State of Charge Estimation of Battery Energy Storage Systems in Low Voltage Electric Drive Applications for Hybrid and Electric Vehicles

This work presents a straightforward solution to estimate the state of charge (SOC) of battery-packs used to supply low voltage electric drives integrated in hybrid and electric vehicles. The main idea is exploiting the electric drive to generate suitable DC bus current profiles to estimate the storage unit (SU) parameters, and thus the SOC, whenever the electric drive is not used as propulsion unit. In particular, the drive is exploited as controlled variable load to generate current steps and monitor the transient response of the SU through the measure of the DC bus voltage and motor phase currents. No additional external circuits are required, and a limited computational burden is required. Simulations and experimental tests confirm the feasibility of the proposed method.