Isolated, Bi-Directional DC-DC Converter for Fuel Cell Electric Vehicle Applications

• Main Authors: Jang, Yungtaek, Jovanovic, Milan M., Kumar, Misha, Ruiz, Juan M., Lu, Robert, Wei, Tony
• Format: Conference Proceeding
• Language: English
• Subjects: auxiliary power module; Batteries; bidirectional power conversion; Control systems; dc-dc converter; Delays; electric vehicle; Frequency control; LC series resonant converter; Resonant frequency; Switching frequency; Voltage control; zero voltage switching
• ISSN: 2470-6647
• DOI: 10.1109/APEC.2019.8722067

An isolated bi-directional dc-dc converter that exchanges energy between the high-voltage battery (330 V±30%) and low-voltage battery (12 V±30%) of fuel cell electric vehicle is introduced. To achieve optimal performance in both directions, a full-bridge (FB) series resonant converter (SRC) is employed because of its symmetrical input-to-output characteristic and soft-switching operation. In addition, a novel secondary-switch delay and/or lead time control method is incorporated with conventional frequency control to make the converter operate in a wide voltage range in both directions and achieve zero-voltage switching (ZVS) over the entire load range. Moreover, a frequency fold-back is automatically achieved by the lead time control, which makes it possible to regulate the output at light load without employing a conventional burst-mode control. The performance of the proposed control method was evaluated on a 1-kW prototype operating between the 240-450-V high-voltage battery and the 9.5-15.5-V low-voltage battery. To increase the power density of the converter, the prototype is implemented by using planar magnetics, as well as GaN switches operating above 300 kHz switching frequency. The prototype circuit exhibits the maximum efficiency of 96.1%.