International Journal of Industrial Electronics and Electrical Engineering, ISSN: 2347-6982
Volume-3, Issue-6, June-2015
H-BRIDGE MULTI LEVEL INVERTER WITH REDUCED THD FOR
AUTOMOTIVE APPLICATION
1
AISWARYA P R, 2AKSHARA JAYAN, 3ARCHA S P, 4MINU MANUEL, 5POOJA JOSE
M.Tech Students, Vedavyasa Institute of Technology, Malapuram, Kerala
Email: aiswarya.kollora@gmail.com
Abstract- This paper presents a compact inverter-battery combination for automotive application as a replacement for DCAC converter. A 9 level H-bridge inverter is introduced for this purpose with a reduced amount of Total Harmonic
Distortion. When compared to the conventional inverter multilevel inverters have an advantage on Total Harmonic
Distortion reduction; by increasing the levels THD can be reduced without changing efficiency. Relevance of H-bridge
inverter, change in THD with respect to multi level inverter levels and comparison in THD values , working principle
circuit design, THD analysis, simulation results of the power circuit using MATLAB-SIMULINK, simulation of control
circuit using Proteus-ISIS schematic capture and Hardware prototype are included in this paper.
Keywords: Multilevel Inverter, Total Harmonic Distortion, Automotive application, 9-level H-bridge inverter.
I.
INTRODUCTION
followed by a DC-DC converter in order to boost up
the voltage level connected to dc link and thereby a
DC-AC converter in [23]. This DC-AC converter is
connected to the motor which is adjusting input
voltage of the motor which result in the speed control
of the vehicle. The block diagram of the electric
vehicle is shown in figure.1.It shows the connection
of DC-AC (Proposed H-bridge multi level inverter)
with the transmission system. Here the DC-AC
converter or the proposed H-Bridge multilevel
inverter is used to feed the main drive of the electric
vehicles; this can be successfully used with other
motors also.
Pollution is an issue of this era; fossil fuel vehicles
are having a major role in polluting the environment.
To overcome this issue electric vehicles can be used
which can be called as a lesser pollutant. General
motor’s president put forward the idea of electric
vehicle with two seats in 1990.Leading car
manufacturers like Ford, Honda, Nissan and Toyota
followed German Motors in manufacturing electric
cars by the end of 90’s [1][16].When coming to the
building blocks of electric vehicles they are
composed of motors, batteries and semiconductor
converters. The semiconductor converters will
liberate heat. In order to overcome the heat cooling
fans are used along with pumps and radiators. EVs
can be classified on the basis of the usage of them.
On-Off road EVs, rail borne EVs, Space rover
vehicles, Air borne EVs are some among them
analysed in [2]-[7].
Figure 1.Block diagram of Electric vehicle
The switching devices in the proposed H-bridge
inverter are selected in such a way the whole system
have
minimized
switching
loss.
These
semiconducting switches are feeding different motors
in an electric vehicle such as 3-phase induction
motor, stepper motor, servomotor depending on the
use of the motors ,such as serving the main drive and
some auxiliary motors which are driving power
steering power windows etc. By considering the use
motor and converters are selected. Converters are
selected depending on the input of the motor or in
other words DC/DC converter if the motor input is
DC and DC/AC converter if the input of the motor is
AC.
A. Block Diagram of Electric Vehicle
The function of the H-bridge multilevel inverter is to
collect energy from the dc- link capacitor and
transfer to the motor. The inverter can be used in
order to give supply for the motor as well as the
speed control.
B. Relevance of H-bridge multi level Inverter in
Automobile Application
DC to AC conversion is done using H-bridge MLI
in order to provide feed appropriate supply to the
motors. Apart from DC to AC conversion H-bridge
multi level inverter can take part in the speed control
of the main drive motor 3-phase induction motor.
