Table Of ContentMODELING, ANALYSIS AND CONTROL OF
MIXED SOURCE MICROGRID
DISSERTATION
Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy
in the Graduate School of The Ohio State University
By
Ajit Anbiah Renjit
Graduate Program in Electrical and Computer Engineering
The Ohio State University
2016
Dissertation Committee:
Dr. Mahesh S. Illindala, Advisor
Dr. Jin Wang
Dr. Jiankang Wang
Dr. Ralf Bundschuh
Copyright by
Ajit Anbiah Renjit
2016
Abstract
Microgrids with natural gas engine driven distributed energy resources (DERs) are
more likely to be favored by both industries and utilities in the near future because of their
low costs, which, in turn, is due to the newly found shale deposits at many places in the
world. Such DERs can be connected either directly or through an inverter to the utility/load.
Therefore, they are referred to as synchronous generator-based DERs and inverter - based
DERs respectively.
In this research work, the synchronous generator-based DER and inverter-based DER
installed at the CERTS Microgrid test bed have been modeled. The dynamic and steady-
state performance of the models were evaluated by verifying the model results against
experimental tests conducted at the CERTS microgrid. A key contribution of this modeling
effort is that the developed models of the DERs are simple and can fairly represent to a
reasonable degree of accuracy the dynamic behavior without infringing on the confidential
information of the commercial equipment manufacturers. Such models can easily be
multiplied wherever necessary with appropriate scaling to facilitate analysis of numerous
scenarios and case studies that may be otherwise impractical due to resource limitations at
the field site to undertake actual testing or at the very least expensive and time
consuming.
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Also, the dissertation examines the stalling behavior of both the DERs. The DERs when
operating under islanded conditions are susceptible to stalling and can bring down the
entire industrial power system. Graphical and analytical methods involving the active
power-frequency for synchronous generator-based DERs to determine its stalling
conditions has been presented. Similarly, graphical methods involving active power-
voltage characteristics for inverter-based DERs have been proposed and stalling analysis
has been conducted.
It is very common for one or more DERs in the islanded microgrid to operate closer to
their maximum electrical and mechanical limits. During a large load change, such DERs
may get temporarily overloaded until the other DERs with sufficient power margin takes
the remaining load burden. Under such overloaded conditions, they exhibit a different
dynamic behavior compared to normal operating conditions which requires thorough
analysis. Therefore, the performance of interconnected DERs when they are operated
against their mechanical limits in an islanded microgrid is also investigated.
This research work also investigates the effect of prime-mover stalling in a mixed
source microgrid comprising both synchronous generator- and inverter-based DERs. It was
observed that the prime-mover stalling of any unit can lead to the collapse of entire
microgrid system while operating in the islanded mode. Finally, a modified droop control
scheme has been proposed for the inverter-based DERs that prevents prime-mover stalling
in a mixed source microgrid.
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Dedicated to my family and friends.
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Acknowledgments
First and foremost, my sincerest gratitude goes to my advisor, Dr. Mahesh S. Illindala
for giving me an opportunity to work under his guidance. Under him, I was able to learn
the fundamental concepts of microgrids and do challenging research on various aspects of
it. I feel very fortunate to learn from his experience in life which will have a huge impact
on my future. Also, I am grateful to my Ph.D. dissertation and qualifying exam committee
members, Dr. Jin Wang, Dr. Jiankang Wang, Dr. Donald Kasten, and Dr. Vadim Utkin, for
their insightful suggestions and beneficial discussions with me.
My research-mates at OSU have made my experience better in various ways. I would
like to thank them for their assistance and valuable communications, whether it is off-the-
wall ideas unrelated to research, or last minute nerve-calming presentation rehearsals. I felt
very fortunate to work with Mr. Dave Klapp and Mr. Amrit Khalsa from American Electric
Power. With their support, I was able to get necessary experimental data from the
CERTS/AEP microgrid testbed to corroborate my work. Also, I would like to thank the
Lawrence Berkeley National Lab for their financial support through January 2012 to
December 2013.
I would never forget all our spirited conversations and beautiful moments with my
friends at OSU. In particular I would like to thank Narendhira Ram, Pravin Krishna and
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Krishnan Veeraraghavan for their encouragement, support and most of all their humor. I
would also like to express my thanks to Mr. Abrez Mondal and Ms. Mariana Costa, with
whom I have worked closely in the last two years and shared all the failures en route to
success in our collaborated projects.
