State of Health Estimation of Battery Charging System and BLDC Motor Drive deployed in Electric Vehicle Applications

The operating unit of an Electric Vehicle (EV) drive comprise of a power energy storage system such as Lithium-Ion (Li-ion) or Valve Regulated Lead Acid (VRLA) batteries. The EVs are mechanically driven through electrical machines such as Brushless Permanent Magnet (PM) Synchronous (or BLDC) Motor which are widely used for its high torque density and dynamic speed performance. However, for the continuous and smooth operation of EVs, the health monitoring becomes vital. The proposed research therefore estimates the State of Health (SOH) of EVs through online health monitoring of battery packs and electrical machine drive system, respectively. The charging and discharging characteristics of a battery is studied through the development of a battery charging system (BCS)/testbed which monitors the health of a battery in terms of voltage (v) and current (i) quantities. The v-i characteristics further aid in estimating the State of Charge (%SOC) using current integration method and consequently determines the life of a battery. Whereas the performance of a mechanical drive system is evaluated through the development of a BLDC motor drive adopting hybrid flux (ψ) model approach. The health of a machine drive system is determined by studying the radial airgap flux signature of the machine under operation. The proposed research therefore concludes that, by monitoring the battery SOC and the PM flux signatures, the %SOH of the EV drive can be eventually estimated.