NI Project Presentation

1. National Instruments
3 Phase Inverter+ VFD using GPIC
Engineering Leadership Program - Project Presentation
Awais Shafique Ahmed Zahid
SEECS,NUST CIIT, Lahore

2. Agenda
• Inverter
• Variable Frequency Drive
• NI Single Board RIO General Purpose Inverter Controller (GPIC)- NI 9683 + NI
9605
• GPIC Inverter Research Board
• LabVIEW code and Multisim Co-simulation
• Getting the Hardware to work
• Problems and Solutions
• Conclusion and Recommendations

3. Inverters
• Converts DC to AC.
• Square wave inverters give square wave for transistor switching and only
control output frequency.
• PWM inverters gives PWM signals for transistor switching which can control
output voltage and frequency.

4. Variable Frequency Drive (VFD)
• A PWM is produced by comparison of
a low frequency sine wave and a high
frequency carrier triangle signal.
• Changing the frequency of
reference sine wave would change the
frequency of the output sine produced.
• Keeping the torque of the motor constant
and changing the frequency of the output produced, we change the power
consumed by the motor load.
• This principal can be used to save upto 40% power.

5. NI SbRIO GPIC
• Xilinx FPGA based development ready Embedded System
for Power Electronics control and monitoring.
• SbRIO NI 9605/06 connects to GPIC through Mezzanine connector
• Used for DC-to-AC, AC-to-DC, DC-to-DC,
and AC-to-AC converters for smart-grid
flexible AC transmission systems
(FACTS).

6. Advantages of SbRIO
1. Graphical Co-Simulation 2. Advanced IP Algorithm Development 3. Development Libraries and IP Cores
4. Smart-Grid-Ready Designs 5. Power Electronics Control and Monitoring I/O 6. FPGA/Processor Board
7. Spartan-6 FPGA. 8. Real-Time Simulation

7. GPIC Inverter Research Board
• Dedicated board with a built in
3-Phase Inverter circuitry
• Ability to perform DC-DC
Conversion
• On board Rectifier
• 50V DC 8A Rating
• Allows input from the Grid for
Grid synchronization
Applications:
• Line frequency conversion
• Chopper for battery and ultracapacitor storage
• DC input with two motor driving
• Photovoltaic cells to grid inverter with Maximum Power Point Tracking (MPPT)

8. GPIC Inverter Research Board
Block Diagram

9. GPIC Inverter Research Board
Schematic

10. GPIC Inverter Research Board
Schematic

11. Dolang ETM-7114 3 Phase Induction Motor
Interface with Inverter A

13. LabVIEW Code

14. LabVIEW Code

15. LabVIEW Code

16. LabVIEW Code

17. LabVIEW Code

18. LabVIEW Code

19. LabVIEW Code

20. LabVIEW Code

21. Multisim Co-simulation
3-Phase inverter and RC LPF Filter

22. Multisim Co-simulation
Motor Solver simulation

23. Multisim Co-simulation
Motor Solver simulation

24. Getting the Hardware to Work
• Install same version of LabVIEW on the SbRIO GPIC as the GPIC Inverter Research
Board LabVIEW project, with the following add-ons:
LabVIEW RT Add-Ons
• NI System Configuration
• System State Publisher
Network I/O
• Network Streams
Protocols and Buses
• NI-Watchdog
• LabVIEW PID and Fuzzy Logic toolkit is required (Built-in in LabVIEW 2014)
• Get your PC on the same network as the device.
• Make sure the RT VI has been deployed before running the Desktop acquisition VI.
• Make Connections as shown in the figure:
1. Setting up the Hardware

25. Getting the Hardware to Work

26. Getting the Hardware to Work
• Deploy the RT.
• Run the FPGA VI.
• The “Connect DC Link” button allows you to run both inverters of the Board with a
single DC point.
• Run the Desktop VI.
• The “Connected” led on the Desktop UI will turn on.
• Click the “Enable” Button to turn on the Pre-charge Capacitor.
• Click “Enable PWM” to enable the PWM generation and convert the available DC to
AC.
• Data Logging is available on the local server or cloud
• The “Grid Sync?” toggle switch allows you switch between Grid tracking and
synchronization or internal reference sine generation for PWM.
• Power Analysis can also be done.
2. Running the Hardware

27. Getting the Hardware to Work

28. Getting the Hardware to Work

29. Getting the Hardware to Work

30. Problems and Solutions
 The Hardware is connected, it runs in simulation mode, but sine wave is not being
produced actually?
Solution:
• Check if the hardware setup is correct and according to the Figure given above.
• The fault is that the 15VDC supply for bootstrapping circuitry is not connected.
 Sine wave output is being produced but it dies down quickly?
Solution:
• The reason is that the circuit is getting no DC to modulate into a sine wave.
• The decaying sine wave is due to the energy provided by the Pre-charge capacitor
when the “Enable” button is pressed.
• The solution is to connect a wall transformer to the “VGRID A+/A-” pins so that the PLL
tracks the grid signal and the rectifier coverts it into DC and provides it to the IGBTs for
switching.