I owe my deepest thanks to my family for their unconditional love and support, which
is the greatest gift I ever received.
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Vita
April 2008 .............................................B.E Electrical and Electronics Engineering, PSG
College of Technology
January 2012 to present ........................Ph.D. Student, Department of Electrical and
Computer Engineering, The Ohio State University
Publications
[1]. Renjit, A.A.; Illindala, M.S.; Klapp, D.A., "Graphical and Analytical Methods for
Stalling Analysis of Engine Generator Sets," in Industry Applications, IEEE Transactions
on , vol.50, no.5, pp.2967-2975, Sept.-Oct. 2014
[2]. Illindala, M.; Khasawneh, H.; Renjit, A., "Flexible Distribution of Energy and
Storage Resources: Integrating These Resources into a Microgrid," in Industry
Applications Magazine, IEEE , vol.21, no.5, pp.32-42, Sept.-Oct. 2015
[3]. Renjit, A.A.; Illindala, M.S.; Klapp, D.A., “Modeling and Analysis of the CERTS
Microgrid with Natural Gas Powered Distributed Energy Resources,” in Proc. of 2015
IEEE Industrial & Commercial Power Systems Technical Conference (I&CPS 2015), 5-8
May 2015
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[4]. Renjit, A.A.; Illindala, M.S., "In-situ reconfiguration for flexible distribution of
energy and storage resources," in Energy Conversion Congress and Exposition (ECCE),
2013 IEEE , vol., no., pp.2378-2384, 15-19 Sept. 2013
[5]. Renjit, A.A.; Illindala, M.S.; Lasseter, R.H.; Erickson, M.J.; Klapp, D., "Modeling
and control of a natural gas generator set in the CERTS microgrid," in Energy Conversion
Congress and Exposition (ECCE), 2013 IEEE , vol., no., pp.1640-1646, 15-19 Sept. 2013
[6]. Renjit, A.A.; Illindala, M.S., "Graphical and analytical methods for stalling of
engine generator set," in Power Electronics, Drives and Energy Systems (PEDES), 2012
IEEE International Conference on , vol., no., pp.1-6, 16-19 Dec. 2012
[7]. Renjit, A.A.; Illindala, M.S.; Yedavalli, R.K., "Stability robustness analysis and its
improvement for an industrial microgrid," in Industry Applications Society Annual
Meeting, 2014 IEEE , vol., no., pp.1-8, 5-9 Oct. 2014
[8]. Mondal, A.; Illindala, M.S.; Renjit, A.A.; Khalsa, A.S., "Analysis of limiting
bounds for stalling of natural gas genset in the CERTS microgrid test bed," in Power
Electronics, Drives and Energy Systems (PEDES), 2014 IEEE International Conference
on , vol., no., pp.1-5, 16-19 Dec. 2014
[9]. Mondal, A.; Renjit, A.A.; Illindala, M.S.; Eto. J., “Operation and Impact of Energy
Storage System in an Industrial Microgrid,” in Proc. of 2015 IEEE Industry Applications
Society Annual Meeting (IAS 2015), 18-22 Oct. 2015
Fields of Study
Major Field: Electrical and Computer Engineering
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Table of Contents
Abstract ............................................................................................................................... ii
Acknowledgments............................................................................................................... v
Vita .................................................................................................................................... vii
Table of Contents ............................................................................................................... ix
List of Tables .................................................................................................................... xii
List of Figures .................................................................................................................. xiii
CHAPTER 1 INTRODUCTION ........................................................................................ 1
1.1 General .......................................................................................................... 1
1.2 Background ................................................................................................... 2
1.3 Technical Challenges .................................................................................. 12
1.4 State-of-the-Art Review .............................................................................. 15
1.5 Chapter Review ........................................................................................... 16
CHAPTER 2 MODELING OF RECIPROCATING ENGINE DRIVEN DISTRIBUTED
ENERGY RESOURCES .................................................................................................. 18
2.1 Introduction .................................................................................................. 18
2.2 CERTS Microgrid Test Bed – System Description .................................... 19
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Description:I feel very fortunate to learn from his experience in life which will have a huge impact on my future. Also, I am grateful to my Ph.D. dissertation and
