Highly Efficient 15kW CLLC Resonant Converter System for Military Vehicles, Built Using Wide Bandgap-Based Power Electronics

We propose to advance the wide bandgap (WBG) semiconductor-based DC-DC bidirectional power conversion technology one step closer to its commercialization through making it a highly efficient, power dense, electromagnetic interference (EMI) compliant, fault tolerant, and cost-effective solution. Our Phase I project ended up with successful development and functionality verification of a Silicon Carbide (SiC) / Gallium Nitride (GaN) hybrid solution-based 2kW 600V-28V (nominal) DC-DC CLLC resonant converter with bidirectional power flow capability and 96.4% peak efficiency at full load, and >93% efficiency at light loads in either power flow direction. The Phase II effort will make this solution scalable up to 15kW, while improving the peak conversion efficiency to 97% through multi-variable switching modulation optimization, soft-switching under wide voltage gain operation, optimized design of magnetics, high-performance time-optimal control methodologies, and superior thermal stability. Specific emphasis will be provided on thermal management system design optimization, high-density packaging considerations, uniformization of the efficiency profiles in 600V-28V and 28V-600V conversion modes, and high-frequency switching enabled power density enhancement for ARINC 600 6MCU compliance. Power electronics miniaturization will further be brought in by fabricating the in-house CoolCAD SiC transistors tailored towards loss minimization demands. The converter optimization will be achieved iteratively using measurements and novel control algorithms, and through parasitic minimized PCB-integrated planar transformers.   The technical objectives of the Phase II project are as follows:   (a) A lightweight power conversion with enhanced power density: With the aid of (a) high-frequency planar transformers with controllable leakage inductance, and (b) low heat flux of power dissipation per power device, the magnetics and thermal management systems will be reduced in size by a considerable margin, leading to a projected weight and volume of 12.8 kg and 11.36L, and hence a gravimetric and specific power densities of 1.17kW/kg and 1.32kW/L, respectively. (b) Bidirectional power flow management with output voltage regulation: We will implement bidirectional power flow control and management strategies with circulating reactive power minimization and hence maximum efficiency tracking for the CLLC converter system.  (c) Peak efficiency and light-load efficiency improvement through hybrid duty/frequency modulation: The converter is projected to exhibit a peak efficiency of 98% (at 70% rated load), rated load efficiency of 97.3% and a light load (10% rated) efficiency of 93.4%, with ~0.5% improvement compared to Phase I results. The efficiency enhancement will be accomplished by multi-variable modulation enabled RMS current minimization, synchronous rectification, and hence near-zero turn-off losses on the load-side full-bridge, and wide-range zero voltage switching (ZVS).