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Dr. Robert Balog Department of Electrical and Computer Engineering

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1 Dr. Robert Balog Department of Electrical and Computer Engineering
Texas A&M University

2 Mitigating Variability of High Penetration Photovoltaic Systems in a Community Smart Microgrid
Dr. Robert S. Balog, PhD PE Assistant Professor, Department of Electrical and Computer Engineering Director, Renewable Energy & Advanced Power Electronics Research Laboratory My name is Robert Balog and I'm the director of the Renewable Energy and Advanced Power Electronics Research Laboratory at Texas A&M. The mission of my research group is to promote increased utilization of photovoltaic energy through our research, teaching, and outreach in power electronics, balance of system, and grid integration. This short talk will highlight a portion of our research aimed at debunking a commonly held belief that photovoltaic energy is too variable to become a substantial portion of our energy portfolio.

3 Teaching, Research & Public Outreach
DOE and the Texas State Energy Conservation Office grant Unique partnership between athletics, faculty, and facilities Equivalent to 5-10 home systems In plain view of 83,000 spectators – diverse target audience Data used in classroom and research STEM outreach - high school teachers I’d like to start off telling you about our campus photovoltaic project. Now, many schools have PV installations. Ours was funded by a grant from the Department of Energy and the Texas State Energy Conservation Office. It was brought to fruition by a unique partnership between athletics, academics, campus facilities services, and our aggie alumni installer. The system was designed to physically and visually represent approximately 5 to 10 residential-sized systems. The goal was that 83,000 game-day spectators would accidentally learn about PV by seeing the system next to the jumbotron while small video clips were played during pauses in the football game. If you happened to catch a game televised on ESPN, you saw my students installing some of the solar panels in the commercial for Texas A&M University. Or the promotional flyer for this symposium. I also use the facility as part of my STEM outreach including hosting high school science teachers to they can see and touch a real system, enriching their ability to teach the material to their students. Additionally, the data collected from the campus grid-tied system is archived and incorporated into classroom and research., including results that will be presented in this talk. Grid-tied inverters 27.6 kW rooftop demonstration PV array

4 High Penetration Perceptions
High Penetration of Photovoltaic (PV) Systems into the Distribution Grid ( More than 30% penetration, indicating very high penetration Grid Operations and High Penetration PV ( High penetration is a concern when... Adverse system performance and reliability Cost of mitigation would be unreasonable Distribution operations issues Feeder characteristics impedance Voltage and frequency control Protection Load characteristics (sometimes a load, sometimes a source) A graduate student in my power electronics for renewable energy class this semester was an intern last summer with a major northeastern utility. His project was to cook up scenarios that would convince the public utility commission regulators that a high level of penetration of solar would cause instabilities in the power system, and hence should not be allowed. <next> Contrast that against the reality that Germany routinely enjoys well over 30% PV penetration and on May 25th, 2012 set a world record in PV generation at 22.4GW. The grid did not collapse and there was no widespread blackout. This presentation will show you a technology option that will allow us to achieve even higher PV penetration level by first illustrating the fact that the variability of solar is not nearly as great as some, particularly the utility companies, may have you believe. May 25th, 2012, Germany generated 22.4GW, setting the world record for PV generation and nearly 40% penetration. Their grid did not go unstable.

5 Variability of Grid-Connected Solar Energy
Variable power output of PV Results in variable power from the utility Today’s distribution power system is typically a radial topology with unidirectional power flowing from the utility to the load. Inherently, solar has variability due to meteorological conditions that can’t be prevented. In a high penetration scenario, this means that the total load on the feeder can varying between a net load and a net generator, without any controllability by the utility. So this is the bad scenario. <next> Consider instead a concept in which a high level of solar penetration in residential neighborhoods is interfaced on a microgrid. Some storage will be necessary to mitigate natural variability but instead of having the storage distributed along with the solar panels, or aggregated at a large-scale in the power system, it is deployed as a community storage facility. We will see through the course of the next few slides how this concept enables the smart community microgrid to mitigate the natural variation in the solar illumination as seen at the point of connection with the utility, thus mitigating the variability of photovoltaic generation.

6 Mitigation of Variability
Temporal resolution of planning data Hourly vs. 10 second Community storage - shared resource Photovoltaic array geometry Planar vs. Non-Planar Let’s explore three scenarios. The first examines the effect of temporal resolution of the PV dataset on how a system may be evaluated during engineering planning. The second examines the effect of using optimized community storage on the variability. The third explored a new concept in which non-planar PV can capture more total energy without requiring a larger footprint of rooftop real-estate.

7 Temporal Resolution Controllable Source Uncontrollable Load
This figure shows a histogram using data obtained from our campus PV system and sampled hourly, like the NREL data commonly used in PV calculators and system design programs. When the net PV generation is less than the community requires, electricity is imported from the utility. If the loads are constant, but the cloud cover changes, this leads to the dreaded variability. Storage can lessen the variability, but from the utility’s perspective the load is still varying and uncontrollable yet they are required to provide stable, high quality power. At times when the PV generation is more than the community requires, the system generates a surplus of power. This, however, is controllable. Using enhanced communications enabled by next-generation smartgrids, the utility would be able to negotiate with the PV systems to control this excess power – hence the PV becomes a controllable source.

