DEPARTMENT OF ELECTRICAL POWER ENGINEERING

COLLEGE OF ENGINEERING

POWER ELECTRONICS

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Topics Covered - Pulse Width Modulated Inverters - Single Phase Inverter - Squarewave Inverter with RL Load

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

 

Single Phase Inverter

Square-wave Inverter with RL Load

An inductive load presents some considerations in designing the switches in full bridge circuit because the switch current must be bidirectional.

At t = 0

Assumptions made: S1 & S2 are closed, S3 & S4 are opened.

Load voltage = + Vdc

I increases in the load, S1 and S2.

Current is expressed as sum of forced and natural responses.

At t = T/2

Assumptions made: S1 & S2 are opened, S3 & S4 are closed.

Load voltage = - Vdc

Click to see the waveform of square wave output voltage and steady state current for an RL load

When circuit is first energized, initial inductor current is zero, a transient occurs before load current reaches a steady state condition.

At steady state, io is periodic and symmetric about zero.

Let current at t = 0 in initial condition to be minimum and current at t = T/2 in initial condition to be maximum.

Click here to show derivation.

The general equation for rms value of a waveform x(t) can be obtained in earlier chapter.

Therefore, rms load current can be determined. Then, power absorbed by load and from dc source are:

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