Fuzzy Logic Controller Based Modified Energy Management Strategy for Battery and UC with Improved Battery Performance

Abstract

The ultracapacitor (UC) acts as a stress reducer for the battery. It is also considered as a fruitful companion for a battery in battery-UC hybrid energy storage system (HESS). Management of power between battery, UC, and drive motor, along with a suitable topology, decides the performance of the battery and drive system. Rule based energy management strategy (EMS) is simple, real-time implementable, ease in control, and based on engineer’s experience. But it lacks in controlling the state-of-charge (SOC) of battery and UC, battery current rate, and its magnitude, dc link voltage control, and UC voltage regulation. In this paper, low pass filter based conventional rule-based EMS is studied and implemented in MATLAB. Then fuzzy logic based modified rule-based EMS is proposed and simulated for the same load profile. Comparative study between conventional and modified EMS shows the proposed EMS is capable to provide constant dc link voltage, stable UC SOC operation, fast response, and reduces the large variation in speed. Proposed EMS saves the 10% of the battery energy for 20 sec load profiles as compared with battery only system. So, by use of UC, shared bus topology, and effective EMS, driving range of the vehicle and battery life can be improved and range anxiety can be reduced.