Modeling and Nonlinear Stability Analysis for Sustainable Electrical Microgrids
Nowadays, one of the trends within power electronics is the application of power
converters in microgrids, which in essence means power electronics applied to electric
power distribution systems. As microgrids can be DC, AC, or even hybrid networks, they
are complex and multi-scale systems with many source-source and source-load-type
nonlinear dynamic interactions. Although dynamic interactions between power electronic
devices have been studied using small-signal stability analysis, large-signal stability
analysis remains to be explored. Furthermore, the coexistence of different time-scale
power electronic components can generate new instabilities mechanisms in sustainable
microgrid systems. Load sharing is one of the major issues within microgrids, and it is
defined as how several voltage sources operate in parallel feeding a given load set. Droop
control is the standard approach towards the load sharing problem in microgrids, but this
control can make the system unstable due to some nonlinearities introduced into the
microgrid’s operation. For this reason, nonlinear dynamic analysis techniques are applied
to understand the microgrid’s dynamic behavior. Bifurcation theory offers a broader insight
into the system dynamics when compared to usual techniques based on linear models.
Moreover, bifurcation theory can optimize the microgrid operation and, thus, increase the
system stability range due to a better understanding on how a group of parameters can
influence the microgrid operation.
A significant part of this talk consists of theoretical studies produced over the last few
years on this subject. Furthermore, a case study is carried out involving the parallelism of
two DC-AC power converters, where experimental results are presented to validate the
theoretical assumptions.
Keywords: microgrids, load sharing, nonlinear stability analysis, nonlinear control,
bifurcation theory.
Daniel J. Pagano, was born in La Plata, Argentina, in 1961. He received the B.Sc. degree in telecommunications
engineering from the National University of La Plata, Argentina, in 1985, the M.Sc. degree in electrical
engineering from the Federal University of Santa Catarina, Florianó polis, Brazil, in 1989, and the Ph.D. degree
in robotics, automation, and electronics from the University of Seville, Seville, Spain, in 1999. He is currently a
Full Professor with the Department of Automation and Systems, Federal University of Santa Catarina,
Florianó polis, Brazil. From September 2006 to October 2007, he was a Visiting Professor with the Department
of Engineering Mathematics, University of Bristol, Bristol, U.K. From January 2016 to December 2016, he was
a Visiting Professor with the School of Electrical Engineering and Telecommunications, University of New South
Wales, Sydney, NSW, Australia. His main research interests include nonlinear dynamical systems, bifurcation
analysis, nonlinear control, and power electronics.
Intensive research in energy efficiency, energy-saving technologies, and sustainable use of renewable energy is needed to enable emerging net-zero energy buildings. These technologies make buildings capable of demand-response, providing the flexibility needed to increase power grid stability. The unfolding paradigm shift to power-electronics-enabled DC residential microgrids will push further the energy performance limits of buildings by reducing residential electricity consumption by up to 30% compared to those with AC distribution. The DC microgrids feature an increased power delivery capacity, perfectly addressing many issues of last-mile electrification. Hence, the application of DC microgrid technology can significantly improve the resilience and demand-side flexibility of residential buildings and energy communities, thus making them future-proof and compatible with global energy transition targets.
Edivan Laercio Carvalho received the B.Sc. and M.Sc. degrees in electrical engineering from the Federal University of Technology—Paraná (UTFPR), Pato Branco, Brazil, in 2015 and 2018, respectively, and the Ph.D. degree in electrical engineering from the Federal University of Santa Maria (UFSM), Santa Maria, Brazil. He is currently a Postdoctoral Researcher with the Power Electronics Group at Tallinn University of Technology, Tallinn, Estonia. His research interests include high-frequency power converter topologies, net-zero energy buildings, and power management systems.
My name is Geise Gulart Sarturi, and I am a technician in electrotechnics and electronics, having
graduated from CTISM. In 2022, I completed my mandatory internship for the Control and Automation
Engineering program at UFSM at the Fraunhofer Institute in Dresden, Germany. I have now been working
for two years as an Application Hardware Engineer at Qorvo Utrecht B.V., in the Netherlands.
