Chapter 4
Results & Conclusion
4.1 Experiment Name
1.
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4.
5.
Familiarization with Power Electronics Trainer PE-1001
Modes of Operations of SCR and its V-I characteristics
Modes of Operations of DIAC/TRIAC and its V-I characteristics
SCR gate firing circuits and its limits of operation
AC-DC Conversion: Single-Phase Half-Wave / Full-Wave Uncontrolled Rectifier with R
and R-L load
6. AC-DC Conversion: Single-Phase Half-Wave / Full-Wave Controlled Rectifier with R
load
7. AC-DC Conversion: Single-Phase Half-Wave / Full-Wave Controlled Rectifier with R-L
load
8. DC-DC conversion: Operation of Buck Converter
9. DC-DC conversion: Performance Analysis of Buck Converter
10. DC-DC conversion: Operation and Performance Analysis of Boost Converter
11. DC-DC conversion: Operation and Performance Analysis of Buck-Boost Converter
12. AC-AC conversion: AC Power Control using TRIAC-DIAC combination
13. Speed Control of DC Motor using Chopper circuit
14. DC-AC conversion: Operation of a PWM Inverter
4.1.1 Objective
Familiarization with Power Electronics Trainer PE-1001
Objective
To know about the applications of Power Electronics
To know the concept of root mean square and average values.
Modes of Operations of SCR and its V-I characteristics
Objective
To study the V.I. Characteristics of the SCR and to determine the break over voltage, on state resistance,
holding current and latching current.
Modes of Operations of DIAC/TRIAC and its V-I characteristics
Objective
To study the V.I. Characteristics of the DIAC & TRIAC and to determine the break over voltage, on state
resistance, holding current and latching current.
SCR gate firing circuits and its limits of operation
Objective
To observe the output voltage waveforms of half controlled rectifier using resistance (R),
resistance-capacitance (RC) and UJT gate firing Circuits of SCR
AC-DC Conversion: Single-Phase Half-Wave / Full-Wave Uncontrolled Rectifier with R
and R-L load
Objective
1.
2.
3.
4.
To study the output wave forms for different rectifier circuits
To understand the difference between the half wave and full wave rectifier
To calculate the average output voltage of half wave and full wave rectifiers
To measure the performance parameters of half wave and full wave rectifiers
AC-DC Conversion: Single-Phase Half-Wave / Full-Wave Controlled Rectifier with R load
Objective
To obtain controlled output waveforms of a single phase fully controlled bridge rectifier with R
and RL Loads
AC-DC Conversion: Single-Phase Half-Wave / Full-Wave Controlled Rectifier with R-L
load
Objective
To obtain controlled output waveforms of a single phase fully controlled bridge rectifier with RL
Loads
DC-DC conversion: Operation of Buck Converter
Objective
1. To understand the basic circuit and operation of a simple Buck Converter.
2. To study the variation in output of Buck Converter by varying
i.
Duty cycle
ii.
Switching frequency
iii.
Load
DC-DC conversion: Performance Analysis of Buck Converter
Objective
I.
II.
III.
To measure and calculate the output voltage of the converter (operating in CCM) for different
duty cycles.
To study the effect of change of switching frequency on the conduction mode of the converter
and to measure the peak-peak ripple of the output voltage for different switching frequencies.
To study the effect of change of resistive load on the conduction mode of the converter and to
measure the output current of the converter by varying the resistive load.
IV.
To study the effect of filter capacitor value on output ripple voltage.
DC-DC conversion: Operation and Performance Analysis of Boost Converter
Objective
i.
ii.
To understand the basic circuit and operation of a simple Boost Converter.
To study Continuous, Discontinuous and Boundary Conduction Modes of the Boost Converter
by varying.
a. Duty cycle
b. Switching frequency
c. Load
DC-DC conversion: Operation and Performance Analysis of Buck-Boost Converter
Objective
I.
To understand the basic circuit and operation of a simple Buck-Boost Converter.
a. To study Continuous, Discontinuous and Boundary Conduction Modes of the Buck-Boost
Converter by varying.
a. Duty cycle
b. Switching frequency
c. Load
II.
To measure and calculate the output voltage of the converter (operating in CCM) for different
duty cycles.
III.
