1. CASCADED MULTILEVEL INVERTER FOR HYBRID ELECTRIC VEHICLES
Authors
Ankit Kumar Verma
P. R. Thakura
K.C.Jana and
G.Buja (Fellow Member, IEEE)

2. OBJECTIVE
HEV are used for increase fuel efficiency and to tackle pollution problems.
To make a transformer less multilevel inverter for high voltage and high current HEV.
The cascaded inverter is IGBT based and it is fired in a sequence.
The simulation has been done in PSIM and MATLAB and its responses match the theoretical concept of multilevel inverter.

3. INTRODUCTION HEV Multilevel inverters ARCHITECTURE ENGINE EFFICIENCY
INCREASE FUEL EMISSIONS
POWER ELECTRONICS
MEET HIGH POWER DEMANDS using BATTERIES.
Multilevel inverters
HIGH VOLTAGES AND HIGH POWER
NO TRANSFORMERS
A STAIRCASE OUTPUT (similar to sinusoidal output waveform )
LOW HARMONIC DISTORTION
INCREASE IN VOLTAGE LEVELS

4. HYBRID ELECTRIC VEHICLES
C O N F I G U R A T I O N S
Series : Single path to power the wheels. Two energy sources. The fuel tank feeds engine coupled to generator to charge battery which provides electrical energy to motor/generator to power the wheels. Motor/generator also used to recharge the battery during deceleration and braking.
Parallel : Two parallel paths - engine path and electrical path to power the wheels. The transmission couples motor or generator and engine, allowing either/ both to power the wheels. Controlling is complex.
Series-parallel: Both Series and Parallel energy paths. A system of motors and/or generators that sometimes includes a gearing or power split device couples allows engine to recharge battery. Variations on this configuration can be very complex or simple, depending on the number of motors/generators and how they are used. Configuration classified as Complex hybrids (Toyota Prius and Ford Escape Hybrids), Split-Parallel hybrids, or Power-Split hybrids. 4

5. Series HEV pe = Mechanical Power ps = Stored Power or pe pw ps HereB S G
ICE W M F pw ps
Here
F = Fuel Tank
ICE = Internal Combustion Engine
G = Generator
S = Energy Storage System
B = Common Bus
M = Motor
W = Wheels
pe = Mechanical Power
ps = Stored Power or
Power drawn by electric drive train
ps = Propulsion Power drawn for wheels
Electrical Link
Hydraulic Link
Mechanical Link

6. Parallel HEV pm = Remaining Power by Electric drivetrain HereS
ICE W M F A pe pw pm ps
Here
pm = Remaining Power by Electric drivetrain
A = adder
Which draws the propulsion power for wheels
cwe and cwm are coefficients that depend on gear arrangement of A.

7. Series-Parallel HEV pe pd pb pm pw ps
ICE W M F A P pb pm pw ps
It’s a combination of series and parallel HEV.
P divides the power generated by ICE in two parts: Pd (mechanical form) and Pb(electrical form).
Addition of Pd and Pw gives propulsion power for wheels (Pw).
So splitting of ICE power is obtained by two ways:
1. an apparatus based on a mechanical devices.
2. an apparatus based on electrical device.

8. TAXONOMY OF MULTILEVEL INVERTER
Neutral Point Clamped (NPC) Inverter
Cascaded
Flyback Capacitor

9. DIODE CLAMPED
Proposed by Nabea,Takahasi and Akagi in Switches are switched in such manner that it will give stair case output. Here for each step four switches are ON and capacitor have equal charge(Vdc/4) .
There are m capacitors and 2(m-1) switches and (m-1)*(m-2)diode per phase.
Advantages
All of the phase share a common DC bus, which
minimizes the capacitance requirement of the converter.
The capacitor can be pre-charged as a group.
Efficiency is high for fundamental frequency switching.
Disadvantages
Real power flow is difficult as the intermediate DC levels
will tend to overcharge or discharge without precise
monitoring and control.
The number of clamping diodes required is quadratic
related to levels which is cumbersome with units of high
number of levels.

