UAE University

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UAE University College of Engineering Electrical
Engineering Department Graduation Project II
Implementation of a Real-Time Plant Controller
Using TI Digital Signal Processor (DSP)
Thursday, Jan 1st, 2004
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Group Members
Mohammed Al Qawasmeh 980211579
Abdulqader Shaikh 960710521
Ayman Elkhidir 980211560
Mohammed Mustafa 980211467
Mohammed Ismaeel Shekfa 980211484
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Overview

• Introduction
• Summary
• PWM
• Space Vector PWM

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Overview

• Q15
• Open Loop Program
• Budget Requirements
• Gantt Chart
• Conclusion

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Introduction
DMC1500
AC Induction Machine
DSP Processor
Constant V/Hz Principle
Space Vector PWM Technique
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24V
Feedback
V/3
Changing Voltage
Start
Code Composer Software
Feedback
110\220 V
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Summary
Main Study for the project
power electronics Transistor, diode, PWM, and
Inverter
Machine that give information about
different types of motor
DSP ( Digital Signal Processor)
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Code Composer
watch window, command window, programming
window, and the graph window.
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Open loop speed control for 3-phase AC induction
motor
Implementation of PWM technique.

• In order to create the required rotating MMF in
  the stator of an AC induction machine, the power
  inverter needs to be driven with the correct
  switching variable vector a, b ,c

• Two major issues must be resolved.
• Generation of revolving reference voltage vector
  Uout.
• Determination of the switching pattern based on
  this reference voltage vector.

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• Generating the reference voltage vector
• Requires precise positioning of the reference
  voltage vector.
• This implies accurately controlling the
  rotational speed ?, and magnitude of this vector,
  M.
• The vector magnitude M controls the resultant
  peak line voltage which is supplied by the
  inverter.

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• 2. Realization of the switching pattern using PWM
  outputs
• For any position of V, it must be transformed
  into the set of appropriate switching variables
  a, b and c.
• Using the decomposed form of V, appropriate
  compare values are calculated for use with C240
  Event manager PWM generation unit.

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Verification of space vector PWM algorithm

• The correctness of the space vector PWM can be
  verified by filtering the PWM outputs of C240
  using low pass filter and viewing the resultant
  signal on a scope.

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Space Vector PWM
Reference vector decomposition

• As the rotor of the motor rotates, the reference
  vector must rotate with it and this requires the
  sector to be changing since this vector will
  rotate 360 degrees with respect to the real
  (Alpha) axis.

• Vector Ua is represented by switch state 1
• Vector Ub by switch state 2
• Null vector U0 by switch states 7 or 8.
• Vector U may be represented by averaging the
  amount of time spent in vectors a, b and 0 over a
  switching period.

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Space Vector Sequence

• The SV sequence should assure that the load line
  voltages have the quarter wave symmetry to reduce
  even harmonics.
• This is done by arranging the switching sequence
  in such a way that the transition from one to the
  next is performed by switching only one inverter
  leg at a time.
• These conditions are met by the sequence
  Vz,Vn,Vn1,Vz

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Example

• Shows the waveform for each sector of a symmetric
  switching scheme.
• Each PWM channel switches twice per every PWM
  period except when the duty cycle is 0 or 100.
• There is a fixed switching order among the three
  PWM channels for each sector.
• Every PWM period starts and ends with O000.
• The amount of O000 inserted is the same as that
  of O111 in each PWM period.

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Software-Determined Switching SV PWM Pattern
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Space Vector PWM Patterns

• Software-determined toggling sequences
• SV PWM hardware module

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Space Vector PWM Patterns

• Implementation of this switching scheme with
  TMS320C24x/F24x involves two steps
• Initialization of the compare units and selected
  GP Timer for symmetric PWM
• Determination of the channel-toggling sequence
  based on the look-up table and the load of
  compare registers based on which sector ( s) Uout
  is in.

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Q-Value Representation
cost effective

• DSP architectures are designed to handle finite
  number precision .
• Q value is a fixed-point.

And
Great performance
But
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Q-Value

• Programmers need to take into consideration
• Numerical operations should avoid overflow.
• The fractional portion of the number should not
  be truncated.
• Q-values are used whenever a fixed-point variable
  is used to store a floating-point value.
• The Q-value specifies how many binary digits are
  allocated for the fractional portion of the
  number.

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Q-Value

• The Q15 is a popular format
• MSB is the sign bit.
• Followed by 15 bits of fraction.
• ?In Decimal the range between (-1 and
  0.9999) (8000H to 7FFFH)

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Q-Value
Where
h is the decimal value n is the fraction
position b is binary value 0 or 1.
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Example
Positive Number Fractional portion (2-1
2-2 .75) The whole portion (22 4) The
variable has a value 4.75
00010011
Using
Q2
Result
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Program
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ACI31_x1.ASM
ain program
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ACI31_x1.ASM
This program implements a sampling loop to carry
out all calculations. The PWM and sampling
frequencies are independently controlled. Constan
t V/Hz principle is used to generate the
magnitude of voltage command from frequency
input. Space vector PWM technique is used to
generate the PWM signals controlling a three
phase voltage source power inverter so that
desired voltage magnitude and frequency are
applied to the phased of a AC induction motor.
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RMP_CNTL.asm

• The ramp function is the method to deliver the
  required value of frequency to the DMC1500.
• Required input for speed period calculation.
• Required input for Pulse Width Modulation.

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RMP_CNTL.asm

Computes the ramp function.
Rmp_cntl.asm
Setpt_value
Target_value
S_eq_t_flg
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Task of the ramp function
S_eq_t_flg
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Volts / hertz control

• Increasing Vs and fs by the same amount.
• No Increasing in the magnetized current
• High starting torque application
• Low power consumption

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• From the equation 
• Magnetic flux is increasing linearly with the
  decreasing in the frequency of the input stator
  voltage.
• Magnetic flux will increase the magnetization
  current
• Solution is by increasing the applied voltage in
  the stator linearly with the frequency.

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VHz_prof.asm
This module generates the output command voltage
for a specific input command frequency according
to specified volts/hertz profile. This is used
for variable speed implementation of AC induction
motor drives.
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VHz_prof.asm
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Speed Experiment
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Excel Result
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Visual Basic
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Budget Requirements
Offered Equipments DSP evaluation board 5520
DHS DMC 1500 4416 DHS AC
induction motor 736 DHS Total
10672 DHS
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Budget Requirements
Needed Equipments Fuses 20 DHS Power
Transistors 300 DHS Poster
100
DHS Total
420 DHS
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Conclusion

• DSP TMS320C24xx
• Power Controller DMC1500
• Motor AC Induction Motor
• Task Controlling the AC induction motor in
  real-time, implementing a TI DSP.