IISc and Delta Electronics India develop fast charging solutions for EVs

Researchers in the Department of Electrical Engineering (EE) at the Indian Institute of Science (IISc), Bengaluru and Delta Electronics India have developed a new fast charging solution for Electric Vehicles (EVs).

This novel cascaded H-bridge (CHB)-based multi-port DC converter directly connects to the medium-voltage AC (MVAC) electricity grid. Besides, it eliminates the need for large and expensive line frequency transformers (LFTs), which conventional charging stations rely on.

“These stations (conventional) also have multiple conversion stages involving stepping up or down current, or converting AC to DC, and vice versa. This can greatly increase cost and reduce efficiency,” according to IISc.

The new converters can help address the growing power demands of fast charging EV stations, crucial for scaling up India’s EV infrastructure.

“Today’s high-power chargers are complex, with multiple conversion stages between the grid, the energy storage, and the vehicle battery. Our invention simplifies this process and offers a 3-5% improvement in energy efficiency. At a megawatt scale, this leads to energy saving, significant reduction in cost, and a smaller material footprint, which makes the charging stations environmentally friendly,” said Kaushik Basu, Associate Professor in EE and corresponding author of the study.

Harisyam P.V., first author and PhD student in EE, said such converters would be especially helpful for stations where multiple vehicles need to charge simultaneously.

“Going from a line frequency transformer-based solution to solid state transformers, we made the solution much smaller and more compact compared to existing solutions,” he said.

Along with power conversion, the technology facilitates a compact bidirectional charging hub that provides key advantages. In addition to powering multiple vehicles, it also enables local storage of charge in batteries, and can easily be hooked up to renewable energy sources like solar panels.

Can serve as support infrastructure during power outage

Storing charge locally in batteries allows for charging when there are sudden high-power demands on the distribution grid, when multiple vehicles are charging simultaneously. The bidirectional converter can not only transfer power from the grid to the vehicles, but also from the station’s storage back to the grid in critical conditions. This feature would allow the charging station to function with uninterrupted power supply. It can also potentially support essential facilities like hospitals during a power outage.

The team built and tested a 1.2 kW lab-scale prototype and found that it was able to supply DC power for charging EVs at an efficiency higher than 95%. They now plan on scaling up the system to handle higher loads.

IISc. said that beyond EV charging, this technology also holds promise for applications in next-generation data centres, wind energy systems, and railway traction by enabling high-efficiency power conversion directly at medium voltages.