Dr. Hollweg holds a degree in Electrical Engineering from the Federal University of Santa Maria
(UFSM), Brazil, obtained in December 2016. He also earned his master's and doctoral degrees in
electrical engineering from UFSM, completed in July 2019 and December 2021, respectively. His primary
research areas include Adaptive Control Theory, Nonlinear Control, Optimization Algorithms, and
Control Applications in Power Electronics and Motor Drives. Currently, he is a Researcher and Adjunct
Professor at the University of Michigan - Dearborn (UM-Dearborn), Dearborn, USA. Additionally, he is
set to become a tenured Assistant Professor at UM-Dearborn starting in Winter 2025. He has authored
over 25 research papers in prestigious engineering and control journals. Moreover, he serves as a faculty
advisor for the IEEE Eta Kappa Nu (HKN) chapter at UM-Dearborn and is an active member of the IEEE
community. He acts as a peer reviewer for renowned journals under IEEE, Springer, Elsevier, Wiley, as
well as Mathematical Reviews from the American Mathematical Society (AMS). He also received the
IFAC Elsevier Control Engineering Practice Feature Paper distinction in March 2023.
It is not new that the government and industries have been giving importance to optimizing the way we produce and consume energy. Much of this focus has been on the conversion of electrical energy into mechanical energy. One reason is the fact that 53% of all electrical energy is consumed by electric motors, according to the International Energy Agency of the United Nations. Considering that the adoption of electric mobility is on the rise, this percentage is likely to increase in the coming decades.
However, to meet this energy demand, approximately 6,800 Mt of carbon dioxide (CO2) is emitted, equivalent to the emissions of 2,200 thermal power plants. Therefore, the use of more efficient electric motors could mean a reduction of 6 billion annually in environmental costs, considering only Europe. For the European industry, this optimization currently means saving 10 billion euros annually. As a result, various projects and products have been offered in the market to reformulate and update industrial processes to make them more energy-efficient.
Despite the economic factor being quite attractive, transforming existing products and processes can be a very challenging task for the professionals involved. Within some organizations, such projects conflict with certain departments due to the availability of resources, a good understanding of costs, and impacts on the resulting product's life cycle. A good example is the fact that the energy savings brought by frequency converters carry with them an increase in sensitivity to voltage sags and the introduction of harmonics, raising costs in system risks as a whole. Coupled with this are warranty contracts that are resilient to changes, especially with very new technologies. Can a system using a permanent magnet motor have the same longevity warranty as an induction motor?
Thus, many new technologies or solutions that seem very economically attractive in isolation always bring with them challenges and impacts when integrated into large systems, mitigating their benefits. In this lecture, I will present some examples of what I have experienced and learned over 15 years as a professional dealing with the updating of processes/products for greater energy efficiency. In the cases presented here, I hope to be able to explain how important it is to understand that any change in a product requires a holistic view. Sometimes, decisive technical and economic factors are initially invisible in layers of complexity of a process or product production. Identifying them at the earliest possible stage can be the essential element for a successful project.
Helder Tavares Câmara holds a degree in Electrical Engineering with an emphasis in Electronics from the Federal University of Santa Maria (2000), a master's degree in Electrical Engineering from the Federal University of Santa Maria (2002), and a doctorate in Electrical Engineering from the Federal University of Santa Maria (2007). Between 2006-2007, he was a professor of electrical engineering at the Jaraguá do Sul University Center. During this same period, he participated in a program, funded by the federal government's research incentive law, for the development of an inverter applied to wind power generation. In 2007, he worked as a Development Engineer at Weg Automation, where he developed drivers for wind turbines and converters for photovoltaic cells. From 2009 to 2010, he was an Adjunct Professor at the Federal Technological University of Paraná in the city of Pato Branco, where he conducted research and development in the field of electrical machines and energy generation systems. Since 2010, he has been working at Danfoss Power Solutions (Denmark) and is currently a Senior Control Engineer at Danfoss.
