Download Three Phase - Single Phase Converter

ECE 4600 Group Design Project
Three Phase - Single Phase Converter
by
Group 11
Stephen Perry
Michelle Ocran
Ali Rezaee
Reena Dhir
Final report submitted in partial satisfaction of the requirements for the degree of
Bachelor of Science in Electrical and Computer Engineering in the
Faculty of Engineering of the University of Manitoba
Academic Supervisor(s)
Shaahin Filizadeh,
Department of Electrical and Computer Engineering
University of Manitoba
Date of Submission
March 10, 2014
Copyright © 2014 Stephen Perry, Ali Rezaee, Michelle Ocran, Reena Dhir
3 Phase - 1 Phase Converter
Abstract
In today’s world, where power demand has increased significantly, the reliance on flexible
energy options has also increased.
Our design is an attempt to take a three phase AC input and convert it to a single phase
AC output. This output would then be connected to a standard household power grid. The
same principle can be applied in the reverse direction.
To achieve this, we use a combination of rectification and inversion processes. These
processes are implemented by using a full bridge and a half bridge converter. The converters
are controlled with Proportional-Integral (PI) controller.
We have completed a full simulation of our entire project. The PI controllers ensure
that the power is transfered at the output of the converter. Whenever the input power
exceeds the required DC voltage, the controller transfers the excess power to the power grid
connection. The PI Controllers are implemented using a microcontroller.
Our project has two major sections, software and hardware. The software algorithm
has been developed and tested. Each hardware component has tested individually. The
hardware and the software part will be assembled together to have our final working model
in the near future.
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3 Phase - 1 Phase Converter
Research and Investigation
Technical Editor
AC-DC Simulation
DC-AC Simulation
PI Controller Simulation
Software Development
Software Testing
Microcontroller Testing
Hardware Selection and Ordering
Hardware Assembly and Testing
Legend:
• Lead task ◦ Contributed
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Reena Dhir
Michelle Ocran
Ali Rezaee
Stephen Perry
Contributions
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3 Phase - 1 Phase Converter
Acknowledgements
The team would like to take this opportunity to acknowledge and thank all those who
assisted and supported us for the completion of the project.
We would like to thank our advisor, Dr. Shaahin Filizadeh for providing us an opportunity
to work on his undergraduate project. He has not only helped us in troubleshooting our
technical issues related with our project but has also provided us with some great comments
whether it involved group dynamics or written reports.
We would also like to send our special thanks to Mr. Erwin Dirks for providing us
suggestion and feedback on our hardware components chosen.
Last but not the least, we would like to send our special regards to Mr. Daniel Card, Dr.
Behzad Kordi and Ms. Aidan Topping for giving us feedback whenever it was required and
making this complete course, a great learning experience.
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3 Phase - 1 Phase Converter
TABLE OF CONTENTS
Table of Contents
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
i
Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ii
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
iii
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
vi
List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
vii
Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
viii
1 Introduction
1
1.1
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
1.2
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
1.3
Problem Definition and Specifications . . . . . . . . . . . . . . . . . . . . .
2
1.4
Motivation
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
1.5
Thesis Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
1.6
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4
2 Modeling and Simulation of Converters
5
2.1
Stage 1: AC-DC Conversion
. . . . . . . . . . . . . . . . . . . . . . . . . .
6
2.2
Stage 2: DC-AC Conversion
. . . . . . . . . . . . . . . . . . . . . . . . . .
8
2.3
Power Grid Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
2.4
PI Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
2.4.1
Design 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
2.4.2
Design 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16
3 Software Development
3.1
19
Software Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19
3.1.1
Sinusoidal Pulse Width Modulation (SPWMs) . . . . . . . . . . . .
20
3.1.2
Creating Sine Wave . . . . . . . . . . . . . . . . . . . . . . . . . . .
20
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3 Phase - 1 Phase Converter
3.2
3.3
TABLE OF CONTENTS
3.1.3
Creating a Triangular Wave . . . . . . . . . . . . . . . . . . . . . . .
22
3.1.4
Creating SPWMs: Comparison of the two Waveforms . . . . . . . .
23
Measuring Voltage and Currents . . . . . . . . . . . . . . . . . . . . . . . .
25
3.2.1
Calculating Average Power . . . . . . . . . . . . . . . . . . . . . . .
27
3.2.2
PI Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27
Microcontroller Integration . . . . . . . . . . . . . . . . . . . . . . . . . . .
29
4 Hardware Implementation
30
4.1
Design Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
4.2
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
31
4.3
Hardware Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33
4.4
Real and Reactive Power Measuring Module . . . . . . . . . . . . . . . . . .
34
4.5
DC Voltage Measuring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
35
4.6
Single Phase Current and Voltage Measuring Module . . . . . . . . . . . . .
36
4.7
Half Bridge Rectifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
36
4.8
Full Bridge Rectifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
37
5 Conclusions
40
References
42
Appendix A Verilog Code
43
Appendix B Budget
57
Appendix C Curriculum Vitae
58
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3 Phase - 1 Phase Converter
LIST OF FIGURES
List of Figures
2.1
AC-DC Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
2.2
AC-DC Converter Voltage Output . . . . . . . . . . . . . . . . . . . . . . .
8
2.3
DC-AC Converter Schematic . . . . . . . . . . . . . . . . . . . . . . . . . .
9
2.4
DC-AC Voltage Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
2.5
DC-AC Current Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
2.6
Complete Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
2.7
AC-DC PI controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
2.8
AC-DC Converter Design 1 . . . . . . . . . . . . . . . . . . . . . . . . . . .
14
2.9
Single Phase Voltage Output Design 1 . . . . . . . . . . . . . . . . . . . . .
15
2.10 Single Phase Voltage Output Design 2 . . . . . . . . . . . . . . . . . . . . .
17
2.11 Shunt Capacitor Output Design 2 . . . . . . . . . . . . . . . . . . . . . . . .
18
3.1
Sine Wave Generated from Look Up table . . . . . . . . . . . . . . . . . . .
21
3.2
Sine Wave Generation Algorithm . . . . . . . . . . . . . . . . . . . . . . . .
22
3.3
Triangular Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24
3.4
Two State SPWM Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . .
25
3.5
Half Bridge SPWM Generation . . . . . . . . . . . . . . . . . . . . . . . . .
26
3.6
Full Bridge SPWM Generation . . . . . . . . . . . . . . . . . . . . . . . . .
26
3.7
PI controller Implementation Block Diagram . . . . . . . . . . . . . . . . .
29
4.1
Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
4.2
Hardware Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33
4.3
Half Bridge Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
37
4.4
Half Bridge Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . .
38
4.5
Control of Full Bridge Rectifier . . . . . . . . . . . . . . . . . . . . . . . . .
