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Sridharan makes electric cars more efficient, receives IEEE Best Paper award


Claire Hettinger, ECE ILLINOIS

A recent PhD graduate is trying to make electric cars more efficient — and he received the IEEE Transportation Electrification Conference and Expo Best Paper Award for his efforts.

The plan: Srikanthan Sridharan (PhD ’15) hopes to optimize what electric cars can do. He is working to achieve more distance out of every battery charge. His work could decrease losses by up to 20 percent.

Srikanthan Sridharan
Srikanthan Sridharan
His research and paper, “Optimizing Variable DC-link Voltage for an Induction Motor Drive over a Dynamic Drive Cycle,” were inspired by the need in the industry to make electric cars more realistic for public use. One problem Sridharan recognized is the inefficient set voltage of the motor in an electric car. 

Sridharan added a voltage converter to the motor of the electric vehicle. It receives commands from the system, then puts out only the necessary voltage. With a wide variation of needed power, this system significantly reduces loss. Variations could include quick accelerating and decelerating, or periods of idle time and heavy lifting for electric vehicles used in construction.

This is a change from the way voltage is handled and accessed in the electric vehicle. In Sridharan’s research, there is no fixed voltage. The car can use high- and low-level voltage for various functions all the while decreasing loss in the system. This way, vehicles can get more distance and range for a single battery charge. 

“The standard is evolving,” Sridharan said, “because people don’t know what is going to work.”

Sridharan explained that the flexibility of the voltage is what makes the loss reduction possible. This way, the electric vehicle only uses as much power as it needs for a given task. Before, the voltage was fixed; every action, regardless of its strain on the motor, used the same amount of power. Over time, added stress could cause the system to break down.

But using Sridharan's approach, a car going up a hill would need more power, but when going down the hill would use less. This flexibility reduces overall loss in the engine. As a result, the system is under less pressure and lasts longer.

Professor Philip T Krein, Sridharan’s adviser and the paper's co-author, said industry participants dominate the conference. 

“It really is a surprise that a paper like this one, with its strong academic and research base, and long-term potential impact, received this recognition,” Krein said.  “I certainly did not expect it, and it is something that Srikanthan should be very proud of.”

At the conference, the industry presents its problems and academia present solutions or completes further research into the problem areas.

“It was great to receive the award from that society,” Sridharan said. 

The work is about ensuring energy efficiency to use in hybrid and electric transportation, Krein said. The industry tends to favor multi-stage designs, but has not considered how to enhance performance.  

Sridharan's work can fit into many pieces of the industry, and Krein and Sridharan hope engineers will pick up the design and apply it in vehicles.

“I think that is the way all power electronics have to be, because you should not fix anything," Sridharan said. "You should be ready for any change, for any dynamic transients."

Sridharan, who is now working at Ford, said he enjoys this field because it is interdisciplinary. The field is full of motor drives, electric machines, power electronics, and control systems, and Professor Krein helped him explore them all.

“He gives you the independence to evolve as a researcher,” Sridharan said. “He encourages you to look at problems yourself, and see the validity of that. Then, he gives direction.”