Electric Vehicle Battery Performance Investigation Based on Real World Current Harmonics

Sid-Ali Amamra,Andrew D Moore,James Marco,Yashraj Tripathy,Anup Barai

doi:10.3390/en13020489

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.

Highlights

A battery electric vehicle (BEV) powertrain typically consists of power subsystems, based on power electronics switches (e.g., insulated gate bipolar transistors (IGBT) and field effect transistors (FET) components)
direct current (DC)–DC and DC–alternating current (AC) bi-directional converters are integrated within the powertrain, which operate at high switching frequencies, in the order of tens of kHz [1,2,3,4]
Another aspect of this study focused on if the AC ripple current contributed to degradation; this might have been too small to measure within the measurement accuracy

Summary

Introduction

A battery electric vehicle (BEV) powertrain typically consists of power subsystems, based on power electronics switches (e.g., insulated gate bipolar transistors (IGBT) and field effect transistors (FET) components). DC–DC and DC–AC bi-directional converters are integrated within the powertrain, which operate at high switching frequencies, in the order of tens of kHz [1,2,3,4]. The commonplace is that operating currents within these power converters contain harmonics. Within the academic literature, little is reported about the impact of the current harmonics on battery lifetime. Uno et al [5] investigated the qualitative impact of high-frequency cycling on the lifetime performance of lithium-ion (Li-ion) cells. The authors found that the capacity of cells cycled at frequencies below 10 Hz significantly deteriorated by circa 1.26% after 50 days of experimentation, whereas the capacity decay of cells cycled at higher frequencies were identical to the corresponding calendar degradation [5]

Objectives

Methods

Results

Discussion

Conclusion