Article

The paper details a hybrid energy storage system (HESS) for power-split hybrid vehicles, integrating a lithium-ion battery and an ultracapacitor. It employs an indirect power balance law and a nonlinear damped PI controller to regulate DC-link voltage effectively.

The ultracapacitor addresses high-frequency transients, while the battery supports mid-frequency energy needs. Key improvements include a reduction in voltage undershoot from 12% to 3%, overshoot below 1.5%, and faster convergence times. Current ripple is reduced by 25%, leading to more robust power-split operations.