Lec 1 Introduction to Power Electronics
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Transcript of Lec 1 Introduction to Power Electronics
MCT 4333Power Electronics
Department of Mechatronics EngineeringIIUM
2MCT2231:A01
Reference Books
Required• Daniel W. Hart (2011)Power electronics McGraw-hill
international Edition. • Rashid M. H., (2004), Power Electronics: Circuits,
Devices, and Applications, 3rd Edition, Prentice-Hall. Recommended• Agrawal J. P., (2001), Power Electronics System: Theory
and Design, Prentice-Hall.• Hart D. W., (1997), Introduction to Power Electronics,
Prentice-Hall. • Mohan N., Undeland T. M., and Robbins W. P., (2003),
Power Electronics: Converters, Applications, and Design, John Wiley and Sons.
3
Method of Evaluation
• Quizzes 15 %• Assigment/ Project 20 %• Midterm Examination 25 %• Final Exam 40 %• Total 100 %
Course Outline:
4
Contents
Definition of power electronics,Power semiconductor devices, Control characteristics of power semi-conductor devices, Power losses in switches, Types of power electronics circuits.Applications of power electronics.
5
Power Electronics
ControlAnalog/ Digital
ElectronicsDevice/Circuit
Power equipmentstatic/rotating
6
• Power electronics involves the study of electronic circuits intended to control the flow and conversion of electric power. Thus power electronics combine power, electronics and control.
• The applications of solid-state and linear devices for the control and conversion of electric power.
Power Electronics
7
Power Electronics System
• Consists of an input source and a load. • One or more converters for power conversion. • Power semiconductor devices, which are used as
switches to perform the power conversion. • A gating circuit to generate the gate drive signals for
the switching devices. • A feedback control circuit implemented either in
analog and/or digital electronics. • One or more static-switches acting as a circuit
breaker.
8
Power Electronics System
Static Applications: No rotating or moving mechanical components. Examples: DC Power supply, Un-interruptible power supply, Power generation and transmission (HVDC), Electroplating, Welding, Heating, Cooling, Electronic ballast.
Drive Applications: for driving moving or rotating equipment such as motors. Examples: Electric trains, Electric vehicles, Air-conditioning system, Pumps, Compressor, Conveyer Belt (Factory automation).
9
Control Center
Micro-Turbine Hospital Commercial
Building
Fuel Cell Smart House Performance
Building
Combined Heat and PowerPlant (CHP)FactoryCommercial BuildingHouseApartment Building
Wind Power Plants Village Commercial
Building
Central PowerStation Solar Power Plants
CHP House
Importance of PES• Increasing applications of Power Electronic Equipment in Power Systems
– Availability of high power semiconductor devices
– Decentralized renewable energy generation sources
– Increased power transfer with existing transmissionsystem
– Effective control of power flow needed in a deregulated environment
– Norms for Power quality
Future Power System
10
Power Semiconductor Devices
Power devices are the key elements of a power converter. The commonly used devices are:
(1) Power Diode(2) Silicon-Controlled Rectifier (SCR) or Thyristor(3) Gate Turn-off Thyristor (GTO)(4) Power Bipolar Junction Transistor (Power BJT)(5) Power Metal-Oxide Field-Effect Transistor (Power
MOSFET)(6) Insulated-Gate Bipolar Transistor (IGBT) (7) Mos-Controlled Thyristor (MCT)
11
Power semiconductor operating regions
voltage vs frequency;
current vs frequency.
12
Power Electronic Applications• Distributed generation (DG)– Renewable resources (wind and photovoltaic)– Fuel cells and micro-turbines– Storage: batteries, super-conducting magnetic energy storage,
• Power electronics loads: Adjustable speed drives• Power quality solutions– Dual feeders– Uninterruptible power supplies– Dynamic voltage restorers
• Transmission and distribution (T&D)– High voltage dc (HVDC) and medium voltage dc– Flexible AC Transmission Systems (FACTS): Shunt and Series
compensation, and the unified power flow controller
13
Function of Power Electronics in Utility Applications
• Enabling technology providing interface between two (ac/dc) electrical systems
Interconnection of two asynchronous ac systems – dc to ac conversion is required to connect fuel cells or
photovoltaic to the utility grid
Converter
Controller
Source Load
14
Role of Power Electronics in Important Utility Applications
• Distributed Generation (DG) ApplicationsPower electronic interface depends on the source characteristics
AC
DC
DC
AC
Wound rotorInduction Generator
Generator-sideConverter
Grid-sideConverter
WindTurbine
IsolatedDC-DC
Converter
PWMConverter
Max. Power-point Tracker
Utility1f
Wind Power Generation with Doubly Fed Induction Motors
Photo-voltaics Interface
15MCT2231:A01
Role of Power Electronics in Important Utility Applications
• Power Electronic Loads: Adjustable Speed Drives
Controller
Motor
Utility
Rectifier
Switch-modeConverter
16MCT2231:A01
Role of Power Electronics in Important Utility Applications
• Power Quality Solutions for– voltage distortion– unbalances– voltage sags and swells– power outages
Load
Feeder 1
Feeder 2
Dual Feeders
Power ElectronicInterface
Load
Dynamic Voltage Restorers (DVR)
Uninterruptible Power Supplies
Rectifier Inverter FilterCriticalLoad
EnergyStorage
Role of Power Electronics in Important Utility Applications
• Transmission and Distribution: DC Transmission– most flexible solution for connection of two ac systems
AC1 AC2
HVDC
AC1 AC2
MVDC
18
Ideal PE System
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.
