Investigating battery current of three-phase two-level DC/AC converters for different modulation methods and operating states

Batteries are one of the key components for electric and hybrid electric vehicles, and also they are one of the major research areas due to they have a critical importance in order to development these vehicles. While batteries supply energy to output at normal working mode by converting internal chemical energy to electric energy (discharging), they restore energy at regenerative working mode as opposed to discharging (charging). During each working mode, battery current is not smooth DC and it has ripple. This ripple current causes to increase battery heating and so decrease batteries lifetime because of additional losses caused by ripple current is considerable. Simulations which include ideal battery model and ideal DC bus capacitor model prevent to observe realistic results about battery ripple current. This paper presents comparative investigations and evaluations about battery current waveform by using high frequency battery model and high frequency DC bus capacitor model with commonly known pulse width modulation (PWM) methods via MATLAB/Simulink. Battery current visual analyses and harmonic spectrums are provided for different operating states and PWM methods. Battery current distortion ratio (IBD) has been described and IBD variations with different operating states have been obtained for each modulation methods. In consequence of the results obtained, PWM methods and operating states have been compared and commented in terms of battery current. The results are valuable battery powered inverter applications as well as electric and hybrid electric vehicle applications.