Modeling and Verification of a Hybrid Energy Storage System for Electric Vehicle

Modeling and Verification of a Hybrid Energy Storage System for Electric Vehicle

This research reported here aimed to implement a hybrid energy storage system (HESS) for electric vehicles by integrating anon-isolated bidirectional converter with lithium batteries and supercapacitors as a hybrid power module. This was to reduce thecomplexity of feedback circuit, to implement a system control based on load power demand, to achieve system simplification andreduce costs. Moreover, the energy change on the supercapacitor was used to estimate the load power, and the impact caused bynon-ideal components was also considered to achieve accurate load power estimation, thereby reducing the component countsthat detects the load power. Furthermore, a rule-based control strategy based on the average load power and the supercapacitorvoltage was employed from the following perspectives: (1) to implement a hybrid energy storage system with multiple workingmodes to reduce the losses caused by the energy consumed between the battery and supercapacitor; (2) to effectively reduce thebattery current stress; and (3) to better extend the battery life. In addition, a hysteresis control strategy was adopted as well to notonly store more energy in the supercapacitors but also stabilize the DC bus voltage. Finally, a system platform was establishedbecause the feasibility of the hybrid energy storage system was verified with simulation and experiment results.