The document provides an introduction and overview of the Power Electronics 2 module. It discusses typical AC/DC/AC power conversion systems using line-side and motor-side converters. The module aims to provide knowledge of power electronics technologies including three-phase rectification, resonant converters, inverters, and high power converter structures. It outlines the lecture topics, recommendations, and reviews three-phase voltage supplies.

1. Power Electronics 2 (H5CPE2)
Dr Christian Klumpner
Power Electronics, Machines and Control Group
School of Electrical and Electronic Engineering, UoN
Tower Building, 508
email: christian.klumpner@nottingham.ac.uk
Module webpage: www.eee.nott.ac.uk/teaching/h5cpe2

2. Introduction
Line-side Converter Motor-side Converter
AC DC
DC AC
DC-link
Typical AC/DC/AC power conversion (Adjustable Speed Drive)
• AC/DC converter (Rectifier): fixed voltage&frequency to DC voltage
• DC/AC converter (Inverter): DC voltage to variable voltage/variable frequency
Why AC/DC/AC? Electrolytic capacitors (compact and cheap), only unipolar devices
available (transistors)
Operation of rectifier, stress on devices ($), design of filter ($), operation of inverter

3. Introduction
Pre requisites
Circuit theory and electronics at first year undergraduate level, knowledge of switching
regulators and single phase rectification (controlled and uncontrolled) such as that provided by
module H5BPE1.
Aims and objectives of the module
The aim of this module is to provide an in depth knowledge of power electronics at a level
suitable for final year undergraduate students.
Since power electronics is a rapidly growing subject the course tries to reflect this by covering
the well established and widely used technologies (such as three phase rectification) as well
as more recent developments such as resonant converters.
The increasing importance of power quality is also addressed and various high power factor
utility interface circuits are discussed.
Inverter circuits employing pulse width modulation (PWM) are studied due to their very
widespread use in variable speed drives and power supply systems. High power (multi-level)
converter structures are then discussed.
Throughout the course, emphasis is placed on circuits and their applications rather than on
the technology of power switching devices.

4. Lecture course syllabus
Lecture TOPIC
1 Introduction to the course, review of 3-phase supplies and the associated waveforms.
2-3 3-phase uncontrolled (diode) rectifiers. Basic mode of operation and waveforms. Concept and
importance of power factor, displacement factor and distortion factor applied to power electronic
equipment.
4-5 Overlap in diode rectifiers, waveforms and calculations. Introduction to thyristor characteristics.
6-7 3-Phase controlled rectification, waveforms and calculations, effect of overlap. Power factor
calculations. Inversion.
8-9 Smoothing circuits. Capacitive smoothing, waveforms and analysis. Inductive smoothing,
waveforms and analysis, discontinuous current. Multiple converter circuits and HVDC.
10-12 Resonant converters, review of hard switching, introduction to soft switching and different types
of resonant switches and converters. Forward converter employing zero voltage switching,
analysis and waveforms.
13-15 Single phase inverters, the H-bridge circuit and its operation, applications, quasi-square wave and
PWM techniques for voltage and frequency control, typical frequency spectra, relationship
between AC and DC side harmonics.
16-17 3-phase PWM inverters, High power (multi-level) converter structures.
18-20 High power factor utility interface circuits, single switch boost converter with input current wave
shaping. PWM rectifiers (pulse converters), control strategies.

5. Recommendations
Booklist
There are no essential books for this course. However, the following book is excellent and
covers most of the material in this course and the second year power electronics course.
POWER ELECTRONICS: Converters, Applications and Design (2-ed) by Mohan,
Undeland and Robbins, Wiley publishing
Another book worth looking at for power electronics in general, rather than specifically this
course is:
ELEMENTS OF POWER ELECTRONICS, by Philip T Krein, Oxford University Press
- familiarize yourself with emergency exits (fire alarm) in the building
- don’t get late (not more than 5 minutes) into the classroom
- switch off mobile phones
- attend to the course equipped with a ruler, 4 or more colored pens/markers
- if you have a computer at home, install a simulation pack (PSPICE, Simcad)

6. Review of 3-phase supplies (1)
Why sinusoidal voltage?
Behavior of passive components
Resistor Inductor Capacitor
v 1 dv
i= i = ∫ v ×dt i=C
R L dt
Proportional Integrative Derivative
Rectangular Voltage:
Rectangular Current Triangular Current Pulse Current
Production, transport & distribution system = Resistors + Inductors + Capacitors
We need to preserve the voltage waveform

7. Review of 3-phase supplies (2)
We need a supply voltage waveform which preserves its
shape when is derivated or integrated ⇒ sinusoidal
Resistor Inductor Capacitor
Behavior of
passive
components v 1 dv
i=
R
i=
L ∫ v ×dt i=C
dt
Proportional Integrative Derivative
Sinusoidal Voltage E
i=− cos ( ω t ) = i = C ×E ×ω ×cos(ω t )
E × ( ωt )
sin ωL
v = E ×sin ( ω t ) i= π
R E  π = C ×E ×ω ×sin(ω t − )
= sin  ω t + ÷ 2
ωL  2
Sinusoidal Current Sinusoidal Current Sinusoidal Current

8. Review of 3-phase supplies (3)
Assume a “STAR” connected supply
In practice, the 3 voltage sources represent the voltages generated by 3 coils
(physically displaced by 120O from each other) in an AC rotating machine (Alternator)
Line A
A Phasor diagram
Phase
Line to VCA
Neutral voltage
line VAN
voltage VAB
VCN
N VBN
VBC
C
B “Line to line” voltage
often called “line voltage”

9. Review of 3-phase supplies (4)
Assuming the peak phase voltage is E (a convention used throughout the course) then:
VAN = E sin(ωt )
B lags A by 120O, C lags B
VBN = E sin(ωt − 2π / 3)
by 120O etc
VCN = E sin(ωt − 4π / 3) = E sin(ωt + 2π / 3)
This is for “phase sequence” A-B-C, A-C-B is also possible – we will always assume
A-B-C
Drawing a phasor diagram and converting back to time functions, it is easy to show
that the line voltages are given by:
VAB = 3E sin(ωt + π / 6)
VBC = 3E sin(ωt − π / 2)
VCA = 3E sin(ωt + 5π / 6)
3-phase supplies are specified using the RMS line voltage. Hence “a 415V, 50Hz,
3-phase system” means:
3E
= 415 V, ω = 100π
2

10. Review of 3-phase supplies (5)
Why three-phase voltage systems (120O displaced)?
E ×I
p = v ×i = E ×sin ( ω t ) ×I sin ( ω t + ϕ ) = sin ( 2ω t + ϕ ) + cos(ϕ ) 
2  
Displacement angle = 0O Displacement angle = 90O
Necessity to deliver - smooth power (require less filtering)
- smooth torque in a motor (less mechanical stress, noise)