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March 2013, IE Tech News The Frontier of Smart Grids: An Industrial Electronics Perspective Xinghuo Yu1, Carlo Cecati2, Tharam Dillon3, M. Godoy Simoes4 1Platform Technologies Research Institute, RMIT University, Melbourne, Australia 2Department 3La of Electrical and Information Engineerining, University of L’Aquila, L’Aquila, Italy Trobe Technology, Melbourne, Australia 4Center for Advanced Control of Energy and Power Systems, Colarado School of Mines, Golden, USA Table of Contents Introduction Power Electronics Intelligent Systems and Control IT Infrastructure Discussions and Conclusions The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 2 Introduction: The Electricity and Electric Grid The electric grid is a massive interconnected network used to deliver electricity from suppliers to consumers. Distinct operations of electric grids include generation, transmission and distribution. Presently, the dominating generation mechanism is by electro-mechanical generators driven by heat engines fueled by chemical combustion or nuclear fission. Figure 1: The traditional electric grid. The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 3 Introduction: The Need for Smart Grids Smart Energy refers to making energy use more efficient by utilizing the integration of advanced technologies such as information and communication technologies (ICT), electronics and material engineering. Smart Energy is needed for a number of reasons, e.g. • Limited availability of non-renewable energy sources such as coal, gas and oil on Earth. • Pollution concerns such as carbon dioxide, nitrous oxide and dust air from burning coal and oil. Smart Energy is about taking a holistic approach in dealing with efficient energy supply and demand considering economic, environmental and social objectives. The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 4 Introduction: The Concept of Smart Grids The term Smart Grid (SG) refers to electricity networks that can intelligently integrate the behavior and actions of all users connected to it, for example generators, customers and those that do both – in order to efficiently deliver sustainable, economic and secure electricity supplies. SG is an enabler for Smart Energy. Figure 2: The future electric grid. The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 5 Introduction: The Concept of Smart Grids The conceptual model of Smart Grid, defined by the National Institute of Standards and Technology (NIST), consists of seven important domains concerning : – Bulk generation – Transmission – Distribution – Customers – service provider – Operations, and – Markets Figure 3: The NIST conceptual model of SG The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 6 Introduction: The Concept of Smart Grids In SG, the traditional role of central generation, transmission, and distribution is transformed by aggregation of distributed resources (see Figure 4). Power from local generation can be directed to the feeder with non-critical loads or be sold to the utility if agreed or allowed by net metering. A microgrid can be designed for the requirements of end-users, a stark difference from the central generation paradigm. The Frontier of Smart Grids: An Industrial Electronics Perspective Figure 4: A microgrid architecture March 2013, IE Tech News 7 Introduction: Key Issues in Smart Grids Several technical challenges: intermittency of RE generation that affects electricity quality; large scale networks of small distributed generation mechanisms, for example photovoltaic (PV) panels, batteries, wind and solar, plug-in hybrid electric vehicles (PHEV). An important characteristic of power usage is the big margin between the peak and average usages; reducing peak demands can help utilize existing infrastructure to meet increase of energy demands due to economic growth. Technological advances required include – Distributed control – Demand prediction – Generation prediction – Demand response. The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 8 Power Electronics: Introduction The technology of power electronics is fundamental in SG because there will be deeper penetration of renewable and alternative energy sources which require power converter systems. A power converter is an interface between SG and local power sources. Moreover, they are required by several sub-systems involving energy storage or harmonic compensation interconnecting areas or separated grids. Figure 5: Active and reactive power balance for alternative energy conversion Power converters are a key technology to enable SG to function. Figure 6: Integration of several sources of energy into the grid The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 9 Power Electronics: Introduction (Contd.) A typical distributed generation system architecture is shown in Figure 7 which consists of: a) a typical dc link integration very commonly used when dc sources (PVs, fuel cells, batteries) are integrated. (a) b) a typical ac link integration, where turbines and rotating machines are integrated through the utility line frequency, and (b) c) a high frequency ac link integration, where fast response and decreased system size can be achieved. (c) Figure 7: Energy Integration with DC, AC or HFAC Link: (a) dc link integration; (b) ac link integration; (c) hfac link integration. The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 