Adaptive Control Techniques for Grid-Integrated Power Electronics Converters
Nowadays, the power systems are submitted to current and voltage harmonics due to the increased presence of nonlinear loads and the wide use of power inverters to interface solar and wind power plants. Nevertheless, these inverters can also be used to compensate current harmonics and improve the system power quality. Traditional harmonic detection methods extract all harmonic current information and the control tuning tends to be complex and less flexible. Therefore, adaptive current harmonic control strategy can be applied in grid-integrated power electronics converters. Voltage and current detection-based harmonic current compensation (VDB-HCC and CDB-HCC, respectively) strategies will be explored in this presentation. CDB-HCC strategies require converter hardware retrofit by inserting an extra current sensor to measure load or downstream grid currents. On the other hand, VDB-HCC strategies are straightforward solutions employing only embedded measurements used for protection, control, and synchronization purposes.
Heverton Augusto Pereira (Senior Member, IEEE) received the B.S. degree in electrical engineering from the Federal University of Viçosa, in 2007, the M.Sc. degree in electrical engineering from the University of Campinas, Brazil, in 2009, and the Ph.D. degree in electrical engineering from the Federal University of Minas Gerais, Brazil, in 2015. In 2014, he was a Visiting Researcher with the Department of Energy Technology, Aalborg University, Aalborg, Denmark. In 2009, he was with the Department of Electric Engineering, Federal University of Viçosa, where he is currently an Associate Professor. He is also Editor-in-Chief of Revista Eletrônica de Potência. His research interests include photovoltaic panels, grid-connected converters and battery energy storage systems.
Power Electronics and Power Quality
A critical and historical (re)view of power quality standards and their relationship and adequacy (or
obsolescence) with the growing presence of electronic power solutions in electricity networks. Analysis of
standards for distribution and onboard networks (avionics).
José Antenor Pomilio (M’92–SM’02) was born in Jundiaí, Brazil, in 1960. He received his B.S., M.S.,
and Ph.D. in electrical engineering from the University of Campinas, Campinas, Brazil, in 1983, 1986,
and 1991, respectively. From 1988 to 1991, he was the Head of the Power Electronics Group, Brazilian
Synchrotron Light Laboratory. He was a visiting professor at the University of Padova in 1993 and 2015
and at the Third University of Rome in 2003 in Italy. He is a Professor at the School of Electrical and
Computer Engineering, University of Campinas, where he has been teaching since 1984. His main
interests are power electronics and power quality. Dr. Pomilio was the President of the Brazilian Power
Electronics Society in 2000–2002 and a member of the Administrative Committee of the IEEE Power
Electronics Society in 1997–2002. He was Associate Editor of the IEEE TRANSACTIONS ON POWER
ELECTRONICS in 2003-2018.
Model Predictive Control in Microgrids Considering Demand Management, Hybrid Energy Storage and User Satisfaction
This lecture presents a Model Predictive Control (MPC) strategy to act as a Energy Management System for Microgrids Considering Demand Management, Hybrid Energy Storage and User Satisfaction. The proposed MPC is responsible for supervising the operation of the microgrid, where it accounts for both economic performance and demand management (DM) actions taking into account user comfort, and adopting a quality of experience (QoE) metric. A smart house is used in the study to analyse the performance of the proposed controller. The energy storage in this smart house is done using batteries and renewable hydrogen, which results in a reduction of pollutant emissions. The Model Predictive Control formulation uses a mixed-integer quadratic programming (MIQP) optimization, which avoids the use of nonlinear optimization tools. Validated by simulation, the system achieves the required standards: runs the smart house for a year with a 21% electricity bill reduction and 77% reduction in user discomfort.
Curriculum
Julio Elias Normey-Rico received his Ph.D. degree from University of Seville, Spain, in 1999. He is currently a Full Professor of the Dept. of Automation and Systems Engineering in Federal University of Santa Catarina (UFSC), in Brazil and head researcher of Renewable Energies Research Team (GPER/UFSC), lead research group in this topic in Latin America. He is the director of several research partnerships with energy industries and international cooperation agreements (Argentina, Uruguay, Spain, Chile and Italy). He is the author of over 260 conference and journal
papers, and published four book chapters and the books Control of Dead-Time Processes (Springer), Introdução ao Controle de Processos (Blucher) and Controle Preditivo Baseado em Modelo (Blucher). He has supervised over 60 PhD/MSc. candidates. He was the Associate Editor of Control Engineering Practice from 2007 to 2018 and Editor of the International Renewable Energy Congress since 2014. Since 2000 he integrates the NOC of several national conferences related with automatic control, and recently, he was the General Chair of the IFAC Symposium DYCOPS 2019. He is the coordinator of the National Institute of Science and Technology in Control and Automation of Energy Processes.
