A Flexible and Efficient DC Power Converter for Sustainable Energy Microgrids

Power Electronics INSIDER

According to the study’s first author, Liu Shiqiang, “Its superior voltage ratio means it can efficiently interface with a wide range of energy sources, while the self-balancing of inductor currents enhances system stability and simplicity. Moreover, the asymmetrical duty limit control offers enhanced performance especially for DC microgrids connected to electric vehicles” (Image:© MISHIMA Tomokazu)

Electric power comes in two kinds, AC and DC. Famously, the question over which kind should be used for national power grids, the “Current War” of the late 19th century, got settled in favor of AC and most power plants today produce it. However, solar power, and batteries in electric vehicles and computers all depend on DC, making lossy AC-to-DC conversion necessary. An alternative to this is the establishment of DC microgrids that integrate various renewable DC energy sources and storage devices and deliver energy directly to data centers and other DC appliances. This eliminates the need for AC-to-DC conversion, but it requires a device that can convert different voltages flexibly, as each DC device typically needs a different voltage. This also needs to be done bidirectionally, since batteries are used both as energy sources and sinks.

The power electronics researchers Mishima Tomokazu from Kobe University, Japan, and Lai Ching-Ming from the National Chung Hsing University, Taiwan, teamed up on a project for the “development of elemental technologies for high power density power distribution systems contributing to low-carbon data centers” and have now achieved a significant breakthrough. “Our diverse team with expertise spanning relevant disciplines allowed us to approach the problem from multiple perspectives, and our access to cutting-edge facilities and resources enabled us to conduct thorough experiments, simulations, and analyses. Additionally, our group has a track record of successful collaborations with industry partners and other research institutions, providing valuable insights and support for our endeavors,” said Kobe University student team member LIU Shiqiang.

They published the design principles, characteristics, and prototype evaluation in the journal IEEE Transactions on Power Electronics. Liu, first author of the study, explained its main advantages over previous designs: “Its superior voltage ratio means it can efficiently interface with a wide range of energy sources, while the self-balancing of inductor currents enhances system stability and simplicity. Moreover, the asymmetrical duty limit control offers enhanced performance especially for DC microgrids connected to electric vehicles.”

The evaluation of their prototype showed an efficiency of up to 98.3 percent. “This highlights the practical feasibility and scalability of the proposed topology for real-world applications, paving the way for future advancements in bidirectional DC-DC conversion technology,” said Liu.

The team has filed for a patent for the design in Japan and is now preparing for its commercialization with UPE-Japan, a Kobe University startup. They also want to keep improving their design, including for higher power densities and a wider variety of applications. “Ultimately, our long-term objective is to contribute to the transition towards more efficient, reliable, and sustainable energy storage and conversion solutions, particularly in the context of electric vehicles and renewable energy integration, said Liu.”

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