Midterm

CONCORDIA UNIVERSITY

Department of Electrical and Computer Engineering

ELEC 6411 – Power Electronics I

Course Outline

Fall 2015

Course Instructor: Dr. Luiz A. C. Lopes

Office: Concordia University

Telephone: 848-2424 ext. 3080

E-mail: [email protected]

Office Hours: Thursday, 15:30 – 17:00 hs.

Course Web site: https://www.moodle.concordia.ca

Textbook: N. Mohan, T.M. Undeland, and W.P. Robbins, Power Electronics:

Converters, Applications, and Design, Media Enhanced Third Edition,

John Wiley & Sons, Inc., 2003, ISBN 0-471-22693-9

Alternate Text: M.H. Rashid, Power Electronics: Converters, Devices and Applications,

Prentice Hall, 1993, ISBN 0-13-678996-X

Course Outline: Objectives of the course

The course presents the operating principles of static power converters

commonly used in practical industrial systems. It addresses the underlying

concepts and methods behind various applications ranging from low-

medium power utility interfaces to high power transmission systems. A

special emphasis will be placed on renewable and alternate energy systems

applications and power transmission and distribution system

compensation and enhancement.

By the end of the course, the student is expected to:

• Understand the operating principles of static power converters and

aspects of their application in electrical power systems.

• Be able to define the analytical expressions related to the operation of

static power converters and to evaluate/compare the electrical

performance of various options and topologies.

• Be able to carry on the basic analysis and specification of static power

converters for specific applications.

• Be able to carry on simulation studies of a power electronic system.

Lecture : Monday, 14:45 – 17:30, SGW H-407

ELEC-6411 Power Electronics I Lopes, Luiz A.C. Course Outline – Fall 2015

Page 2 of 3

Project: Teams of up to four students. Focus on the analytical study, ideally

including a design, and simulation and discussion of a

converter/application chosen by the students.

Content:

1) Power conversion context: Role of the equipment and design specifications. 2) Discussion of possible power converter configurations and modulation techniques and reason for your choice 3) Basic design: Power switches, passive components and modulation technique 4) Simulation of the converter with PSIM or MATLAB (H-921) 5) Analysis of simulation results to check if the design specifications are met and to validate the design procedure 6) Final remarks and conclusions

Assignments: Assignments will be handed out every other week and are due in a week.

Late assignments may be turned in but are subject to a penalty of 10 points

per day. Assignments are not received after the solutions are posted.

Marker: Mrs. Nazli Kalantari [email protected]

Grading Scheme: Assignments 10 %

Project report 20 %

Mid-term exam 25 %

Final exam 45 %

Total 100 %

Note: The final exam is scheduled by the examinations office, not by the

instructor.

Marking: Partial marks are assigned by the instructor. Students must present sound arguments when questioning marks. Bringing up non-technical and personal arguments is highly unethical and unprofessional. There is no supplementary work and no “HELP” can be provided after the letter grades are entered.

Academic conduct: Academic dishonesty is not acceptable. It will be documented and punished as per Concordia University regulations. Please do not ruin

your career.

Professionalism: Employers expect our graduates to behave like professionals.

- A professional is reliable – gets the job done on time.

- A professional has initiative – finds out what he/she does not know.

- A professional is respectful to others.

ELEC-6411 Power Electronics I Lopes, Luiz A.C. Course Outline – Fall 2015

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Tentative Schedule – Fall 2015

"In the event of extraordinary circumstances beyond the University's control, the content and/or evaluation scheme in

this course is subject to change".

Wk Date Topic Chapter/Sections Assignments (suggested problems)

1 Sept. 14 Introduction: Power electronic systems

1.1 – 1.7 , 3.1 – 3.2

P1-1, P1-3, P1-4, P3-6, P3-7

2 Sept. 21 Power semiconductor switches

2.1 – 2.12 Assign. #1

3 Sept. 28 Line frequency AC-DC converters (diodes)

5.1, 5.2, 5.3.1, 5.3.4.2, 5.3.4.4, 5.5, 5.6.1, 5.6.4, 5.7, 5.9

P5-3, P5-4, P5-6, P5-23

4 Oct. 5 Line frequency AC-DC converters (thyristors)

6.1, 6.2, 6.3.1, 6.3.4, 6.4.1, 6.4.3

Assign. #2 P6-2, P6-5, P6-6, P6-13, P6-20

Oct. 12 Thanksgiving

5 Oct. 19 AC-DC (cont.) DC-DC converters

7.1, 7.2, 7.3.1, 7.3.2, 7.3.4, 7.4.1, 7.4.2, 7.4.4, 7.7, 7.8, R9.6

P7-1, P7-2, P7-7, P7-8, P7.18

6 Oct. 26 Midterm exam

(1.4 hour) DC-DC converters (cont.)

