Power conversion is the process of converting electrical energy from one form to another, such as changing the voltage or conversion 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 industrial drives and renewable energy systems such as photovoltaic (PV) systems and wind energy systems. Demand for renewable energy is increasing, and most of these new energy sources are coupled to our AC grid through power electronic-based power converters and large bulky isolation transformers. The attributes of these converters, including their weight, volume, efficiency, cost, and lifetime, have a significant impact on the performance of renewable energy systems and industrial factories. In PV systems, power converters are responsible for more than 50% of the total failures, and need to be replaced once or twice within the lifetime of a PV module. Moreover, a 500kW isolated PV inverter weighs more than 4,500kg and requires a crane for installation, which imposes additional costs on the system. Advanced high-performance power converters can operate with improved power densities, lifetime, and efficiency, while reducing the costs associated with shipping, installation, repair, and replacement of traditional converters.
Project Innovation + Advantages:
Sandia National Laboratories will develop a prototype DC-DC converter in a modular, scalable, mass-producible format that is capable of 10kW or greater and could fit onto a single circuit board. Inefficiency and construction costs associated with AC distribution/transmission and DC-AC conversion are motivating many to consider direct connection of PV to DC distribution (and even DC transmission) circuits. The prototype proposed in this project would enable PV panels to be connected to a medium-to-high voltage DC distribution circuit using a power converter about the size of an average textbook. The team will demonstrate a high-voltage, high-power density, hybrid switched-capacitor power conversion circuit that relies on the concurrent use of silicon carbide (SiC) active switches and leading-edge, 1200V rated, vertical gallium nitride (GaN) diodes. Both SiC and GaN have individually led to improvements in converter performance that permits higher switching frequencies, blocking voltages, and operating temperatures. The team plans to exploit the use of SiC switches coupled with GaN diodes, utilizing the benefits of both materials to achieve improved power density and better performance. These devices would enable improved efficiency and small size, which would reduce assembly, transportation, and installation costs. The proposed circuit topology would be scalable to 100s of kW and 10s of kV, enabling a whole string of modules in a PV plant to be connected to a DC distribution circuit through a converter of about the size of a midsize microwave oven. The converter can be applied to other renewable sources, but in particular, this technology could greatly accelerate the adoption of PV onto the grid by enabling cheaper and more efficient medium voltage and high voltage DC distribution networks.