31. Problems and Solutions
 A stable sine wave is being produced but the motor is not running?
Solution:
• The motor given to us was a 250W 380V/660V 3Phase Induction Motor. But the DC
level given to the IGBTs through rectification of the signal from the wall transformer
was below 50V because the board is rated at 50VDC 8A.
• The solution was to connect
a step up transformer per
phase with the same turn ratio
as the grid transformer.
The 3 transformers were
connected in Y-Y configuration
and the motor was also
connected in Y configuration
with the inverter.

32. Problems and Solutions
 Even with the transformer configuration the motor is not running properly?
Solution:
• The problem was that the wall transformer, simulating the grid was of lower ratings
which got saturated when the motor was connected and hence it wasn’t able to
provide the necessary current to run the motor properly.
• This also distorted the voltage waveform of the grid. To solve this problem, all the
transformers bought were of higher ratings, around 300W.

33. Problems and Solutions
 Motor is running but VFD cannot be implemented?
Solution:
• The motor runs smoothly with the transformers but the VFD could not be
implemented using this solution because the transformers cannot sustain the
continuous frequency variations.
• So the solution was to enhance the voltage ratings for the board. The limitation of the
board was set by the 50V AC-DC bridge Rectifier and 2 100V Smoothing capacitors.
Replacing them with higher ratings would allow us to give 220Vrms directly to the
board from the grid.
• Another option was to remove these low rating components and place an external
rectifier which would give 300VDC directly to the IGBTs, bypassing the Rectifier and
smoothing capacitors.

34. Problems and Solutions
 Giving 300VDC to the Board generates a fault and the systems halts?
Solution:
• Using the external rectifier creates another problem, that the Code generates a fault
when the DC input exceeds 100V and even after enabling PWM the inverter doesn’t
work.
• The problem is with the voltage acquisition sensors. A potential divider circuit is used
and the value is scaled by the GPIC to estimate and show the output value on the
screen. At 100V DC input the sensor would give around 10V to the GPIC which would
be scaled by 10 times and shown as 100V on the screen. At 300V the divider would
read around 29V and after scaling it would exceed the limit set by the code.
• This fault can be masked using the
“Ignore Fault” button in the FPGA VI.
• This allows the motor to run but the
fault stays, the upper/lower limits in the
memory blocks are changed.

35. Problems and Solutions
• Changing the upper/ Lower limits solves the fault problem but the sensors still acquire
false data because they are operating at range near the limits of the GPIC I/Os.
• Possible solution is to replace the 11kΩ resistor in the potential divider with 3.3k Ω
and change the scaling factors in the FPGA VI.

36. Problems and Solutions
• Changing the upper/ Lower limits solves the fault problem but the sensors still acquire
false data because they are operating at range near the limits of the GPIC I/Os.
• Possible solution is to replace the 11kΩ resistor in the potential divider with 3.3k Ω
and change the scaling factors in the FPGA VI.

37. Problems and Solutions
• Changing the upper/ Lower limits solves the fault problem but the sensors still acquire
false data because they are operating at range near the limits of the GPIC I/Os.
• Possible solution is to replace the 11kΩ resistor in the potential divider with 3.3k Ω
and change the scaling factors in the FPGA VI.

38. Problems and Solutions
 Project not loading, some file is missing?
Solution:
• Find the missing file at the location
shown in the figure.

39. Conclusion and Recommendations
• We have completed the tasks given to us and shown them to supervisors at
each step. A 3- Phase inverter for a 250W load and linear mapped open loop
VFD , has been implemented with a project extension of making a DC-DC
converter.
• The project got delayed initially due to the unavailability of the Research
Board, no information regarding the board or motor. The initial project file
given to us was of a Power Hands-on workshop, not the GPIC Research Board.
Unavailability of a 15V DC supply for Bootstrapping circuitry and lack of many
components dragged the project further.