To study the effect of change of switching frequency on the conduction mode of the converter
and to measure the peak-peak ripple of the output voltage for different switching frequencies.
IV.
To study the effect of change of resistive load on the conduction mode of the converter and to
measure the output current of the converter by varying the resistive load.
V.
To study the effect of filter capacitor value on output ripple voltage.
VI.
To explain the effect of parasitic resistances (Non-ideal circuit).
AC-AC conversion: AC Power Control using TRIAC-DIAC combination
Objective
To study AC voltage control using TRIAC-DIAC combination.
Speed Control of DC Motor using Chopper Circuit
Objective
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To understand the basic circuit and working of 1st quadrant Chopper
To study the wave forms across the motor during on and off period
To understand the purpose of freewheeling diode
DC-AC conversion: Operation of a PWM Inverter
Objective
To understand the operation of a simple Inverter Circuit
4.1.2 Theory over review
Familiarization with Power Electronics Trainer PE-1001
We need to convert electrical energy from one form to another when the power source available is
not according to load requirements. For example in office we have 220V AC available and if we have
to power up a device which operates at 20V DC than I need to convert the power from 220V AC to
20V DC. All the digital devices which use backup batteries need the power converters.
Power Electronics is an interdisciplinary field which is the need of many other fields like
 Digital/analogue electronics
 Power and energy
 Microelectronics
 Control system
 Solid-state physics and devices
 Heat transfer
In all the mentioned fields Power Electronics provide the desired power for the operation of the
systems. Power electronics is of much importance these days when devices are getting smaller and
smaller in size and need more power for fast operation.
Modes of Operations of SCR and its V-I characteristics
The Silicon Controlled Rectifier (SCR) is a semiconductor device that is a member of a family of control
devices known as Thyristors. The SCR has become the workhorse of the industrial control industry. Its
evolution over the years has yielded a device that is less expensive, more reliable, and smaller in size
than ever before. Typical applications include: DC motor control, generator field regulation, Variable
Frequency Drive (VFD) DC Bus voltage control, Solid State Relays and lighting system control.
Modes of Operations of DIAC/TRIAC and its V-I characteristics
TRIAC is a bi-direction thyristor and can be drawn as two thyristors in anti parallel connection and its gates
are joined together as in Fig 3.1. TRIAC can also be considered as an AC electronic switch which has the
capability to block or conduct on both directions.
SCR gate firing circuits and its limits of operation
In power electronic applications SCR is used as switching device to control power flow from
source to load. SCR is a semi controlled device and has three modes of operation forward
blocking, forward conduction and reverse blocking mode. In order to bring SCR to ON state, a
minimum gate current (latching current) is required. This experiment shows simple method of
obtaining gate current for triggering the SCR using R, RC and UJT to control SCR.
AC-DC Conversion: Single-Phase Half-Wave / Full-Wave Uncontrolled Rectifier with R
and R-L load
A rectifier is a circuit that converts an ac signal into a unidirectional signal. Depending on types of input
signal Rectifiers are of two types (1) Single Phase Rectifiers (2) Three Phase Rectifiers. In this Lab we will
deal with the single phase rectifiers only.
AC-DC Conversion: Single-Phase Half-Wave / Full-Wave Controlled Rectifier with R load
A single phase half wave controlled converter only has one SCR is employed in the circuit. The
performance of the controlled rectifier very much depends upon the type and parameters of the
output (load) circuit.
AC-DC Conversion: Single-Phase Half-Wave / Full-Wave Controlled Rectifier with R-L
load
A single phase half wave controlled converter only has one SCR is employed in the circuit. The
performance of the controlled rectifier very much depends upon the type and parameters of the
output (load) circuit.
DC-DC conversion: Operation of Buck Converter
The simplest way to reduce a DC voltage is to use a voltage divider circuit, but voltage dividers waste
energy, they operate by bleeding off excess voltage as heat; also, output voltage is not regulated (varies
with input voltage). A buck converter, on the other hand, can be remarkably efficient (easily up to 95%
for integrated circuits) and self-regulating, making it useful for tasks such as converting the 12-24V typical
battery voltage in a laptop down to the few volts needed by the processor.
