2. Content
• Introduction
• Basics of DC-DC Converter
• Types of DC-DC Converter
Buck Converter or Step-Down Chopper
Boost Converter or Step-Up Chopper
• Design and Simulation of Buck Converter using MATLAB / Simulink
• Design and Simulation of Boost Converter using MATLAB / Simulink
• Design and Simulation of PV System with Boost Converter
• Design of PV System with MPPT and Boost Converter using MATLAB / Simulink
Source: L&T EduTech Team
4. Introduction
• A DC-DC Converter is a power converter that converts a source of direct
current (DC) from one voltage level to another, by storing the input energy
temporarily and then releasing that energy to the output at a different
voltage.
• The store of electric energy may be done in either magnetic field storage
components (inductors, transformers) or electric field storage components
(capacitors).
• DC-DC converter is needed to convert and stabilize voltage. A device that
stabilize the voltage using DC-DC converter is referred to as a voltage
regulator.
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5. Key Applications of DC-DC Converter
• Renewable Energy Integration
• Electric Vehicles
• Smart Lighting
• Spacecraft Power Systems
• DC Motor Drives
• Battery Systems
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6. Main Components of a DC-DC Converter
• DC-DC converters consist of a
Power switch (preferably MOSFET or IGBT)
Snubber Circuit
Inductor Coil
Diode
Capacitor
• The number of these components and their arrangement can differ
• The input voltage is applied in pulses, but the capacitor smoothens it.
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7. Duty Cycle of a DC-DC Converter
• The duty cycle of DC-DC converter is the ratio of the on-time to the total
switching period of the converter.
• Important parameter in the design and operation of DC-DC converters.
• The duty cycle determines the average output voltage of the converter and is
used to control the power transfer from the input to the output.
• Duty Cycle = Ton / (Ton+Toff), where Ton is the on-time and Toff is the off-
time of the switching period.
• Suppose the switching frequency is 2 MHz, which means switching period
T=1/2 MHz=500 ns, If the duty is 0.5 or 50%, then the on-time is 250 ns and
off time is 250 ns.
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11. Buck Converter
• A buck converter or step down converter is a DC-to-DC converter which
decreases voltage, while increasing current, from its input (supply) to its
output (load).
• It is also called as Step-down DC to DC Converter or Step-down Chopper or
Buck Regulator.
• The DC input for the buck converter can be derived from rectified AC or
from any DC supply or battery unit.
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13. Design of Components in Buck Converter
• Given:
Vin=48 V, Vout=15 V (expected), R=8 Ohm, fs=40 KHz.
Step 1: Determine the duty ratio
D=Vout / Vin = 15 V / 48 V = 0.3125 = 31.25 %
Step 2: Determine Inductance Value (L)
Lmin=(1-D)R/2fs = (1-0.3125) 8 / 2 * 40k = 68. 75 micro Henry.
Assume 25 % safety margin for L (for inductor current to be
continuous)
Lactual = 1.25 * Lmin = 1.25 *68.75 = 85.93 micro Henry
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14. Design of Components in Buck Converter
Step 3: Determine Capacitance Value (C)
C=(1-D) / 8L (Ripple Factor) f2
Assume Ripple factor to be less than 5%
C=(1-0.3125) / (8*85.93(0.05)(40*103)2=12.5 micro Farad.
• Choose MOSFET rating with operating voltage atleast two times the output
voltage and operating current atleast three times the output current
• As per EMI standards, switching frequency range is 20 kHz to 2 MHz for
conveters / inverters
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15. Components in MATLAB Simscape – Buck Converter
• DC Voltage Source
• MOSFET (including with snubber circuit)
• Pulse Generator (to trigger Gate of MOSFET)
• Diode (included with Snubber Circuit)
• Series RLC Branch (converted to Inductance)
• Series RLC Branch (converted to Capacitance)
• Series RLC Branch (converted to Resistance)
• Voltage Measurement (to measure output voltage)
• Scope (to view the output voltage graphically)
• Continuous Powergui
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20. Boost Converter
• A boost converter or step-up converter is a DC- to – DC converter that
increases voltage, while decreasing current, from its input (supply) to its
output (load).
• It is also called as Step-Up DC to DC Converter or Step-Up Chopper or
Booster.
• The DC input for the boost converter can be derived from rectified AC or
from any DC supply or battery unit.