39
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3 Phase - 1 Phase Converter
LIST OF TABLES
List of Tables
1.1
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4
B.1 Budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
57
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3 Phase - 1 Phase Converter
LIST OF TABLES
Abbreviations
Abbreviation
SPWM
IGBT
MOSFET
Description
Sinusoidal Pulse Width Modulation
Insulated Gate Bipolar Transistor
Metal-Oxide Semiconductor Field Effect Transistor
RMS
Root Mean Square
ADC
Analog to Digital Converter
PI Controller
Proportional Integral Controller
AC
Alternating Current
DC
Direct Current
IC
Integrated Circuits
FPGA
Field Programmable Gate Array
DE2
Development and Educations Board 2
CT
Current Transformer
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3 Phase - 1 Phase Converter
1. Introduction
Chapter 1
Introduction
The objective of this project is to convert a three-phase power to a single-phase power.
The three-phase source is rectified to obtain DC Voltage. The DC voltage is then inverted
to 120 Vrms. The same principle can be applied in the reverse direction. This can be used
to operate a three-phase system using a single-phase system.
1.1
Background
The background can be explained through the idea of rectification and inversion. Rectification is the process of taking three-phase or single-phase Alternating Current (AC) and
converting it to Direct Current (DC). This can be done in a controlled or uncontrolled
manner. For our design project, we are using a controlled process. To accomplish this
Insulated-Gate Bipolar Transistor’s (IGBT), or Metal-Oxide-Semiconductor Field Effect
Transistor’s (MOSFET) are used in conjunction with controlling pulses. Inversion is simply
rectification in reverse; DC power is converted into AC power.
These devices are controlled using signals, known as firing angles which are responsible for
turning on IGBT’s. These signals are generated using Sinusoidal Pulse Width Modulation
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3 Phase - 1 Phase Converter
1.2 Applications
(SPWM). A Proportional-Integral (PI) Controller can adjust the SPWM waveform. The
PI Controller will determine the error between its input and its reference input and adjust
the SPWM.
By combining these systems, we can have an AC input and convert to any AC output.
For example, a 60 Hz, three-phase input can be used to output as a 50 Hz single-phase
system. This is possible by introducing a DC link between the two systems.
1.2
Applications
The application for our project can be seen everywhere in today’s power system world.
In power systems the rectification, inversion scheme is used when connecting systems with
varying frequencies especially, when transferring large amounts of power over long distances.
As this process involves conversion of AC into DC (rectification) and then converted back
to AC at the receiving end (inversion).
Smaller scale systems are used in industries where three-phase power is being supplied,
and single-phase is needed. In the household this method can be used to run three-phase
machines off of the household mains.
1.3
Problem Definition and Specifications
For this project, we use three-phase 220 Vrms input and convert it to a single-phase 120
Vrms output. This power is then send back to single-phase household network. This is
achieved by using PI Controllers, which ensure that maximum power is supplied back to
the network. If this goal is achieved, the PI Controllers will control SPWM waveforms,
which in turn will control our rectification and inversion process.
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3 Phase - 1 Phase Converter
1.4
1.4 Motivation
Motivation
In today’s demanding world of power system more and more households and industries
rely heavily on electricity than ever before. Along with this reliance and the advancements
of technology comes a demand for more flexible energy options. Our project design allows
the three-phase to single-phase conversion and vice versa as needed by the consumer.
1.5
Thesis Organization
In order to complete our project, the following approaches were taken to accomplish the
working model of the project.
The first approach involved understanding of how the power electronics devices work as
a whole. In addition to this, the project demanded in depth understanding of each stage,
i.e Stage 1 AC-DC conversion and Stage 2 DC-AC conversion processes.
The second approach was to have a running simulation of our design using PSCAD
software. This software was new to all of the members of the group, so we were required to
educate ourselves on this. In order do this completed as efficiently as possible we divided
it into separate parts.
Lastly, we were responsible for the hardware implementation of the design. To achieve this
Ali worked in the software sections to implement the PI controller using a SPWM waveform.
Michelle handled the signal conditioning between the high voltage and low voltage device
and Stephen and Reena were responsible for the hardware integration of the devices.
As a whole, although section responsibility was assigned to individual members of the
group, every member contributed to each section of the project.
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3 Phase - 1 Phase Converter
1.6
1.6 Specifications
Specifications
Table 1.1 will show the specifications needed to meet our design goal.
Table 1.1: Specifications
Input Voltage
Input Power
Output Voltage
Output Power
Stage 1: AC-DC
240 Vrms, three-phase AC
0 ≤ P ≤ 500W
200 Vdc
0 ≤ P ≤ 500W
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Stage 2: DC-AC
200 Vdc
0 ≤ P ≤ 500W
120 Vrms, single-phase AC
0 ≤ P ≤ 500W
3 Phase - 1 Phase Converter
2. Modeling and Simulation of Converters
Chapter 2
Modeling and Simulation of
Converters
In order to design the working model of our project it was required to know the parts and
components necessary to implement our design. The best method to estimate these values
was to perform a simulation of the entire system.
Initially, the complete simulation was assigned to only one of the group members. However, it was soon found that the simulation was too complex for one member to handle. It
was then divided in two stages. Stage 1 was to convert the kinetic energy of the three-phase
220 Vrms induction machine that outputs single-phase DC. Stage 1 is called AC-DC conversion. Stage 2 was to take Stage 1’s DC voltage and convert it back to the single phase
120 Vrms. This stage is called DC-AC conversion. For both of the converters, IGBT’s
were chosen as the switches and the switching pulses were generated using SPWM method,
which is explained in Stage 1.
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3 Phase - 1 Phase Converter
2.1
2.1 Stage 1: AC-DC Conversion
Stage 1: AC-DC Conversion
In this stage, a controlled AC-DC converter was designed and simulated to convert the
kinetic energy of a three-phase induction 220 Vrms machine into a DC voltage. Since the
input power and voltage drops in time, the converter keeps the DC voltage constant by
controlling SPWM that generates the switching pulses of the converter.
Fig. 2.1: AC-DC Converter
The SPWM controls six switches as shown in Figure 2.1. To accomplish control, three
sinusoidal waveforms with adjustable phase shifts were introduced as the SPWM references.
The frequencies of these sinusoidal waveforms were chosen to be 60 Hz to match the maximum input frequency of the induction machine. To avoid even harmonics the carrier to
reference frequency ratio should be an odd number. A higher frequency will also provide
lower switching loses. Due to the IGBT speed limitations the carrier frequency needed to
be less that 2 kHz. The SPWM waveforms were compared with 1860 Hz triangular waveform that acted as a carrier waveform, which satisfied all requirements. Each of the SPWM
waveforms control a complimentary pair of the switches.
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3 Phase - 1 Phase Converter
2.1 Stage 1: AC-DC Conversion
The IGBT switches are typically used with switching frequencies of less than 2 KHz.
