Improving PHEV batteries

May 31, 2011

Kettering's Dr. Hua Bai has two research contracts designed to solve practical problems related to Plug-in Hybrid Electric Vehicles: power factor correction and battery life.

Kettering University is becoming one of the leading research institutions in the country when it comes to Plug-in Hybrid Electric Vehicle (PHEV) research, and new contracts with Magna E-Car Systems and Progressive Dynamics will further enhance that position.

Both contracts are with Dr. Hua Bai, assistant professor of Electric and Computer Engineering at Kettering, and both projects seek to solve practical problems related to PHEVs: power factor correction and battery life.

The contract with Magna, one of the largest and most diverse automotive suppliers world-wide, is to develop a power factor correction controller for PHEVs within six months. The funding enables three Kettering students, Allan Taylor, Gyula Szatmari-Voicu and Nelson Wang, to work on the project with Bai.

“One of the most important components for PHEVs is the charger,” Bai said. “In the future, we will see a lot of PHEVs on the road, and  therefore a lot of chargers hooked up into the power grid. In that case, you can expect that this charging power will impact the grid system significantly.”

The solution to this problem involves designing a controller that connects the grid with the charger. That controller will raise the power factor of the charger, making the electric current have less impact on the grid.

“A power factor correction controller is trying to increase the power factor to one, the maximum value,” Bai said. “Presently a lot of the commercial chargers have the low-power-factor issue, which means that their current impact to the grid will be high. When the power factor increases, you expect to see a smaller current peak at the same input voltage and power, so the electric stress to the grid will be mitigated, which is a pretty important issue,” he said.

One challenge of this project lies in reaching high-efficiency (greater than 97 percent) at high power. Another factor in the project that has to be considered is that the United States and European countries have dual power grids. Europe and the United States have three-phase power grids and single-phase power grids. Because the power factor correction controller will be marketed in both Europe and North America, developers of the controller must account for the different power specifications.

“They really want to reach the market with this product in the U.S. and European countries simultaneously,” Bai said. “Magna expects that the product resulting from this project will be compatible with a three phase power grid and a single phase power grid, so that’s another characteristic of this power factor correction controller. In this case, novel semiconductor devices, new topologies and advanced control algorithms will be employed.”

The opportunity to research and test such an important product at Kettering has obvious benefits for the university, but Bai also notes the importance of forming partnerships with leading companies like Magna.

“Magna is the largest automotive supplier in North America and fifth in the world,” Bai said. “Collaborating with Magna will give faculty and students the direct impression of what the current auto industry really looks like, what they are really interested in and how Kettering students should prepare for future career development. The students in the lab will be able to use the facilities at Magna and design the system based on real requests of the actual automotive industry.”

The second project that Bai is overseeing is dealing with improving the life of batteries in PHEVs.

“How to use the battery appropriately is the next search for electrical engineering,” Bai said. “The biggest question is how to charge the battery fast and without damaging the battery?”

The contract with Progressive Dynamics is for six months and involves four other students, Mori Yatsui, Mohammadhossein Azhinehfar, Xi Zheng and Nicholas Cramer. This group will determine the impact of different charging algorithms on useful battery life. Along with funding, Progressive Dynamics is providing necessary hardware including 10 power converter/chargers and 10 each 550 Cranking Amp Lead Acid batteries.

“We have 10 chargers with different charging algorithms inside,” Bai said. “The students help to test the impact on the battery lifetime by each of the charging algorithms embedded in the chargers. That will give us more benefits in education and technological innovation.

“Presently, a lot of chargers on the market use a similar charging algorithm which is believed not good for the battery, but it’s hard to prove. Therefore we set up a battery test bench to identify the battery’s internal resistance and process the on-line state of charge (SOC) estimation using a Kalman Filter. What we try to do is to charge/discharge the battery for many cycles with specific algorithms, observe the aging process of each battery, summarize the merits and demerits of each, and eventually develop an excellent charging algorithm to prolong the life of the battery.”

Contact: Patrick Hayes
(810) 762-9538