DEPARTMENT OF ELECTRICAL POWER ENGINEERING

COLLEGE OF ENGINEERING

POWER ELECTRONICS

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Topics Covered - Pulse Width Modulated Inverters - Single Phase Inverter - Amplitude & Harmonics Control

TOPICS COVERED:

DC TO DC CONVERTER

•  Introduction

Buck (Step Down) Converter

•  Assumptions Made for Analysis of the Buck Converter

•  *Circuit Operation Switching Modes

•  Output Voltage Average

•  The Inductor Current Ripple

•  The Load and the Capacitor Current

•  Continuous Conduction Condition

•  The Capacitor Voltage Ripple

Boost (Step Up) Converter

•  Assumptions Made for Analysis of the Boost Converter

•  *Circuit Operation Switching Modes

•  Output Voltage Average

•  The Inductor Current Ripple

•  The Inductor Current

•  Continuous Conduction Condition

•  The Diode and Capacitor Currents

•  The Capacitor Voltage Ripple

Designing DC-DC Converters

•  Converter Design Consideration

PULSE WIDTH MODULATED INVERTERS

•  Introduction

•  Inverter Types

•  Basic Inverter

•  Performance Parameters

•  Fourier Series

•  Total Harmonic Distortion

Single Phase Inverter

•  Single Phase Half Bridge Inverter

•  Single Phase Full Bridge Inverter

•  Square-wave Inverter

•  Square-wave Inverter with RL Load

•  Pulse-Width Modulation (PWM) Control Strategy

•  Amplitude & Harmonics Control

•  Sinusoidal Pulse Width Modulation (SPWM)

•  PWM Definitions & Considerations

Bipolar Switching (Single Phase)

•  PWM Outputs

•  PWM Harmonics

Unipolar Switching (Single Phase)

•  PWM Outputs

•  PWM Harmonics

Three Phase Inverter

•  Introduction

•  Switch State for Six Step Inverter

•  Six Step Inverter (continue)

•  Three Phase SPWM

 

 

Amplitude & Harmonics Control

The amplitude of the fundamental frequency for a square wave output from the full bridge inverter is determined by dc input voltage.

The switching scheme can be modified to produced a controlled output.

An output voltage has intervals when the output is zero , + Vdc and - Vdc.

The output voltage can be controlled by adjusting the interval on each side of the pulse where the output is zero.

 

Figure in (a) shows inverter output for amplitude and harmonic control while figure in (b) shows the swithicng sequence for the full bridge inverter.

Click here to show derivation.

is the angle of zero voltage on each end of the pulse.

The amplitude of the fundamental frequency (n=1) is controllable by adjusting .

Harmonic content can be eliminated by adjusting . Harmonic n is eliminated if = 90 0 /n

Note:

To control both amplitude and harmonics using the switching scheme, it is necessary to be able to control the dc input voltage to the inverter.

A dc-dc converter placed between the dc source and the inverter can provide a variable dc input.

How to obtain variable dc input? click me.

See example

 

 

 

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