Since IGBTs are non-ideal switches, there would be a small delay for them to start fully
conducting or completely stop. Therefore, each IGBT switch was put in parallel with a
diode to provide continuity of currents for inductive loads.
Due to the non-idealities of the switches, the continuous current was found to have some
harmonics. Because of the AC-DC converter’s characteristics, the third harmonics at the
output would be cancelled. To address the output harmonics, they were considered in two
groups: even harmonics and odd harmonics for each phase. The ratio of career frequency
to reference frequency was chosen as an odd integer to avoid even harmonics at the output
of the converter. The ratio used was the highest possible odd integer of 31 such that the
carrier over reference frequency was still less than 2 KHz. To address the remaining odd
harmonics, a DC shunt capacitor was added to the system to maintain a steady DC voltage.
The value of this capacitor was chosen to be 10 mF. The DC output was then made
adjustable via a feedback loop that uses PI Controllers. The PI Controllers maintained a
constant DC voltage at the output by controlling the SPWM, which is further explained in
section 2.4.
Figure 2.1 shows the design topology of the Stage 1 and the simulation result obtained
using the PSCAD software are shown in Figure 2.2.
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3 Phase - 1 Phase Converter
2.2 Stage 2: DC-AC Conversion
Fig. 2.2: AC-DC Converter Voltage Output
2.2
Stage 2: DC-AC Conversion
In stage 2, a controlled DC-AC converter was designed and simulated to convert the DC
output of stage one to a single phase, 120 Vrms. This output is then connected to the power
grid. The switches of the device were controlled by a SPWM waveform, which is explained
above. Furthermore, a feedback loop that has a PI controller enables the converter to
produce a clean AC waveform. This is explained in section 2.4.
At the end of stage two, a shunt capacitor of 180 uF was connected at the output to
maintain a stable voltage, thereby filtering out the higher harmonics. Figure 2.3 to Figure
2.4 show the design topology and the simulation results obtained using the PSCAD software
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3 Phase - 1 Phase Converter
2.2 Stage 2: DC-AC Conversion
for Stage 2.
Fig. 2.3: DC-AC Converter Schematic
Fig. 2.4: DC-AC Voltage Output
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3 Phase - 1 Phase Converter
2.3 Power Grid Connection
Fig. 2.5: DC-AC Current Output
2.3
Power Grid Connection
Stage 1 and Stage 2 were combined together and was successfully simulated using PSCAD
software. The simulation was done to convert three phase 220 Vrms to a single phase 120
Vrms which is then connected back to the power grid. When making this connection, we
had to make sure that the output voltage phase is in synchronism with the phase angle of
power grid. If the voltages were out of phase at the time of connection; a spike of current
might flow from high voltage to the lower voltage, which could damage the system. To
address this issue, an inductive impedance of 0.02 H was added. This inductance was later
replaced by a 1 to 1 transformer to eliminate the phase difference problem at the time of
connection.
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3 Phase - 1 Phase Converter
2.4 PI Controller
The result gave 2 A peak to peak and 170V peak to peak at the output. Due to the
non-availability of the 1:1 transformer, the simulations were then rerun with several other
inductance values. A larger inductance was added instead. Moreover, with the PI controller
design focusing on the phase modulation index took care of the phase difference and hence
helped in replacing the 1:1 transformer from our design. The PI controller is explained in
more detail in the section 2.4.
Figure 2.6 shows the complete schematic when both of the stages are combined.
Fig. 2.6: Complete Schematic
2.4
PI Controller
The PI Controllers are the control systems that monitor the input/output of the AC-DC
or DC-AC converters and adjust the SPWM waveforms of the IGBTs’ accordingly. During
the course, the design of the PI Controllers was modified twice. In the first design, the PI
Controllers were controlled by the output voltages of the AC-DC and DC-AC converters.
In the second design, the PI Controllers were controlled by monitoring the power of the
source and voltage of the shunt capacitor.
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3 Phase - 1 Phase Converter
2.4.1
2.4 PI Controller
Design 1
The objective of PI Controllers were to control the SPWM waveforms of the IGBT’s by
using the output voltage from either the AC-DC and DC-AC. The Pl Controller had two
methods to control the SPWM waveforms, Amplitude Control and Phase Control. In ACDC converter, the two PI Controllers utilized the Amplitude Control and Phase Control
separately. While in the DC-AC converter the PI Controller managed the Phase Control.
PI Controllers designed for the AC-DC converter had the PI Controller managing the
Amplitude Control reaching steady state at 4 second at value 100 Vdc. While the PI
Controller managing the Phase Control reaching steady state at 6 second and maximum
valve around 170 Vdc. In Figure 2.7, the differences between Amplitude Control and Phase
Control are shown. When the two PI Controllers were combined, the AC-DC output was
to be at steady state at 0.2 second to the desired output of 200 Vdc as seen in Figure 2.8.
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3 Phase - 1 Phase Converter
2.4 PI Controller
Fig. 2.7: AC-DC PI controls
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3 Phase - 1 Phase Converter
2.4 PI Controller
Fig. 2.8: AC-DC Converter Design 1
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3 Phase - 1 Phase Converter
2.4 PI Controller
Fig. 2.9: Single Phase Voltage Output Design 1
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3 Phase - 1 Phase Converter
2.4 PI Controller
In the first iteration of the PI Controller design for the DC-AC converter, the PI controlled
the modulation index (Amplitude Control) of the SPWM waveform. This controller did
produce the single-phase amplitude but the phase difference was found to be a mismatch
with the desired output.
With advice of our advisor, the PI Controller for the DC-AC converter was redesigned
to control the firing angle of the IGBT’s, (Phase Control). To do this, we change the phase
of the SPWM waveform applied to the rectiers. By focusing on the PI design iteration to
Phase Control, the output waveform could be held within ten percent of our desired output.
The simulation was run with and without the 1:1 transformer with no effects on the result.
To optimization the PI Controllers of the first design we had to find the values that ensured
the settling time of the system output was around 0.03 seconds as seen in Figure 2.9.
2.4.2
Design 2
The PI Controllers in the second design were changed to reflect the industry standard of
monitoring the system. The two PI Controllers for AC-DC side manage the Phase Control
by observing the real power of the source. The Amplitude was controlled by observing
the reactive power. By designing the PI Controllers in this way, we could ensure that the
maximum output is given to the shunt capacitor at all times.
The PI Controller on the DC-AC converter was changed to monitor the changes in voltage
of the shunt capacitor bank. When the shunt capacitor would be voltage higher than the
desired voltage of 170 Vdc, the DC-AC Converter would transfer the excess power to the
grid.
The PI Controllers for the second design obtain steady state within 7 seconds and are
able react to changes of the source voltage as seen in Figures 2.10 and 2.11.
