Introduction To Power Electronics

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Lecture 1: August 27, 2012 Introduction to Power ElectronicsECEN 4797/5797 Robert W. Erickson University of Colorado, Boulder Fall 2012 1 Introduction to Power ElectronicsECEN 4797/5797 Instructor: Prof. Bob Erickson – – – – – Of ce: ECOT 356 Telephone: (303) 492-7003 Email: [email protected] Of ce hours: MW 3:00 - 4:00 pm Telephone of ce hours: M 3:00 - 4:00 pm Course web site: – http://ece.colorado.edu/ ecen5797 – Includes lecture slides, handouts, homeworkassignments, links to online lecture les Textbook: – Erickson and Maksimovic, Fundamentals of Power Electronics, second edition,Springer, ISBN 0-7923-7270-0. Prerequisite: – A 3-4 semester sequence of undergraduate EE circuits and electronics courses (at Univ. of Colorado: ECEN 3250) 2

Coursework in Power Electronicsat the University of Colorado Power electronics courses – ECEN 4797/5797 (this course): Intro to power electronics (Fall) – ECEN 5807 Modeling and Control of Power Electronics Systems (AltSpring semesters, including S 13) – ECEN 5817 Resonant and Soft-Switching Techniques in PowerElectronics (Alt Spring semesters, including S 14) – ECEN 4517/5517 Power Electronics Laboratory (Spring) Professional Certi cate in Power Electronics – ECEN 5797, 5807, and 5817 Formats for this course – On-campus, for senior or graduate credit – Web-based lectures: recorded with ECHO 360 system, withviewing through the Flash viewer. For technical help, [email protected] (CAETE) 3 Grading Homework – – – – – Due at beginning of class on date listed on Lecture Schedule web page Submit online via D2L dropbox; late homework not accepted Homework counts 50% of grade You may speak with others about the homework, but turn in your own work Homework and exam problems of additional depth and complexity forthose earning graduate credit; separately graded Exams – – – – Midterm exam: one-week take-home exam, 17% of grade Final exam: ve-day take-home exam, 33% of grade See course schedule page for dates See course vitals page for details 4

Desire-2-Learn (D2L) Site learn.colorado.edu Log on with your campus IdentiKey Dropbox for submission of homework and exams Scan, save as pdf, then upload to the D2L dropbox For on-campus students: a scanner is available within the SRC Automatic deadline at beginning of class A log of your grades for all assignments When grading is complete, your grade will appear online Running total of your overall course grade Grader will post comments and annotations online Homework solutions Posted within D2L after submission deadline Student discussion forum You can post questions and discussions with your classmates Normally questions will not be answered by Prof. Erickson Posting of homework solutions in the forum is prohibited 5 Off-campus students Viewing of lectures – Lectures are normally available online by the end of the day of the oncampus lecture Assignments – Use the D2L site to upload your pdf le: same as for on-campus students – Generally, by Friday the lectures will nish covering the material needed forthe homework assignment due the following Friday. So you can work thehomework over the weekend. Professor Erickson will be available fortelephone of ce hours on Monday afternoon, to answer any questions. – Check out the D2L student forums – Due dates are the same as for the on-campus students Educational Of cers – Not needed See course vitals page – Link to academic calendar for CAETE students, including add/dropdeadlines 6

Key dates Drop deadlines – September 12: last day to drop the course and receive full tuition refund, withno W grade appearing on transcript – October 10: last day to drop the course without petitioning the Dean s of ce Tentative exam dates – Midterm exam: 1 week take-home exam. Available through D2L on Oct. 19,due on Oct. 26. – Final exam: Four day take-home exam. Available through D2L on Dec. 14,due on Dec. 18. Grades assigned in May appear on your permanent universitytranscript Campus holidays – Labor day: Sept. 3 – Fall break / Thanksgiving holiday: Nov. 19-23 7 Chapter 1: Introduction 1.1. Introduction to power processing 1.2. Some applications of power electronics 1.3. Elements of power electronics Summary of the course 7

1.1 Introduction to Power Processing tDc-dc conversion:Ac-dc recti cation:Dc-ac inversion: Change and control voltage magnitude Possibly control dc voltage, ac current Produce sinusoid of controllablemagnitude and frequency Ac-ac cycloconversion: Change and control voltage magnitudeand frequency 8 Control is invariably required tfeedforwardfeedbackControllerreference9

High ef ciency is essential 1 PoutPin 0.81 – 1Ploss Pin – Pout Pout 0.6High ef ciency leads to lowpower loss within converter Small size and reliable operationis then feasible Ef ciency is a good measure ofconverter performance 0.40.200.51Ploss / Pout10 A high-ef ciency converter PinConverterPoutA goal of current converter technology is to construct converters of smallsize and weight, which process substantial power at high ef ciency 11 1.5

–Devices available to the circuit designer d-modeSemiconductor devices12 –Devices available to the circuit designer DTResistorsCapacitorsMagneticsSignal processing: avoid magnetics 13 TssLinearmodeSwitched-modeSemiconductor devices

–Devices available to the circuit designer d-modeSemiconductor devicesPower processing: avoid lossy elements 14 Power loss in an ideal switch Switch closed: v(t) 0 Switch open: i(t) 0 In either event: p(t) v(t) i(t) 0 Ideal switch consumes zero power 15 v(t) –i(t)

