A SEMINAR REPORT ON MICROGRID
SUBMITTED BY Akshata. A. S Madhuri. S
Harshada. V. H Mandasmita. R. K
Department of Electrical & Electronics Engineering S. G. BALEKUNDRI INSTITUTE OF TECHNOLOGY SHIVABASAVNAGAR, BELGAUM-590010
S. G. BALEKUNDRI INSTITUTE OF TECHNOLOGY SHIVABASAVNAGAR, BELGAUM-590010
Department of Electrical & Electronics Engineering SEMINAR REPORT ON MICROGRID
Is result of the bonafide work carried out by Akshata. A. S
EE001
Harshada. V. H
EE010
Madhuri. S
EE015
Mandasmita. K
EE018
Submitted in partial fulfilment of requirement for VII semester examination of Degree in Bachelor of Engineering in Electrical &Electronics Engineering for the year 2012-13
SEMINAR COORDINATOR Contents
Introduction to Microgrid.
Microgrid Operating Modes.
The Need of Microgrid.
Interconnected Microgrids – Power Parks.
Environmental Aspects.
Conventional Grid versus Microgrid.
Advantages & Disadvantages of Microgrid.
H.O.D
Future Directions on Microgrid Research.
References.
INTRODUCTION
Up till now small generation units have been dispersed throughout power systems basically as uninterruptible power supplies. Generally these sources are not synchronized with the grid power supply though, but rather cut in when the primary supply is interrupted. With the role of distributed generation changing from backup to primary energy supply, more flexible connection strategies are required. To realize the emerging potential of distributed generation a system approach is to be taken which views generation and associated loads as a subsystem or a ―microgrid‖ . The concept of Micro Grid has grown out of this desire for truly interconnected operation of distributed generation. It is envisioned that this microgrid concept will prove to be an ideal solution to rural electrification besides its very well use in industrial parks, commercial and institutional campuses and many other situations requiring improved reliability and power quality. A micro grid enables small communities to take control of their energy use and reduce their carbon footprint through a new and innovative way of generating and managing electricity.
THE MICRO-GRID CONCEPT
A microgrid can be simply defined as an aggregation of electrical generation, storages and loads. The generators in the microgrid may be microturbines, fuel cells, reciprocating engines, or any of a number of alternate power sources. A microgrid may take the form of shopping center, industrial park or college campus. To the utility, a microgrid is an electrical load that can be controlled in magnitude. The load could be constant, or the load could increase at night when electricity is cheaper, or the load could be held at zero during times of system stress A microgrid combined with power electronic interface is a completely self-sufficient network, with preferably autonomous control, communication and protection. It is capable of providing capacity support to the transmission grid while in grid-connected mode, and with capacity in excess of coincident peak demand. So, the Micro grids comprise low voltage LV distribution systems with integration of Diverse Energy Resources DER such as photovoltaic, wind, bio-mass, bio fuel and fuel cell together with Distributed storage DS like flywheels, energy capacitors and batteries and Controllable Loads that behave as a coordinated entity networked by employing advanced power electronic conversion and control capabilities The MicroGrid assumes three critical functions that are unique to this architecture:
1. Microsource Controller regulate power flow on a feeder as loads on that feeder change their operating points regulate the voltage at the interface of each microsource as loads on the system change Insure that each microsource rapidly picks up its share of the load when the system islands. It responds in milliseconds and uses locally measured voltages and currents to control the microsource during all system or grid events. 2. Energy Manager • • • •
The Energy Manager provides for system operation of the MicroGrid through dispatch of power And voltage set points to each Microsource Controller. • • • •
Insure that the necessary heat and electrical loads are met by the microsources Insure that the MicroGrid satisfies operational contracts with the bulk power provider Minimize emissions and/or system losses Maximize the operational efficiency of the microsources
3. Protection The protection coordinator must respond to both system and MicroGrid faults. For a fault on the grid, the desired response may be to isolate the critical load portion of the MicroGrid from the grid as rapidly as is necessary to protect these loads.
Operating modes of Microgrid
Operating modes of Microgrid are: 1. Grid connected 2. Island connected Basic Microgrid architecture is shown below. This consists of a group of radial feeders, which could be part of a distribution system or a buildings electrical system. There is single Point of connection to the utility called as point of common coupling. Some feeders (feeders A-C) have sensitive loads, which require common generation. The non-critical load feeders do not have any local generation. In our example this is feeder Feeders A-C can island from the grid using static switch which can separate in less the cycle. In this case, there are four micro sources at nodes 8, 11, 16 and 22 which control the operation using only local voltages and currents measurements. There is a problem with utility supply. The static switch will open, isolating the sensitive loads from the power grid. If it is assumed that there is sufficient generation to meet the loads demands. When the micro grids are grid connected power from the local generation can be directed to feeder D.Static switch is closed and utility grid is active.
