Power systems are the core heartbeat of any advanced vehicle. Reliability and flexibility of these systems are of the highest priority. This innovation is a highly efficient and modular isolated bidirectional DC converter for battery energy applications that has been translated into high-priority NASA power system applications, demonstrating transferability, robustness, and scalability.

This bidirectional DC converter offers extremely high power density and utilizes a novel hybrid resonance and PWM (pulse width modulation) technique. It also offers flexibility for many power system topologies, including distributing large single cells throughout the vehicle, and using smaller cells in a centralized location, or a combination of banked smaller cells distributed throughout the system. This is accomplished through independent charging and discharging control of state-of-charge and state-of-health for each battery module, inherent active maximum current limit and short-circuit protection, and ease of module balancing.

In the charging operation, the bidirectional DC converter is used to transfer renewable energy to the battery and/or supercapacitors when the DC bus voltage is high, while delivering energy to the load when the DC bus voltage is low. In the discharging operation, the converter manages energy and power flow between the DC bus and the battery, which allows the use of low-voltage batteries with high-voltage invertermotor drive. Bidirectional power flow enables the efficient energy capture of regenerative braking and reliable energy release during startup, accelerating, and other momentarily heightened points of power consumption.

Using this architecture, the power system is distributed through the application with knowledge and control of each individual battery of cells. This allows dynamic addition and removal of battery modules, storage balance across the system, dynamic digital control of available power into or out of the combined system-wide total cell storage, and reduction of overall system monitoring otherwise required.

Highly efficient, modular DC converters are coveted throughout numerous applications due to the increased flexibility and reliability they offer to the power system. In terms of flexibility, the modular DC converters offer the ability to design a centralized or decentralized power system topology. This is relevant within electric propulsion systems of vehicles, but is also applicable to power delivery systems within the wider categories of human spaceflight, space exploration, and earth science missions. Many redundant power systems can be avoided through the self-healing (rerouting) nature of battery strings incorporating these modular DC converters.

This work was done by Chad Eckhardt, Hongmei Wan, and Stephen Watts of GridBridge, Inc. for Glenn Research Center. NASA invites and encourages companies to inquire about partnering opportunities. Contact NASA Glenn Research Center’s Technology Transfer Program at This email address is being protected from spambots. You need JavaScript enabled to view it. or visit us on the Web at https://technology.grc.nasa.gov/. Please reference LEW-19275-1.