10 Power Electronics: Generation from Solar Energy DC/DC converters may provide the necessary voltage boost and regulation. Typically MPPT control algorithms are used in extracting the highest power from the sun. Usually the dc/dc converter is connected to a PWM inverter with grid synchronization capabilities, or multilevel converter topologies for high voltage applications. The inverter must attain correct synchronous operations, with a good low pass filter, in order to observe utility interconnection standards. An energy storage system may be connected in parallel at the inverter input terminal for balancing the impact of PV energy fluctuations. The inverter can have several smart functionalities allowing the communication with utilities, users and local neighborhood. The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 11 Power Electronics: Generation from Wind Energy Wind Energy Conversion Systems consists of an ac generator (synchronous or asynchronous machine) and a power converter, usually consisting of • a cascade ac/dc rectifier • dc/dc converter (useful for dc link voltage regulation and control) • and dc/ac converter. Dc/ac conversions are similar from those used in PV converters, but usually designed for higher power levels (up to 10 MVA). Typically, multilevel converters are promising solutions. But, other topologies like neutral point clamped or flying capacitor may be employed in both ac/dc and dc/ac stages. Matrix converters can also be considered for ac/ac applications. The MPPT is often designed to optimize the turbine aerodynamics and sometimes improve efficiency in induction generators with optimized excitation flux. The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 12 Power Electronics: FACTS Systems & Power Quality Issues Flexible Alternating Current Transmission Systems (FACTS) increase grid efficiency and stability through the use of power converters providing to: • Voltage regulation • Reactive Power balance (fundamental in large WECS located in rural area) • Power Factor Control • Power Quality enhancements Typical power converters are: Static VAR Compensators, Power Factor Controllers. They often have different topologies, including the recent multilevel converters. In this area, converters for High Voltage Direct Current are also important. The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 13 Intelligent Systems and Control: Introduction SGs are highly complex, nonlinear dynamical networks by nature that present many theoretical and practical challenges. Monitoring and control are key issues that need to be addressed to make SG more intelligent and equipped with self-healing, self-organizing, and selfconfiguring capabilities. Another important issue is the Big Data environment that SG is in, which pose the questions that – How to automate the acquisition of useful operation information in order to make informed operation decision in a timely fashion? – How to present the information to users in a most compelling and informed way to help users make high-level operation decision without bogging down into unnecessary waste of time in understanding rather raw data? The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 14 Intelligent Systems and Control: Dealing with Network Complexity With increasing complexity compounded by distributed nature of RE, real-time performance is a bottleneck in deriving just-enough and just-in-time information for. One promising methodology is the Complex Networks (CN) theory originated from the graph theory which can be used in combination with existing methods and tools to simplify the analysis and design so that timely response is possible. Figure 8: Typical types of complex networks The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 15 Intelligent Systems and Control: Intelligent Systems Future SG requires not only automation of operations at the lower operational levels, but also high-level decisions to take consideration of macro economic and social requirements. Decision-support is a key in making SG more responsive to user demands. A typical decision support framework is shown in Figure 9, which is a knowledgebased meta-fuzzy system incorporating expert systems and extended fuzzy systems including a new meta-fuzzy logic mechanism and a discourse semantics as an explanatory mechanism. Figure 9: An industrial decision support framework The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 16 Intelligent Systems and Control: Intelligent Systems (contd.) Multi-agent systems are another approach that enable distributed decision making and automation in SG. An agent is a software entity that can represent and control a hardware component. Agents can communicate and interact with each other and their environment. This allows them to cooperate or compete towards local and/or global goals. Figure 10: A multi-agent system The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 17 Intelligent Systems and Control: Control Systems SG systems exhibit the following features: – a) a large scale network structure; – b) many of the controls are embedded in the system; future control designs which must make use of these existing controls; – c) the overall control scheme has a hierarchical structure; – d) the available control actions are already largely physically determined and have diverse timing, cost and priority for action; – e) the control goals are multi-objective with