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The security and resiliency of electric power supply to serve critical facilities are of highimportance in todays world. Instead of building large electric power grids and high capacitytransmission lines, an intelligent microgrid (or smart grid) can be considered as a promisingpower supply alternative. In recent years, multi-agent systems have been proposed to provideintelligent energy control and management systems in microgrids. Multi-agent systems offer their inherent benefits of flexibility, extensibility, autonomy, reduced maintenance and more. The implementation of a control network based on multi-agent systems that is capable ofmaking intelligent decisions on behalf of the user has become an area of intense research. The objective of this research is to design, develop and implement a multi-agent system thatenables real-time management of a microgrid. These include securing critical loads andsupporting non-critical loads belonging to various owners with the distributed energyresource that has limited capacity during outages. In summary, the multi-agent system is designed, developed and implemented in severalsimulation test cases. It is expected that this work will provide an insight into the design anddevelopment of a multi-agent system, as well as serving as a basis for practical implementationof an agent-based technology in a microgrid environment. Furthermore, the work alsocontributes to new design schemes to increase multi-agent system's intelligence. In particular,these include control algorithms for intelligently managing the limited supply from a DERduring emergencies to secure critical loads, and at the same time supporting non-critical loadswhen the users need the most.
A multi-agent system is collection of a number software programs (agents) working together in pursuit of different tasks. It can be defined as: a combination of several agents working in collaboration in pursuit of achieving their assigned tasks resulting in the achievement of overall goal of the system. Today's world, inundated with technological advancements, incorporates virtually limitless applications of multi-agent systems. In this chapter, the area of research is introduced i.e. multi-agent systems' application in microgrids. Importance of this research is briefly discussed, followed by the thesisstatement.
1.1 Multi-Agent System in Microgrids
The increase in demand for electricity put many challenges of securing critical equipement.To deal with such situations more power plants and transmission lines are built to overcome the electrical shortages. This approach has limitations such as fuel availability, landuse, health effects due to electromagnetic waves etc.
Electricity needs for critical equipment could be met by the concept of microgrid instead of building bigger power plants and high capacity transmission lines. A microgrid is on-site Distributed Energy Resource (DER) that can serve a section of distributed network and group of loads. Loads may consist of homes, offices and buildings. A microgid improves the reliability of the system by allowing the local network more resilient which results in failures and outages.
1.2 Need of Multi-agent system
For any power system it is very to have control and communication architecture. To serve this purpose power systems used supervisory control and data acquisition.SCADA uses different signaling protocols that makes it able to control and maintain power systems, These products ,however are installed with different protocol software's which has limitations in communicating with Distributed Energy Resources. This results in increased deployment costs.
To overcome this drawback deployment of multi-agents system for the control of micro grids is introduced. To control and operate the microgrid multi-agent system theory seems to be very useful. The main element of the MAS is an agent which has properties of sociality, autonomy and reactivity. MAS has following advantages
- Multi-agent systems provide benefits of flexibility.
- Multi-agent systems have certain level of autonomy that makes them able to take decisions on their own such as transition from grid-connected to island mode, load shedding etc.
- In Multi-agents systems huge and complex tasks are divided into smaller tasks which reduce the need for maintenance and processing of large data.
1.3 Thesis Statement
The objective of this research is to design, develop and implement a multi-agent systemthat enables real-time energy management of a microgrid. These include the managementand control algorithms during the transition from grid-connected to islanding mode; thealgorithms to secure critical loads and share limited capacity from DER to support noncriticalloads belonging to various owners with the available distributed energy resourceduring outages. This work also studies the execution delay for the multi-agent system's commands.
In summary, the multi-agent system is developed, designed and implemented in severalsimulations. This work will provide a guide to the designand development of a multi-agent system, as well as serving as a basis for practicalimplementation of an agent-based technology in a microgrid system. Furthermore, the work also includes the new design schemes to increase multi-agent system'sintelligence in the context of micro grids. In particular, these include control algorithms formanaging limited supply from DER to secure critical loads during emergencies while at thesame time supporting prioritized non-critical loads that belong to various users.
1.5 Organization of the Thesis
The rest of the thesis is organized as follows Chapter 2 Summarizes Related Work
2.1 Multi-agent system and Application
A multi-agent system is a powerful tool in developing a complex system. A multi-agent system is a collection of different agents working together in pursuit of accomplishing their assigned tasks resulting in the achievement of overall goal of the system. A software program is declared as agent if it contains following characteristics.
- Communicating with its environment (which may include other agents) (Sociality)
- Learning from its environment (Autonomy)
- Responding to its environment in a timely manner (Reactivity and Pro-activity)
- Making decisions to achieve its goals, and (Autonomy and Pro-activity)
- Achieving tasks on behalf of its user (Sociality and Reactivity)
These properties show the importance multi-agent systems in developing complex sysytems.Applications of agent based systems are divided into two categories
In these applications human may require assistance when using these applications e.g. search engine, mail management engine, news filtering engine etc.
Multiple agents work together to accomplish a specific goal. These can either be physical systems or simulation of physical systems. Examples may include traffic monitoring, decision support system, telecommunication and network management etc.
2.2 History of Smart grid
The concept of smart grid is not new. Years back there were ideas of how to efficiently and actively monitor the and control the electric grid. A good definition of smart grid is provide by the EU technology platform: A smart grid is an electricity network that can efficiently integrate the actions of all users connected to it,generators,consumers and those that do both in order to efficiently deliver sustainable, economic and secure electricity supplies. The smart grid introduces the way how the future electrical grids need to be planned, build, operated and maintained.
The deployment of smart grid will give the following benefits
1Improved energy efficiency
A smart grid can provide benefits through improving the grid's reliability by reducing the power outages and the number of power quality disturbances.
2Better Efficiency and enhanced service in electricity supply and grid operation.
A smart grid can make electrical supply more efficient through active control, automation and management in distribution grid
3More secure and quality of supply
A smart grid offers well coordination of transmission and distribution.
Smart grid provides consumer friendly environment in which consumers can get more detailed energy data
A smart grid is a grid that delivers electricity from generation point to the consumers, and the electricity delivery network functions via two primary systems: the transmission system and the distribution system. The transmission system delivers electricity from power plants to distribution substations, while the distribution system delivers electricity from distribution substations to consumers. The grid uses distributed energy resources to serve local loads.Microgrid has following key characteristics
- Self-Healing from power disturbances
- Consumer friendly
- Resilient against attack
Our project discusses the design and development of multi-agent system in the context of smart grid located at distribution level
2.3 Multi-agent systems implementation in Microgrids
In the context of power systems, multi-agent systems can be applied in a variety of applications, such as to perform power system disturbance diagnosis, power system restoration, power system secondary voltage control and power system visualization. Two strategies have been considered for the control and communication within microgrids: Centralized control and decentralized or distributed control.
Centralized control requires a central controller that manages the entire system. This concept is based on the same approach used for SCADA systems in the past. Decentralized or distributed control approach is implemented using the multi-agent systems technology. The idea behind any multi-agent is to breakdown a complex problem handled by a single entity. The IDAPS (Intelligent Distributed Autonomous Power Systems) multi-agent system comprises four types of agents
- Control agent
- DER agent
- User agent
- database agent.
When working in collaboration, four agents will work toward achieving the overall goal of an IDAPS microgrid, which is to secure critical loads within the microgrid during outages.