DC-DC conversion: Performance Analysis of Buck Converter
A Buck converter operates in continuous conduction mode if the current through the inductor (IL) never
falls to zero during the commutation cycle. The voltage across the inductor is VL = Vi-Vo. The current
through the inductor rises linearly. When the transistor turns off the voltage across the inductor is VL = Vo.
DC-DC conversion: Operation and Performance Analysis of Boost Converter
A boost converter (step-up converter) is a power converter wit an output dc voltage greater than its
input dc voltage. Since power (V*I) must be conserved, the output current is lowered from the source
current. It is a class of switching-mode power supply (SMPS) containing at least two semiconductor
switches (a diode and a transistor) and at least one energy storage element
DC-DC conversion: Operation and Performance Analysis of Buck-Boost Converter
The buck-boost converter is a type of DC-DC converter that has an output voltage magnitude that is
either greater than or less than the input voltage magnitude. It is a switch mode power supply with a
similar circuit topology to the boost converter and the buck converter. The output voltage is adjustable
based on the duty cycle of the switching transistor. One possible drawback of this converter is that the
switch does not have a terminal at ground; this complicates the driving circuitry. Also, the polarity of the
output voltage is opposite the input voltage.
DC-AC conversion: Operation of a PWM Inverter
In the circuit shown, 4047 is a multi vibrator IC used to generate the square wave of desired frequency.
The frequency of the output depends on the value of capacitor connected to pin1 and resistors connected
between the pin2 and pin3. Pin10 gives the output pulse and pin11 gives the inverted pulse. We use these
two pulses to switch the transistors for the operation of inverter.
4.1.3 Circuit Diagram
4.1.4 Apparatus Used
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SCR BT152,
Resistances (470 ohm, 1K (5W))
TRIAC BT136,
Resistor
CRO with Probes
Multimeter
Capacitors
SCR (Silicon Control Rectifier)
Diodes
Variable DC Power Supply
Dual Channel Oscilloscope
DMM
Function Generator
MOSFET IRFZ44
Diode
Inductor
Capacitors ( 1uF, 4.7uF, 10uF, )
Resistors: 10E, 100E, 1000E.
Variable DC Power Supply
Dual Channel Oscilloscope
DMM
Function Generator
EMOSFET (IRF510)
Diode 1N4007
Inductor
Capacitors (1.0, 4.7, 10, 100uF)
Resistors (10, 100, 1K Ω and 1-1K variable load)
Variable DC Power Supply
Dual Channel Oscilloscope
DMM
Function Generator
EMOSFET
Diode
Inductor
Capacitors
Resistors:
EMOSFET (IRFZ44)
4.1.5 Procedure
Modes of Operations of SCR and its V-I characteristics
Procedure
1.
2.
3.
4.
5.
6.
7.
Make the connections as shown in the Fig 3.2.
Set Gate voltages to a specific value (e.g. 2V).
Gradually increase the voltages VAA step by step and measure the voltages VAK, VR and Current IA.
The point at which SCR fires gives the value of break over voltage VBO.
Plot a graph of VAK v/s IA.
Switch off the gate supply voltage.
Observe the value of IA by reducing the voltage VAA. The point at which IA suddenly goes to 0 gives
the value of Holding Current IH.
8. Repeat steps 3 to 7 for another value of gate voltage.
Modes of Operations of DIAC/TRIAC and its V-I characteristics
Procedure
1. Make the connections as shown in the Fig 3.3.
2. Set Gate voltages to a specific value (e.g. 2V).
3. Gradually increase the voltages VAA step by step and measure the voltages VA21(or VMT21), VR2 and
Current IAflowing through the TRIAC.
4. The point at which TRIAC fires gives the value of break over voltage VBO.
5. Plot a graph of VA21 v/s IA.
6. Switch off the gate supply voltage.
7. Observe the value of IA by reducing the voltage VAA. The point at which IA suddenly goes to 0 gives
the value of Holding Current IH.
