power electonics

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Power Electronics

College of Automation and Electronic Engineering

Qingdao University of Science and Technology


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

that is optimally suited for user loads.


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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


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Power electronic systemGeneric 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 inputController

Reference

Power

input

Power

output

Feedback

(measurements

of output signals )Feedforward

( measurements

of input signals )


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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

MeasurementsController

Reference

Power input Power output

Electric Motor

light

heating

other electric equipment

power converter

Electric utility

batteryother electric energy source

power converter

Source Loadio VoiiVi


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2) Relation with information electronicsA 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 devicesApplied electronics: application of electronic

devices to various areas


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3) The interdisciplinary natureWilliam E. Newells description

Power electronics is the interface between electronics and power.

PowerElectronics

Electronics Power

ControlContinuous,

discrete

Static & rotating

power equipment

Devices,circuits


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Relation with multiple disciplines

Power electronics is currently the most active discipline in electric power

engineering.

Power

electronics

Electric

machines

Circuit Ct

theory

Systems&

Control theorySignal

processing

Simulation &

computing

electronics

Solid state

physics

Electromagnetics

Power

systems


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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 humansociety.

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.


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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

GTOGTR

Power MOSFET

Thyristor

(microprocessor)

IGBT

Power MOSFET

Thyristor

(DSP)

Pre-history 1st phase 2nd phase 3rd phase

19571900 late 1980smid 1970s


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III. Applications

Industrial applications

Motor drives

Electrolysis

ElectroplatingInduction heating

Welding

Arc furnaces and ovens

Lighting


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Transportation applications

Trains & locomotives

Subways

Trolley buses

Magnetic levitation

Electric vehicles

Automotive electronics

Ship power systems

Aircraft power systems


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Utilitystems applications

High- voltage dc transmission(HVDC)

Flexible ac transmission(FACTS)

Static var compensation & harmonics

suppression: TCR, TSC, SVG, APF

Custom power & power quality control

Supplemental energy sources :

wind, photovoltaic, fuel cells

Energy storage systems


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Power supplies for electronic equipment

Telecommunications

Computers

Office equipment

Electronic instruments

Portable or mobile

electronics


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Residential and home appliances

Lighting

Heating

Air conditioning

Refrigeration & freezers

Cooking

Cleaning

Entertaining


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Applications in space technology

Spaceship power systems

Satellite power systems

Space vehicle power systems


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Other aplications

Nuclear reactor control

Power systems for particle accelerators

Environmental engineering


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Trends

It is estimated that in developed countries now 60% of the electricenergy goes through some kind of power electronics converters beforeit 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 pollutionreduction of pollution produced by power converters

direct applications to environment protection technology


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IV. A simple exampleA simple dc-dc converter example

Input source:100VOutput load:50V, 10A, 500W

How can this converter be realized?

Dc-dc

converter+-

+

-

V50V

R5

I10A

Vg

100V


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Dissipative realizationResistive voltage divider

+-

+

-

V50V

R5

I10A

Vg

100V

Pout=500WPin=1000W

+ -50V

Ploss=500W


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Series pass regulator:

transistor operates in active region

+

-

+

-

V

50V

R

5

I10A

Vg

100V

Pout=500WPin1000W

+ -50V

Ploss500W

l inear amplif ier

And b ase driver

-+

Vref


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Use of a SPDT switch

+-

+

-

V(t)

50VR

I10A

Vg

100V

+

-

Vs(t)

Vs(t)

Vg

switch

position:

Vs=DVg

DTs (1-D)Ts

0

1 12

t

12


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The switch changes the dc voltage level

Vs(t)

Vg

switch

position:

Vs=DVg

DTs (1-D)Ts

0

1 12

t

D=switch duty cycle

0


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Addition of low pass filter

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

switching harmonics:

Choose filter cutoff frequency f0 much smaller than switching frequencyfs.

This circuit is known as the buck converter.

+-

+

-

V(t)

50V

R

I10A

Vg

100V

+

-

Vs(t)

1

2 L

C

Pin500WPlosssmall Pout=500W


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Addition of control system for regulation of output voltage

+-

+

-

V

iVg

H(s)

Pulse-widthmodulator

sensor

gain

Gc(s)-

+

transistor

gate driver

Power

input

LoadSwitching converter

error

signal

VeVc

VrefReferenceinput

compensator

(t)

tdTsTs


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Major issues in power electronics

How to meet the requirement of the load or gain better control of the load

How to improve the efficiency

-- for reliable operation of power semiconductor devices

-- for energy saving

How to realize power conversion with less volume, less weight, and lesscost.

How to reduce negative influence to other equipment in the electric powersystem and to the electromagnetic environment.


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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

power electonics

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