Introduction to power electronics

Power Electronics

Content

Introduction

Chapter 1 Power Electronic Devices

Chapter 2

Chapter 3

Chapter 4

Chapter 5

Introduction

Outline What is power electronics? The history Applications About this course

I. What is power electronics?

1) Definition

Power Electronics: is the electronics applied to conversion and control

of electric power.

Range of power scale :

milliwatts(mW) megawatts(MW) gigawatts(GW)

A more exact explanation:

The primary task of power electronics is to process and control the

flow of electric energy by supplying voltages and currents in a form

that is optimally suited for user loads.

Conversion of electric power

Other names for electric

power converter:

-Power converter

-Converter

-Switching converter

-Power electronic circuit

-Power electronic converter

Electric Power Converter

Power output

Power input

Control input

Power electronic system

Generic structure of a power electronic system

Control is invariably required.Power converter along with its controller

including the corresponding measurement and interface circuits, is

also called power electronic system.

Power Converter

Control input Controller

Reference

Power input

Power output

Feedback (measurements of output signals )

Feedforward ( measurements of input signals )

A typical power electronic system

The task of power electronics has been recently extended to also ensuring the currents and power consumed by power converters and loads to

meet the requirement of electric energy sources.

Power Converter

Measurements

Controller Reference

Power input

Power output

Electric Motor light heating other electric equipment power converter

Electric utility battery other electric energy source power converter

Source

Load

io

Vo

ii

Vi

2) Relation with information electronics

A Classification of electronics by processing object

Other classifications of electronics

Electronics

Information electronics: to process information Power electronics: to process electric power

Electronics

Vacuum electronics: using vacuum devices, e.g, vacuum tubes devices

Solid (Solid state) electronics: using solid state devices,

e.g, semiconductor devices

Electronics

Physical electronics: physics,material,fabrication, and manufacturing of electronic devices

Applied electronics: application of electronic

devices to various areas

3) The interdisciplinary nature

William E. Newell’s description

Power electronics is the interface between electronics and power.

Power Electronics

学

Electronics

Power

学

Control

Continuous,

discrete

连续、离

散

Static & rotating

power equipment

Devices,circuits

Relation with multiple disciplines

Power electronics is currently the most active discipline in electric power engineering.

Power electronics

electronics electr

Electric machines

Circuit Ct theory

Systems& Control theory

Control

theory

Signal processing

Simulation & computing

electronics

Solid state

physics

Electromagnetics

Power systems

4) Position and significance in the human society

Electric power is used in almost every part and everywhere of modern

human society.

Electric power is the major form of energy source used in modern

human society.

The objective of power electronics is right on how to use electric power,

and how to use it effectively and efficiently, and how to improve the

quality and utilization of electric power.

Power electronics and information electronics make two poles of

modern technology and human society: information electronics is the

brain, and power electronics is the muscle.

II. The history

Mercury arc rectifier Vacuum- tube rectifier

Thyratron

Invention of Thyristor

Applicat ion of fast- switching fully- controlled semiconductor

devices

Power diode Thyristor

GTO GTR

Power MOSFET Thyristor

(microprocessor)

IGBT Power MOSFET

Thyristor (DSP)

Pre-history

1st phase

2nd phase

3rd phase

1957

1900

late 1980s

mid 1970s

III. Applications

Industrial applications

Motor drives

Electrolysis

Electroplating

Induction heating

Welding

Arc furnaces and ovens

Lighting

Transportation applications Trains & locomotives Subways Trolley buses Magnetic levitation Electric vehicles Automotive electronics Ship power systems Aircraft power systems

Utility stems applications High- voltage dc transmission(HVDC)Flexible ac transmission(FACTS)Static var compensation & harmonicssuppression: TCR, TSC, SVG, APFCustom power & power quality controlSupplemental energy sources :wind, photovoltaic, fuel cellsEnergy storage systems

Power supplies for electronic equipment

Telecommunications

Computers

Office equipment

Electronic instruments

Portable or mobile

electronics

Residential and home appliances

Lighting

Heating

Air conditioning

Refrigeration & freezers

Cooking

Cleaning

Entertaining

Applications in space technology

Spaceship power systems

Satellite power systems

Space vehicle power systems

Other aplications

Nuclear reactor control

Power systems for particle accelerators

Environmental engineering

Trends It is estimated that in developed countries now 60% of the electric

energy goes through some kind of power electronics converters before it is finally used.

Power electronics has been making major contributions to: --better performance of power supplies and better control of electric

equipment --energy saving --environment protection reduction of energy consumption leads to less pollution reduction of pollution produced by power converters direct applications to environment protection technology

IV. A simple example

A simple dc-dc converter example

Input source:100V

Output load:50V, 10A, 500W

How can this converter be realized?

Dc-dc converter

+ -

+

-

V

50V

R

5Ω

I

10A

Vg

100V

Dissipative realization

Resistive voltage divider

+ -

+

-

V

50V

R

5Ω

I

10A

Vg

100V

Pout=500W Pin=1000W

+

-

50V

Ploss=500W

Series pass regulator:

transistor operates in active region

+ -

+

-

V

50V

R

5Ω

I

10A

Vg

100V

Pout=500W Pin≈1000W

+

-

50V

Ploss≈500W

linear amplifier

And base driver

- +

Vref

Use of a SPDT switch

+ -

+

-

V(t)

50V

R

I

10A

Vg

100V

+

-

Vs(t)

Vs(t) Vg

switch position:

Vs=DVg

DTs

(1-D)Ts

0

1

1

2

t

1

2

The switch changes the dc voltage level

Vs(t) Vg

switch position:

Vs=DVg

DTs

(1-D)Ts

0

1

1

2

t

D=switch duty cycle

0<D<1

-

- Ts=switching period

fs=switching frequency

=1/ Ts DC component of Vs(t)=average value:

Vs

=

∫ 0

Ts Vs(t)

dt

=DVg

Addition of low pass filterAddition of (ideally lossless) L- C low- pass filter, for removal of

switching harmonics:

Choose filter cutoff frequency f0 much smaller than switching frequency fs.

This circuit is known as the “buck converter”.

+ -

+

-

V(t)

50V

R

I

10A

Vg

100V

+

-

Vs(t)

1

2

L C

Pin≈ 500W Ploss small

Pout=500W

Addition of control system for regulation of output voltage

+ -

+

-

V

i

Vg

H(s)

Pulse-width modulator

sensor gain

Gc(s)

-

+

transistor gate driver

Power input

Load Switching converter

error signal

Ve

Vc

Vref

Reference input

compensator

δ

δ (t)

t

dTs

Ts

Major issues in power electronicsHow to meet the requirement of the load or gain better control of the loadHow to improve the efficiency -- for reliable operation of power semiconductor devices -- for energy savingHow to realize power conversion with less volume, less weight, and less

cost.How to reduce negative influence to other equipment in the electric power

system and to the electromagnetic environment.

V. About this course

Three parts of the content

Power electronic devices: Chapter 1 Power electronic circuits: Chapter 2, 3, 4, 5, 8 Control techniques: Chapter 6 and 7