8. Repeat steps 3 to 7 for another value of gate voltage.
SCR gate firing circuits and its limits of operation
R-Triggering
1. All connections are to be made as per the circuit diagram given in Fig. 2.1. (a).
2. Keep all resistances in max position.
3. Connect the Oscilloscope across the load.
4. Turn on power supply.
5. Vary the firing angle and observe the output voltage and gating pulse waveforms on the CRO.
6. Draw the corresponding waveforms.
RC-Triggering
1. All connections are to be made as per the circuit diagram given in Fig. 2.1. (b).
2. Keep all resistances in max position.
3. Connect the Oscilloscope across the load.
4. Turn on power supply to the module.
5. Vary the firing angle (00 - 1800 ) and observe the waveforms on the CRO
6. Draw the corresponding waveforms
AC-DC Conversion: Single-Phase Half-Wave / Full-Wave Uncontrolled Rectifier with R
and R-L load
Procedure:
1. Construct the circuit for Half Bridge Rectifier as shown in fig 1.
2. Set the autotransformer to give 15V AC.
3. Draw the wave for voltage at the output of the transformer
4. Draw the wave for voltage across the load.
5. Note down the Performance parameters for the half wave rectifier as described before.
6. Now Construct the circuit for full bridge rectifier and repeat the steps 2 to 5.
AC-DC Conversion: Single-Phase Half-Wave / Full-Wave Controlled Rectifier with R load
1.
2.
3.
4.
5.
Make all connections as per the circuit diagram.
Connect first 50V AC supply from Isolation Transformer to circuit.
Connect resistive load R to load terminals.
Connect firing pulses from firing circuit to Thyristor as indication in circuit.
Connect CRO probes and observe waveforms in CRO, Ch-1 or Ch-2, across load and
device in single phase half controlled bridge converter.
6. By varying firing angle gradually up to 180 and observe related waveforms.
7. Measure output voltage and current by connecting AC voltmeter & Ammeter.
8. Tabulate all readings for various firing angles.
AC-DC Conversion: Single-Phase Half-Wave / Full-Wave Controlled Rectifier with R-L
load
1.
2.
3.
4.
5.
Make all connections as per the circuit diagram.
Connect first 50V AC supply from Isolation Transformer to circuit.
Connect resistive load R to load terminals.
Connect firing pulses from firing circuit to Thyristor as indication in circuit.
Connect CRO probes and observe waveforms in CRO, Ch-1 or Ch-2, across load and
device in single phase half controlled bridge converter.
6. By varying firing angle gradually up to 180 and observe related waveforms.
7. Measure output voltage and current by connecting AC voltmeter & Ammeter.
8. Tabulate all readings for various firing angles.
DC-DC conversion: Operation of Buck Converter
1. Construct the circuit of Fig 3.1 on the bread board provided.
2. In order to observe and measure IL& IC with oscilloscope, add series resistors of very small value
with inductor and capacitor in circuit of Fig 3.1.
3. Make sure that the devices are installed in the correct polarity.
4. Apply square wave with adjustable duty ratio using signal generator to the gate of transistor for
switching as shown. The gate of MOSFET, for proper turn-on, must be raised significantly above
the threshold voltage of the device, therefore connect the signal generator between the source
terminal and the gate terminal of the MOSFET. Select square wave on function generator and
using offset adjust the voltage from zero to any positive value i.e. 0 to +10V. you can also use the
voltage as -10 to +10V but the positive value is better for this practical. Another possibility is to
use the CMOS output of the Function Generator set to 12V.
5. Apply input voltage from DC power supply ranging from 5V to 10V. Adjust the source current to
2.5A.
6. Before measuring voltage calibrate the oscilloscope. During measurement set oscilloscope’s
channels to DC coupling. For measuring output voltage ripples adjust channels to AC coupling.
DC-DC conversion: Performance Analysis of Buck Converter
Measurement and calculation of the output voltage of the buck converter (operating in CCM) for
different duty cycles
7. For the given value of the inductor, adjust the following values such that the converter can
operate in continuous Conduction Modes by changing the duty cycle.
VI = …………..
FS = …………… RL = ……………….
8. Measure and calculate the output voltage as indicated in Table 3.1.
Effect of change of switching frequency on the conduction mode of the converter
9. For given value of the inductor, adjust the following values such that the converter can operate
in Continuous and Discontinuous conduction Modes by changing the switching frequency.
VI = …………..
D = ……………
RL = ……………….
10. Measure the peak-peak ripple of the output voltage for different switching frequencies as
indicated in Table 3.2.