8 Temporal Resolution Increased control Decreased variability
(frequency and intensity) Using the exact same system, with data samples every 10 seconds instead of hourly reveals that the true instantaneous variability is much less than previously predicted. Why? The community storage provides the instantaneous power balance to absorb short-term transients between PV generation and end-user loads. Whereas the dynamics of the power system control are too slow to react, the power electronics interfaces easily has enough dynamic response. We see that there is a decrease in the variability as a load and a shift toward behavior as a controllable source.

9 Optimized Community Storage
Controlled Source Uncontrolled Load If we look at the community smart microgrid without storage, we can see that there is in fact a large variable in the load.

10 Optimized Community Storage
Increased control Decreased variability (frequency) The storage can be optimized for cost/benefit, decreasing the frequency of the variability and increasing the frequency of operation as a controllable source.

11 Terracotta Solar Roof Tiles
Increased control Eliminated variability In the third scenario, consider the next generation of photovoltaic material need no longer be flat and instead can be applied conformally to terracotta roof tiles. The resulting solar shingle, which occupy the same rooftop real-estate generate more electricity at a wider range of solar angles, which increases the generation of the system. In the example shown here, when combined with some storage, the resulting high penetration PV residential neighborhood microgrid has been transformed to behave, from the perspective of the utility, as a controllable source. Reducing the generation from the PV system is easily accomplished through signals sent via the smart grid to the power electronic converters and controls. This is somewhat analogous to curtailment in the wind energy industry but it has not been applied to highly-distributed, million solar rooftop, residential systems.

12 Electric Power and Power Electronics Courses
Graduate courses (17 existing) ECEN 611 General Theory of Electromechanical Motion Devices ECEN 612 Comp. Aided Design of Electromech. Motion Devices ECEN 613 Rectifier and Inverter Circuits ECEN 614 Power System State Estimation ECEN 615 Methods of Electric Power Systems Analysis ECEN 616 Power System Electromagnetic Transients ECEN 630 Analysis of Power Electronic Systems ECEN 632 Motor Drive Dynamics ECEN 643 Electric Power System Reliability ECEN 666 Power System Faults and Protective Relaying ECEN 667 Power System Stability ECEN 668 High Voltage Direct Current Transmission ECEN 677 Control of Electric Power Systems ECEN 679 Computer Relays for Electric Power Systems ECEN 686 Electric and Hybrid Vehicles ECEN 690 DC-DC converters ECEN 711 Sustainable Engineering New graduate courses (3) ECEN 689 Energy Conversion for Renewable Energy ECEN 689 Electrical Aspects of Sustainable Energy Production, Storage, and Utilization ECEN 689 Engineering and Economics of Sustainable Energy Systems Undergraduate courses (5) ECEN 459 Electric Power Systems I ECEN 460 Electric Power Systems II ECEN 438 Power Electronic ECEN 441 Electric Motor Drives ECEN 442 DSP-Based Electromechanical Motion Control In this brief presentation I gave you a glimpse of one of the activities of my research lab. My teaching and research are part of the larger Electric Power and Power Electronics Group. We have a total of 10 faculty advising 65 graduate students and teaching 20 graduate level classes and 5 undergraduate classes. We are one of the largest programs in the country for power. Total Faculty: 10 Graduate students: 65 12

13 Electrical & Computer Engineering Department
7 Focus Areas: Analog & Mixed Signal Electronic Circuits Biomedical Imaging & Genomic Signal Processing Computer Engineering Electromagnetics & Microwave Devices Power Systems & Power Electronics Solid State, Nano Electronics & Electro optics Telecommunications, Controls & Signal Processing Students: ~850 undergrad (Dept) ~545 graduate (Dept) ~65 graduate (Power) Faculty: 70 Rankings (US News and World Report): Our group is one of seven research focus areas of the Department of Electrical and Computer Engineering. We have 70 faculty that teach and mentor approximately 850 undergrads and 550 graduate students in our top 10 ranked program in electrical engineering.

14 Dwight Look College of Engineering
Fall 2012* Dwight Look College of Engineering 11,281 engineering students (21% of University total) 3rd largest undergraduate engineering program in the U.S. (ASEE, Fall 2011) 8th largest graduate program in the U.S. (ASEE, Fall 2011) 82 New National Merit Scholars (52% of University total) 2nd highest research expenditures in the U.S. 8,398 Undergraduate Engineering Students 2,883 Graduate Engineering Students The department is part of the Dwight Look College of Engineering. The 11,300 students represent over 20% of the University's total student body and is the 3rd largest undergraduate and 8th largest graduate engineering program in the country. 53,187 Total Students at Texas A&M University * Official 12th day data, Texas A&M University Data and Research Services

15 $140.7 M in Sponsored Research (FY12)
5,586 research projects 943 collaborations 2,743 industrial research sponsors 1,379 students supported in research activities M. Katherine Banks, Ph.D., P.E. Vice Chancellor and Dean of Engineering Director, Texas A&M Engineering Experiment Station Harold J. Haynes Dean’s Chair Professor Dimitris C. Lagoudas, Ph.D., P.E. Deputy Director, Texas A&M Engineering Experiment Station Senior Associate Dean for Research Associate Vice Chancellor for Engineering Research John and Bea Slattery Chair Professor On the research side, the Texas Engineering Experiment Station supports a staggering number of research projects and collaborations. Including my PV project which I use for teaching, research, and outreach. $140.7 M in Sponsored Research (FY12)


17 Dr. Robert Balog Department of Electrical and Computer Engineering
Texas A&M University

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