ECEN 4517 ECEN 5517 POWER ELECTRONICS AND PHOTOVOLTAIC

ECEN 4517 ECEN 5517 POWER ELECTRONICS AND PHOTOVOLTAIC POWER SYSTEM LABORATORY http: //ece. colorado. edu/~ecen 4517 • Photovoltaic power systems • Power conversion and control electronics Prerequisite: ECEN 4797 or ECEN 5797 Instructor: Prof. Bob Erickson Power Electronics Laboratory 1 Lecture 1

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 2 Lecture 1

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 Power Electronics Laboratory 3 Lecture 1

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 Power Electronics Laboratory 4 Lecture 1

Mini-Project ECEE Expo Competition • Operate your complete system • Competition during ECEE Expo: capture the most energy with your system outside • Morning of Thursday, May 3 A previous year’s competition poster Power Electronics Laboratory 5 Lecture 1

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 I 0 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 Power Electronics Laboratory 6 Lecture 1

Development of Electrical Model of the Photovoltaic Cell, slide 2 Current source I 0 models photo-generated current I 0 is proportional to the solar irradiance, also called the “insolation”: I 0 = k (solar irradiance) Solar irradiance is measured in W/m 2 Full sun: irradiance is approximately 1000 W/m 2 Power Electronics Laboratory 7 Lecture 1

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 (el. Vd – 1) The diode current Id causes the terminal current Ipv to be less than or equal to the photo-generated current I 0. Power Electronics Laboratory 8 Lecture 1

Development of Electrical Model of the Photovoltaic Cell, slide 4 Modeling nonidealities: R 1 : defects and other leakage current mechanisms R 2 : contact resistance and other series resistances Power Electronics Laboratory 9 Lecture 1

Cell characteristic Cell output power is Ppv = Ipv. Vpv At the maximum power point (MPP): Vpv = Vmp Ipv = Imp At the short circuit point: Ipv = Isc = I 0 Ppv = 0 At the open circuit point: Vpv = Voc Ppv = 0 Power Electronics Laboratory 10 Lecture 1

Direct Energy Transfer Power Electronics Laboratory 11 Lecture 1

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 12 Lecture 1

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 Power Electronics Laboratory 13 Lecture 1

Bypass Diodes Bypass diodes: • Limit the voltage drop across reversebiased cells or strings of cells • Reduce the power consumption of reverse-biased cells Power Electronics Laboratory 14 Lecture 1

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 15 Lecture 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 this week Final report for Exp. 1 due in D 2 L dropbox by 5: 00 pm on Friday Feb. 1 Power Electronics Laboratory 16 Lecture 1

Lab Format Two-person groups, up to 10 groups per section 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. Power Electronics Laboratory 17 Lecture 1

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 18 Lecture 1

Upcoming assignments Experiment 1: PV DET system • • • Do Exp. 1 in lab this week Exp. 1 report due in D 2 L dropbox by 5: 00 pm on Friday Feb 2. One report per group Experiment 2: Intro to MSP 430 microcontroller • Do Exp. 2 in lab during week of Jan. 30 – Feb. 1 • Exp. 2 scoresheet initialed by your TA and uploaded to D 2 L by 5: 00 pm on Friday Feb. 1 Experiment 3: Buck MPPT converter • Exp. 3 prelab assignment due in D 2 L dropbox by 12: 00 pm on Tuesday Feb. 6: Buck converter power stage design. • Start Exp. 3 during week of Feb. 6 -8 Power Electronics Laboratory 19 Lecture 1

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 D 2 L dropbox at the times listed in the course schedule page. Late assignments will not be accepted. Weightings for assignments are listed in the course D 2 L site. Power Electronics Laboratory 20 Lecture 1