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In case of island mode utility grid is not supplying power. Static switch is open. Feeder A, B, C is being supplied by micro sources and feeder D is dead.
Expected Microgrid features •
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Autonomy: Microgrids include generation, storage, and loads, and can operate autonomously in grid-connected and islanded mode. In the first case, a Microgrid can independently optimize its own power production and consumption under the consideration of system economics such as buy or sell decisions. In islanded mode the system is capable of balancing generation and load and can keep system voltage and frequency in defined limits with adequate controls. Stability: Independent local control of generators, batteries, and loads of Microgrids are based on frequency droops and voltage levels at the terminal of each device. This means that a Microgrid can operate in a stable manner during nominal operating conditions and during transient events, no matter whether the larger grid is up or down. Scalability: Microgrids can simply grow through the additional installation of generators, storage, and loads. Such an extension usually requires an incremental new planning of the Microgrid and can be performed in a parallel and modular manner in order to scale up to higher power production and consumption levels. Efficiency: Centralized as well as distributed Microgrid supervisory controller structures can optimize the utilization of generators, manages charging and discharging energy storage units,
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and manages consumption. in this way energy management goals can be profoundly optimized, for example in economic as well as environmental respects. Peer-to-peer model: Microgrids can support a true peer-to-peer model for operation, control, and energy trade. In addition, interactive energy transactions with the centralized utility grid are also possible with this model. The proposed concept does not dictate the size, scale, and number of peers and the growth rate of the Microgrid.
Interconnected Microgrids
Local interconnection standards vary considerably from one bulk power provider to the next. A national standard, ANSI standard P1547 (Draft) Standard for Distributed Resources Interconnected with Electric Power Systems is being drafted by the IEEE working group. This standard rests on certain assumptions about the contribution of DER to power quality and System reliability. The standard applies at the point where a Microgrid connects to the grid and is related to the aggregate DER rating within the Microgrid. In other words, the rules applied to a Microgrid containing many small DER devices would be the same as for one large DER.However, the applicability of P1547 is limited to a DER rating of 10 MVA, which is larger than The ratings expected for MicroGrids. Because a Microgrid exploits low voltage, use of waste heat, and the flexibility of power electronics, its practical size may be limited to a few MVA (even Though IEEE draft standard P1547 specifies an upper limit of 10MVA). In a large complex, loads could be divided into many controllable units e.g., among buildings or industrial sites. Each unit Could be supplied by one or more Microgrids connected through a distribution system. The advantages of this system are that the Microgrid structure insures greater stability and controllability, Allows for a distributed command and control system, and provides redundancy to insure greater power supply reliability for the power park.
Environmental aspects
Growing environmental awareness and government directives have set the stage for an increase in the fraction of electricity supplied using renewable sources .Renewable generation could appear in microgrids,especially those interconnected though power electronic devices, such PV systems or some wind turbines. Biofueled micro turbines are also a possibility. Environmentally, fuel cells and most renewable sources are a major improvement over conventional combustion engines. A microgrid is located in a geographically limited area. Its generation and load, as well as load balance, are controlled by reliable electronic components, and it can disconnect from the utility grid and run in “island”mode if required. Distributed generation , especially solar and wind power collected across different small generation locations, is gaining considerable importance and their deployment is perceived as vital in achieving carbon reduction goals .The gains of increased conversion efficiency are threefold. First, fuel co will be reduced both because individual fuel purchases will decrease And constrained overall demand will drive down fuel prices. Second, carbon emissions will be reduced. And, thir environmental problem of disposing of large power plant waste heat Into the environment will diminish.
Conventional Grid verses Microgrid
Performance Measures Cost
Traditional grid power At most location in US delivered grid power effectively cost between 6 and 15 cents per KWh
Fuel Efficiency
Delivered grid power is 30% to 50% efficient depending on the mix of power plant used.
Reliability
Grid power is on average 99.97%reliable.No single DG technology without redundancy Can beat this figure.
Emissions
Modern natural gas combine cycle power plants pollute less than fuel oil/diesel DG engine units.
Security
Damage to a few measure transmission lines can cause regional blackouts affecting millions of customers. It is difficult to built new lines and substations due to NIMBY (“not in my backyard syndrome”).
