Ultracapacitor-battery hybrid energy storage for pulsed, cyclic and intermittent loads

The pulsed loads, when supplied by the battery energy storage often degrades its life cycle and the performance over a period. The ultracapacitors can perform the duty of providing the burst of the load current. The ultracapacitor energy storage devices are designed to have high power density, but they fall regarding the energy density. The parallel combination of the battery-ultracapacitor can deliver both high power density and high energy density. A test bench in the paper is considered to supply high magnitude pulsed, cyclic and the intermittent loads to test out the adaptability of the parallel combination. A control strategy with DC-DC Converters, PI controller along with PWM control, is presented in the paper. The battery is regulated by the boost converter and the ultracapacitor by a buck-boost converter. The results verified by the MATLAB/Simulink® software prove the versatility of the control strategy. The transient power is mostly supplied by the ultracapacitor whereas the steady power is provided by the battery. Thus, SOC of the battery is maintained at the safe levels which otherwise would have created the degradation of its lifetime without ultracapacitor energy storage devices in parallel.