<img src="https://spectrum.ieee.org/media-library/cluster-of-electronic-circuit-boards-connected-to-a-module-all-on-a-black-background.jpg?id=61740697&width=1245&height=700&coordinates=0%2C81%2C0%2C81"/> 
This article is part of our exclusive <a href="https://spectrum.ieee.org/collections/journal-watch/" target="_blank">IEEE Journal Watch series</a> in partnership with IEEE Xplore.
The rapid build-out of <a href="https://spectrum.ieee.org/ev-charging-2671242103" target="_self">fast-charging stations for electric vehicles</a> is testing the limits of today’s power grid. With individual chargers drawing 350 to 500 kilowatts (<a href="https://spectrum.ieee.org/byd-megawatt-charging" target="_blank">or more</a>)—which makes EV charging times now functionally equivalent to the fill-up time for a gasoline or diesel vehicle—full charging sites can reach megawatt-scale demand. That’s enough to strain <a href="https://spectrum.ieee.org/power-line-sensors-smart-grid" target="_self">medium-voltage distribution networks</a>—the segment of the grid that links high-voltage transmission lines with the low-voltage lines that serve end users in homes and businesses.DC fast-charging stations tend to be clustered in urban centers, along highways, and in fleet depots. Because the load is not spread evenly across the network, particular substations are overworked—even when overall grid capacity is rated to accommodate the load. Overcoming this problem, as more charging stations, with greater power demands, come online requires power electronics that are not only compact and efficient but also capable of managing local storage and renewable inputs.<h2>Solid-State Transformers in EV Charging</h2>One of the most promising technologies for modernizing the grid so it can keep up with the demands of vehicle electrification and renewable generation is the solid-state transformer (SST). An SST performs the same basic function as a conventional transformer—stepping voltage up or down. But it does so using semiconductors, high-frequency conversion with silicon carbide or gallium nitride switches, and digital control, instead of passive magnetic coupling alone. An SST’s setup allows it to control power flow dynamically.For decades, charging infrastructure has relied on <a href="https://spectrum.ieee.org/transformer-crisis" target="_self">line-frequency transformers</a> (LFTs)—massive assemblies of iron and copper that step down medium-voltage AC to low-voltage AC before or after external conversion from alternating current to the direct current that EV batteries require. A typical LFT can contain as much as a few hundred kilograms of copper windings and a few tonnes of iron. All that metal is <a href="https://spectrum.ieee.org/transformer-shortage" target="_self">costly and increasingly difficult to source</a>. These systems are reliable but bulky and inefficient, especially when energy flows between local storage and vehicles. SSTs are much smaller and lighter than the LFTs they are designed to replace. “Our solution achieves the same semiconductor device count as a single-port converter while providing multiple independently controlled DC outputs.” —Shashidhar Mathapati, Delta Electronics But most multiport SSTs developed so far have been too complex or costly (between five and 10 times as much as the upfront cost of LFTs). That difference—plus SSTs’ reliance on auxiliary battery banks that add more expense and reduce reliability—explains why solid-state’s obvious benefits have not yet incentivized shifting to the technology from LFTs. <img alt="Surjakanta Mazumder, Saichand Kasicheyanula, Harisyam P.V. and Kaushik Basu holding their prototype in a lab." class="rm-shortcode" data-rm-shortcode-id="27b015c07054f6fdc5f63f93391977fb" data-rm-shortcode-name="rebelmouse-image" id="188c5" loading="lazy" src="https://spectrum.ieee.org/media-library/surjakanta-mazumder-saichand-kasicheyanula-harisyam-p-v-and-kaushik-basu-holding-their-prototype-in-a-lab.jpg?id=61740711&width=980"/> Surjakanta Mazumder, Saichand Kasicheyanula, Harisyam P.V., and Kaushik Basu hold their SST prototype in a lab.<a href="https://ieeexplore.ieee.org/document/11131460" target="_blank">Harisyam P.V., Saichand Kasicheyanula, et al.</a><h2>How to Make Solid-State Transformers More Efficient</h2><h2></h2>In a <a href="https://ieeexplore.ieee.org/document/11131460" target="_blank">study</a> published on 20 August in <a href="https://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=63" target="_blank">IEEE Transactions on Power Electronics</a>, researchers at <a href="https://iisc.ac.in/" target="_blank">the Indian Institute of Science</a> and <a href="https://www.deltaelectronicsindia.com/en-IN/index" target="_blank">Delta Electronics India</a>, both in Bengaluru, proposed what’s called a cascaded H-bridge (CHB)–based multiport SST that eliminates those compromises. “Our solution achieves the same semiconductor device count as a single-port converter while providing multiple independently controlled DC outputs,” says <a href="https://www.linkedin.com/posts/delta-electronics-india_deltaelectronicsindia-designinindia-designforindia-activity-7311299447068471296-NUOX" target="_blank">Shashidhar Mathapati</a>, the chief technology officer of Delta Electronics. “That means no additional battery storage, no extra semiconductor devices, and no extra medium-voltage insulation.”The team built a 1.2-kilowatt laboratory prototype to validate the design, achieving 95.3 percent efficiency at rated load. They also modeled a full-scale 11-kilovolt, 400-kW system divided into two 200-kW ports.<h2></h2>At the heart of the system is a multiwinding transformer located on the low-voltage side of the converter. This configuration avoids the need for costly, bulky medium-voltage insulation and allows power balancing between ports without auxiliary batteries. “Previous CHB-based multiport designs needed multiple battery banks or capacitor networks to even out the load,” the authors wrote in their paper. “We’ve shown you can achieve the same result with a simpler, lighter, and more reliable transformer arrangement.”A new modulation and control strategy maintains a unity power factor at the grid interface, meaning that none of the current coming from the grid goes to waste by oscillating back and forth between the source and the load without doing any work. The SST described by the authors also allows each DC port to operate independently. In practical terms, each vehicle connected to the charger would be able to receive the appropriate voltage and current, without affecting neighboring ports or disturbing the grid connection.<h2></h2>Using silicon carbide switches connected in series, the system can handle medium-voltage inputs while maintaining high efficiency. An 11-kV grid connection would require just 12 cascaded modules per phase, which is roughly half as many as some modular multilevel converter designs. Fewer modules ultimately means lower cost, simpler control, and greater reliability.Although still at the laboratory stage, the design could enable a new generation of compact, cost-effective fast-charging hubs. By removing the need for intermediate battery storage—which adds cost, complexity, and maintenance—the proposed topology could extend the operational lifespan of EV charging stations.According to the researchers, this converter is not just for EV charging. Any application that needs medium-voltage to multiport low-voltage conversion—such as data centers, renewable integration, or industrial DC grids—could benefit.For utilities and charging providers facing megawatt-scale demand, this streamlined solid-state transformer could help make the EV revolution more grid-friendly, and faster for drivers waiting to charge.