Effect of change of resistive load on the conduction mode of the converter
11. For given value of the inductor, adjust the following values such that the converter can operate
in continuous and discontinuous conduction modes by changing the load.
VI = …………..
FS = …………… D = ……………….
12. Measure the output current of the converter by varying the resistive load as indicated in Table
3.3
Effect of filter capacitor value on output ripple voltage
13. Adjust Vi to 5V and keep it fixed for the experiment.
14. Set the duty ratio to 50%, switching frequency at 5KHz and RL = 10 Ohm.
15. Varying the values of capacitor measure the peak-peak output ripple voltage. Record these values
in Table 3.4
DC-DC conversion: Operation and Performance Analysis of Boost Converter
1. Construct the circuit of Fig 3.1 on the breadboard provided.
2. In order to observe and measure IL& IC with oscilloscope, add series resistors of very small value
with inductor and capacitor in circuit of Fig 3.1.
3. Make sure that the devices are installed in the correct polarity.
4. Apply square wave with adjustable duty ratio using signal generator to the gate of transistor for
switching as shown. The gate of MOSFET, for proper turn-on , must be raised significantly above the
threshold voltage of the device, therefore connect the signal generator between the Source terminal
and the Gate terminal of the MOSFET. Select square wave on function generator and using offset
adjust the voltage from zero positive value is better for this practical. Another possibility is to use the
CMOS output of the Function Generator set to 12V.
5. Apply input voltage from DC power supply ranging from 5V to 10V. Adjust the source current to
2.5A.
DC-DC conversion: Operation and Performance Analysis of Buck-Boost Converter
1. Construct the circuit of Fig 3.1 on the breadboard provided.
2. In order to observe and measure IL& IC with oscilloscope, add series resistors of very small value
with inductor and capacitor in circuit of Fig 3.1.
3. Make sure that the devices are installed in the correct polarity.
4. Apply square wave with adjustable duty ratio using signal generator to the gate of transistor for
switching as shown. The gate of MOSFET, for proper turn-on, must be raised significantly above the
threshold voltage of the device, therefore connect the signal generator between the Source terminal
and the Gate terminal of the MOSFET. Select square wave on function generator and using offset
adjust the voltage from zero positive value is better for this practical. Another possibility is to use the
CMOS output of the Function Generator set to 12V.
5. Apply input voltage from DC power supply ranging from 5V to 10V. Adjust the source current to
2.5A.
6. Before measuring voltage calibrate the oscilloscope. During measurement set oscilloscope’s
channel to DC coupling. For measuring output voltage ripples adjust channels to AC coupling.
AC-AC conversion: AC Power Control using TRIAC-DIAC combination
A.
1.Make the connections as shown in the circuit diagram (a).
2.By varying the variable resistance R1 step by step, observe the variation of intensity of light.
B.
1. Construct the circuit as shown in fig b.
2. By varying the variable resistance R1 step by step, note down the corresponding values of by
Oscilloscope and Vac by DMM. Note the readings in the given table.
3. Calculate the current by using the formula
Iac = Vac/R
4. Plot the graph for load voltage on the reference of input voltage.
5. Plot the graph for load voltage vs .
6. Firing angle Is calculated by using formulae


7. The conduction angle can be calculated as
= 180- 
Speed Control of DC Motor using Chopper circuit
1. Make the circuit as shown in the figure 3.1
2. Include a small resistance in series with the diode and motor to see the wave forms of current
using oscilloscope.
3. First set V1 = 15V, f = 10K.
4. Note the Motor RPMs by using tachometer at different duty cycles as shown in table 10.1.
5. Also draw the waveforms for VGS, V0, I0 and ID.
6. Repeat 4 and 6 for f = 1K and f=25K
DC-AC conversion: Operation of a PWM Inverter
Procedure
1) Construct the circuit as shown in fig1.
2) Connect the oscilloscope at pin 10 to note the frequency of the generated pulse. Also draw its
wave form.
3) Connect the oscilloscope at pin11 to note the frequency of the inverted pulse. Also draw its wave
form.
4) Connect the oscilloscope at the output of transformer and note the output voltage level and
frequency.
5) Draw the wave form of the output.