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3 Phase - 1 Phase Converter
2.4 PI Controller
Fig. 2.10: Single Phase Voltage Output Design 2
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3 Phase - 1 Phase Converter
2.4 PI Controller
Fig. 2.11: Shunt Capacitor Output Design 2
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3 Phase - 1 Phase Converter
3. Software Development
Chapter 3
Software Development
The software implementation for this project was done with a combination of programming in the Verilog language and Schematic designs used Altera’s Quartus, and the FPGAs
used the DE2 development unit.
3.1
Software Implementation
Several codes were written in Verilog language until an effective algorithm was developed.
After compiling these codes, Quartus optimizes the logical implementation of software instructions for the fastest operational speed and demand on the FPGAs physical resources.
As the next step, Quartus uses the optimized version of software instructions to program
the FPGAs’ look up tables. The DE2 unit holds these hardware implementations until
an external source reset the DE2 unit. The instructions embedded into the FPGAs are
represented in the software implementation section by a combination of algorithms, block
diagrams, and sample of the codes when appropriate. The code used for the project can be
found in the Appendix A: Verilog Code, with repetitive section not shown.
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3 Phase - 1 Phase Converter
3.1.1
3.1 Software Implementation
Sinusoidal Pulse Width Modulation (SPWMs)
There were two methods, which were considered for generating controllable SPWM using
FPGA; the microcontroller used in this project. In the first method, an external source such
as a function generator generates the waveforms required and these are supplied to the DE2
unit via an Analog to Digital converter (ADC). In the second method, the SPWM waveforms
are created within the DE2 units and by programming the FPGAs. After comparing the
two different methods and advise from the project’s supervisor, the second method was
selected due to FPGA’s control speed.
This method uses digital representations of sinusoidal and triangular waveforms. To
optimize the execution speed, such representations were done so that:
1. Their waveform values are always positive.
2. The samples can be represented with binary numbers.
3.1.2
Creating Sine Wave
During the research for the SPWM implementation in FPGAs, a verilog look up table
with 256 sampled values for a sine wave was found that on a webpage that was used to
generate audio files [1].
A sine waveform of desired frequency can be created by increasing the table’s index from
0h00 to 0hff (or 0 to 256 in base 10). This gives a sine wave, with 0hFFFF (65534 height in
base 10) maximum peak, 0h7FFF offset(or 0.5*65534 = 32767 in base 10), and minimum
of 0h0000(0 in base 10), as seen in Figure 3.1.
This sine wave also has an adjustable frequency by choosing the appropriate clock speed
for using the sine wave look up table. Since there are 256 samples in one cycle, and the
- 20 -
3 Phase - 1 Phase Converter
3.1 Software Implementation
Fig. 3.1: Sine Wave Generated from Look Up table
desired frequency of the sine wave is 60Hz, the clock speed needs to be:
Clockspeed = 256 ∗ 60 = 15360Hz.
The clock used for this program is 50 MHz supplied by the DE2. To get the desired
frequency, a new clock was defined for the sine wave. The speed of the desired clock is: 50
MHz / 15360 Hz = 3255. In other words, for every 3255 cycles of 1 MHz, the slowed clock
toggles once. This moves the index of the sine look up table once and thereby creating the
sine wave with a frequency of 60 Hz. The simplified algorithm for this process is shown in
Figure 3.2:
- 21 -
3 Phase - 1 Phase Converter
3.1 Software Implementation
Fig. 3.2: Sine Wave Generation Algorithm
3.1.3
Creating a Triangular Wave
Since the output reactive power of a power supply is normally kept to a minimal value
(Q is very close to 0) to reduce losses and increase the efficiency of the supply system, it
is possible to set the modulation index reference to a consent. This consent should be less
than 1 to avoid over modulation. A high modulation index improves performance, so an
index of 0.9 was chosen. In this manner, the PI controller unit controls the full bridge
rectifier by adjusting phase angles of sine waveforms.
- 22 -
3 Phase - 1 Phase Converter
3.1 Software Implementation
To have the modulation index set at 0.9, the ratio of the peak of the sine wave form
(0hFFFF) to the ratio of the peak of the triangle waveform should be equal to 0.9. In other
words, the maximum peak of the triangle waveform is 0h11C6F:
P eakof T riangle =
65534
= 72815 = 0H11C6FHex
0.9
This triangle can be constructed in steps size of 100. Therefore, there are approximately,
729 steps from zero to the peak of the triangle. Next the triangular waveform is created by
a counter value. In the first half cycle, the counter value increases from 0h0000 to 0h11C6F
one step at a time, and then decreases to 0h0000 with the same step size. A simplified
algorithm for generating a triangular waveform is shown in figure 3.3.
This triangular waveform also has an adjustable frequency by choosing the appropriate
clock speed very similar to the sine wave. There are 2*729 = 1458 samples in one cycle of
the triangle. In order to avoid even harmonics, an odd ratio of carrier to reference frequency
was used. The triangle frequency was then selected to be 19*60 = 1020 Hz. Therefore, the
required clock speed to generate this triangle waveform should slow down the 50 MHz clock
by:
SlowedClock = 50M Hz/(19 ∗ 60 ∗ 729 ∗ 2) = 30
In other words, every 30 cycles of clock 50 MHz, will make one cycle of slowed clock.
3.1.4
Creating SPWMs: Comparison of the two Waveforms
For the half bridge, a comparator detects when a sine wave value and a triangle value are
equal and this drives two complimentary switches as seen in Figure 3.4.
- 23 -
3 Phase - 1 Phase Converter
3.1 Software Implementation
Fig. 3.3: Triangular Algorithm
The same methodology applies to the full bridge SPWM but with a slight modification.
A variable td is used as a time delay between the sine waveforms. This time delay is used
to create the phase differences between the three sine wave forms as seen in Figure 3.5 and
Figure 3.6.
- 24 -
3 Phase - 1 Phase Converter
3.2 Measuring Voltage and Currents
Fig. 3.4: Two State SPWM Algorithm
3.2
Measuring Voltage and Currents
The measured voltages and currents are converted to digital values by aid of Analog to
Digital Convertors (ADCs), as described in the hardware section. Since there are three
measurements, and each measurement requires 8 bits, there are 24 pins required to read
the sampled digital values. The microcontroller takes these values as an input by using 24
of the 32 available pints of the GPIO O ports.
- 25 -
3 Phase - 1 Phase Converter
3.2 Measuring Voltage and Currents
Fig. 3.5: Half Bridge SPWM Generation
Fig. 3.6: Full Bridge SPWM Generation
- 26 -
3 Phase - 1 Phase Converter
3.2.1
3.2 Measuring Voltage and Currents
Calculating Average Power
The average power of an AC power can be calculated as:
P = V rms ∗ IrmsCos(θ)
Where,
V rms =
V peak
√
2
&
Irms =
Ipeak
√
2
or alternatively:
P
Pave
P
Psampled
Vsampled
=
=
∗ Isampled
N umberof Samples
N umberof Samples
To implement this design, the microcontroller constantly reads samples of voltage and
current values. These samples are stored in memory over a period of 30 seconds. Next,
these samples are added together, and divide by the number of samples to give the average
power.