19
Power Semiconductor Devices
BJT MOSFET Thyristor IGBT
GTO
Diode
Inductor
Capacitor Transformer
Ferrite core
Powerdered ion core
2200£gF 250 V 85 ¢J
Electrolytic capacitor
104/250V
Metalizedpolypoyester capacitor
102
Ceramiccapacitor
20MCT2231:A01
Inductors and Capacitors in PE
Inductor: V = L di/dt• The current in an inductor cannot change
instantaneously!Capacitor: i = C dV/dt• The voltage across a capacitor cannot change
instantaneously!These passive components are fundamental to the
operation of all power electronics.
21MCT2231:A01
Control Characteristics
DiodeUncontrolled turn on and off
++
VOVS
VS
VO
VS
VO
22MCT2231:A01
Control CharacteristicsThyristors ( SCR):
Controlled turn on and uncontrolled turn off
23MCT2231:A01
Control Characteristics
Thyristors:
Once it is in conduction mode, it cannot be turned off by gate signal
++
VOVS
VO
VS
Vg
24MCT2231:A01
Control CharacteristicsGTO, BJT, MOSFET, SITH, IGBT, SIT, MCT:Controlled turn on and off.
VO
VS
Vg
++
VOVS
+
Vg
25MCT2231:A01
Control CharacteristicsBJT, MOSFET, IGBT, SIT:Continuous gate signal requirement
VO
VS
VB
++
VOVS
+
VB
++
VOVS
+
VGS
26MCT2231:A01
Other CharacteristicsBidirectional current capability: TRIAC, RCTUnidirectional current capability: SCR, BJT, MOSFET, etc
See table 1.3 and Figure1.9 of the text book for more information.
Self Study: Characteristics of Ideal switches
27MCT2231:A01
The Practical Switch
1. Limited power handling capabilities, limited conduction current in the on-state, and limited blocking voltage in the off-state.
2. Limited switching speed caused by the finite turn-on and turn-off times. This limits the maximum operating frequency of the device.
3. Finite on-state and off-state resistances, that is, forward voltage drop exists when in the on-state, and reverse current flow (leakage) exists when in the off-state.
4. Because of characteristics 2 and 3, the practical switch experiences power losses in the on- and off-states (known as conduction loss), and during switching transitions (known as switching loss).
28MCT2231:A01
Losses in Power ElectronicsIn semiconductor components:• Switching losses• Conduction lossesIn passive components (C & L):• Effective series resistance
Typical efficiencies are in the range of 90-99% for each conversion stage, depending on the exact converter topology.
29MCT2231:A01
Power switch losses• Why it is important to consider losses of power switches?– to ensure that the system operates reliably under prescribed
ambient conditions, – so that heat removal mechanism (e.g. heat sink, radiators,
coolant) can be specified. Losses in switches affects the system efficiency
– Heat sinks and other heat removal systems are costly and bulky. Can be substantial cost of the total system.
– If a power switch is not cooled to its specified junction temperature, the full power capability of the switch cannot be realized.
Main losses:– forward conduction losses,– blocking state losses– switching losses
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Switching Power Losses
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Types of PE Circuits
• Diode Rectifier• AC-DC Converter (controlled rectifier)• AC-AC Converter (ac voltage controller)• DC-DC converter (dc chopper)• DC-AC Converter (inverter)• Static Switches
32MCT2231:A01
Diode Rectifier
It converts ac voltage into a fixed dc voltage.
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AC-DC Converter
It converts ac voltage into dc voltage of variable magnitude by varying the conduction time of a Thyristor.
34MCT2231:A01
AC-AC Converter
It converts ac voltage into variable ac voltage by varying the conduction time of a TRIAC.
35MCT2231:A01
DC-DC converter
It converts the dc voltage into variable dc, by controlling the conduction time of transistor.
36MCT2231:A01
DC-AC Converter
It converts the dc voltage into ac, by controlling the conduction time and sequence of transistors.
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Static Switches
Static Switches: Uninterruptible Power Supply (UPS): Mains1 supplies the normal power to the load. The ac-dc converter charges the standby battery. The dc-ac converter supplies the emergency power to the load.
38MCT2231:A01
Conclusions
• Power electronic System and its scope, applications and importance
• Control Characteristics of PE devices.• Losses in solid state switches• Types of Power Electronic Circuits.• Properties of Capacitor and Inductor in PE
circuits.