10. FLYBACK CAPACITOR Advantages : Disadvantages:
Introduced by Meynard and Foch in Structure similar to diode clamped. The voltage increment between two adjacent capacitor leg gives the size of the voltage steps in output waveform.
There are (m-1) *(m-2)/2 capacitor and 2(m-1) switches per phase
Advantages :
Phase redundancies are available for balancing the voltage levels of the capacitor.
Real and reactive power flow can be controlled.
The large number of capacitor enables to ride through short duration outages and deep voltage sags.
Disadvantages:
Control is complicated to track the voltage levels for all of the capacitors and pre-charging all of them to same level and startup is complex.
Switching utilization and efficiency are poor for real power transmission.
Large number of capacitor makes it expensive and bulky.

11. Multilevel Inverter Topologies
Per-Phase Diagram

12. Cascaded Multilevel Inverters
Topics to be discussed
H-Bridge Inverter
Cascaded Multilevel Inverter

13. H-Bridge Inverter S1 and S4; S1 and S2; S3 and S2; S3 and S4;
180o conduction mode
Complementary
Switch pairs:
S1 and S4;
S3 and S2;
Firing Switch pairs at the same time:
S1 and S2;
S3 and S4;

14. PWM technique vAB from -Vd to +Vd PWM: or from +Vd to –Vd
Just we can see that the output waveform is modulated.

15. CHB Multi-level Inverter Topologies
Eleven-Level CHB Inverter
Output Voltage Level
Here
Van = Phase Voltage
m = no. of levels
and
m = 2s+1
where
s = no. of H-bridge

16. Phase Voltage Fourier series
Waveform of vAN is composed of Eleven voltage levels:
5E, 4E, 3E, 2E, E, 0,
-E, -2E, -3E, -4E, and -5E

17. Calculation of Switching Angles
Set of Non-linear Transcendental Equation
Solving the above equation by NEWTON RAPHSON iterative method
and considering M = 0.8 then m = 11 (for Eleven-Level cascaded Multilevel Inverter)

18. Simulation and Results
PSIM
MATLAB

19. Eleven level Cascaded Multilevel Inverter
Simulation on PSIM

20. Output Voltage for Eleven Level CMI

21. Input – Output Response

22. Model of Eleven-level CMI in MATLAB
Controlling block

23. Analysis of waveform in MATLAB
(c)Line-to-line voltage
(d)Phase voltage
at modulation index 0.9
(b)
(a)
(c)
(d)
Line-to-line voltage
Phase voltage
at modulation index 0.8
From the analysis its seen that
The Total Harmonic Distortion (THD) is less than 5%

24. Change of Modulation Index
(b)
Change of
Phase voltage and
Line-to-line voltage
at different modulation index (0.8 and 0.9) using MATLAB

25. THREE PHASE SQUIRREL CAGE INDUCTION MOTOR
Specifiation
THREE PHASE SQUIRREL CAGE INDUCTION MOTOR
Power = 20 kW,
line-line voltage = 400 V,
frequency = 50Hz,
stator resistance (Rs) = Ω,
rotor resistance (Rr) = Ω,
stator leakage inductance (Ls) = 991 μH,
rotor leakage inductance (Lr) = 991μH,
mutual inductance (M) = mH,
moment of inertia = JKg.m2,
friction factor = FNms

26. CMI circuit for application in laboratory
H-bridge
Pulses to the H-Bridge is given by DSPACE/OPAL-RT
Eleven-level CMI

27. Selection of components for Cascaded H-Bridge Inverter
Motor Ratings
Vl-l=400V,
Prated=5HP,
Cosθ = 0.8 = power fatcor
IGBT ratings
Vp= Vl-l/√3
Vp(peak)= Vpx √2
V1max= 4 sVdc/π
Vp(peak) = V1max
Vpx √2 = 4 sVdc/π

28. Isolation transformer ratings
Capacitor ratings
Isolation transformer ratings
Taking a frequency of 50 Hz, the dc ripple would have a frequency of 50x6 Hz =300 Hz for a three phase rectifier.
Transformer rating for prototype will be
100V and 1.5A and 300VA with a turn ratio of 1:2 and it should be electrically isolated.
If the Transformer is not for prototype then rating will be 307 V and 23A and 7KVA with a turn ratio of 1:2 and it should be electrically isolated.

