DEPARTMENT OF ELECTRICAL POWER ENGINEERING

COLLEGE OF ENGINEERING

POWER ELECTRONICS

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Topics Covered - Pulse Width Modulated Inverters - Single Phase Inverter - PWM Control Strategy

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 - PWM Control Strategy

Criteria Considered for Controlling Single Phase Inverter

There are several methods of controlling single phase inverter. However, these are few criterias that we need to look at:

  1. Output voltage range
  2. Maximum output voltage
  3. Switching losses
  4. Distortion in output and input sides ( Distorion is measured based on inverter performance)

Pulse Width Modulation (PWM)

  • PWM provides a way to decrease the total harmonic distortion of load current.
  • Generally, THD requirements is met easily than the square wave switching scheme for PWM inverter output after filtering.
  • The unfiltered PWM output will have a relatively high THD. But, it can be filtered easily due to high frequencies of harmonics.

click to see this webpage http://www.acroname.com/robotics/info/concepts/pwm.html

It may give you some rough idea on PWM.

There are two main types of PWM control strategy that we are going to learn here:

Amplitude & Harmonics Control

  • Amplitude of the output voltage can be controlled with the modulating waveforms.
  • Harmonics can be decreased and output voltage amplitude can be controlled with the reduced filter requirements.
  • But, control circuits for the switches is complex, losses increase due to more frequent switching.

Click me to go to Amplitude & Harmonics Control

Sinusoidal Pulse Width Modulation (SPWM) - Bipolar & Unipolar switching

Control of the switches for sinusoidal PWM output requires:

  • reference signal (modulating or control signal) - sinusoid in the case we are going to learn
  • carrier signal (triangular wave that controls the switching frequency)

Click me to go to SPWM

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