

Thermal Design Consideration of Medium Voltage High Frequency Transformers

This paper describes a thermal design using epoxy potting for high frequency transformer (HFT) for medium voltage high power electronic applications, namely emerging solid-state transformers. To address HFT’s thermal stress problem, thermal performance of the HFT with air and epoxy potting cooling method are both simulated by magnetothermal-fluid coupling method (MTFCM). The effectiveness of the simulation analysis is verified in a 100 kW DC-DC resonant converter. Influencing factors including distance between the high frequency transformer and the metal enclosure, epoxy thermal conductivity and heat sink placements are simulated and analyzed. Finally, an optimal cooling structure is proposed for future high power HFTs.

Wang, Haoming↗

DOE OSTI2020

A Single-Stage Isolated Resonant SiC DC/AC Inverter for Efficient High-Power Applications

This paper presents a single-stage series-resonant dual active half bridge (SR-DAHB) inverter suitable for high power applications. The topology is an isolated dual half-bridge circuit with an unfolding bridge. A combined phase-shift and frequency modulation technique is utilized to generate AC power output. In high-power applications where the switching devices operate at relatively high current and voltage, the switching loss becomes the major portion of the converter’s total loss as the devices are turned on and off under hard switching condition. The primary merit of the proposed single-stage SR-DAHB inverter with the combined phase-shift and frequency modulation control is to significantly reduce the switching loss so that it is not a function of load current. A precise and comprehensive power loss model is developed for both the SR-DAHB and DAHB to optimize the operation of the inverters. The objective of the optimization is to minimize the inverter total loss while calculating the optimum combination of frequency and phase shift. A 1.5 kV, 50 kW prototype was built to demonstrate the performance of the SRDAHB versus DAHB inverters with the combined phase-shift and frequency modulation control, and validate the theoretical analysis.

Tayebi, S. Milad↗