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22. Components in MATLAB Simscape – Boost Converter
• DC Voltage Source
• MOSFET (including with snubber circuit)
• Pulse Generator (to trigger Gate of MOSFET)
• Diode (included with Snubber Circuit)
• Series RLC Branch (converted to Inductance)
• Series RLC Branch (converted to Capacitance)
• Series RLC Branch (converted to Resistance)
• Voltage Measurement (to measure output voltage)
• Scope (to view the output voltage graphically)
• Continuous Powergui
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27. PV Array Configuration and Specifications
• Model Make : Trina Solar TSM 350DEG 14 (II)
• Max. Output Power (Pmax) = 349.965 W
• No. of cells per module (Ncell) = 72
• Open Circuit Voltage (Voc) = 46.9 V
• Short Circuit Current (Isc) = 9.6 A
• Max. Peak Voltage (Vmp) = 38.5 V
• Max. Peak Current (Imp) = 9.09 A
• Temperature Coefficient of Voc = -0.3014 % / deg. C
• Temperature Coefficient of Isc = 0.054604 % / deg. C
• No. of Parallel Strings = 1
• Series Connected modules per string = 2
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35. MPPT
• MPPT or Maximum Power Point Tracking is algorithm that included in
charge controllers used for extracting maximum available power from PV
module under certain conditions.
• The voltage at which PV module can produce maximum power is called
maximum power point (or peak power voltage).
• The function of an MPPT charge controller is analogous to the transmission
in a car. When the transmission is in the wrong gear, the wheels do not
receive maximum power.
• The main benefits of MPPT charge controllers is
Increase the charging efficiency.
Increase the power output of the solar system, especially in low-light or cold
conditions
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36. Types of MPPT Algorithms
1. Perturb and Observe (P & O)
2. Incremental Conductance (IC)
3. Fractional Open Circuit Voltage
4. Fractional Short Circuit Voltage
5. Fuzzy Logic Control
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MPPT
Conventional
Artificial Intelligence
Metaheuristic
37. Perturb & Observe (P&O) Algorithm
• A P&O method is the simplest method, which moves the operating point
toward the maximum power point periodically increasing or decreasing the
PV array voltage.
• Because of constant step width, the system faces high oscillation especially
under unstable environmental consitions.
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38. Incremental Conductance (IC) Method
• Widely preferred MPPT algorithm in PV system for maximum power point
tracking.
• Can perform better at quickly varying atmospheric circumstances.
• The incremental conductance algorithm detects the slope of the P-V curve,
and the MPP is tracked by searching the peak of the P-V curve.
• Thus, this algorithm works by measuring the change in power with respect
to the change in voltage and current at each step, and then adjusts the
operating point to keep the system at the MPP.
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39. Concept of IC
• The incremental conductance method is developed under the fact of slope of
the PV array power curve is zero at the MPP.
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41. PV Array Configuration and Specifications
• Model Make : Trina Solar TSM 350DEG 14 (II)
• Max. Output Power (Pmax) = 349.965 W
• No. of cells per module (Ncell) = 72
• Open Circuit Voltage (Voc) = 46.9 V
• Short Circuit Current (Isc) = 9.6 A
• Max. Peak Voltage (Vmp) = 38.5 V
• Max. Peak Current (Imp) = 9.09 A
• Temperature Coefficient of Voc = -0.3014 % / deg. C
• Temperature Coefficient of Isc = 0.054604 % / deg. C
• No. of Parallel Strings = 2
• Series Connected modules per string = 2
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42. PV Array with MPPT Boost Converter Design
Parameters
• Duty Ratio will be determined by MPPT
• Switching frequency = 5 kHz
• Sample Time = 5e-6 sec
• Load Resistance = 20 Ohm
• Lactual = 2 mH
• C=100 MicroFarad
• Capacitance connected across PV array = 100 micro Farad (to supress input
voltage ripple and filter ripple current).
• Constant (delta) for MPPT =125e-6
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43. MATLAB Script for P&O Algorithm
• The function gets PV array voltage, PV array current and a constant value
delta as input arguments and gives duty cycle as output or return value.
• Initialize the minimum, maximum and initial value of duty cycle.
• Initialize the interval values of Vpv, Ppv, and duty cycle for the initial run.
• Calculate the PV power and change in Power and Change in Voltage.
• Check if change in power and change in voltage is less than zero and vary
the duty cycle by incrementing / decrementing from the original value.
• Check whether the calculated duty cycle is within the minimum / maximum
value already initialized else not to min. or max. value whichever violates.
• Update the values of Vpv, Ppv and duty cycle with the newly calculated
values for the next run.
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44. Components in MATLAB Simscape – PV with MPPT and
Boost Converter
• PV Array
• Constant (for Irradiance and Temperature)
• MATLAB Function (for P&O Algorithm)
• PWM Generator
• Goto and from Blocks
• MOSFET (including with snubber circuit)
• Diode (included with Snubber Circuit)
• Series RLC Branch (converted to Inductance)
• Series RLC Branch (converted to Capacitance)
• Series RLC Branch (converted to Resistance)
• Voltage Measurement (to measure output voltage and input voltage)
• Current Measurement (to measure output current and input current)
• Scope (to view the output voltage graphically)
• Continuous Powergui
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45. MATLAB Built-in Model for PV System with MPPT
and Boost Converter
• Type the following in the command prompt in MATLAB
open example (‘simscapeelectrical/SolarPVMPPTBoostExample’)
• To open a script that design the Solar PV system with MPPT using boost
converter, at the MATLAB command line, enter:edit
‘SolarPVMPPTBoostData’
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