1. Photovoltaic Power Converter
Students:
Thomas Carley
Luke Ketcham
Brendan Zimmer
Greg Landgren
Advisors:
Dr. Woonki Na
Dr. Brian Huggins
Dr. Yufeng Lu
Bradley University
Department Of Electrical Engineering
11/30/11

2. Presentation Outline Summary and Overall System Block Diagram
DC Subsystem
Maximum Power Point Tracking
Boost Converter Testing
AC Subsystem
Schedule
Component List

3. Project Summary Supplies DC and AC Power Photovoltaic Array
Boost Converter to step up PV voltage
Maximum Power Point Tracking
DC-AC converter for 120Vrms
LC filter

4. System Block Diagram

5. DC Subsystem Boost Converter
Maximum Power Point Tracking (MPPT) System

6. Simulation Results

7. Boost Converter Full Bridge

8. DC Subsystem Requirements
The boost converter shall accept a voltage from the photovoltaic cells.
The input voltage shall be 48 Volts.
The average output shall be 200 Volts +/- 25 Volts.
The voltage ripple shall be less than 3 Volts
The boost converter shall perform maximum power point tracking.
The PWM of the boost converter shall be regulated based on current and voltage from the PV array.
The efficiency of the MPPT system shall be above 85%.

9. DC Subsystem Key Components
Inductor
1mH 25A
500uH 35A
Gate Driver
MOSFET or IGBT
2.5A 500V
Solar Panel x 4
50W
12V
MOSFET
Vds = 250V
Id = 110A
Pdiss = 694W
Heatsink

10. DC Subsystem Components
Current Sensor
30A
63-69 mV/A
Sensing Op amp
Used with voltage divider
DSP Board
TMS320F2812

11. MPPT “Perturb and Observe” method
Change Boost Converter duty cycle based on change in PV power
Changing duty cycle changes the current drawn from the PV
Anytime the system is not at the maximum power point, it is not at it’s most efficient point

12. MPPT Flowchart

13. Boost Without MPPT

14. Boost With MPPT

15. MPPT Circuit

16. Output Power Without MPPT

17. Output Power With MPPT

18. Solar Insolation Peoria, IL
PV Models in Simulink
Made models of PVs using resources from the University of Colorado at Boulder
Insolation – a measure of solar energy on an area over a given amount of time.
Usually in units of W/m^2
Solar Insolation Peoria, IL
Jan
Feb
March
April
May
June
July
Aug
Sep
Oct
Nov
Dec
kWh/(m^2 day)
3.271
4.109
4.642
4.921
5.239
5.740
5.880
5.727
5.639
4.562
2.957
2.721
W/m^2

23. I P V V

24. Insolation = 200, 400, 600, 800, 1000 W/m2 P I V V

25. I V P V

26. Boost Converter Lab Testing
Built boost converter from components Dr. Na provided.

27. Boost Converter Lab Testing
0 to 3.3V signal from DSP board controlling the MOSFET
At a switching frequency of 10kHz with a 50% duty cycle the 5V input voltage was boosted to about 10V.
Increasing duty cycle, increased Vout
Decreasing duty cycle, decreased Vout
After testing this setup we will be able to build our Boost converter circuit quickly.

28. DSP Board Programming Spectrum Digital eZdsp F2812
Texas Instruments Code Composer
Matlab/Simulink

29. Simulink A/D Interfacing

30. Simulink PWM Generation

31. Manual PWM Duty Ratio Control

32. PWM Generation Experimental Results
80% Duty Ratio
30% Duty Ratio

33. AC Subsystem
Inverter
Output filter

34. AC Subsystem - Inverter
Inverter topology
Inverter operation
Simulations

35. AC Subsystem Inverter Topology
Inverter single phase H-bridge

36. AC Subsystem Inverter Operation - Bipolar
A reference sinusoidal waveform is compared to a triangular carrier waveform
When the reference voltage is equal to the carrier voltage a transition in the switching signal occurs

37. AC Subsystem Inverter Operation - Bipolar
Simulation schematic

38. AC Subsystem Inverter Operation - Bipolar
Reference (blue) and carrier (red) waveforms
Switching signal

39. AC Subsystem Inverter Operation - Bipolar
Inverter output. Switches from +Vd to -Vd

40. AC Subsystem Inverter Operation - Bipolar
Switching signal is inverted and fed to other pair of switches
Switch pairs are switched simultaneously
Only one reference signal needed, but performance is poor

41. AC Subsystem Inverter Operation - Unipolar
Two reference sinusoids are compared to a triangular waveform
Switch pairs not switched simultaneously

42. AC Subsystem Inverter Operation - Unipolar
Simulation schematic

43. AC Subsystem Inverter Operation - Unipolar
References and carrier waves
Switching signal 1
Switching signal 2
Output
Image source: Tian

44. Inverter Operation - Comparison
Bipolar harmonic output
Unipolar harmonic output

45. AC Subsystem - Output Filter
Inverter output includes switching harmonics
Filter smoothes output

46. AC Subsystem Requirements
The AC side of the system shall invert the output of the boost converter.
The output of the inverter shall be 120 Volts RMS.
The output shall be 60Hz +/- 0.1Hz.
The inverter output shall be filtered by a LC filter.
The filter shall remove high switching frequency harmonics.
Total harmonic distortion of the output shall be less than 15%.

47. AC Subsystem Key Components
Inverter switches
Gate drives
Power supplies

48. Commercial Grid Tie Inverters
Company
SMA Solar Technology
Xantrex
Product
Sunny Boy 700-US
GT2.8
AC Power
460W, 120Vac
2700 W, 208Vac / 2800W, 240Vac
AC Voltage Output
Vac
Vac / Vac
Output Frequency Hz
Harmonics
> 3%
Max. efficiency
92.4%
94.6%
Power Factor
Unity
> 0.95 %

49. Schedule

50. Component List

51. References
“PV Module Simulink Models.” ECEN2060. University of Colorado Boulder.
Rozenblat, Lazar. "A Grid Tie Inverter for Solar Systems." Grid Tie Inverter Schematic and Principles of Operation. 6 Oct <
Tafticht, T., K. Agbossou, M. Doumbia, and A. Cheriti. "An Improved Maximum Power Point Tracking Method for Photovoltaic Systems." Renewable Energy 33.7 (2008):
Tian, Yi. ANALYSIS, SIMULATION AND DSP BASED IMPLEMENTATION OF ASYMMETRIC THREE-LEVEL SINGLE-PHASE INVERTER IN SOLAR POWER SYSTEM. Thesis. Florida State University, 2007. 
Zhou, Lining. EVALUATION AND DSP BASED IMPLEMENTATION OF PWM APPROACHES FOR SINGLE-PHASE DC-AC CONVERTERS. Thesis. Florida State University, 2005.

52. Questions?