تصميم جديد للمحول الصلب من المقرر أن يحدث ثورة في شحن المركبات الكهربائية (EV) من خلال تقليل أوقات الشحن بشكل كبير. هذه التطورات مهمة حيث تزداد الحاجة إلى حلول شحن أسرع وأكثر كفاءة مع تزايد اعتماد المركبات الكهربائية. من خلال تحسين البنية التحتية التي تدعم المركبات الكهربائية، لا تعمل هذه التكنولوجيا على تحسين تجربة المستخدم فحسب، بل تساهم أيضًا في الهدف الأوسع المتمثل في النقل المستدام، مما يجعلها خطوة مهمة نحو الانتقال إلى الطاقة الخضراء.

Un nuevo diseño de transformador de estado sólido está a punto de revolucionar la carga de vehículos eléctricos (VE) al reducir significativamente los tiempos de carga. Este avance es crucial a medida que la demanda de soluciones de carga más rápidas y eficientes crece junto con la adopción de vehículos eléctricos. Al mejorar la infraestructura que apoya a los VE, esta tecnología no solo mejora la experiencia del usuario, sino que también contribuye al objetivo más amplio de un transporte sostenible, lo que representa un paso importante en la transición hacia una energía más ecológica.

Un nouveau design de transformateur à état solide est sur le point de révolutionner la recharge des véhicules électriques (VE) en réduisant considérablement les temps de recharge. Cette avancée est cruciale alors que la demande de solutions de recharge plus rapides et plus efficaces augmente avec l'adoption croissante des véhicules électriques. En améliorant l'infrastructure qui soutient les VE, cette technologie améliore non seulement l'expérience utilisateur, mais contribue également à l'objectif plus large d'un transport durable, représentant ainsi une avancée significative dans la transition vers une énergie plus verte.

A new solid-state transformer design is set to revolutionize electric vehicle (EV) charging by significantly reducing charging times. This advancement is crucial as the demand for faster and more efficient charging solutions grows alongside the increasing adoption of electric vehicles. By enhancing the infrastructure that supports EVs, this technology not only improves user experience but also contributes to the broader goal of sustainable transportation, making it a significant step forward in the transition to greener energy.

Solid-State Transformer Design Unlocks Faster EV Charging

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