1. ECEN 4517
ECEN 5517
POWER ELECTRONICS AND PHOTOVOLTAIC POWER SYSTEM LABORATORY
Photovoltaic power systems
Power conversion and control electronics
Prerequisite: ECEN 4797 or ECEN 5797
Instructor: Prof. Bob Erickson

2. Experiment 1 Direct Energy Transfer System
Model PV panel
Investigate direct energy transfer system behavior
Investigate effects of shading
Observe behavior of lead-acid battery

3. Experiments 2 and 3 Maximum Power Point Tracking
Design and construct dc-dc converter
Employ microcontroller to achieve maximum power point tracking (MPPT) and battery charge control

4. Experiments 4 and 5 Add Inverter to System
Build your own inverter system to drive AC loads from your battery
Step up the battery voltage to 200 VDC as needed by inverter
Regulate the 200 VDC with an analog feedback loop
Change the 200 VDC into 120 VAC

5. Mini-Project ECEE Expo Competition
Operate your complete system
Competition during ECEE Expo: capture the most energy with your system outside
A previous year’s competition poster

6. Development of Electrical Model of the Photovoltaic Cell, slide 1
Photogeneration
Semiconductor material absorbs photons and converts into hole-electron pairs if
Photon energy hn > Egap (*)
Energy in excess of Egap is converted to heat
Photo-generated current I0 is proportional to number of absorbed photons satisfying (*)
Charge separation
Electric field created by diode structure separates holes and electrons
Open circuit voltage Voc depends on diode characteristic, Voc < Egap/q

7. Development of Electrical Model of the Photovoltaic Cell, slide 2
Current source I0 models photo-generated current
I0 is proportional to the solar irradiance, also called the “insolation”:
I0 = k (solar irradiance)
Solar irradiance is measured in W/m^2

8. Development of Electrical Model of the Photovoltaic Cell, slide 3
Diode models p–n junction
Diode i–v characteristic follows classical exponential diode equation:
Id = Idss (elVd – 1)
The diode current Id causes the terminal current Ipv to be less than or equal to the photo-generated current I0.

9. Development of Electrical Model of the Photovoltaic Cell, slide 4
Modeling nonidealities:
R1 : defects and other leakage current mechanisms
R2 : contact resistance and other series resistances

10. Cell characteristic Cell output power is Ppv = IpvVpv
At the maximum power point (MPP):
Vpv = Vmp
Ipv = Imp
At the short circuit point:
Ipv = Isc = I0
Ppv = 0
At the open circuit point:
Vpv = Voc

11. Direct Energy Transfer

12. Maximum Power Point Tracking (MPPT)
MPPT adjusts DC-DC converter conversion ratio M(D) = Vbatt/Vpv such that the PV panel operates at its maximum power point.
The converter can step down the voltage and step up the current.
Battery is charged with the maximum power available from the PV panel.

13. Series String of PV Cells to increase voltage
To increase the voltage, cells are connected in series on panels, and panels are connected in series into series strings.
All series-connected elements conduct the same current
Problems when cells irradiance is not uniform

14. Bypass Diodes Bypass diodes:
Limit the voltage drop across reverse- biased cells or strings of cells
Reduce the power consumption of reverse-biased cells

15. Apparent path of sun through sky
Baseline Rd. is 40˚N
Times are not corrected for location of Boulder in Mountain Time Zone
Net panel irradiation depends on cos(j) with
j = angle between panel direction and direction to sun
So take your data quickly

16. Experiment 1 Experiment 1: Photovoltaic System
Characterize the SQ-85 PV panels, and find numerical values of model parameters for use now and later in semester
Test the inverter provided
Charge the battery from the panel, using the Direct Energy Transfer method
Hope for sun!
Experiment 1 to be performed next week
Final report for Exp. 1 due in D2L dropbox by 5:00 pm on Friday Jan. 29

17. Lab Format Two-person groups, up to 10 groups per section
This week: lab organizational meetings
Parts kits:
Available from E Store
One kit needed per group
Cost: $180. Contains power and control electronic parts needed for experiments.
You will also need other small resistors etc. from undergraduate circuits kit
Lab:
Access via CUID card reader
Computer login via CU Identikey
You may optionally store your parts in your own locked drawer in your lab bench. Lock and key deposit for the semester at E Store.

18. Lab reports
One report per group. Include names of every group member on first page of report.
Report all data from every step of procedure and calculations. Adequately document each step.
Discuss every step of procedure and calculations
Interpret the data
It is your job to convince the grader that you understand what is going on with every step
Regurgitating the data, with no discussion or interpretation, will not yield very many points
Concise is good

19. Upcoming assignments Experiment 1: PV DET system
Do Exp. 1 in lab next week
Exp. 1 report due in D2L dropbox by 5:00 pm on Friday Jan. 29.
One report per group
Experiment 2: Intro to MSP430 microcontroller
Do Exp. 2 in lab during week of Jan
Exp. 2 scoresheet initialed by your TA and uploaded to D2L by 5:00 pm on Friday Jan 29
Experiment 3: Buck MPPT converter
Exp. 3 prelab assignment due in D2L dropbox by 12:00 pm on Tuesday Feb. 2: Buck converter power stage design.
Start Exp. 3 during week of Feb. 2-4

20. Required Work Your course grade will be based on the following:
Prelab assignments
Lab final reports
Quizzes
Project proposal and report
Expo
Attendance and lab performance
Assignments are due in the appropriate D2L dropbox at the times listed in the course schedule page. Late assignments will not be accepted.
Weightings for assignments are listed in the course D2L site.