Improved Energy Management Algorithm With Time-Share-Based Ultracapacitor Charging/Discharging for Hybrid Energy Storage System

The efficiency, durability, and health of the energy storage system components depend on controlling the power flow subjected to proper operational constraints. It is achieved by energy management algorithm (EMA). Conventional EMAs restrict the ultracapacitor (UC) operation to a reference voltage to prevent it from overcharging/undercharging. This leads to very narrow utilization of the UC voltage range. However, UC voltage can safely be varied from zero to maximum-rated voltage. Rather than employing a UC voltage control loop that operates concurrently to transient load demand, a time-share-based approach has been used for UC charging/discharging. Hence, EMA has been modified in the present work by utilizing the UC voltage band instead of a UC reference voltage, which increases its power delivery capacity by approximately two to four times. In this paper, the proposed EMA improves the transient performance of the system and reduces the UC size. An experimental prototype of the system is designed, and the proposed EMA is tested in the different operating regions for validation.