Exam on topics of week 1-4 (up to thyristor AC-DC converters)

Nov. 1, deadline for

academic

withdrawal Fall

courses

7 Nov. 2 DC-AC converters 8.1, 8.2, 8.3. Assign. #3 P8-1a, P8-10, P8-11

8 Nov. 9 DC-AC converters (cont)

8.4.1, 8.4.2, 8.4.5, 8.7

9 Nov. 16 Power electronic interfaces

8.6, 10.5.5, 18.1 – 18.6. Assign. #4 P18.2, P18.3

10 Nov. 23 High power DC transmission

17.1, 17.2 (HVDC) P17-2, P17-3

11 Nov. 30 AC controllers 6.2.1, 6.2.2, 16.3.3, 17.3.1, 17.2.4.2 R6.2, R6.4, R6.7

R6-1, R6-6, R6.8, R6-13 P17-5, P17-8 Assign. #5

12 Dec. 7 Utility applications: SVC, TCSC, STATCOM and renewables

17.3.3, 8.6.3, 17.4, 17.5 Additional papers

P17-6

13 Dec. 8 (Tuesday)

Review and additional examples

TBA Final exam All topics. Period: Dec. 9 to 22

CONCORDIA UNIVERSITY

DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING

Power Electronics (I) ELEC-433/6411

Assignment #1: Introduction

Due date: September 25th 2012

1) A 60 Hz three-phase Y-connected induction motor draws 50kVA at 0.85 lagging power

factor when supplied directly from a 400 VLL – 60 Hz source. A) Compute the equivalent RL

impedance of the motor for this condition. B) Assuming that the motor (represented by the

RL impedance) is connected to the source through a three-wire feeder with impedance of 0.05

+ j 0.01 Ω (per phase), what would be the active power developed by the motor? C) What

would be the three-phase losses in the feeder? D) Compute the reactive power required from

a capacitor bank placed in parallel to the motor to improve the power factor to 0.92 at the

load side of the feeder. E) For a per-phase equivalent circuit, show the phasor diagram of the

motor current, capacitor current, source current and source voltage (reference phasor).

2) Consider the circuit below regarding a three-phase diode rectifier with capacitive dc filter and

an LC input filter. The three-phase source is 110 VLL 60 Hz. One plot shows the waveforms

of the source voltage, capacitor voltage and output voltage, followed by the harmonic spectra

of the ac waveforms. The other shows the current in one phase of the source (iRLS) and that in

the input of the diode rectifier (iLf). The harmonic spectra of the latter are also shown. Based

on this: A) List the order of the harmonics found in both current waveforms; B) compute and

compare the magnitude of the harmonics and the THD of both currents. C) Compute the crest

factor of iLf. D) Compute the reactive power supplied by the (three-phase) capacitor bank.

CONCORDIA UNIVERSITY

DEPARTMENT OF ELETRICAL AND COMPUTER ENGINEERING

ELEC 433/6461 – Power Electronics/Power Electronics I

Assignment #1: Review of basic concepts and definitions

Due date: September 28 2015 in the mailbox of Dr. Lopes (EV5.175).

1) A 60 Hz three-phase induction motor draws 25kVA at 0.8 lagging power factor from a 220-VLL

source. It is desired to improve the power factor to 0.92 by connecting a capacitor bank in parallel

with the motor. A) Specify the required kVA (kVAr) rating of the capacitor bank. B) If the

capacitor bank is ∆-connected, find the value of the capacitors. C) Determine the line current

before and after the addition of the capacitor bank. D) For a per-phase equivalent circuit, show

the phasor diagram of the load current, capacitor current, source current and source voltage

(reference phasor).

2) A single-phase full-bridge diode rectifier was simulated with PSpice and the following results

were obtained: 1) Waveforms of the ac side current, ac side voltage and dc side voltage; 2)

Harmonic spectrum of the ac side current. Assuming that φ1 = 10°, compute: a) The total rms

value of the ac side current; b) The THD of the ac side current; c) The crest factor of the ac side

current; d) The active, reactive and apparent power absorbed by the converter; e) The power

factor and the displacement power factor of the converter.

