NUST UNIVERSITY CEME CAMPUS
Selected Topics In power
Shahzain Sajid
361918
Assignment#1
Part#1 DC modulation wave
❖ Case #1(Single phase half bridge converter)
In the above diagram a single-phase half bridge converter with R-L load is shown. In that
converter we are going to apply DC modulation Wave to turn ON and turn OFF the different
switches used in the half bridge converter.
In this diagram are using two MOSFET’s which have internal body diode in them. Each of MOSFET
is acting as a switch which can offer bidirectional current to follow but allow only Unidirectional
Voltage across the R-L Load (because internal i-v characteristics curves of the MOSFET show that
it is a device which can work only in the 1st and 4th quadrant which make it Unidirectional voltage
and bidirectional current device).
To adjust the times of switching of Two MOSFETS we are comparing the magnitude of DC
modulation wave (of zero frequency) with carrier wave (of high frequency) using comparator and
then
✓ If the magnitude DC modulation wave is greater than Carrier wave, then s1 is on and
Upper MOSFET conducts and allow the applied input voltage to came across load and the
current can flow from the source towards load (MOSFET itself conducts) or form load
towards source (body diode conducts)
✓ If the magnitude of carrier wave is greater than DC modulation wave, then s2 is on (which
is performed by using NOT gate Infront of comparator) and lower MOSFET conducts in
that time and disconnect the applied input source from load and the current loop is
complected by conduction of either MOSFET or body diode. Hence in this cycle the
voltage across output is zero but the current flow in both positive and negative direction
Results:
•
•
As our duty cycle is 0.8 hence we are getting more output voltage (which is shown by the
difference in Ton and Toff of voltage cycle{max time v is 100v and min time it is 0v})
The current wave we obtain is sawtooth
❖ Case #2 (Single phase full bridge converter)
In the above diagram a single-phase full bridge converter with R-L load is shown. In that converter
we are going to apply DC modulation Wave to turn ON and turn OFF the different switches used
in the full bridge converter.
In this diagram are using four MOSFET’s which have internal body diode in them. Each of MOSFET
is acting as a switch. In this full bridge converter, we are seeing that is just a replica of singlephase half bridge converter. The left leg (Having two MOSFET’s which s1 and s4 as driving pulse)
is responsible for feeding positive source voltage across the R-L load and the right leg (Having
two MOSFET’s which s2 and s3 as driving pulse) is responsible for feeding negative source voltage
across the R-L load and the current is also bidirectional in that full bridge converter like it was in
half bridge converter.
To adjust the times of switching of four MOSFETS we are comparing the magnitude of DC
modulation wave (of zero frequency) with carrier wave (of high frequency) using comparator and
then
✓ If the magnitude DC modulation wave is greater than Carrier wave, then s1 and S4 is high
and respective MOSFET’s (at position 1 and 4 respectively) conducts and allow the applied
input positive voltage to came across load and the current can flow from the source
towards load (MOSFET itself conducts) or form load towards source (body diode
conducts)
✓ If the magnitude of carrier wave is greater than DC modulation wave, then s2 and s3 is
high (which is performed by using NOT gate Infront of comparator) and respective
MOSFET’s(at position 2 and 3 respectively) conducts in that time and allow the negative
input voltage to came across R-L load and the current can flow from the source towards
load (MOSFET itself conducts) or form load towards source (body diode conducts).
Results:
•
•
As I have mentioned above current and the voltage both are bidirectional ,the results also show
that both the voltage and current are at positive and negative axis showing that they are
bidirectional .
Using a DC modulation wave for a full bridge converter gives a continuous current sawtooth
waveform at the load side with Less frequency than the half bridge converter output waveform.
Part#1 Sine PWM modulation wave
❖ Case #1 (Single phase half bridge converter)
In the above diagram a single-phase half bridge converter with R-L load is shown. In that
converter we are going to apply sine modulation Wave to turn ON and turn OFF the different
switches used in the half bridge converter.
In this diagram are using two MOSFET’s which have internal body diode in them. Each of MOSFET
is acting as a switch which can offer bidirectional current to follow but allow only Unidirectional
Voltage across the R-L Load (because internal i-v characteristics curves of the MOSFET show that
it is a device which can work only in the 1st and 4th quadrant which make it Unidirectional voltage
and bidirectional current device).