A simple dc-dc converter example I10A Vg100VDc-dcconverter –R5 V50V –Input source: 100V Output load: 50V, 10A, 500W How can this converter be realized? 16 Dissipative realization Resistive voltage divider I10A Vg100V – 50V –Ploss 500WR5 V50V –Pout 500WPin 1000W17

Dissipative realization Series pass regulator: transistor operates inactive region I10A50V – Vg100Vlinear amplifierand base driver – – VrefR5 V50VPloss 500W –Pout 500WPin 1000W18 Use of a SPDT switch I10 A1 Vg100 V2 –vs(t)R –vs(t) –VgVs DVgswitchposition:DTs0(1 – D) Tst12119 v(t)50 V

The switch changes the dc voltage level vs(t)VgVs DVgswitchposition:DTs0(1 – D) Tst121D switch duty cycle 0 D 1 Ts switching period fs switching frequency 1 / Ts DC component of vs(t) average value: Vs 1TsTsvs(t) dt DVg020 Addition of low pass lter Addition of (ideally lossless) L-C low-pass lter, forremoval of switching harmonics: i(t)1 Vg100 V – L2vs(t)CR –Pin 500 Wv(t) –Ploss smallPout 500 W Choose lter cutoff frequency f0 much smaller than switchingfrequency fs This circuit is known as the “buck converter ” 21

Addition of control systemfor regulation of output voltage PowerinputSwitching converterLoad –vH(s) –Transistorgate driverErrorsignalvePulse-width vc G (s)cmodulatorCompensator (t)dTs Ts – vgiHvReferencevrefinputt22 The boost converter 2 LVg1 –CRV –5Vg4VgV3Vg2VgVg000.20.40.6D23 0.81Sensorgain

A single-phase inverter 1 –Vgvs(t) 2 – v(t) –21load “H-bridge ” vs(t)tModulate switchduty cycles toobtain sinusoidallow-frequencycomponent 24 1.2 Several applications of power electronics Power levels encountered in high-ef ciency converters less than 1 W in battery-operated portable equipment tens, hundreds, or thousands of watts in power supplies forcomputers or of ce equipment kW to MW in variable-speed motor drives 1000 MW in recti ers and inverters for utility dc transmissionlines 25

A laptop computer power supply system t)Displaybacklightingac line input85 –265 rmanagementDiskdrive26 Power system of an earth-orbiting spacecraft Dissipativeshunt regulator Solararrayvbus rDc-dcconverterPayloadPayloadBatteries27

An electric vehicle power and drive system ac machineInverterac machineInvertercontrol busbattery Psystemcontroller 3øac line50/60 HzBatterychargerDC-DCconvertervb –Low-voltagedc busInverterInverterac machineac e-voltage ac28 A standalone photovoltaic power system The system constructed in ECEN 4517/5517 PowerElectronics and Photovoltaic Systems Laboratory 29

1.3 Elements of power electronics Power electronics incorporates concepts from the elds of analog circuits electronic devices control systems power systems magnetics electric machines numerical simulation 30 Part I. Converters in equilibrium Inductor waveforms vL(t)Averaged equivalent circuit RLt – V1iL(t)20D' : 1 Vg – VLVg –R – iLPredicted ef ciency 100% – VLDTsVI1iL(DTs)IiL(0)D' RDD'TsDTsswitchposition:D' VDD Ron –Vg – V0.00290%0.01Ts80%t0.0270%0.0560% 50%RL/R 0.140%Discontinuous conduction mode 30%Transformer isolation 10%20%0%00.10.20.30.40.5D31 0.60.70.80.91

Switch realization: semiconductor devices The IGBT collectorSwitching loss mitterdiodewaveformsGateiLiB(t)vB(t)00tnpnnn-parea –Qrn –Vgminority carrierinjectiontrppA(t) vA iAarea QrVgCollectorarea iLVgtrt0t1 t232 Part I. Converters in equilibrium 2. Principles of steady state converter analysis 3. Steady-state equivalent circuit modeling, losses, and ef ciency 4. Switch realization 5. The discontinuous conduction mode 6. Converter circuits 33 t

Part II. Converter dynamics and control Closed-loop converter system PowerinputAveraging the waveforms Switching converterLoadgatedrive vg(t) –v(t)Rfeedbackconnection – (t)compensatorpulse-width vcGc(s)modulatordTs Tsvaveraged waveform v(t) Tswith ripple neglectedvoltagereference vrefvc(t) (t)actual waveform v(t)including ripple – transistorgate t circuit vg(t) –Vg – V d(t) –1:DI d(t)D' : 1 I d(t)Cv(t) –34 Part II. Converter dynamics and control 7. Ac modeling 8. Converter transfer functions 9. Controller design 10. Input lter design 11. Ac and dc equivalent circuit modeling of the discontinuousconduction mode 12. Current-programmed control 35 R

Part III. Magnetics n1 : n2transformerdesign iM(t)i1(t)i2(t)theproximityeffect 0.080.0618110.04Bmax (T)Pot core kHz1000kHzSwitching frequency36 Part III. Magnetics 13. Basic magnetics theory 14. Inductor design 15. Transformer design 2i –i layer1transformersize vs.switchingfrequency –2i layer2ik(t): nk3ilayer337 id

! Power electronics courses / ECEN 4797/5797 (this course): Intro to power electronics (Fall) / ECEN 5807 Modeling and Control of Power Electronics Systems (Alt Spring semesters, including S 13) / echniques in Power Electronics (Alt Spring semesters, including S 14) / ECEN 4517/55