Julio Elias Normey-Rico received his Ph.D. degree from University of Seville, Spain, in 1999. He is currently a Full Professor of the Dept. of Automation and Systems Engineering in Federal University of Santa Catarina (UFSC), in Brazil and head researcher of Renewable Energies Research Team (GPER/UFSC), lead research group in this topic in Latin America. He is the director of several research partnerships with energy industries and international cooperation agreements (Argentina, Uruguay, Spain, Chile and Italy). He is the author of over 260 conference and journal
papers, and published four book chapters and the books Control of Dead-Time Processes (Springer), Introdução ao Controle de Processos (Blucher) and Controle Preditivo Baseado em Modelo (Blucher). He has supervised over 60 PhD/MSc. candidates. He was the Associate Editor of Control Engineering Practice from 2007 to 2018 and Editor of the International Renewable Energy Congress since 2014. Since 2000 he integrates the NOC of several national conferences related with automatic control, and recently, he was the General Chair of the IFAC Symposium DYCOPS 2019. He is the coordinator of the National Institute of Science and Technology in Control and Automation of Energy Processes.
Reliability and Condition Assessment
of Power Transformers
Accurate information about the service experience of high voltage equipment is of significant value to both the electric utilities and to manufacturers of such equipment. It helps the manufacturers improve their products, and provides important inputs for the utilities when organizing maintenance and benchmarking their performance. Statistical analysis of the past failure data can display useful features with respect to the future failure behavior. Equipment reliability data are also required when assessing the overall reliability of an electric power system, including studies of the electric energy supply security.
This presentation addresses the analysis of transformer failures collected by Cigre WG A2.62. Based on a transformer population with more than 425,000 unit-years and 1,159 major a failure rate of app. 0.3 % p.a. was determined. Failure location and mode analysis is presented for different voltage classes, along with external effects. Winding related failures appear to be the largest contributor of major failures. Bushing failures most often lead to severe consequences like explosion or fire. The collected age distributions enable the determination of the hazard rate, making this study unique due to its international scope. Information on retirements is valuable because it indicates units that are nearing failure but have not yet failed.
The deployment of new inspection and condition assessment strategies further increase the reliability of power transformers. By leveraging tools such as UHF PD measurement and FRA, manufacturers can proactively identify potential issues and ensure compliance with acceptance criteria. Digital innovation, such as online monitoring and remote diagnostics, offer insights into transformer performance, strengthening predictive maintenance strategies and minimizing downtime. However, these technologies must be carefully integrated and configured to maximize their effectiveness and security. Looking ahead, the power sector must embrace digital transformation across the entire lifecycle of transformers, from design and manufacturing to operation and maintenance. By leveraging cutting-edge technologies and best practices, stakeholders can ensure the resilience and reliability of power infrastructure in the face of evolving operational challenges and dynamic grid environments.
Stefan Tenbohlen (IEEE M’04, S’14, F’23) received his Diploma and Dr.-Ing. degrees from the Technical University of Aachen, Germany, in 1992 and 1997, respectively. 1997 he joined ALSTOM Schorch Transformatoren GmbH, Mönchengladbach, Germany, where he was responsible for basic research and product development. From 2002 to 2004 he was the head of the electrical and mechanical design department. 2004 he was appointed to a professorship and head of the Institute of Power Transmission and High Voltage Technology of the University of Stuttgart, Germany. In this position his main research fields are high voltage technique, power transmission and electromagnetic compatibility (EMC). Prof. Tenbohlen holds several patents and published more than 600 papers. He is member of the IEEE, CIGRE study committee A2 (power transformers), german committees of A2 (Power Transformers and Reactors), D1 (Materials and Emerging Test Techniques), C4 (Power System Technical Performance), several international working groups. Furthermore, he is convenor of Cigre WG A2.62 “Analysis of Transformer Reliability”.