Time

100ms 105ms 110ms 115ms 120ms 125ms 130ms 135ms 140ms 145ms 150ms

V(Rload:1) - V(Rload:2) V(Vs:+)

-200V

0V

200V

I(Ls)

-40A

0A

40A

SEL>>

Frequency

0Hz 0.1KHz 0.2KHz 0.3KHz 0.4KHz 0.5KHz 0.6KHz 0.7KHz 0.8KHz 0.9KHz 1.0KHz

I(Ls)

0A

4A

8A

12A

16A

(900.000,439.489m)

(780.000,468.070m)

(660.000,922.143m)

(540.000,1.0312)

(420.000,2.2032)

(300.000,6.4795)

(180.000,11.734)

(60.000,15.348)

CONCORDIA UNIVERSITY

DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING

Power Electronics (I) ELEC-433/6411

Assignment #2: Line frequency AC-DC converters

Due date: October 10 2012

1) A three-phase diode rectifier is used to supply the field current of a dc motor

whose ratings are: 200 V, 10A. Assume that the dc current of the rectifier is ripple

free (pure dc). A) Calculate the turns ratio of a transformer and its apparent power

to interface the rectifier to a 220V/60 Hz source. B) Calculate the voltage (peak)

and current (average and RMS) ratings of the diodes. C) Explain why the strength

of the power source affects significantly the voltage distortion created by the

rectifier at the PCC (Point of Common Coupling).

2) Consider a single-phase thyristor-based AC-DC converter supplying a highly

inductive load with a resistance of 5 ohms. The grid voltage is 120V/60Hz but it

is allowed to vary by +/-10% of its rated value. A) Calculate the range of firing

angle of the thyristors so that the load voltage can be kept at 96 V at all times. B)

Compute the (maximum) rms values of the current harmonics that could occur in

the ac side of the AC-DC converter. C) Consider that a free-wheeling diode is

placed in parallel with the load. Describe how the circuit would operate in this

case. D) Derive an equation for the average value of the load voltage (with the

free-wheeling diode.) E) Calculate the “new” range of firing angle of the

thyristors so that the load voltage can be kept at 96 V at all times (with the free-

wheeling diode.) F) Compute the voltage ratings required from the free-wheeling

diode as well as its required minimum average current.

CONCORDIA UNIVERSITY

DEPARTMENT OF ELETRICAL AND COMPUTER ENGINEERING

ELEC 433/6461 – Power Electronics/Power Electronics I

Assignment #2: AC-DC converters

Due date: October 13 2015 at NOON in the mailbox of Dr. Lopes (EV5.175).

1) One wishes to supply 5 kW to a highly inductive DC load. There is a 4-wire 220VLL, 60 Hz three-phase source

with impedances of Rs = 0.1 Ω and Ls = 100 µH available at the site. Thus, it is possible to use either a single-

phase or a three-phase AC-DC converter connected as shown in the figure below. The breakers were included and

controlled so that the single-phase is supplied from t = 0s to 1.5s and the three-phase from 1.5s to 2s. The load

impedances of the 2 converters where computed so that one obtains rated load power (5kW) with the average

output/load voltage one gets when neglecting the voltage drops in the line impedances. Compute: A) The current

(RMS and average) and the voltage (peak) ratings of the diodes of both AC-DC converters, neglecting the voltage

drop across the source impedance; B) The total ohmic power losses on the impedances of the source due to the

single-phase and the three-phase converters; C) The voltage drop (fundamental component) across the

impedances of the source, due to the input currents of the single-phase and three-phase converters. Note: The

PSIM circuit is available on the course web site for additional tests.

2) The field winding of a DC machine, with resistance of 2 Ω and an inductance of 32mH, is to be fed with 400 V,

using a three-phase 220 VLL/60 Hz source a Y:Y transformer and a diode rectifier, all assumed “ideal”. A)

Considering that the grid voltage does not vary much, compute the turns ratio of the transformer as well as its

(total) apparent power (S3φ= 3S1φ). Recall that in this case, the harmonic components of the input current of the

AC-DC converter need to be taken into consideration. Now, assume that the grid voltage can vary by +/- 10 %

and that a thyristor AC-DC converter is used for regulating the load voltage at 400 V using the same transformer.

B) what would be the minimum and maximum values of firing angle (α) and when would they be used, (Vsmax or

Vsmin)? C) For Vs = Vsmax, compute the active and the reactive powers absorbed by the AC-DC converter.