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DEPARTMENT OF ELECTRICAL POWER ENGINEERING

COLLEGE OF ENGINEERING

POWER ELECTRONICS

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Topics Covered - Pulse Width Modulated Inverters - Three Phase Inverters - Sinusoidal PWM

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

 

 

Three Phase Inverter

Sinusoidal PWM

  • Pulse width modulation can also be used for three phase inverters besides single phase inverters.
  • The PWM switching and advantages are the same for both single and three phase inverters.
  • Basically, each switch is controlled by comparing a sinusoidal reference wave with a triangular carrier wave. The fundamental frequency of the output is similar to reference wave. The amplitude of the output is obtained from relative amplitudes of the reference and carrier waves.
  • The three reference sinusoidals are 120 degrees apart to produce a balanced three phase output. Switch controls are:

      S1 is on when Va > Vtri

      S 2 is on when Vc > Vtri

      S3 is on when Vb > Vtri

      S4 is on when Va < Vtri

      S5 is on when Vc < Vtri

      S6 is on when Vb < Vtri

  • Harmonics will be minimized if the carrier frequency is chosen to be an odd or multiple of 3 of the reference frequency, which is 3, 9, 15, ... times the reference.

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| Home | Topics | Summary of Topics | Examples | Test Your Understanding | Survey |