To adjust the times of switching of Two MOSFETS we are comparing the magnitude of sine
modulation wave (of low frequency) with carrier wave (of high frequency) using comparator and
then
✓ If the magnitude sine modulation wave is greater than Carrier wave, then s1 is on and
Upper MOSFET conducts and allow the applied input voltage to came across load and the
current can flow from the source towards load (MOSFET itself conducts) or form load
towards source (body diode conducts)
✓ If the magnitude of carrier wave is greater than sine modulation wave, then s2 is on
(which is performed by using NOT gate Infront of comparator) and lower MOSFET
conducts in that time and disconnect the applied input source from load and the current
loop is complected by conduction of either MOSFET or body diode. Hence in this cycle the
voltage across output is zero but the current flow in both positive and negative direction
Results:
Zoomed one
•
•
•
As mentioned earlier the current is bidirectional and voltage is unidirectional means voltage
waveform is only on the x-axis making it unidirectional .
In sine modulation , when the magnitude of sine modulation wave reaches to maximum peak
value and become equal to the magnitude of carrier wave. At that point the max voltage
concentration is obtained at the output load because it is the point where the Ton is maximum
and Toff is minimum and after that the concentration of output voltage decrease as the
magnitude of modulation wave decreases and came to minimum when modulation wave
reaches to its negative peak(here is the point where Toff is max and Ton is minimum
The current waveform at the output terminal is a sinusoidal waveform.
With modulation wave and carrier wave
Difference of output when DC modulation wave and sine PWM wave is applied
The key difference is when we apply Dc modulation, we are not getting the sine wave form of
current on the load but when we apply sine PWM we are getting sine waveform of Current and
a better voltage waveform at the output which have more on time when the sine modulation
wave achieves its peak and varies as it decreases.
❖ Case #2 (Single phase full bridge converter)
In the above diagram a single-phase full bridge converter with R-L load is shown. In that converter
we are going to apply sine modulation Wave to turn ON and turn OFF the different switches used
in the full bridge converter.
In this diagram are using four MOSFET’s which have internal body diode in them. Each of MOSFET
is acting as a switch. In this full bridge converter, we are seeing that is just a replica of singlephase half bridge converter. The left leg (Having two MOSFET’s which s1 and s4 as driving pulse)
is responsible for feeding positive source voltage across the R-L load and the right leg (Having
two MOSFET’s which s2 and s3 as driving pulse) is responsible for feeding negative source voltage
across the R-L load and the current is also bidirectional in that full bridge converter like it was in
half bridge converter.
To adjust the times of switching of four MOSFETS we are comparing the sine modulation wave
(of low frequency and pi degree apart for each leg)) with carrier wave (of high frequency) using
comparator and then
✓ If the magnitude DC modulation wave is greater than Carrier wave, then s1 and S4 is high
and respective MOSFET’s (at position 1 and 4 respectively) conducts and allow the applied
input positive voltage to came across load and the current can flow from the source
towards load (MOSFET itself conducts) or form load towards source (body diode
conducts)
✓ If the magnitude of carrier wave is greater than DC modulation wave, then s2 and s3 is
high (which is performed by using NOT gate Infront of comparator) and respective
MOSFET’s(at position 2 and 3 respectively) conducts in that time and allow the negative
input voltage to came across R-L load and the current can flow from the source towards
load (MOSFET itself conducts) or form load towards source (body diode conducts).
Results:
With modulation waves
•
•
•
As mentioned earlier the current and voltage both are bidirectional means voltage waveform is
on both x-axis and y-axis making it bidirectional .
The current waveform at the output terminal is a sinusoidal waveform.
In sine modulation , when the magnitude of sine modulation wave reaches to maximum peak
value and become equal to the magnitude of carrier wave. At that point the max voltage
concentration is obtained at the output load because it is the point where the Ton is maximum
and Toff is minimum and after that the concentration of output voltage decrease as the
magnitude of modulation wave decreases and came to minimum when modulation wave
reaches to its negative peak(here is the point where Toff is max and Ton is minimum
❖ Case #3 (Three phase bridge converter)
In the above diagram a three-phase bridge converter with R-L load is shown. In that converter
we are going to apply sine modulation Wave to turn ON and turn OFF the different switches used
in the three-phase bridge converter.
