Date post: | 06-Jan-2018 |
Category: |
Documents |
Upload: | marilynn-fox |
View: | 248 times |
Download: | 2 times |
Power Electronics Laboratory
Lecture 11
ECEN 4517ECEN 5517
POWER ELECTRONICS AND PHOTOVOLTAIC POWER SYSTEM LABORATORYhttp://ece.colorado.edu/~ecen4517
• Photovoltaic power systems• Power conversion and control electronics
Prerequisite: ECEN 4797 or ECEN 5797
Instructor: Prof. Bob Erickson
Power Electronics Laboratory
Lecture 12
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
Power Electronics Laboratory
Lecture 13
Experiments 2 and 3Maximum Power Point Tracking
• Design and construct dc-dc converter• Employ microcontroller to achieve maximum power point tracking
(MPPT) and battery charge control
Power Electronics Laboratory
Lecture 14
Experiments 4 and 5Add 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
Power Electronics Laboratory
Lecture 15
Mini-ProjectECEE Expo Competition
• Operate your complete system
• Competition during ECEE Expo: capture the most energy with your system outside
A previous year’s competition poster
Power Electronics Laboratory
Lecture 16
Development of Electrical Modelof the Photovoltaic Cell, slide 1
PhotogenerationSemiconductor material absorbs photons and
converts into hole-electron pairs ifPhoton 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 separationElectric field created by diode structure separates holes and electrons
Open circuit voltage Voc depends on diode characteristic, Voc < Egap/q
Power Electronics Laboratory
Lecture 17
Development of Electrical Modelof 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
Power Electronics Laboratory
Lecture 18
Development of Electrical Modelof 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.
Power Electronics Laboratory
Lecture 19
Development of Electrical Modelof the Photovoltaic Cell, slide 4
Modeling nonidealities:
R1 : defects and other leakage current mechanisms
R2 : contact resistance and other series resistances
Power Electronics Laboratory
Lecture 110
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
Ppv = 0
Power Electronics Laboratory
Lecture 111
Direct Energy Transfer
Power Electronics Laboratory
Lecture 112
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.
Power Electronics Laboratory
Lecture 113
Series String of PV Cellsto 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
Power Electronics Laboratory
Lecture 114
Bypass Diodes
Bypass diodes:• Limit the voltage drop across reverse-
biased cells or strings of cells• Reduce the power consumption of
reverse-biased cells
Power Electronics Laboratory
Lecture 115
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
Power Electronics Laboratory
Lecture 116
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
Power Electronics Laboratory
Lecture 117
Lab Format
Two-person groups, up to 10 groups per sectionThis week: lab organizational meetingsParts kits:
Available from E StoreOne kit needed per groupCost: $180. Contains power and control electronic parts needed for
experiments. You will also need other small resistors etc. from undergraduate
circuits kitLab:
Access via CUID card readerComputer login via CU IdentikeyYou may optionally store your parts in your own locked drawer in your lab
bench. Lock and key deposit for the semester at E Store.
Power Electronics Laboratory
Lecture 118
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
Power Electronics Laboratory
Lecture 119
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. 26-28• 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
Power Electronics Laboratory
Lecture 120
Required Work
Your course grade will be based on the following:
Prelab assignmentsLab final reportsQuizzesProject proposal and reportExpoAttendance 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.