An introduction toA Novel Cell Equalizer Topology for Plug-

In Hybrid Electric Vehicle Energy Storage System

Kun Zhugekzhuge@uwaterloo.ca

Overview• Significance of Cell Equalization• Battery Model• Novel Topology Analysis• Simulation Result• Conclusion

Significance of Cell Equalization• A battery of a plug-in hybrid electric vehicle (PHEV)

consists of a long string of cells (typically 100 cells, about 360V)

• Cost: 500$/KW for a typical 16KWh battery, which can provide about 80KM in urban area, surcharge of $5000

• Cycle life and calendar life: – 500 cycles of 80% the capacity– Expecting 6000-7000 cycles for future PHEV

• Safety:– Safety improvement of the system if there is continuously

monitoring the cell current, voltage and temperature

Battery Model

[1]. Accurate Electrical Battery Model Capable of Predicting Runtime and I-V Performance, Min Chen, Student Member, IEEE, and Gabriel A. Rinc´on-Mora, Senior Member, IEEE, IEEE TRANSACTIONS ON ENERGY CONVERSION, VOL. 21, NO. 2, JUNE 2006

Cell Equalization Topology

• Current Ieq will flow in or out of the battery through the inductor• “Control” of the system monitors the battery voltage and responses to

equalize the battery voltage by turning on or off the switches

Cell Equalization Topology

Optimal choice: One equalizer unit is limited to four to five cells

• Low cost constraint• Voltage margin to improve the reliability

Cell Equalization Formula

Cell Equalization Formula

Cell Equalization

Cell Equalization

VOC estimation

Ieq: equalizing current, active only at To and interrupted after T1

: is one at To and zero thereafter

: is the battery pack current

/ : are the dynamic resistances

/ : are constants

0

aR bRbattI

aTaT

Conclusion• In summary, the feasibility of the novel

battery cell equalizer was explored• Cell equalization does contribution to

battery cost, battery life and cycle, and battery safety

Reference• [1]. Accurate Electrical Battery Model Capable of Predicting Runtime and I-V

Performance, Min Chen, Student Member, IEEE, and Gabriel A. Rinc´on-Mora, Senior Member, IEEE, IEEE TRANSACTIONS ON ENERGY CONVERSION, VOL. 21, NO. 2, JUNE 2006

• [2]. Feasibility Analysis of a Novel Cell Equalizer Topology for Plug-in Hybrid Electric Vehicle Energy-Storage System, Pablo A. Cassani, Student Member, IEEE, and Sheldon S. Williamson, Member, IEEE, IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 58, NO. 8, OCTOBER 2009

• [3]. Design, Testing, and Validation of a Simplified Control Scheme for a Novel Plug-In Hybrid Electric Vehicle Battery Cell Equalizer, Pablo A. Cassani, Student Member, IEEE, and Sheldon S. Williamson, Member, IEEE, IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 57, NO. 12, DECEMBER 2010

Thanks!Q&A