Overview
State-of-the-art DC fast chargers are large, heavy and relatively inefficient. They are typically designed to connect to three-phase 208V or 480V and are supplied by a dedicated service transformer. The installation cost of such systems can be as high as $50,000.
The Principal Investigator for this project is Dr. Srdjan Lukic.
Method
FREEDM researchers designed and built a 50 kW prototype EV charger using commercially available silicon carbide modules. This new design eliminates the bulky service transformer by connecting directly to medium voltage. This feature provides 30x reduction in total system volume, 15x reduction in total system weight and 50% reduction in both the system losses and the system cost when compared to traditional DC fast chargers.
Results
Powered directly from a 2.4 kV AC line, the developed medium-voltage EV charger achieves 97.6% efficiency, 1 kW/L power density and less than 4% total harmonic distortion of the input current at full load. The modular design allows for simple scaling to higher grid voltages and higher power levels by adding more modules. The underlying SST-based technology can serve many other applications, such as industrial DC loads, DC data centers and naval shipboard applications. This project was funded by PowerAmerica.
References
- S. Srdic, C. Zhang, X. Liang, W. Yu and S. Lukic, “A SiC-based power converter module for medium-voltage fast charger for plug-in electric vehicles,” 2016 IEEE Applied Power Electronics Conference and Exposition (APEC), Long Beach, CA, 2016, pp. 2714-2719.
- S. Srdic, X. Liang, C. Zhang, W. Yu and S. Lukic, “A SiC-based high-performance medium-voltage fast charger for plug-in electric vehicles,” 2016 IEEE Energy Conversion Congress and Exposition (ECCE), Milwaukee, WI, 2016, pp. 1-6.
- X. Liang, C. Zhang, S. Srdic and S. Lukic, “Predictive Control of a Series-Interleaved Multi-Cell Three-Level Boost Power Factor Correction Converter,” in IEEE Transactions on Power Electronics, Early Access.
- J. Won, G. Jalali, X. Liang, C. Zhang, S. Srdic and S. Lukic, “Auxiliary power supply for medium-voltage power electronics systems,” 2018 IEEE Applied Power Electronics Conference and Exposition (APEC), San Antonio, TX, 2018, pp. 173-179.
Intellectual Property
- Srdjan Lukic, Xinyu Liang, Chi Zhang, and Srdjan Srdic “Modular Medium Voltage Fast Chargers,” PCT Application (May 2018).
- Jehyuk Won, Srdjan Srdic, Xinyu Liang, and Srdjan Lukic “Cascaded Modular Multilevel Converter for Medium Voltage Power Electronics Systems,” Provisional Patent (February 2018).
What is protected?
- Control approach
- Modulation strategy to reduce power losses
- Protection system for medium-voltage power electronics
- High-isolation low-coupling-capacitance pulse transformer
- High step-down ratio converter topology
