Electric Vehicle Battery Performance Investigation Based on Real World Current Harmonics

Abstract

Electric vehicle (EV) powertrains consist of power electronic components as well as electric machines to manage the energy flow between different powertrain subsystems and to deliver the necessary torque and power requirements at the wheels. These power subsystems can generate undesired electrical harmonics on the direct current (DC) bus of the powertrain. This may lead to the on-board battery being subjected to DC current superposed with undesirable high- and low- frequency current oscillations, known as ripples. From real-world measurements, significant current harmonics perturbations within the range of 50 Hz to 4 kHz have been observed on the high voltage DC bus of the EV. In the limited literature, investigations into the impact of these harmonics on the degradation of battery systems have been conducted. In these studies, the battery systems were supplied by superposed current signals i.e., DC superposed by a single frequency alternating current (AC). None of these studies considered applying the entire spectrum of the ripple current measured in the real-world scenario, which is focused on in this research. The preliminary results indicate that there is no difference concerning capacity fade or impedance rise between the cells subjected to just DC current and those subjected additionally to a superposed AC ripple current.

The Impact of an Overlaid Ripple Current on Battery Aging: The Development of the SiCWell Dataset

“…However, these long-term studies conclude different concerning the influence of the ripples. While some studies describe a shortening of the lifetime due to, e.g., local warming, formation of temperature gradients [5,6] or an increased RMS [3], no increase of the aging rate was found in [7][8][9][10]. In [11,12], even an increased performance of the examined cells was found for a charge or discharge with superimposed alternating currents (AC).…”

“…Due to the increase in the effective current and the associated increase in power loss and temperature, ripple currents are suspected of harming cell performance and lifetime [3,4]. Therefore, the influence of alternating and ripple currents on the degradation of LIBs (lithium-ion batteries) has been investigated in recent years [5][6][7][8][9]. However, these long-term studies conclude different concerning the influence of the ripples.…”

Short-Term Impact of AC Harmonics on Aging of NiMH Batteries for Grid Storage Applications

“…Previous work on Li-ion batteries for traction systems disagree on what effect AC frequency overlay has on the batteries. Some studies show no effect on aging when cycling with an AC frequency overlay [ 4 , 5 , 6 , 7 ]. The studies that do show an effect disagree on what frequencies are causing it.…”

An Adaptive Control Strategy for a Low-Ripple Boost Converter in BLDC Motor Speed Control

“…Within the EV powertrain, a low-pass filter is commonly used to eliminate these harmonics. However, it is almost impossible to eliminate them, but can only decrease them (Amamra et al, 2020). There are various shortcomings in the method of using filters.…”