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```							 FPGA Control of Induction Motors

Final Report

Group SD1019
Bibek Bhattarai
Tom Conlin
Sharan Ghimire

ECE 405, Spring Semester 2011.
May 6, 2011
Dr. Ababei, Dr. Yuvarajan, and Dr. Kavasseri, advisors.

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Introduction……………………………………………………….3

Requirements……………………………………………………...5

Software…………………………………………………………..6

Schematics………………………………………………………..13

Hardware/Troubleshoot…………………………………………..25

Appendix A: Matlab/Simulink Code…………..……………........27

Appendix B: Xilinx ISE burn steps……………………………….31

Appendix C: Space Vector Modulation Conference Paper..……...33

Appendix D: Costs………………………………………………..39

Appendix E: Inverter Data Sheet….……………………………...40

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Introduction
A brief background of what we did was to simply control a motor, an induction motor that is. An
induction motor has a three-phase, AC (sinusoidal) electric voltage power supply. The only two
ways to control the motor is to change the physical load or to change the three-phase voltage
frequency. The electric frequency changes the motor speed and torque. So what we are pretty
much doing is changing a three-phase voltage frequency. You will need to brush up on some
Power Electronics.

If you want to change the three-phase AC voltage frequency coming straight off the utility power
lines you must first rectify it to a DC voltage using an AC to DC converter. These are common,
simple, and well-developed. You just simply buy one or use a DC power supply like we did from
the lab. Once you have a DC power supply you must change it back to three-phase AC voltage
and this requires an inverter. When go back to AC voltage you have the option to choose the
frequency.

http://en.wikipedia.org/wiki/File:3-phase_inverter_cjc.png   Our inverter module with heat sink, capacitors, and wire connections

Shown above is the circuit diagram of the inverter. You have a rectified DC power supply and
the motor which is the load. Shown are six IGBT transistors or switches. These switches turn on
and off very fast in a certain way to create a three-phase current supply to the load (motor).
These switches are controlled by small low-voltage DC impulses (gate pulses) coming from a
controller.

Creating these six gate pulses, to maximize efficiency, is the hard part. The more efficient you
create these pulses with feedback from motor running data the more you can reduce unwanted
harmonics. Reducing harmonics has great energy saving impacts in the world today. On large
scale motors like wind turbine generators (motors and generators are one in the same) or in large
industry project motors, this would make the world a little more green because of less energy
resource consumption but with the same service. Pretty much what we want to do is make those
AC current sinusoidal waveforms coming out of the inverter as smooth as possible.

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The FPGA Torque Control project focuses on being able to fully control a motor using a field-
programmable gate array as the controller, outputting those six gate pulses. The FPGA is the
latest and most efficient PLC (programmable logic component). In layman’s terms we are going
to control and manipulate the motor digitally with our own homemade processor computer.
These are the most efficient because you don’t have any wasted digital logic space (like DSPs
and Microcontrollers) therefore you have more processing power, faster performance, and at a
reduced cost. The FPGA computer will generate six gate pulses that control the inverter three-
phase frequency output power supply for the motor.

In the above graphs we can see the advantages of using an FPGA. The drawbacks are that you
have to create your own processor which is hard to do and requires significant digital logic
experience, knowledge of advanced software, and high cost of maintenance because it is hard to
change logic gates within the FPGA. However if you own or have intellectual property which
has already figured out all of this you can configure your homemade processor, maintenance
becomes much easier, and you don’t need as much in depth knowledge of digital system design.

Plan A:
In order to generate the gate pulses using an FPGA we used a technique called Space Vector
Modulation. This is the most advanced method used by universities and industry right now and
this will help bring about cheaper and more efficient motor control. Using this method is the
most efficient and most desired. This will be discussed in detail in the schematic section of this
paper. Also discussed in schematics is Direct Torque Control.

Plan B: (backup)
The Space Vector Modulation method is part of intellectual property and has to be designed. It is
pretty complicated for a non-digital system expert designer. Another simpler, more crude, and
less efficient way is to use the J-K Flip Flop processor method for three-phase inverter control.
This is also further discussed in detail in the schematic section of this paper.

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