Construction constraints
Microgrid Well designed microgrid projects with good fuel cost or availability can be under 10 cents per KWh so some are less costly than grid power in some locations. Microgrid with CHP can be 70% to 90% efficient. Without CHP microgrid may be less efficient than grid power. Microgrid with bulk system as backup achieves higher reliability than the bulk system alone and usually at lower cost than upgrading the bulk system reliability. Microgrid alone is not a reliable as traditional power without use of costly redundancy. Fuel cells and renewable energy systems used in DG have little or no emission and pollute much less that most grid sources. Natural gas DG sources pollute less than coal fired traditional grid generation. Severe damage to a microgrid affects only thousands of customers or less. Microgrid can be a solution to overloaded and constrained T&D systems. But they also have their own pollution, noise and zoning issues.
Advantages of Microgrid 1. Microgrid includes generation ,storage and loads and can operate autonomously in grid connected islanded mode 2. In peak load periods it prevents the utility failure by reducing the load on the grid 3. Microgrid can operate in stable manner during nominal operating conditions and during transient events. 4. Microgrids are completely compatible with existing utility grid. 5. It supports the growth of existing system in an economical and environmentally friendly way. 6. Microgrids are more efficient because of it can optimise the utilisation of generators, manage charging and discharging storage units, manage the power consumption. 7. Microgrids are able to operate with diverse mixture of generators. 8. Microgrid supports a true peer-to-peer model for operation, control and energy trade Disadvantages 1. Electrical energy needs to be stored in battery banks thus requiring more space and maintenance. 2. Resynchronization with utility grid is difficult. 3. Microgrid protection is one of the most important challenges facing the implementation of Microgrids.
OVERALL CONCLUSIONS Micro grids can provide improved electric service reliability and better power quality to end customers and can also benefit local utilities by providing dispatch able load for use during peak power conditions or allowing system repairs without effecting customer loads. A micro grid enables small communities to take control of their energy use and reduce their carbon footprint through a new and innovative way of generating and managing electricity. The state-of-the-art of issues of Micro Grid research projects, especially in Europe, United State, Japan, Canada and India has been presented. Although the researches and activities of Micro Grids across the globe have not yet reached significant levels, however is experiencing a rapid growth.
References
A. A. Salam, A. Mohamed and M. A. Hanna. "TECHNICAL CHALLENGES ON MICROGRIDS" (DECEMBER 2008) http://www.arpnjournals.com/jeas/research_papers/rp_2008/jeas_1208_146.pdf S. Abu-Charkha, R.J. Arnold, J. Koehler, R. Lia, T. Markvarta, J.N. Rossb, K. Steemersc, P. Wilsonb, R. Yaoc. "Can microgrids make a major contribution to UK energy supply?" (September 2004) http://eprints.ecs.soton.ac.uk/11276/1/Microgrids.pdf John Stevens. "Characterization of Microgrids in the United States", Sandia National Laboratories (January 2005) http://www.electricdistribution.ctc.com/pdfs/RDC_Microgrid_Whitepaper_1-7-05.pdf Robert H. Lasseter, Paolo Piagi. "Microgrid: A Conceptual Solution", University of Wisconsin Madison (June 2004) http://www.pserc.wisc.edu/ecow/get/publicatio/2004public/lasseterpesc04us.pdf
"Integration of Distributed Energy Resources - The CERTS MicroGrid Concept", Consultant Report (October 2003) http://www.pserc.org/cgi pserc/getbig/researchdo/certsdocum0/certspubli/certsmicrogridwhitepaper.pdf "Why the Microgrid Could Be the Answer to Our Energy Crisis" http://www.fastcompany.com/magazine/137/beyond-the-grid.html "How a Microgrid Works" http://science.howstuffworks.com/microgrid.htm “The Rise of Microgrid Power Networks"
http://www.sustainablefacility.com/Articles/Feature_Article/58905d08bd629010VgnVCM100000f932a8 c0____
ABSTRACT Innovations in technologies, economic benefits, quality requirements and environmental concerns are changing the face of the existing power system. Centralized generating facilities are giving way to smaller, more distributed generation partially due to the loss of traditional economies of scale. The need of an intelligent grid, better known as Micro grid at the distribution end, has been recognized to accommodate distributed energy resources (DERs) and renewable energy technologies on large scale. Micro grids can provide improved electric service reliability and better power quality to end customers and can also benefit local utilities by providing dispatch able load for use during peak power conditions or allowing system repairs without effecting customer loads. This report highlights the concept, benefits and features of Micro Grids.
