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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 - Six Step Inverter (continue)

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

Six Step Inverter (cont.)

  • The Fourier series for the output voltage has a fundamental frequency equal to the switching frequency.
  • Harmonic frequencies are in order of 6k +/- 1 for k =1, 2, ... (n = 5, 7, 11, 13 ...).
  • The even harmonics, third harmonic and multiples of the third do not exist.
  • For a dc input voltage, the output for an ungrounded wye-connected load has the Fourier coefficients as derived below.
  • Click to see the derivation of line to line voltage waveform.

  • The output frequency can be controlled by changing the switching frequency.
  • DC input voltage can be adjusted to control the output voltage of a six step inverter.
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