29. Controlling of Five-level CMI for lab experiment
Gate pulses for the Five-level CHB inverter is provided by DSPACE or OPAL-RT.
Simulation is done on MATLAB as RT-simulators are accessible by MATLAB

30. Gate driver (HIP-4081A) PC Board schematic layout
A0 and B0 is the voltage we get from one H-bridge
IN1 and IN2 are gate pulses provided from DSPACE or OPEL-R
B+ and Com gets the power from the capacitor
+12V supply is provided after regulating the voltage

31. Components Rating No. of pieces
Components required for Gate driver (HIP-4081A)
Components
Rating
No. of pieces
CD4096UB
(cmos inverter)
1µA and 18V 1
Capacitor
C6 and C5
12V, 4.7mF
12V, 0.22mF
(each)
C3 and C4
(ceramic)
100V and 0.1 mF
Bootstrap Diodes
CR1 and CR2
(fast recovery diodes)
100V and 1A
Resistors
R33 and R34
(for deatime control)
100kW-500kW
R30 and R31
(current limiting signal)
0.1W-2W

32. Components selected and order placed for prototype of
CHB Inverter
Components
rating
No. of pieces
P-MOSFET
IRF 520
100V 9A 24
CAPACITOR
280µF 6
RECTIFIER MODULE
8AKBU8G
VPIV = 400V
Vrms = 280
Ifwd(avg) = 8A
GATE DRIVER IC
HIP4081A
VDD = 15V
Igate(peak) = 2.5A
VIN ≤ 2V
ISOLATION TRANSFORMER
1.5A
300VA 3

33. Conclusion
In this work cascaded multilevel inverter is interfaced with electric drive of HEVs because of following special features:
The number of components used in cascaded is less than other types
of multilevel inverters like diode clamped and flyback capacitor
multilevel inverter.
It is suitable for high voltage and high current rating electric drives.
HEV has high current and low voltage rating in order to reduce
weight of the batteries.
Cascaded multilevel inverters are switched at low frequency so it will
create low noise which can be suppressed and comfortable for driving
HEVs.
This converter will have high power factor and also have less EMI and
voltage unbalance problem.

34. References:
C C Chan, “The State of the Art of Electric, Hybrid, and Fuel Cell Vehicles”, proceeding of IEEE, 2007.
M. Ehsani, Y. Gao, Ali Emadi, Modern electric ,Hybrid Electric and Fuel Cell Vehicles; Fundamentals theory and design 2nd edition, CRC Press , 2009.
C C Chan and K.T. Chau, Modern Electric Vehicles Technology, Oxford University Press, 2001.
L. M. Tolbert and F. Z. Peng, “Multilevel inverters for large automotive drives,” All Electric Combat Vehicle 2nd Int. Conf.,Dearborn, MI, vol. 2, pp. 209–214 ,June 8–12, 1997.
P.R.Thakur et.al,” Technology and role of power split apparatus for hybrid electric vehicles, IEEE, IECON, Taiwan, Nov. 2007, pp
A.Emadi, K.Rajashekara, S.S.Williamson and S.M.Lukic, ”Topological overview of hybrid electric and fuel cell vehicular power system architectures and configurations”, IEEE Trans. on Vehicular Technology, vol.54, no.3, pp , May 2005.
“The Insight-Honda’s First Hybrid Electric Vehicle”, Special Auto Technology, pp , Converters used in railways.
K.C. Jana, S. Biswas and P.R.Thakura “A simple and generalized space vector pulse width modulation of multi-level voltage source inverter” IEEE, ICIT-06 Mumbai, Dec.2006.
M.H.Rashid, Fundamental of power electronics, Prentice Hall India, 2nd Edition, Delhi, 2004.
Leon M. Tolbert, Fang Zheng Peng, and Thomas G. Habetler,“Multilevel converters for large electric drives” IEEE Trans. Indus. Applicat., vol. 35, no.1, pp , Jan. /Feb., 1999.
J. S. Lai and F. Z. Peng, “Multilevel converters—A new breed of power converters,” IEEE Trans. Ind. Applicat., vol. 32, pp , May/June 1996.

35. Thanks