3.2.2
PI Controller
The formal equation[7] of a PI Controller in s domain is :
G(s) = Kp + KI/S
- 27 -
3 Phase - 1 Phase Converter
3.2 Measuring Voltage and Currents
This equation can be implemented in a digital logic system [4,5,6] as:
I(k) = (E(k) + E(k − 1)) ∗
Ki ∗ T s
2 + I(k − 1)
/
P (k) = Kp ∗ E(k)
The PI controller can be logically implemented in by using the following algorithms: For
the stage 1’s (full bridge rectifier) PI controllers the average AC power and average DC
power are measured, as seen in Figure 3.7. Their difference is the error for the PI controller
responsible for the phase angles of sine waves. For the modulation index, constant 0.9 was
used as the modulation index.
For the stage 2, whenever the capacitor voltage becomes higher than 200V, the stage 2’s
PI controller is activated. This device measures the single-phase ac output and compares
is to 120 Vrms. The error drives the phase angle of stage 2’s SPWM.
- 28 -
3 Phase - 1 Phase Converter
3.3 Microcontroller Integration
Fig. 3.7: PI controller Implementation Block Diagram
3.3
Microcontroller Integration
One of the project design challenges was connecting a low voltage, low power microcontroller to high voltage, high power systems. The microcontroller was required to monitor
voltages and currents in different stages, the real and the reactive power supplied to the
system and to control the IGBT switching signals. To protect the microcontroller from any
damage any possible leakage of high power should be avoided. Thus, different alternatives
and methods were considered. It was then decided to employ a combination of optoisolators and step down transformers to safely communicate between the high voltage and low
voltage sides of the system. These sections are further explained in Chapter 4, Hardware
Implementation.
- 29 -
3 Phase - 1 Phase Converter
4. Hardware Implementation
Chapter 4
Hardware Implementation
4.1
Design Topology
The objective of this project is to develop a three phase- single-phase converter. The
project converts power of an Alternating Current (AC) source of any frequency and voltage
value, within the specifications of the system, to a single phase AC of desired voltage and
frequency in two stages.
Fig. 4.1: Topology
From figure 4.1, in stage one, a controlled full bridge rectifier, with six IGBTs convert
the three-phase AC power to a DC power. Two PI controllers that control the phase and
- 30 -
3 Phase - 1 Phase Converter
4.2 Components
modulation index monitor this conversion. The average of the three-phase AC source’s real
power is measured and is used as the reference. This reference is then compared with the
stage 1’s DC output power. The comparison provides an error that is used to drive the
phase angle of SPWM waveforms. This process optimizes the firing angles of the full bridge
rectifier’s IGBTs so that the maximum real power is transferred to the DC side, which is
the input of stage two.
In stage two, a PI controller monitors the energy stored in a shunt DC capacitor by
measuring the capacitor’s voltage. When the capacitor voltage exceeds a set value, the PI
controller of stage 2 transforms the excessive DC energy to the desired single phase AC
power. Finally, the converter transfers this converted AC power to the power grid via a 1:1
transformer, which damps the possible phase difference between the output power and the
power grid.
4.2
Components
1. Full bridge rectifier: After research and simulation we found that a full bridge rectifier
was needed to convert the three-phase input to DC. To implement this we decided that a prebuilt IGBT bridge would best suit our needs. This was chosen for high voltage MOSFET’s
since it was more economical to use the IGBT components since they were available at the
University of Manitoba.
2. Half bridge rectifier: Independent DC power supply for half bridge rectifier The dc
output of stage 2 is measured with respect to neutral not ground. Therefore, to supply the
required voltages to drive the half bridge switches, an independent dc power supply was
used. This dc power supply, provides the require power for an optoisolators and Integrated
Circuits (ICs).
- 31 -
3 Phase - 1 Phase Converter
4.2 Components
3. IGBT’s: The IGBT switches are typically used with switching frequencies of less than
2 KHz. Since these switches were readily available in the university, we ended up choosing
them for our design project.
4. Capacitor Bank: A capacitor bank was provided by the university. This device was
to simulate the AC capacitor 180 uF at the final output. Instead of ordering a single
capacitor, we decided to use the capacitor bank to tune our final single phase AC output.
The capacitor bank has three rows of standard values (0.1 uF to 150 uF) giving us control
of remove harmonics that will occur in our final single phase AC output.
5. Optoisolators: Independent DC supply: The optoisolator circuit that drives the full
bridge rectifier requires a 24 V power supply. The design team ordered a 24-power supply
with the input of 120 Vrms.
6. Three-phase voltage and current transducers: The three phase voltage and current
transducer was obtained from the university. This device will be used to provide the voltages
and currents of each three phases of the source. All outputs of this device are given as
voltages. Testing and measuring of this device was reacquired to find the range of the
device.
7. Isolation Amplifiers: The Isolated Amplifier used to measure our high DC voltage at
the shunt capacitor. This amplifier provides isolated protection while reading voltage and
provides zero to five Volts output. A voltage divider is connected to the input ensuring it
is with in the range of zero to five Volts.
8. Microcontroller: The project demands a fast and reliable microcontroller to control
the system adequately and safely. Additionally, good development software and available
- 32 -
3 Phase - 1 Phase Converter
4.3 Hardware Assembly
technical support were required. The selection was also limited by the cost of the microcontroller and its availability. Considering the requirements and constraints, the design team
selected Altera’s DE2 Development and Educational Board. This board uses a Cyclone
II Field-Programmable Gate Array, (FPGA) which satisfied our clock speed requirements.
Furthermore, this controller can process different tasks in parallel (such as creating sine
wave and triangle waves) unlike software with one processor, where one task has to be
processed before then next one begins.
4.3
Hardware Assembly
Figure 4.2 shows the hardware assembly of the design topology with the measuring device modules and the microcontroller. There are three measuring device modules: Real
and Reactive Power Measuring Module, DC Voltage Module and the Single-Phase Current and Voltage Measuring Module. All the Measuring Module outputs are inputs to the
microcontroller.
Fig. 4.2: Hardware Assembly
- 33 -
3 Phase - 1 Phase Converter
4.4 Real and Reactive Power Measuring Module
The source is model using LabVolt three-phase power supply. The power supply is adjusted to the voltage of 220 Vrms and is connected to the real and reactive power measuring
module. The full bridge rectifier receives input from the real and reactive power measuring
module. Simultaneously, it receives SPWM waveform from the microcontroller.
The equivalent DC shunt capacitor of 10 mF connects the full-bridge rectifier and the halfbridge rectifier. Measurements are taken from the shunt capacitor through the DC voltage
module, and the output received from the DC voltage module is given to the microcontroller.