In this diagram are using six MOSFET’s which have internal body diode in them. Each of MOSFET
is acting as a switch. In this three-phase bridge converter, we are seeing that it is just a replica of
single-phase half bridge converter with additional two legs added.
❖ The left leg (Having two MOSFET’s which s1 and s4 as driving pulse) is responsible for
feeding source voltage across the R-L load of one of the phases
❖ The right leg (Having two MOSFET’s which s5 and s2 as driving pulse) is responsible for
feeding source voltage across the R-L load of one of the phases
❖ The central leg (Having two MOSFET’s which s3 and s6 as driving pulse) is responsible for
feeding source voltage across the R-L load of one phase
and the current is also bidirectional in that three-phase bridge converter like it was in full bridge
converter.
To adjust the times of switching of six MOSFETS we are comparing the sine modulation wave (of
low frequency and 2*pi/3 degree apart for each leg) with carrier wave (of high frequency) using
comparator and then
In this circuits each of the diode covers 180 degrees angle and the ON and OFF during the one
complete cycle(360degree) is given below
Results
Part #3 Square modulation wave
❖ Case #1 (Single phase half bridge converter)
In the above diagram a single-phase half bridge converter with R-L load is shown. In that
converter we are going to apply square modulation Wave to turn ON and turn OFF the different
switches used in the half bridge converter.
In this diagram are using two MOSFET’s which have internal body diode in them. Each of MOSFET
is acting as a switch which can offer bidirectional current to follow but allow only Unidirectional
Voltage across the R-L Load (because internal i-v characteristics curves of the MOSFET show that
it is a device which can work only in the 1st and 4th quadrant which make it Unidirectional voltage
and bidirectional current device).
To adjust the times of switching of Two MOSFETS we are applying square PWM of 50%duty cycle
directly to S1 and inverted duty cycle is given to s2 using NOT operation
✓ When s1 is high s2 is low (OFF) and Upper MOSFET conducts while lower MOSFET remains
OFF and the ON MOSFET allow the applied input voltage to came across load and the
current can flow from the source towards load (MOSFET itself conducts) or form load
towards source (body diode conducts)
✓ When s2 is high s1 is low then lower MOSFET conducts in that time and disconnect the
applied input source from load and the current loop is complected by conduction of either
MOSFET or body diode. Hence in this cycle the voltage across output is zero but the
current flow in both positive and negative direction
Results:
Difference of output when square modulation wave and sine PWM wave is applied
The key difference is when we apply square modulation, we are not getting the sine waveform
of current on the load (A triangular one) but when we apply sine PWM we are getting sine
waveform of Current but when we apply square modulation wave, we are getting the same
output at smaller on duty cycle which concludes than its voltage gain at load is better than sine
PWM modulation.
❖ Case #2 (Single phase full bridge converter)
In the above diagram a single-phase full bridge converter with R-L load is shown. In that converter
we are going to apply square modulation Wave to turn ON and turn OFF the different switches
used in the full bridge converter.
In this diagram are using four MOSFET’s which have internal body diode in them. Each of MOSFET
is acting as a switch. In this full bridge converter, we are seeing that is just a replica of singlephase half bridge converter. The left leg (Having two MOSFET’s which s1 and s4 as driving pulse)
is responsible for feeding positive source voltage across the R-L load and the right leg (Having
two MOSFET’s which s2 and s3 as driving pulse) is responsible for feeding negative source voltage
across the R-L load and the current is also bidirectional in that full bridge converter like it was in
half bridge converter.
