IEEE Electrification - June 2021 - 24

There are incentives to pursuing
integrated chargers to simplify circuit
structures, lower costs, and achieve
better efficiency and power density.
The concept of integrated charging
for electric vehicles was introduced,
in 1985, by David Timmersch. The
goal is to make dual use of existing
onboard power electronics components
as part of the charging system.
In the early 1990s, a series of patents
for integrated chargers by Rippel and
Cocconi were awarded. Since then,
many different types of integrated
chargers have been proposed.
Due to the desired low cost and
minimal reconfiguration of the traditional electric
power train, most integrated charger solutions are nonisolated.
They are seen not only as a potential low-cost
solution but also as an opportunity to enable onboard
level 3 fast charging. The high power rating and a potential
bidirectional capability also make them particularly
suitable for V2G and V2H applications. As a result, there
have been multiple industrial efforts to bring integrated
nonisolated chargers to the market. But nonisolated
chargers are also known to have safety- and
electromagnetic inference (EMI)-related challenges due
to a potentially large CM current and a lack of isolation
against potential ground faults, as explored by Elshaer
et al. in 2017.
Lower cost, higher
power, and more
accessible battery
chargers are among
potential solutions
to address the
expense and range
anxiety issues.
Review of Integrated Chargers
and Nonisolated Electric
Vehicle Chargers
Isolated Integrated
Charging Solutions
Figure 1 shows the general configuration
of the power train of an electric
vehicle. The traction inverter and battery
are typically connected via contactors.
If isolated integrated charging
should be realized, either a large number
of reconfiguration switches is
needed or an isolated dc-dc converter
stage has to be permanently inserted
between the battery pack and the traction
inverter. Some research efforts have focused on realizing
isolation with machine windings. For example, as
reported in Thong and Pollock's work, in 1999, isolated battery
charging was achieved by adding an auxiliary winding,
which was coupled with one of the windings of a twophase
switched reluctance machine in the traction drive.
Another approach is to reconfigure a specially designed
interior permanent magnet synchronous machine into a
line-frequency transformer with multiple reconfiguration
relays, as demonstrated by Haghbin et al. in 2011.
Battery
Pack
Traction
Inverter
(Three-Phase,
Level 2)
Machine
Figure 1. The typical power train configuration of an electric vehicle.
Add-on CSR
Traction Drive
Inverter
A
B
C
Machine Winding
With Neutral
Point Access
Figure 2. Renault's integrated charger topology. CSR: current source rectifier.
24
IEEE Electrification Magazine / JUNE 2021
Nonisolated Integrated Charging Solutions
Although isolated integrated charging solutions have been
offered by academia, most industry-proposed solutions
feature nonisolated integrated topologies. This, on the one
hand, is due to the cost of an extra isolation stage, which
defeats the purpose of low-cost charging, and, on the other
hand, because of the complicated reconfiguration procedures
that are required. Single-phase, nonisolated integrated
charging typically requires two cascaded power stages:
an ac-dc stage for power factor control and a dc-dc stage.
Although three-phase-based charging can achieve good
current control with a single-stage ac-dc converter, twostage
charger topologies are still widely studied due to the
need for downward charging compatibility with singlephase
arrangements. Level 3 integrated
chargers are often expected
to be compatible with three-phase
and single-phase networks; thus,
vehicles can be charged at home
and at fast-charging stations.
Figure 2 presents the nonisolat+
-
ed
integrated charger topology presented
in a patent filed by Renault
in 2012. The two-stage circuit consists
of an add-on current source
rectifier (CSR) as the grid-connected
front end and a dc-dc converter
utilizing machine windings as
inductors and the traction driver
Battery
IEEE Electrification - June 2021

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