The half-bridge rectifier receives its SPWM waveform from the microcontroller and output
a single-phase 120 Vrms to the 1:1 transformer. The 1:1 transformer then passes this signal
to the capacitor bank that filters out the unwanted harmonics. This signal is then connected
back to the power grid.
4.4
Real and Reactive Power Measuring Module
The Real and Reactive Power Measuring Modules consist of the following components:
three-phase voltage and current transducers, six ADCs. This module takes the three-phase
current and the voltage measurement and sends out a 6 to 8 bit outputs to the microcontroller. These outputs are then converted to power measurements and are used in the PI
Controller algorithms controlling the full bridge rectifier.
For the three-phase measurements, we use a single board which is capable of measure
each phase independently. For the voltage measurements, a transformer is mounted on the
board. We send it the phase voltage of our input and it produces a more manageable low
voltage value. For current measurements 3 individual current transformers (CT) are used.
Each CT produces a low current. This current than must be sent through a resistor. The
voltage of the resistor is read, and the current is in turn calculated :
- 34 -
3 Phase - 1 Phase Converter
4.5 DC Voltage Measuring
Iin =
Vresistor
∗N
R
Where N is the number of turns in the current transformer.
ADC will take in the output of the current transducer and voltage reading (, range 0-5V)
and will convert the input to the 8-bit input for the microcontroller. The ADCs are setup
on a continuous mode output which allows the microcontroller to sample the bits at its
bit rate. The microcontroller then formulate a numerical conversion of current and voltage
8-bit reading to appropriate power values. These values are used in the microcontroller
which controls the full bridge rectifier.
When we are looking at the single phase side, a measurement of the output current is
needed. This is a pre-built board. This board consists of a CT and group of resistors.
When we initially took the measurements, the current output was too low. When we apply
addition coil turns to the device.
4.5
DC Voltage Measuring
The DC Voltage Module consist of a voltage divider, an isolation amplifier and an ADC.
The DC voltage of 200 V is stepped down to 5 V, by the voltage divider, filter through an
isolated amplifier, and is then converted to 8-bit output by the ADC. The 8-bit output is
then returned to the microcontroller which controls the half-bridge rectifier.
The step down voltage was created with the voltage divider to the top railing of the shunt
capacitor. The current through the voltage divider was selected to be 10mA. This current
will generate some power loss on the DC side. The resistors values were calculated based
on the input of 120 Vdc and the input of 5Vdc. Thus, we choose R1 = 100 k ohms and R2
- 35 -
3 Phase - 1 Phase Converter
4.6 Single Phase Current and Voltage Measuring Module
= 2.7 k Ohms.
The shunt capacitor is referenced with respect to the neutral. We cannot connect the
voltage divider directly to an ADC as this might create a large current to be driven into the
ACD. Thus, an isolated amplifier was used to provide the isolation and protection required.
The isolated amplifier takes the voltage across the 2.7 k ohms resistor as its input. This
input signal then goes through the voltage transformations within the amplifier and produces an output with reference to ground ( range 0 to 5V). This output is then passed
through ADC which is then converted to 8-bit output to be used in the microcontroller.
4.6
Single Phase Current and Voltage Measuring Module
Single Phase Current and Voltage Measuring Module monitors the output of the single
phase system. The module consists of multi-meter, single phase current transducer and an
ADC. The mulit-meter is used to monitor the voltage output. The single phase current
transducer converts the current into voltage. This allows the ADC chip to read the voltage
and provide us the current reading via the microcontroller.
4.7
Half Bridge Rectifier
In stage two, a half bridge rectifier converts DC to AC as shown in Figure 4.3. This
rectifier receives a controlled DC, which is measured with respect to neutral. To convert
DC to AC, the microcontroller unit sends complementary signals to the IGBT gates to turn
them on and off, and the speed of these signals determines the output’s frequency.
For the IGBT half bridge rectifier, device CM50DY-12H was selected. This device is a
collection of two back to back IGBTs. On the dc side, collector of the first IGBT (C1) and
- 36 -
3 Phase - 1 Phase Converter
4.8 Full Bridge Rectifier
Fig. 4.3: Half Bridge Schematic
the emitter of the second IGBT (E2) are connected to the dc capacitor, which keeps a stiff
dc voltage of 200 V. The emitter of the first IGBTS (E1) and the collector of the second
IGBT (C2) are connected together and their output provides 120 Vrms, output with respect
to the ground.
This conversion is controlled by DE2 s FPGAs via a collection of an optoisolator and
an Integerated Circuit (IC), ( Digi-Key part part CNY17F2MFS-ND ) as shown in Figure
4.4. To power the optoisolator and the IC circuit, and independent power supply,( Digi-Key
part 835-1118-ND ) was used to supply 15 Vdc with respect to neutral. The microcontroller
unit sends pulses to the IC circuit. At this stage the IC chip sends out two complementary
signals of 15 Vdc. To turn these complementary switches on, S2 switch requires supply 15
Vdc with respect to neutral while the S1 requires 15 Vdc with respect to E1 C2 point.
4.8
Full Bridge Rectifier
To convert the three phase 220 Vrms to 200 Vdc, a combination of an IC circuit and a
full IGBT bridge rectifier was used, as seen in Figure 4.5, similar to the control algorithm
of the half bridge rectifer. In this stage, FPGAs send their commanding signals to the IC,
- 37 -
3 Phase - 1 Phase Converter
4.8 Full Bridge Rectifier
Fig. 4.4: Half Bridge Block Diagram
part number BP7A. This IC circuit isolates the microcontroller from the IGBT switches
and is powered by a 24V power supply, part number 285-1827-ND. On the output of the IC,
the full bridge rectifier, part PH150CLA060, made by FRX, receives switching commands
and converts the ac to dc as specified.
- 38 -
3 Phase - 1 Phase Converter
4.8 Full Bridge Rectifier
Fig. 4.5: Control of Full Bridge Rectifier
- 39 -
3 Phase - 1 Phase Converter
5. Conclusions
Chapter 5
Conclusions
This project report has outlined the design and implementation of a three-phase system to
a single-phase system. Although this report demonstrated only one model of the converter
that was designed i.e., going from three-phase system to single-phase system direction, this
project opens up a window to develop a converter going into the reverse direction i.e singlephase system being used to operate a three-phase system. Thereby, bestowing the idea of
a regenerative breaking system.
In order to meet our goal, a complete PSCAD simulation was done. Based on the results,
we selected our individual hardware components. To monitor the input or output of the
AC-DC or DC-AC converters and adjust the SPWM waveforms of the IGBTs accordingly,
we used a PI control system in the simulation. To optimize control performance of the
system a fast control unit was desired. This led to choose FPGAs as our control unit.
As of now, the controller algorithm has been developed and is at testing and debugging
stage. For the hardware implementation, each component has been tested individually and
made sure that they meet our project specification.
