A New Era for Ultra-Fast EV Charging
As electric vehicle adoption accelerates, charging infrastructure seeks to deliver higher power with fewer limitations. A collaboration between the Indian Institute of Science (IISc) and Delta Electronics India has produced a breakthrough: a cascaded H-bridge (CHB) multiport DC converter that connects directly to a medium-voltage grid (11 kV), eliminating bulky line-frequency transformers (LFTs) and the multiple AC–DC conversion stages that typically accompany megawatt-scale charging.
Published in IEEE Transactions on Industrial Electronics, the research demonstrates notable efficiency gains—about 3–5% at megawatt power levels—and promises reductions in energy loss, material use, and footprint for high-power fast charging stations.
How the CHB Multiport DC Converter Works
Traditional fast chargers rely on transformers to step down high-voltage grid electricity and often require several power conversion stages before the energy reaches the vehicle battery. The IISc Delta team’s CHB-based design connects directly to the high-voltage medium grid and uses high-frequency operation to keep the hardware compact and lighter. This approach enables multiple isolated output ports for simultaneous charging of several EVs and supports bidirectional energy flow, including potentially feeding power back to the grid during peak demand or outages.
In Prof. Kaushik Basu’s explanation, the system acts as a solid-state transformer (SST). Moving from a 11 kV source straight to DC outputs reduces the need for heavy copper and iron transformers and decreases the number of conversion steps. The result is a more compact, efficient, and flexible charging solution capable of supporting renewables integration and local energy storage alongside multiple vehicles.
Prototype Milestones and Scaling Challenges
The IISc team has demonstrated a 1.2 kW lab prototype achieving over 95% efficiency, a promising foundation for megawatt-scale development. Scaling from kilowatts to megawatts introduces hurdles, including device costs and high-frequency losses. While high-frequency operation shrinks physical size, it can necessitate more semiconductor devices and introduce additional losses through extra conversion stages.
Prof. Basu notes that although the concept is not new, the challenge is to match or surpass conventional transformer efficiency. The team continues to pursue megawatt-class demonstrations, with plans to build a 250–500 kW (half-megawatt) system and an eventual megawatt-level converter for direct 11 kV-to-low-voltage DC charging. A new lab facility, funded by the Department of Science and Technology (DST) and Delta Electronics, will host this effort and serve as Delta-IISc’s centre of excellence on medium-voltage power electronics.
Industry and Policy Implications
The collaboration includes Delta Electronics providing car-emulator testing for the new hardware, enabling field-like trials within a 2,500–3,000 square foot lab tailored to high-power ESS and vehicle charging simulations. The envisioned megawatt-scale converter would simultaneously charge a 200 kW bus and a 50 kW car directly from an 11 kV grid, bypassing traditional transformer rooms and reducing physical footprint.
Beyond EV charging, the technology could power data centers, wind energy systems, and railway traction, where high-efficiency conversion at medium voltages can cut losses and simplify infrastructure. The approach aligns with India’s broader EV policy goals to expand high-power charging along national highways and to enable renewable energy integration for charging networks.
What’s Next and the Long-Term Vision
Field trials are expected within about a year, with the lab ready in a month. If successful, the megawatt-class converter could reshape the economics of fast charging, enabling under-10-minute charges and the widespread deployment of multiport, high-power charging hubs that cooperate with solar and other renewables. In the longer term, Prof. Basu envisions a future where high-power converters are embedded throughout generation and consumption, creating low-carbon, highly efficient energy systems with reduced reliance on traditional transformer rooms.
As power electronics mature and semiconductor costs decline, the promise of compact, transformer-free megawatt converters becomes more tangible. This development could accelerate the adoption of ultra-fast charging, support grid stability through bidirectional flows, and bring high-performance EV charging closer to the mainstream.
Key Quotes
“We’ve replaced bulky transformers with a compact, solid-state solution,” says Prof. Kaushik Basu, reflecting the core value of the CHB approach.
