Power conversion is the process of converting electrical energy from one form to another, such as converting from alternating current (AC) to direct current (DC) to adapt to the needs of an electronic device. Power converters are used in a wide variety of applications, including commercial power supplies, industrial motors, electric vehicles, data centers, the electric grid, and renewable electric power generation such as solar and wind. The attributes of these converters, including their weight, volume, efficiency, cost, reliability, and lifetime, have a significant impact on the performance and appeal of the converters in the various applications. Traditional power converters use fast-switching transistors to convert the electrical energy. These transistors add cost, reduce efficiency, and negatively impact the reliability of the converter. In the standard converter, power/speed demand, loss, and failure are mostly related to the fast-switching transistor. Eliminating the fast-switching transistors would allow for advanced, high-performance power converters that can operate with improved power densities, lifetime, and efficiency, while reducing the costs associated with installation, repair, and replacement of traditional converters.
Project Innovation + Advantages:
Harvard University in partnership with Sandia National Laboratories will develop a transistor-less 16kW DC to DC converter boosting a 0.5kV DC input to 8kV that is scalable to 100kW. If successful, the transistor-less DC to DC converter could improve the performance of power electronics for electric vehicles, commercial power supplies, renewable energy systems, grid operations, and other applications. Converting DC to DC is a two-step process that traditionally uses fast-switching transistors to convert a DC input to an AC signal before the signal is rectified to a DC output. The Harvard and Sandia team will improve the process by replacing the active, fast-switching transistors with a slow switch followed by a passive, nonlinear transmission line (NLTL). The NLTL is a ladder network of passive components (inductors and diodes) that provide a nonlinear output with voltage. The combination of the nonlinear behavior with dispersion converts a quasi-DC input into a series of sharper and taller (amplified) voltage pulses called solitons, thus executing the DC to AC conversion without the use of active, fast-switching transistors. The NLTL will be followed by a high breakdown voltage silicon carbide and/or gallium nitride diode-based accumulator that converts the series of solitons to a DC output. Replacing the fast-switching transistors with a slow switch and a NLTL addresses the cost, size, efficiency, and reliability issues associated with fast switching based converters. Diodes also cost less and last longer because they are simpler structures than transistors and use no dielectrics. Efficiency, cost, and reliability improvements provided by a NLTL-based power converter will drastically benefit commercial power supplies, industrial motors, electric vehicles, data centers, the electric grid, and renewable electric power generation such as solar and wind.