Dr. Chris R. Gould
The University of Sheffield
United Kingdom
Design and Implementation Of A 4kW High-Frequency Resonant On-Board Bidirectional
Charger (OBBC) for EVs
“ecoCity eMotion” 24-25th September 2014, Erlangen, Germany
European Conference on Nanoelectronics and Embedded Systems for Electric Mobility
Presentation Outline
Introduction
OBBC Review & Comparison Results
Specification of 4kW HFT OBBC
Optimised CLL resonant tank design
Ideal Component Parameters
Full AC-DC System
Results
Summary
Introduction
In the Internet of Energy project (IoE), the UK demonstrator
at Haslar demonstrated a residential system comprising of
solar array, Li-ion battery storage system, 3-phase inverter
and Electric Vehicle (EV)
Introduction
In order to provide stabilization of the utility power supply
during peak-load times, the use of an EV traction battery
for energy buffering has been proposed
An On-Board Bidirectional Charger (OBBC) allows efficient
battery charging (Grid-to-Vehicle or G2V), whilst enabling
power to be fed back to the grid (Vehicle-to-Grid operation
or V2G)
Investigation into the weight, cost and efficiency trade-offs
between 50Hz grid-tied OBBC and high-frequency
resonant OBBC technologies has previously been
undertaken for 2.2kW µ-Class EV (NESEM 2013)
OBBC Variants
HighHigh--frequency Dual frequency Dual
Active Bridge (DAB) Active Bridge (DAB)
AC/DCAC/DC
GridGrid--tied 50Hz AC/DCtied 50Hz AC/DC
Making “ReMaking “Re--Use” of Use” of
EV InverterEV Inverter
2.2kW OBBC Comparison Results
??? Do charger malfunctions affect the drive system of the EV ???
Specification of 4kW OBBC
Single-phase UK residential utility supply currently runs at
230Vrms at a fused level of 13A (3kW)
Most solar installations are installed with a 4kW, 230Vrms
capability
The comparison matrix identified the HFT system as being
better suited to OBBC, and the idea is now extended to
4kW charging of an A-Class EV (Nissan Leaf specification)
Specification of 4kW OBBC
4kW On-Board Bidirectional Charger: features Efficiency under full load > 90% (4kW input power)
Input voltage 50Hz, 230Vrms +/- 10% (giving 380V DC-link)
Input current AC < 20 A
DC Output power 3.6kW @ 90% eff. during full charge of battery
DC Output voltage 240V (depleted) – 403V (fully charged) - Nissan Leaf
Control PWM for AC-DC, Frequency control for DC-DC
EMC standard IEC61000-1-1 and < 5% THD
Protection class Galvanic isolation
Cooling Air-cooled
Optimised resonant tank design
HFT turns ratio of N = 1.66:1 is selected to allow the
converter to develop a DC-link voltage of 380V+5% near
the series-resonant frequency (fsr) from a fully discharged
battery (240V)
Series-resonant frequency of 130kHz selected as a control
bandwidth limit – G2V mode operates below fsr and V2G
mode has to operate above fsr
Control Bandwidth of 100kHz – 170kHz is selected for
initial investigation (SiC will allow higher frequencies)
Normalised bandwidth-limited design procedure previously
investigated and published by USFD allows optimised CLL
resonant components to be selected
Component-based simulations validate operation points
Ideal component parameters
HFT system specification/metrics Primary turns 15 turns 20/84/0.071 Litz
Secondary turns 9 turns 20/84/0.071 Litz
Parallel inductance Lp 137µH (Gapped HFT)
Total series inductance Ls 97µH (Leakage + Discrete)
Series capacitance Cs 15.5nF polypropylene (Discrete)
Operating frequency 100kHz – 170kHz
Power rating 4kW (input)
Core material / type 3C95 / ETD59 cores
HFT + CLL DAB weight ~10Kg incl. fans
HFT + CLL DAB efficiency >90%
HFT + CLL DAB cost £539.70
N.b. MOSFETS are SiC
Full AC-DC System Flow-Diagram
Front-end AC-DC Resonant DC-DC
Full AC-DC OBBC System - Built
System volume ~ 450mm x 200mm x 110mm System weight ~10kg
Results – DAB - Charging
0 0.5 1 1.5 2 2.5
x 10-5
-500
-400
-300
-200
-100
0
100
200
300
400
500380V 45R 99kHz 10.04Ain 406Vout
Time (s)
Vo
lta
ge
(V
) /
Cu
rre
nt
(A)
Vchop
Isec x 10
VGS1
x 10
VGS2
x 10
0 0.5 1 1.5 2 2.5
x 10-5
-500
-400
-300
-200
-100
0
100
200
300
400
500380V 25R7 121kHz 625Ain 240Vout
Time (s)
Vo
lta
ge
(V
) /
Cu
rre
nt
(A)
Vchop
Isec x 10
VGS1
x 10
VGS2
x 10
(a) (b)
Resonant transformer current (secondary) with respect to switched bridge voltage
in charging mode for (a) fully charged battery, and (b) fully depleted battery
100kHz – 403V/9A DC out 125kHz –240V/9A DC out
Results – DAB - Discharging
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
x 10-5
-600
-400
-200
0
200
400
600
Time (s)
Vo
lta
ge
(V
) /
Cu
rre
nt
(A)
Vchop
Isec x 10
VGS1 x 10
VGS1 x 10
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
x 10-5
-600
-400
-200
0
200
400
600
Time (s)
Vo
lta
ge
(V
) /
Cu
rre
nt
(A)
Vchop
Isec x 10
VGS1 x 10
VGS1 x 10
403V in - 173kHz – 380V DC-link 240V in - 141kHz –380V DC-link
(a) (b)
Resonant transformer current (secondary) with respect to switched bridge voltage
in discharging mode for (a) fully charged battery, and (b) fully depleted battery
Results: Integrated and Front-End
(a) (b)
(a) 230V rms grid voltage providing 380V DC-link in charging mode for
a 380V battery voltage (maximum 3kW input power for UK 13A
utility)
(b) 380V battery providing 360V DC-link (threshold limit of 2.2kW
power back to grid before RCD trip limit = 210Vrms)
Integrated 3kW (380V/7.5A DC out) Front-End V2G (2.2kW into grid)
0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05-400
-300
-200
-100
0
100
200
300
400
Time (s)
Vo
lta
ge
(V
) /
Cu
rre
nt
(A)
V
Grid
IGrid
x 10
VDClink
0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05-400
-300
-200
-100
0
100
200
300
400
Time (s)
Vo
lta
ge
(V
) /
Cu
rre
nt
(A)
V
DClink
IGrid
x 10
VGrid
Summary
A 4kW HFT DAB OBBC has been designed and
constructed to validate its capability to bidirectionally
charge/discharge an EV battery of Nissan Leaf
specification with a CC-CV charging scenario (9A CC,
403V CV)
Practical validation of the DC-DC converter has been
achieved at the minimum and maximum operating points
Integrated testing of the complete AC-DC system in G2V
mode has been completed at a 3kW power rating
Integrated testing of the system in V2G mode has been
achieved at low power, but further research into the noise
and ringing on the SiC devices needs to be undertaken for
full system validation and control implementation
Internet of Energy
Thank you for your attention!
Questions ???
Contact: Dr. Chris R. Gould - [email protected]