Speed of main drive motor can be controlled in two
methods they are i) by stator voltage control and ii)
by v/f control by varying the output voltage of the H-
The block diagram comprises of a battery which is
feeding energy to the engine of the car. The battery is
H-Bridge Multi Level Inverter With Reduced THD For Automotive Application
84
International Journal of Industrial Electronics and Electrical Engineering, ISSN: 2347-6982
bridge multi level to a desired voltage level. Also the
different levels of multi level inverter can be used for
feeding motors of different input voltage
specifications. Like stepper motor in power steering,
servomotor used in power windows, glass wiper
driving motors etc.
Volume-3, Issue-6, June-2015
combination of switches S2 and S3 yields - Vdc. Zero
voltage level when all the switches are OFF.
The circuit diagram for a 9 level H-bridge multi
level inverter with 4 single phase full bridge along
with switching patterns table are given in the below.
II. PROPOSED H-BRIDGE MULTI LEVEL
INVERTER FOR AUTOMOTIVE
APPLICATION
In multi level inverter the input voltage is vdc and
its different levels [28] are forming the output
voltage levels of the inverter as following. Consider
Vm is the output voltage levels and the input voltage
is vdc
Then the output voltage level is given by
Vm= vdc/m-1
Where m is the number levels of the multi level
inverter.
An H-bridge multilevel inverter consist of m
number of single phase full bridge inverter cascaded
connected .In cascaded inverter voltage-clamping
diodes or voltage balancing capacitors are not used.
For real power conversion (AC-DC-AC) separate dc
input voltage is required which is from fuel cell,
solar cell or battery. Components required for
cascade inverter are lesser compared to other form of
multi level inverters. Soft switching can be
performed if required.
Circuit design is done as follows: number of single
phase full bridge inverter can be calculated using the
equation given below by considering the number of
voltage levels and input voltage.
N=m-1/2
Where,
N=number of DC voltage source
M=output phase voltage level
For a 9 level cascade inverter 4 individual
batteries and 4 single phase full bridges are required.
As the level of the output phase voltage is 9 voltage
waveform is almost sinusoidal and the Total
Harmonic Distortion (THD) is a small value.
Figure 2.Circuit diagram of 9 level H-bridge MLI
Table.1 switching patterns
A. Working Principle
The output voltage is obtained between first and
fourth H-bridge end terminals. The phase output
voltage is the sum of individual H-bridge outputs.
Each H-bridge consist of a DC source of Vdc. In a
single H-bridge inverter it is generating three output
voltage levels and they are + Vdc, - Vdc and zero.
The switching combinations of switches S1 and S4
yields output voltage of single H-bridge as +Vdc and
S1
S2
S3
S4
OFF
ON
OFF
OFF
OFF
ON
OFF
OFF
ON
OFF
ON
OFF
Output
Voltage
0
+Vdc
-Vdc
The pulses given to each single phase full bridge
inverter are shown in figure.3 as the input DC
H-Bridge Multi Level Inverter With Reduced THD For Automotive Application
85
International Journal of Industrial Electronics and Electrical Engineering, ISSN: 2347-6982
voltage of each inverter are equal the voltage levels
are symmetrical and are equally divided as 4 Vdc , 3
Vdc , 2 Vdc , 1 Vdc, 0, -1 Vdc,-2 Vdc,-3 Vdc, -4 Vdc as
the sum sum with corresponding triggering pulses.
These equally divided voltage level forms the 9
voltage levels as mentioned earlier.
Volume-3, Issue-6, June-2015
From this comparison it is clear that as the level of
the H-bridge increases the THD value decrease by
using lesser number of switching components and
control circuits for these semiconducting switches.
As a result of lesser number of switching devices and
control circuit the system is compact as well as it can
be designed easily. In other multi level inverters
switching devices like diode clamped multilevel
inverter and flying capacitor multi level inverter the
number of switches clamped diodes voltage
balancing capacitors are high and a complex
controlling unit which result in a high value of THD
[21]-[26]. This drawback is overcame by the usage of
H-bridge of high voltage levels without sacrificing
the efficiency.