4.1.6 Precautions
Safety precautions to minimize these hazards
General Precautions
 Be calm and relaxed, while working in Lab.
 When working with voltages over 40V or with currents over 10A, there must be at least two people
in the lab at all times.
 Keep the work area neat and clean.
 No paper lying on table or nearby circuits.
 Always wear safety glasses when working with the circuit at high power or high voltage.
 Use rubber floor mats (if available) to insulate yourself from ground, when working in the Lab.
 Be sure about the locations of fire extinguishers and first aid kits in lab.
 A switch should be included in each supply circuit so that when opened, these switches will
deenergize the entire setup. Place these switches so that you can reach them quickly in case of
emergency, and without reaching across hot or high voltage components.
Precautions to be taken when preparing a circuit
 Use only isolated power sources (either isolated power supplies or AC power through isolation
power transformers). This helps using a grounded oscilloscope and reduces the possibility of risk of
completing a circuit through your body or destroying the test equipment.
Precautions to be taken before powering the circuit
 Check for all the connections of the circuit and scope connections before powering the circuit, to
avoid shorting or any ground looping that may lead to electrical shocks or damage of equipment.
 Check any connections for shorting two different voltage levels.
 Check if you have connected load at the output.
 Double-check your wiring and circuit connections. It is a good idea to use a point-to-point wiring
diagram to review when making these checks.
Precautions while switching ON the circuit
 Apply low voltages or low power to check proper functionality of circuits.
 Once functionality is proven, increase voltages or power, stopping at frequent levels to check for
proper functioning of circuit or for any components is hot or for any electrical noise that can affect
the circuit’s operation.
Precautions while switching off or shutting down the circuit
 Reduce the voltage or power slowly till it comes to zero.
 Switch of all the power supplies and remove the power supply connections.
 Let the load be connected at the output for some time, so that it helps to discharge capacitor or
inductor if any, completely.
Precautions while modifying the circuit
 Switch Off the circuit as per the steps
 Modify the connections as per your requirement.
 Again check the circuit as per steps in section 1.3.3, and switch ON as per steps in section 1.3.4.
Other Precautions
 No loose wires or metal pieces should be lying on table or near the circuit, to cause shorts and
sparking.
 Avoid using long wires that may get in your way while making adjustments or changing leads.
 Keep high voltage parts and connections out of the way from accidental touching and from any
contacts to test equipment or any parts, connected to other voltage levels
 When working with inductive circuits, reduce voltages or currents to near zero before switching
open the circuits.
 BEWARE of bracelets, rings, metal watch bands, and loose necklace (if you are wearing any of
them), they conduct electricity and can cause burns. Do not wear them near an energized circuit.
 Learn CPR and keep up to date. You can save a life.
 When working with energized circuits (while operating switches, adjusting controls, adjusting test
equipment), use only one hand while keeping the rest of your body away from conducting surfaces.
4.1.7 Results
Modes of Operations of SCR and its V-I characteristics
A detailed study of the characteristics reveal that the thyristor has three basic modes of operation,
namely the reverse blocking mode, forward blocking (off-state) mode and forward conduction (onstate) mode. Which are discussed in great details below, to understand the overall characteristics of a
thyristor.
Modes of Operations of DIAC/TRIAC and its V-I characteristics
To resolve the issues resulting from the non-symmetrical operation, a DIAC is often placed in series with
the gate. This device helps make the switching more even for both halves of the cycle. This results from
the fact that the DIAC switching characteristic is far more even than that of the TRIAC.
SCR gate firing circuits and its limits of operation
For gate SCR triggering to be used, the SCR must operate below its breakdown voltage, and a suitable
safety margin also allowed to accommodate any transients that may occur. Otherwise forward voltage
or breakdown triggering may occur.
DC-DC conversion: Operation of Buck Converter
The efficiency of buck converters can be very high, often over 90%, making them useful for tasks such
as converting a computer's main supply voltage, which is usually 12 V, down to lower voltages needed
by USB, DRAM and the CPU, which are usually 5, 3.3 or 1.8 V.
DC-DC conversion: Performance Analysis of Buck Converter
By varying the duty cycle of the DC buck converter, the output voltage can be varied proportionally.