- 40 -
3 Phase - 1 Phase Converter
Given the time frame and the budget allotted for the project, the team is optimistic to
finish the working model by the presentation date.
- 41 -
3 Phase - 1 Phase Converter
REFERENCES
References
[1] J. Loomis. (2009, 18 November). Digital Labs using the Altera DE2 Board [Online].
Available:
http://www.johnloomis.org/digitallab/ [January 11, 2014]
[2] Z. Chaunwei, B. Zhifeng, C. Binggang, and L. Jingcheng (August 14-16, 2004). Studies of Regenerative Braking in Electric Vehicle [Online]. IEEE Xplore Digital Library.
Available:
http://ieeexplore.ieee.org/xpl/login.jsp?tp=arnumber=1375826url=http
[3] S.R. Cikanek, and K.E. Bailey (February 12, 2002). Regenerative braking system for
a hybrid electric vehicle [Online]. IEEE Xplore Digital Library. Available:
http://www.researchgate.net/publication/3961650 Regenerative braking system for a hybrid electric vehicle [June 3, 2013]
[4] P. Schad, and D. Carney (January 17, 2011). Case study of PID control in an FPGA
[online]. IEEE Xplore Digital Library. Available:
http://www.embedded.com/design/configurable-systems/4212241/Case-Study-of-PID-Controlin-an-FPGA- [December 25, 2013]
[5] N. Watjanathepin, N. Eawsakul, M. Puangpool, A. Namahoot, and S. Yimman. (October 22, 2003 ). Implementation of PI Controllers with the FPGA [online]. Available:
http://eng.rmutsb.ac.th/events/admin2/Redearchp apers/Implementaiono fP Ic ontrollerw ithF P GA.pdf [January5
[6] M. Hassan, S. Mahmood, and M. Croock. (September 3, 2006). Design of FPGA
Based P/PI/PD/PID Controller for Industrial Applications [Online].Available:
http://www.iasj.net/iasj?func=fulltextaId=10213 [accessed February 11, 2014]
[7] D. Tilbury, and B. Messner. (2012, Oct 21). PID Control [Online]. Available:
http://www.ni.com/white-paper/6440/en/ [February 11, 2014]
- 42 -
3 Phase - 1 Phase Converter
A. Verilog Code
Appendix A
Verilog Code
This modules slows down its input clock by a factor of 15360
module sine_clock(clk,slow_clock);
input clk;
output slow_clock;
reg [31:0]temp;
reg slow_clock;
always @ (posedge clk)
if (temp < 15360) begin
temp = temp + 1’b1;
end
else begin
temp <= 32’b0;
slow_clock = ~slow_clock;//1’b1;
end
endmodule
- 43 -
3 Phase - 1 Phase Converter
This program gets receives the appropriate clock for the sine wave, and creates an index
for a sine table that follows it.
contenmodule sine_index (clock, count,up_down);
input clock;
output
[15:0] count;
output up_down;
reg [7:0] count;
reg up_down;
always @ (posedge clock)
begin
if (up_down > 0)begin// && up_down) begin
count = count + 1’b1;
up_down = 1’b1;
if (count > 254) begin
up_down = 1’b0;
end
end
else begin
count = count - 1’b1;
up_down = 1’b0;
if (count <1)begin
up_down = 1’b1;
end
end
end
endmodule
- 44 -
3 Phase - 1 Phase Converter
This module is essentially a look up table that receives an index and outputs the appropriate sine value according to that index.
module sine_look_up_table (
input [7:0] table_index,
output [15:0] sine_wave
);
reg [15:0] sine_wave;
always@( sine_look_up_table)
begin
case(sine_look_up_table)
8’h00: sine_wave = 16’h0000 ;
8’h01: sine_wave = 16’h0192 ;
8’h02: sine_wave = 16’h0323 ;
8’h03: sine_wave = 16’h04b5 ;
// look up table continues
8’hfc: sine_wave = 16’hf9bb ;
8’hfd: sine_wave = 16’hfb4b ;
8’hfe: sine_wave = 16’hfcdd ;
8’hff: sine_wave = 16’hfe6e ;
default: sine_wave = 16’h0000;
endcase
end
endmodule
- 45 -
3 Phase - 1 Phase Converter
This program synthesises a simple triangular wave by using a binary counter that counts
up and down as a part of the SPWM waveform generator.
module t_wave(clock, count, up_down, sample);
input clock;
output [15:0] count;
output up_down;
output [3:0]sample;
reg [15:0] count;
reg up_down;
always @ (posedge clock)
begin
if (up_down > 0)begin// && up_down) begin
count = count + 100;
up_down = 1’b1;
if (count > 16’hefff) begin // reached more than 72815 or Oh11CF6
up_down = 1’b0;
end
end
else begin
count = count - 100;
up_down = 1’b0;
if (count <1000)begin
up_down = 1’b1;
end
end
end
assign sample[0] = count[12];
assign sample[1] = count[13];
assign sample[2] = count[14];
assign sample[3] = count[15];
endmodule
- 46 -
3 Phase - 1 Phase Converter
This is a comparator of sine and triangle wave form. When they cross, the module will
change its output state: pulse
module wave_comparator(clk, sine,triangle, pulse);
input clk;
input [15:0] triangle;
input [15:0] sine;
output pulse;
reg pulse;
always @ (posedge clk)
if (triangle == sine) begin
pulse = ~pulse;
end
endmodule
- 47 -
3 Phase - 1 Phase Converter
This module adjust the possible phase shifts between three SPWM wave forms for the
full bridge rectifier as phase shift between identical waveforms of fixed frequency, can be
also represented by a shift on the time axes. In this case, this phase / time shift is done by
shift in sine waves look up table index.
module full_bridge_sines(clk, t1,
input clk;
input [1:0] t1;
input [1:0] indx1;
output [1:0] indx2;
output [1:0] indx3;
always @ (posedge clk)
begin
indx2 = indx1+t1;
indx3 = indx2+t1;
end
endmodule
indx1, indx2, indx3);
- 48 -
3 Phase - 1 Phase Converter
This module adjust the possible phase shifts for the half bridge rectifier phase control
unit.
module half_bridge_sine_shift(clk, t1,
input clk;
input [1:0] t1;
input [1:0] indx1;
output [1:0] indx2;
always @ (posedge clk)
begin
indx2 = indx1+t1;
end
endmodule
- 49 -
indx1, indx2);
3 Phase - 1 Phase Converter
This module calculates an error between two signals
module error(clock,reference, feedback, error);
input clock;
input [7:0] reference;
input [7:0] feedback;
output [7:0] error;
reg [7:0] error;
always @ (posedge clock)
begin
error = reference -feedback;
end
endmodule
- 50 -
3 Phase - 1 Phase Converter
This module is part of the PI controller. Particularly, this is the module for time delay
where the module receives an input signal, outputs that signal while it holds the output
value until the next positive edge of clock.
