Selection of power sharing factor for hybrid battery/ultracapacitor energy storage‐based EV through load emulation technique

Abstract

The hybrid battery/ultracapacitor (UC) energy storage system for electric vehicles (EVs) proved more reliable and cost‐effective. Even with the best possible sizing of these energy storage devices, unforeseen EV loading cycles are causing a single‐source transition. Mainly, the UC exhaustion in acceleration or transient loading shifts the loading to the battery, causing overdischarge and reducing the life span. This paper presents a deterministic current control algorithm to restrict the maximum allowable battery discharge current. The current discharge control in the battery/UC is implemented using symmetrical carrier‐based digital average current mode (DACM). The proposed energy management algorithm (EMA) with variable battery current sharing factor typically controls the current flow between the battery and the UC so that the battery current is always within safe limits. The DC‐DC converter with proposed novel EMA allows the system to regulate the voltage and current flow between the two power sources. By sharing the currents in this way and limiting the battery current to a safe value, the system helps to prolong the battery's life and ensures that the vehicle operates safely and reliably over the long term. The EV load profile emulator provides the current sharing under dynamic operating conditions. The hardware results are supported to validate the single‐source transition under hybrid energy sources.