Even though the hardware implementation shows the output voltage is reduced by half from the
simulation and calculated results, this problem can be solved with including a second MOSFET in
replacing the diode to reduce the losses and lower voltage drop as compared to diode.
DC-DC conversion: Operation and Performance Analysis of Boost Converter
We have taken into account the real behavior of the passive and active component of the boost
converter and we analyzed its voltage gain factor and conversion efficiency. It has been showed that
inductor series resistance and transistor rDSon resistance play the most important role leading to a
decrease to up to 50% in the voltage gain factor. We also showed that it is not recommended to use
duty cycle close to unity because losses effects are most important there with a markedly decrease of
both voltage gain factor and conversion efficiency.
DC-DC conversion: Operation and Performance Analysis of Buck-Boost Converter
The converter has to maintain output voltage and low voltage source current at their respective
reference levels, irrespective of the variation in loads. A decoupling scheme is proposed for the DSBBFC,
which in turn results in two individual control loops for the said converter. This developed control
strategy ensures the control of the variables independently, irrespective of their coupling nature of the
operation.
AC-AC conversion: AC Power Control using TRIAC-DIAC combination
In this diac tutorial we have seen that the diac such as the ST2 or DB3 is a two-terminal voltage blocking
device that can conduct in either direction. Diacs posses negative resistance characteristics which allows
them to switch “ON” rapidly once a certain applied voltage level is reached.
Speed Control of DC Motor using Chopper circuit
The chopper circuit receives a signal from the firing circuit and then gives a signal to the armature voltage
controller of the separately excited dc motor and the speed is accordingly increased or decreased. In
this system we use two different control loops, in for speed and another for current.
DC-AC conversion: Operation of a PWM Inverter
For every half cycle, there is only one pulse available to control the technique. The square wave signal
will be for reference and a triangular wave will be the carrier. The gate pulse generated will be the result
of the comparison of the carrier and the reference signals. Higher harmonics is the major drawback of
this technique.
4.1.8 Conclusions
Nowadays power electronic converters play key roles within a variety of applications that fulfill
important functions in modern society such as those of renewable energy conversion systems, electric
vehicular applications or power delivery devices, to mention only a few. The operation of power
converters in a very demanding context – requiring a performance set to be ensured along with hard
real-time constraints – renders crucial the necessity of well-performing control structures.
The most typical control approaches of power electronic converters employing both DC and AC power
stages. To this end a formalization effort was detailed in the first part of the book – the first five
chapters – aimed at providing a unified modeling framework, to be further employed in the control
design.
Modeling tools developed in the first part offer sufficient generality to be applied (possibly with minor
adaptations) to any type of switching converter. Control approaches presented in the second part first
provided insights on small-signal model-based linear control, which is simple and intuitive, but relies
upon approximations, hence it lacks robustness. A second class of nonlinear control approaches aims at
alleviating this drawback; these mainly use the large-signal nonlinear models and result in quite complex
control structures – such as feedback linearization or passivity-based – or in less complex variablestructure sliding mode controllers.
The discourse was addressed to students already in mastery of the basis of power electronic circuits and
control systems theory. Insights provided may be used in order to implement control laws either in
analog or in digital form and to analyze the behavior of open-loop and closed-loop power electronic
converters. Although the discourse has been mainly intended for pedagogical goals, the issues
considered indicate some still unexplored paths for research.
Typically a chapter within this book began with an introduction regarding its contents, followed by an
algorithm reflecting a systematic way to solve the stated problem. The core of each chapter consisted of
application.
Since the energy of the coupled inductor’s leakage inductor has been recycled, the voltage stress across
the active switch S1 is constrained, which means low ON-state resistance R DS(ON) can be selected.
Thus, improvements to the efficiency of the proposed converter have been achieved. The switching
signal action is performed well by the floating switch during system operation; on the other hand, the
residential energy is effectively eliminated during the non-operating condition, which improves safety to
system technicians. From the prototype converter, the turns ratio n = 5 and the duty ratio D is 55%;
thus, without extreme duty ratios and turns ratios, the proposed converter achieves high step-up
voltage gain, of up to 13 times the level of input voltage. The experimental results show that the
maximum efficiency of 95.3% is measured at half load, and a small efficiency variation will harvest more
energy from the PV module during fading sunlight.