module time_delay(clock, input_value,output_value);
input clock;
input [7:0] input_value;
output [7:0] output_value;
reg [7:0] output_value;
always @ (posedge clock)
begin
output_value = input_value;
end
endmodule
- 51 -
3 Phase - 1 Phase Converter
This module calculates the sum of two signals
module sum(clock,sig1, sig2, sum);
input clock;
input [7:0] sig1;
input [7:0] sig2;
output [7:0] sum;
reg [7:0] sum;
always @ (posedge clock)
begin
sum = sig1 + sig2;
end
endmodule
- 52 -
3 Phase - 1 Phase Converter
This module multiplies KI ∗ T s and divides them by 2 as a part of the PI controller
implementation.
module ki_ts(clock,ki, ts, res);
input clock;
input [7:0] ki;
input [7:0] ts;
output [7:0] res;
reg [7:0] temp;
reg [7:0] res;
always @ (posedge clock)
begin
temp = ki*ts;
res = temp/2;
end
endmodule
- 53 -
3 Phase - 1 Phase Converter
This module multiplies KI*Ts and divides them by 2 as a part of the PI controller
implementation for the full bridge.
module pi_control_half(clock, reference_, feed_back_, phase_shift);
input clock;
input [7:0] reference_;
input [7:0] feed_back_;
output [7:0] phase_shift;
reg [7:0] phase_shift;
wire kp = 2;
wire ki = 0.005;
reg [7:0] ts = clock;
reg [7:0] error;
reg [7:0] perv_error;
reg [7:0] res;
reg [7:0] kp_times_error_res;
reg [7:0] ki_sum;
reg [7:0] kp_sum;
reg [7:0] perv_sum;
error e1(clock,reference, feedback, error);
kp_times_error res2(clock,kp, error, kp_times_error_res);
time_delay delay1 (clock, eror,perv_error);
sum error_and_pervious_error(clock,e1, delay1, ki_sum);
ki_ts ki_ts_dev_by2(clock,ki, ts, res);
time_delay delay2 (clock, ki_sum,perv_sum);
sum pi_output(clock,ki_sum1, kp_times_error_res, phase_shift);
endmodule
- 54 -
3 Phase - 1 Phase Converter
This module multiplies KI*Ts and devides them by 2 as a part of the PI controller
implementation for the half bridge.
module pi_half_bridge(
// Clock Input (50 MHz)
input CLOCK_50, // 50 MHz
input CLOCK_27, // 27 MHz
// Push Buttons
input [3:0] KEY,
// DPDT Switches
input [17:0] SW,
// 7-SEG Displays
output [6:0] HEX0, HEX1, HEX2, HEX3, HEX4, HEX5, HEX6, HEX7,
// LEDs
output [8:0] LEDG, // LED Green[8:0]
output [17:0] LEDR, // LED Red[17:0]
// TV Decoder
output TD_RESET, // TV Decoder Reset
// I2C
inout I2C_SDAT, // I2C Data
output I2C_SCLK, // I2C Clock
// Audio CODEC
output/*inout*/ AUD_ADCLRCK, // Audio CODEC ADC LR Clock
input AUD_ADCDAT, // Audio CODEC ADC Data
output /*inout*/ AUD_DACLRCK, // Audio CODEC DAC LR Clock
output AUD_DACDAT, // Audio CODEC DAC Data
inout AUD_BCLK,
// Audio CODEC Bit-Stream Clock
output AUD_XCK,
// Audio CODEC Chip Clock
// GPIO Connections
input [35:0] GPIO_0,
output [35:0] GPIO_1
);
wire [7:0]voltage_feedback;
reg [7:0]voltage_reference;
reg [7:0] phase_shift;
reg [7:0] count;
reg [7:0] count_triangle;
reg [15:0] sine_value;
reg s;
- 55 -
3 Phase - 1 Phase Converter
//receiving measured voltage
//of half bridge control
assign voltage_feedback[0] =
assign voltage_feedback[1] =
assign voltage_feedback[2] =
assign voltage_feedback[3] =
assign voltage_feedback[4] =
assign voltage_feedback[5] =
assign voltage_feedback[6] =
assign voltage_feedback[7] =
//output s goes to the IC
assign GPIO_1[29] = s;
as the reference
GPIO_0[19];
GPIO_0[21];
GPIO_0[23];
GPIO_0[25];
GPIO_0[27];
GPIO_0[29];
GPIO_0[31];
GPIO_0[31];
//controlled slow clocks for sine wave and triangle
sine_clock c1(CLOCK_50,slow_clock1);
clock_1M c2(CLOCK_50,slow_clock2);
//pi controller’s controll of the sine of SPWM
pi_control_half p1(slow_clock2, voltage_reference, voltage_feedback, phase_shift);
//generating the sine waveform
sine_index(clock, count,up_down);
half_bridge_sine_shift shift(slow_clock2, phase_shift, count, indx2);
sine_look_up_table ( indx2, sine_wave);
//generating the triangle waveform
t_wave(clock, count_triangle, up_down, sample);
//compare the sine and triangle of SPWM and when they cross, pulse s
wave_comparator w(slow_clock2, sine_value,triangle, s);
endmodule
- 56 -
3 Phase - 1 Phase Converter
B. Budget
Appendix B
Budget
The Electrical Engineering Department had allocated $400 for this project. In addition,
the project supervisor, Dr. Shaahin Filizadeh, has agreed to provide an additional $300 if
required. Table III shows the estimated budget summary the project.
Table B.1: Budget
Part Description
AC Capacitor 22000 uF 100V
IC OPamp Isolation 2kHz SIP
Opt isolation
Half Bridge Driver
24V DC Supply
15V supply
10 pin Connector
2 pin Connector
Thermal Past
Connectors
Half Bridge Rectifier
Full Bridge Rectifier
Microcontroller
Heat Sink
Total
DigiKey Part Number
338-1990-ND
AD202JY-ND
CNY17F2MFS-ND
IR2111PBF-ND
285-1827-ND
835-1118-ND
WM2818-ND
WM3200-ND
345-1007-ND
298-10304-ND
CM50DY-12H
PH150CLA060
Altera DE2
N/A
Vendor
Digi-Key
Digi-Key
Digi-key
Digi-Key
Digi-Key
Digi-Key
Digi-Key
Digi-Key
Digi-Key
Digi-Key
U of M
U of M
U of M
U of M
Quantity
2
2
4
4
1
2
1
3
1
10
1
1
1
2
Cost
$37.52
$98.50
$2.20
$12.04
$25.08
$39.56
$2.04
$0.93
$11.97
$2.50
$0
$0
$0
$0
$232.34
Table B1 suggests a total cost of $232.34 has been utilized from $700 budget. Hence, the
groups expenditure is well within its budget.
- 57 -