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Simulation of Sinosoidal Pulse Width Modulation (Unipolar) Inverter

Presented by Supervised By• Tanzeel Ahmad SP14EPE095 Dr. abdul majid

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INTRODUCTION

What is Modulation??

Modulation can be defined as the process of varying a parameter of

carrier signal in accordance with the instantaneous value of the

message signal.

• Modulation is used to reduce the size of the antenna and increases

efficiency.

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Types of modulation techniques

• FM: Frequency Modulation• AM: Amplitude Modulation• PM: Pulse ModulationTypes Of Pulse Modulation:

1. PWM—Pulse Width Modulation

2. PPM— Pulse Position Modulation3. PAM— Pulse Amplitude Modulation

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What is PWM…?

Pulse-width modulation (PWM) is a modulation process or technique used in most communication systems for encoding the amplitude of a signal right into a pulse width or duration of another signal, usually a carrier signal, for transmission.

OrThe Pulse Width Modulation (PWM) is a technique which is

characterized by the generation of constant amplitude pulse by modulating the pulse duration by modulating the duty cycle.

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Block Diagram of PWM

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Techniques of PWM

• 1. Linear modulation• 2. Saw tooth PWM• 3. Single Pulse Width Modulation• 4. Multiple Pulse Width Modulation• 5. Sinusoidal Pulse Width Modulation

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Principle

• Pulse-width modulation uses a rectangular pulse wave whose pulse width is modulated resulting in the variation of the average value of the waveform.

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The simplest way to generate a PWM signal is the intersective method, which requires only a saw tooth or a triangle waveform (easily generated using a simple oscillator) and a comparator.

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What is an Inverter ??• An inverter is basically a device that converts electrical energy of DC

form into that of AC.• The purpose of DC-AC inverter is to take DC power from a battery

source and converts it to AC• The inverter receives DC supply from 12V battery and then inverter

converts it to 230V AC with a desirable frequency of 50Hz• These DC-AC inverters have been widely used for industrial

applications such as uninterruptible power supply (UPS), AC motor drives.

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SINUSOIDAL PULSE WIDTH MODULATION (SPWM)• Instead of, maintaining the width of all pulses of same as in case of

multiple pulse width modulation, the width of each pulse is varied in proportion to the amplitude of a sine wave evaluated at the Centre of the same pulse.• The gating signals are generated by comparing a sinusoidal reference

signal with a triangular carrier wave of frequency • The frequency of reference signal ,determines the inverter output

frequency and its peak amplitude ,controls the modulation index ,and Vrms output voltage

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• The inverters job is to take this input voltage and output ac where the magnitude and frequency can be controlled• In order to output a sinusoidal waveform at a specific

frequency a sinusoidal control signal at the specific frequency is compared with a triangular waveform• The inverter then uses the frequency of the triangle

wave as the switching frequency

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PWM with Unipolar Voltage Switching• The two types of pulse width modulation inverters are

bipolar and unipolar switching.• Each unique switching technique creates either a

unipolar or bipolar output at the load.• The control signals depend on comparing a reference

signal and carrier signal

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• Unipolar PWM uses a high frequency for one pair and a low frequency for the other pair of switches

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BLOCK DIAGRAM OF THE SPWM SYSTEM

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SIMULINK MODEL OF UNIPOLAR VOLTAGE SWITCHING

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PWM PULSE GENERATOR FOR UNIPOLAR VOLTAGE SWITCHING

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GATE PULSES GENERATION FOR UNIPOLAR VOLTAGE SWITCHING

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GATE PULSES WAVEFORMS

• The PWM pulse generator block generator block generator block generates the four PWM pulses and these pulses are given to the gates of the MOSFET s for turning on and turn off.

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RESULT Simulation Waveform

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CONCLUSION• The electronic devices is smaller, therefore the efficiency of

power supply used in electronic devices should be improved from time to time.• The different switching techniques and switching elements

were used in single phase inverter also considered when inverters become the best power supply for converting DC power to AC power. • Based on studied, SPWM techniques is a common method

used in single phase inverter circuit are Unipolar and Bipolar voltage Switching.

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Applications of PWM

Servos

PWM is used to control servomechanisms.Telecommunication

In telecommunications, PWM is a form of signal modulation where the widths of the pulses correspond to specific data values encoded at one end and decoded at the other.Power delivery

PWM can be used to control the amount of power delivered to a load without incurring the losses that would result from linear power delivery by resistive means

• High frequency PWM power control systems are easily realisable with semiconductor switches

• Variable-speed fan controllers for computers usually use PWM, as it is far more efficient when compared to a potentiometer or rheostat

• Light dimmers for home use employ a specific type of PWM controlVoltage regulation• PWM is also used in efficient voltage regulators. By switching voltage

to the load with the appropriate duty cycle, the output will approximate a voltage at the desired level. The switching noise is usually filtered with an inductor and a capacitor.

Electrical• SPWM (Sine–triangle pulse width modulation) signals are used in

micro-inverter design (used in solar and wind power applications). These switching signals are fed to the FETs that are used in the device. The device's efficiency depends on the harmonic content of the PWM signal

• Another common application is in robotics where PWM signals are used to control the speed of the robot by controlling the motors.

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The End

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