local and global requirements which vary with system operating states; – f) there is a need for a high level of distributed global control mechanism which can provide a meta-view to coordinate local controllers. There is a need to rethink about how SG should be controlled in such a complex environment. Complex networks and multi-agent systems provide an alternative approach in dealing with complexity. The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 18 IT Infrastructure: Introduction IT Infrastructure is the backbone enabler for SG to be aware of what is going on, deciding best strategies for monitoring and control and responding to demand side responses while keeping the grids to operate efficiently, cost less and neutralize the negative impact on environments. A platform for information exchange is needed that enables smart appliances and smart meters to exchange the information between them as shown in Figure 10. Figure 11: Smart link between the utility grid and smart gateway The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 19 IT Infrastructure: Cyber-Physical Systems The Cyber-Physical Systems (CPS) can offer such a platform that allows for both the digital information as well as traditional energy (for example electricity) to flow through a two-way smart infrastructure. CPS was defined by the National Science Foundation (NSF) as physical and engineered systems whose operations are monitored, coordinated, controlled and integrated by a computing and communication core. Figure 12: Reference architecture of CPS CPS involves computation, human activities, and automated decision making enabled by ICT. The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 20 IT Infrastructure: Realization of WoT Bsed CPS Architecture CPS can be achieved by using the Internet of Things or Web of Things (WoT) computing paradigm as a dynamic global network infrastructure with self configuring capabilities based on standard and interoperable communication protocols. WoT framework for CPS has five layers, namely, device, kernel, overlay, context and API. The challenges are – IP addressable things and smart gateways – Flexibility in wireless communication – Common embedded platform for information exchange – Representation of events – Abstraction of suitable events The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 21 Discussions and Conclusions We have presented some future research and development challenges and opportunities in SG in three related but distinct focal areas as pertinent to IEEE IES. Future developments in these three focal areas need to be integrated. We hope this paper serves the purpose of inspiring researchers and practitioners to get further involved in this exciting frontier of SG. The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 22 References (1) • F.A. Farret and M. G. Simões, Integration of Alternative Sources of Energy, IEEE Press/Wiley, 2006 • J.M. Guerrero, J.C. Vasquez, J. Matas, L.G. de Vicuna and M. Castilla, "Hierarchical control of droop-controlled AC and DC microgrids—A general approach toward standardization," IEEE Transactions on Industrial Electronics, vol.58, no.1, pp.158172, Jan. 2011. • M. Liserre, T, Sauter, and J. Y. Hung, ‘‘Future energy systems: Integrating renewable energy sources into the smart power grid through industrial electronics,’’ IEEE Industrial Electronics Magazine, vol. 4, no. 1, pp. 18–37, Jan. 2010 • C. Cecati, F. Ciancetta and P. Siano, "A multilevel inverter for photovoltaic systems with fuzzy logic control,” IEEE Transactions on Industrial Electronics, vol. 57, no. 12, pp. 4115–4125, Dec. 2010. • M. Malinowski, K. Gopakumar, J. Rodriguez and J. M.A. Pérez, “A survey on cascaded multilevel inverters,” IEEE Transactions on Industrial Electronics, vol. 57 , no.7, pp. 2197 – 2206, Jul. 2010. The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 23 References (2) • X. F. Wang and G. R. Chen, “Complex networks: Small-world, scale-free and beyond,” IEEE Circuits and Systems Magazine. vol. 3, no. 1, pp. 6–20, Jan. 2003. • A. Dwivedi and X. Yu, “A maximum-flow-based complex network approach for power system vulnerability analysis,” IEEE Transactions on Industrial Informatics, vol. 9, no.1, pp. 81-88, Jan. 2013. • A. I. Zecevic and D. D. Siljak, Control of Complex Systems, Communication and Control Engineering, Springer, 2010. • D. J. Hill, Y. Guo, M. Larsson and Y. Wang, “Global control of complex power systems,” in Bifurcation Control, LNCIS, vol. 293, pp. 155-187, 2003. • T. S. Dillon, H. Zhuge, C. Wu, J. Singh, and E. Chang, "Web-of-things framework for cyber–physical systems", Concurrency and Computation: Practice and Experience, vol. 23, no. 9, pp.905-923, Jun. 2011. • European Commission Information Society and Media (ECISM), "Future Internet Enterprise Systems (FInES) Cluster," http://cordis.europa.eu/fp7/ict/enet/finespositionpaper_en.html, 2009. The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 24 Disclaimer These slides are made by authors to help readers quick and better understanding of the subject. The opinions made or information presented here belong to the sole responsibility of the authors. IE Tech News (ITeN) neither endorses nor denounces any opinions made or information presented. Part or full of these material may be used only with written permission from the authors. The Frontier of Smart Grids: An Industrial Electronics Perspective March 2013, IE Tech News 25