Figure 3. Triggering pulses
III. TOTAL HARMONIC DISTORTION (THD)
ANALYSIS
The total harmonic distortion is defined as the
measure of closeness of the obtained waveform to the
shape of its fundamental waveform. And is given by
the equation
Figure 5. THD value of 7 level H-bridge multi level inverter
Where,
=voltage of the fundamental voltage
=voltage of the nth wave
For the purpose of calculating the THD of a 9 level
H-bridge inverter. The proposed circuit diagram is
simulated with the help of MATLAB R2014a
SIMULINK with appropriate triggering pulses. From
the simulation result it is clear that the 9 level Hbridge multi level inverter has a THD value of 8.54%
which is a low value as shown in figure.4. A 7 level
H-bridge inverter has a THD of 12.13 greater than
that of 9 level from figure.5, 5 level has a THD value
of 16.89obtained from figure.6.
Figure 6. THD value of 7 level H-bridge multi level inverter
From the FFT analysis of 9 level H-bridge multi
level inverter, 7 level H-bridge multi level inverter, 5
level H-bridge multi level inverter the comparison of
THD values are done and tabulated in table 2.It is
giving a fair idea about the relationship between
number of levels and the THD values. As the number
of levels increase the Total Harmonic Distortion
decreases with a mentionable amount,
Table 2. Comparison of THD values
INVERTER LEVELS
9
7
5
Figure 4.THD value of 9 level H-bridge multi level inverter
H-Bridge Multi Level Inverter With Reduced THD For Automotive Application
86
THD(%)
8.54
12.13
16.89
International Journal of Industrial Electronics and Electrical Engineering, ISSN: 2347-6982
Volume-3, Issue-6, June-2015
this circuit is obtained as shown in figure 8. A sine
wave is also included along with the output phase
voltage in order to show the closeness to the
fundamental wave.
Control circuit simulation done using PROTEUS
ISIS schematic capture. The controller used to
generate pulses are explained in the hardware
session.
IV.SIMULATION RESULTS
The power circuit of the proposed H-bridge multi
level inverter is simulated using MATLAB
R2014a version SIMULINK. And the simulation
diagram is shown in figure 7.
Figure 9.PROTEUS ISIS schematic capture of control circuit
The corresponding pulses as the simulation result
of the PROTEUS ISIS schematic capture is shown in
figure 10.These pulses are same as that of the pulses
shown in figure 3.
Figure 7.Simulation diagram of proposed 9 level H-bridge Multi
level inverter
Figure 10.Pulses of control circuit
V.
Figure 8.Output phase voltage of proposed 9 level H-bridge
Multi level inverter
EXPERIMENTAL RESULT
The 9 level H-bridge Multi level inverter is
shown in figure 11. The switching devices are
Here IGBT s are used as power switches of
inverter and gate is triggered using individual pulses
named subsystem 1 to subsystem 8( set of 2) . Output
terminals are connected to a R-load followed by
voltage measurement block and scope. The output of
commercially available 600-V IGBT/IPM modules.
The microcontroller used for generating control
pulses are ATMEGA328P which is a 32-bit
microcontroller available
in market. This
microcontroller is selected for the construction of
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International Journal of Industrial Electronics and Electrical Engineering, ISSN: 2347-6982
Volume-3, Issue-6, June-2015
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prototype by considering the availability of the
microcontroller as well as the easiness in writing the
program codes for generating pulses. The output side
of the inverter is connected to a 6V servo motor in
order to show the automobile application. The
application of the servomotor in a electric
vehicle/automobile is in power window. Output
terminal can be connected across a CRO in order to
observe the output phase voltage.
Figure 11.prototype of proposed 9 level H-bridge Multi level
inverter
VI. FUTURE SCOPE
The THD of the multi level can be further
reduced by increasing the levels. Or in other
words this 9 level H-bridge MLI can be replaced
with 15 level H-bridge MLI without sacrificing
the efficiency. This replacement can also be used
for electric vehicle and automobile application.
CONCLUSION
In this paper the flying capacitor multi level inverter
is replaced with 9 level H-bridge multi level inverter
in order to overcome the demerits of the existing
system. Analysis has shown that the proposed 9 level
H-bridge Multi level inverter requires a lesser
number of switching devices and a compact and easy
method is used for the control circuit. Moreover it
reduces the THD levels compared to other MLIs.
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