The Second IASTED International Conference on
Solar Energy
SOE 2010

July 15 – 17, 2010
Banff, Alberta, Canada

TUTORIAL SESSION

Photovoltaic Applications and Their Embedding in the Distribution System

Prof. Ewald Fuchs
University of Colorado at Boulder, USA
ewald.fuchs@colorado.edu

Duration

3 hours

Abstract

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While photovoltaic revenue growth slowed slightly in the last year, Gartner Group published that photovoltaic implementation, measured on a power basis, has grown 24% during 2009 to 6.4 GW and will grow to 23.4 GW by 2013. Such increased growth indicates that significantly more high-penetration PV implementations are likely to occur in the near future, due both to consumer demand and portfolio standards requiring more renewable energy generation.
Simultaneously, “smart grid” implementations are accelerating. A key goal of SmartGrid City and similar integrative projects is to enable integration of significantly higher penetrations of renewable resources, both in concentrated utility-scale plants and dispersed residential-scale units. For example, Xcel Energy has announced that Boulder, Colorado, will be the first “SmartGrid City” in its regional network. Xcel Energy intends this forward-thinking project to transform the way to do business. When fully deployed, the new system will provide customers with smart-grid technologies designed to provide environmental, financial, and operational benefits. In addition to advanced utility controls, such as smart meters, SmartGrid City combines encompasses a range of renewable resources. Within Boulder, several hundred residential photovoltaic plants ranging from 2-10 kW are interconnected with the grid.
Xcel’s system includes an 8 MW PV plant in the San Luis Valley with an additional 17 MW PV plant to be commissioned in 2010 by Xcel Energy and SunPower. Interest exists for additional plants in this size range.
Present-day frequency and load control takes place at the transmission level and is based on load sharing and demand-side management. Load sharing relies on drooping characteristics where natural gas-fired plants or those with spinning reserves supply the additional load demand. If this additional load cannot be provided by one of the plants then demand-side management (e.g., load shedding) will set in and some of the less important loads will be disconnected. This method of frequency and load control cannot be employed if renewable sources operate at peak power exploiting the renewable sources to the fullest in order to displace as much fuel as possible. Control of renewable sources occurs at the distribution level and communication between transmission and distribution levels become important. A new control algorithm must be designed to replace some of the large conventional (e.g., coal, nuclear, natural gas) by a great number of much smaller renewable and storage plants.

Tutorial Materials

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1) Introduction discussing present state of the art of the power/distribution system with frequency/load and voltage control. Intermittent operation of photovoltaic (PV) plants. Insolation levels within the US.
2) Measured output power of a 6 kW residential PV plant during a two-year period and measured performance of a battery charger fed by a solar panel.
3) Various methods of peak-power tracking using current and voltage sensing and batteries.
4) Harmonic current generation of current-controlled inverters connected between peak power tracker and distribution pole transformer. Influence on power quality of distribution systems.
5) Mitigation of intermittent operation of PV plants through short-term and long-term energy storage based on batteries, super-capacitors, hydro-storage, flywheel, and compressed air storage facilities.
6) Efficiency improvement through locating PV plants near the load/consumer of electricity.
7) The need to use balancing networks (e.g., zigzag transformer) to eliminate zero-sequence and negative sequence-components due to the imbalances in the three phases caused by residential single-phase PV plants.
8) Design example for a 6 kW residential PV plant with utility connection (e.g., net metering).
9) Design example for a 5 MW PV plant with parallel connected inverters to improve efficiency of generation.
10) The role of bypass diodes and aging effects of solar panels.
11) Change in control approaches: the conventional approach controls frequency/ load and voltage at the high-voltage level while the deployment of PV plants calls for a participating control at the distribution level. The interplay of conventional power plants (e.g., natural-gas fired plants) with PV plants.
12) Payback period of PV plants and comparison with conventional power plant payback periods. The role of carbon tax. Comparison of payback periods in the US with those in Europe in particular in Germany.

Qualifications of the Instructor(s)

Tutorial Session Portrait

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Ewald F. Fuchs received his Dipl.-Ing. from the University of Stuttgart, Germany, in electrical engineering and his Ph.D. from the University of Colorado in 1970.
He joined the Siemens Corporation in Mülheim/Ruhr in 1971, where he was involved in the design of power plants and their synchronization/operation with the power system. From 1977 until present he is a Professor of Electrical Engineering in the Department of Electrical, Computer, and Energy Engineering (ECEE) at the University of Colorado, Boulder teaching circuits/electronics, energy conversion, power system, and renewable energy classes. Prof. Fuchs serves as an Associate Editor for the International Journal of Electrical Power and Energy Systems. From 1997-2001 he was Director of Graduate Studies in ECEE.
His research interests include renewable energy sources, power quality, optimization using nonlinear programming, fuzzy-set theory, genetic algorithms, energy conversion, energy conservation, power electronics, monitoring, and fundamental/harmonic power flow.
He coauthored the textbook Power Quality in Power Systems and Electrical Machines, Elsevier/Academic Press, February 2008, 638 pages, and is lead author of the forthcoming textbook Power Conversion of Renewable Energy Systems, to be published in 2010, approx. 600 pages, by Springer. Dr. Fuchs has published about 95 journal papers and 90 conference papers.
Dr. Fuchs was awarded the best paper prize in 1972 by VDE (Verein Deutscher Elektrotechniker), the IEEE 1989 Power System Relaying Committee Award, and the IEEE 1989 Prize Paper Award of the Power Engineering Society. He is a Life Fellow of IEEE.

References

[1] 
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M.A.S. Masoum, H. Dehbonei, and E.F. Fuchs, "Theoretical and Experimental Analyses of Photovoltaic Systems with Voltage- and Current-Based Maximum Power Point Tracking," IEEE Trans. on Energy Conversion, Vol. 17, No. 4, December 2002, pp. 514- 522.
[2] M.A.S. Masoum, S.M. Mousavi Badejani, and E.F. Fuchs, "MicroProcessor-Controlled New Class of Optimal Battery Chargers for Photovoltaic Applications," IEEE Trans. on Energy Conversion, Vol. 19, No. 3, September 2004, pp. 599 - 606.
[3] E.F. Fuchs and M. A. S. Masoum, Power Conversion of Renewable Energy Systems, Springer, 101 Philip Drive, Assinippi Park, Norwell, MA 02061, USA, June 2010, 550 pages.
[4] E. F. Fuchs and M. A. S. Masoum, Power Quality in Power Systems and Electrical Machines, Elsevier/Academic Press, February 2008, 638 pages. ISBN: 978-0-12-369536-9.
[5] E.F. Fuchs, D.J. Roesler, and M.A.S. Masoum, "Are Harmonic Recommendations According to IEEE and IEC Too Restrictive?," IEEE Trans. on Power Delivery, Vol. 19, No. 4, October 2004, pp. 1775- 1786.
[6] E.F. Fuchs, Teaching of on-line graduate course ECEN 5017 Conventional and Renewable Energy Issues at the University of Colorado at Boulder.