Article

This study introduces a hybrid energy storage system for power-split hybrid vehicles, combining lithium-ion batteries and ultracapacitors. A control framework utilizing an indirect power balance law and a nonlinear damped PI controller is presented.

The ultracapacitor manages high-frequency transients while the battery provides mid-frequency energy. Performance improvements include reduced voltage undershoot from 12% to 3%, overshoot below 1.5%, and enhanced torque delivery with a 25% reduction in current ripple.