Investigating DC Link Current Ripple and PWM Modulation Methods in Electric Vehicles

Abstract

Batteries are one of the key components for Electric Vehicles (EVs). 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. The ripple current influence battery lifetime negatively. Simulations which include ideal battery model and ideal DC bus capacitor model do not give realistic results about battery ripple current. This paper presents comparative investigations and evaluations about battery current waveform, battery current harmonic spectrum and the ratio of battery current harmonic components to battery average current for different modulation methods and operating states for motor (i.e. speed and torque) by using high frequency battery model and high frequency DC bus capacitor model.