To adjust the times of switching of four MOSFETS we are applying square modulation wave of
50%duty cycle directly to S1 and s4 and inverted duty cycle is given to s2 and s3 using NOT
operation
✓ When s1 and s4 are high s2 and s3 are low (OFF) and the respective MOSFET’s (at position
1 and 4) conducts while the MOSFET’s (At position 2 and 3) remains OFF and the ON
MOSFET allow the applied input voltage to came across load and the current can flow
from the source towards load (MOSFET itself conducts) or form load towards source
(body diode conducts)
✓ When s2 and s3 are high and s1 and s4 are low then respective MOSFET’s (At position 2
and 3) conducts in that time while the MOSFET’s (At position 1 and 4) remains OFF and
the ON MOSFET allow the inverted applied input voltage to came across load.
Results:
❖ Case #3 (Three phase bridge converter)
In the above diagram a three-phase bridge converter with R-L load is shown. In that converter
we are going to apply square modulation Wave to turn ON and turn OFF the different switches
used in the three-phase bridge converter.
In this diagram are using six MOSFET’s which have internal body diode in them. Each of MOSFET
is acting as a switch. In this three-phase bridge converter, we are seeing that it is just a replica of
single-phase half bridge converter with additional two legs added.
❖ The left leg (Having two MOSFET’s which s1 and s4 as driving pulse) is responsible for
feeding source voltage across the R-L load of one of the phases
❖ The right leg (Having two MOSFET’s which s5 and s2 as driving pulse) is responsible for
feeding source voltage across the R-L load of one of the phases
❖ The central leg (Having two MOSFET’s which s3 and s6 as driving pulse) is responsible for
feeding source voltage across the R-L load of one phase
and the current is also bidirectional in that three-phase bridge converter like it was in full bridge
converter.
To adjust the times of switching of six MOSFETS we are Applying square modulation waves each
of duty cycle 33.5% and adjusted as
✓ When pulse1 is high pulse2 and pulse3 are low
✓ When pulse2 is high pulse1 and pulse3 are low
✓ When pulse3 is high pulse2 and pulse1 are low
In this circuits each of the diode covers 180 degrees angle and the ON and OFF during the one
complete cycle(360degree) is given below
Results
Part#4 Sine with noise modulation wave
❖ Case #1 (Single phase half bridge converter)
Difference of output when noise is added in sine PWM wave
When we apply noise to a sine PWM wave, we get disturb current and voltage output on the load
side and if the magnitude and frequency of noise is significant then it has a great impact to
destroy the actual wave form of Voltage and current.
❖ Case #2 (Single phase full bridge converter)
With modulation and carrier wave
❖ Case #3 (Three phase bridge converter)
In the above diagram a three-phase bridge converter with R-L load is shown. In that converter
we are going to apply sine modulation Wave to turn ON and turn OFF the different switches used
in the three-phase bridge converter.
In this diagram are using six MOSFET’s which have internal body diode in them. Each of MOSFET
is acting as a switch. In this three-phase bridge converter, we are seeing that it is just a replica of
single-phase half bridge converter with additional two legs added.
❖ The left leg (Having two MOSFET’s which s1 and s4 as driving pulse) is responsible for
feeding source voltage across the R-L load of one of the phases
❖ The right leg (Having two MOSFET’s which s5 and s2 as driving pulse) is responsible for
feeding source voltage across the R-L load of one of the phases
❖ The central leg (Having two MOSFET’s which s3 and s6 as driving pulse) is responsible for
feeding source voltage across the R-L load of one phase
and the current is also bidirectional in that three-phase bridge converter like it was in full bridge
converter.
To adjust the times of switching of six MOSFETS we are comparing the sine modulation wave with
noise signal (of low frequency and 2*pi/3 degree apart for each leg) with carrier wave (of high
frequency) using comparator and then
In this circuits each of the diode covers 180 degrees angle and the ON and OFF during the one
complete cycle(360degree) is given below
Results
Explanation for noise added to the modulating wave:
When we add noise signal of higher frequency with low magnitude is will disturb the actual sinusoidal
waveform of the modulation wave and hence in comparison with the carrier wave we are not getting
the desired output voltage and current waveforms as we are getting in pure sinusoidal modulation
wave, (square v, sine i) rather some sort of ripples introduced in the load waveforms because the noise
irregulate our pure sine wave .so ,if magnitude of noise is less the less effect on the output (as in our
case)but if it have higher magnitude as compared to modulation wave it has a great impact on the
output.