A Non-Isolated Multiport Converter with Wide Input Voltage Range to Enhance Ultracapacitor Utilization for Electrified Vehicles

To enhance the utilization of the ultracapacitor (UC) energy in a battery-UC based hybrid energy storage system (HESS) for electrified vehicles (EVs), the UC needs to be discharged up to its minimum operating terminal voltage, resulting in higher duty cycle operation of the power converter with excessive high current at source side. This tends to cause instability in the close loop control and necessitates high current rated magnetic and switching components of the converter. Addressing to this, a non-isolated bidirectional multiport converter is proposed, which is capable of ensuring deep discharging of UCs without increasing the operating duty cycle or component ratings of the converter. The proposed converter offers the unique feature of energizing the inductor co-operatively through both UC and battery in the same switching cycle, during certain transient events of peak power delivery or regenerative energy recuperation. This eventually facilitates in extending the range of UC operation, thereby ensuring improved dynamic performance of EV. The operation of the proposed converter is validated through simulation and preliminary experimentation performed in a laboratory scale hardware prototype.