Power Electronics Introduction to Power Electronic

Systems

1

Dr. Firas Obeidat

2

Table of contents

1

• What is Power Electronics ?

2

• Goal of power electronic systems

3

• Advantages and disadvantages of Power Electronic Systems

4

• Converter Classification

5

• Interdisciplinary Nature of Power Electronics

6

• Applications of Power Electronics

Dr. Firas Obeidat Faculty of Engineering Philadelphia University

3 Dr. Firas Obeidat Faculty of Engineering Philadelphia University

What is Power Electronics ?

A field of Electrical Engineering that deals with the application of power

semiconductor devices for the control and conversion of electric power.

Power Electronics

Converters Load

Controller

Output - AC

- DC

Input

Source - AC

- DC

- unregulated

Reference

sensors

Introduction

Power Electronic Converters – the heart of power electronics system

4 Dr. Firas Obeidat Faculty of Engineering Philadelphia University

Introduction

Power electronics relates to the control and flow of electrical energy.

Control is done using electronic switches, capacitors, magnetics, and control systems.

Scope of power electronics: milliWatts ⇒ gigaWatts.

Power electronics is a growing field due to the improvement in switching technologies and the need for more and more efficient switching circuits.

5 Dr. Firas Obeidat Faculty of Engineering Philadelphia University

Introduction

Goal of power electronic systems

To convert electrical energy from one form to another, i.e. from the source to

load with:

highest efficiency

highest availability

highest reliability

lowest cost,

smallest size

least weight.

6 Dr. Firas Obeidat Faculty of Engineering Philadelphia University

Introduction

Advantages of Power Electronics System

High efficiency due to low loss in power semiconductor devices.

High reliability of power electronic converter system.

Long life and less maintenance due to absence of any moving parts.

Flexibility in operation

Fast dynamic response compared to electromechanical converter system.

Small size and less weight, thus low installation cost.

Disadvantages of Power Electronics System

Circuits in power electronics system have a tendency to generate harmonics in the supply system as well as the load circuit.

AC to DC and AC to AC converter operate at low input power factor under certain operating condition.

Regeneration of power is difficult in power electronic converter system.

Power Electronic controllers have low overhead capacity

7 Dr. Firas Obeidat Faculty of Engineering Philadelphia University

Introduction

Power electronics systems can operate in the range from few watts up to GW,

with frequency range from some 100 Hz up to some 100 kHz, depending on the

power handled.

8 Dr. Firas Obeidat Faculty of Engineering Philadelphia University

Converter Classification

AC/DC

Rectifier

DC/AC

Inverter

AC/AC

Converter

DC/DC

Converter

The objective of a power electronics circuit is to match the

voltage and current requirements of the load to those of the

source. Power electronics circuits convert one type or level

of a voltage or current waveform to another and are hence

called converters.

Converters are classified by the relationship between input

and output:

9 Dr. Firas Obeidat Faculty of Engineering Philadelphia University

Converter Classification

1- AC input/DC output

• The AC-DC converter produces a DC output from an AC input. Average power is transferred from an ac source to a DC load. The AC-DC converter is specifically classified as a rectifier.

2- DC input/AC output

• The DC-AC converter is specifically classified as an inverter. In the inverter, average power flows from the DC side to the AC side.

3- DC input/DC output

• The DC-DC converter is useful when a load requires a specified (often regulated) dc voltage or current but the source is at a different or unregulated DC value.

4- AC input/AC output

• The AC-AC converter may be used to change the level and/or frequency of an AC signal.

10 Dr. Firas Obeidat Faculty of Engineering Philadelphia University

Interdisciplinary Nature of Power Electronics

The advent of microelectronics and computer control made

it possible to apply modern control theory to power

electronic (PE) and at same the time made possible very

complex circuit functions. Therefore, the area of PE,

became interdisciplinary.

11 Dr. Firas Obeidat Faculty of Engineering Philadelphia University

Applications of Power Electronics

Power electronics is a key technology for transmission, distribution,

storage, renewable energy sources and users sub-systems, and has

spread in many applications such as:

Residential Refrigeration and freezers, Space heating, Air conditioning, Cooking, Lighting, Electronics (personal computers, other entertainment equipment).

Commercial Heating, ventilating, and air, conditioning, Central refrigeration, Lighting, Computers and office equipment, Uninterruptible power supplies (UPSS), Elevators.

Industrial Pumps, Compressors, Machine tools (robots), Arc furnaces, induction furnaces, Lighting, Industrial lasers, Induction heating, Welding.

Transportation Traction control of electric vehicles, Battery chargers for electric vehicles, Electric locomotives, Street cars, trolley buses, Subways, Automotive electronics including engine controls.

Utility systems High-voltage dc transmission (HVDC), Static VAR compensation (SVC), Supplemental energy sources (wind, photovoltaic), fuel cells, Energy storage systems, Induced-draft fans and boiler, feed water pumps.

Aerospace Space shuttle power supply systems, Satellite power systems, Aircraft power systems.

Telecommunications Battery chargers, Power supplies (DC and UPS).

12