A micro grid is a small-scale power grid that can operate independently or collaboratively with other small power grids. The practice of using micro grids is known as distributed, dispersed, decentralized, district or embedded energy production
A micro-grid is a group of interconnected loads and distributed energy resources (DER) with clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid.
Introduction
Any small-scale, localized power station that has its own generation and storage resources and definable boundaries can be considered a micro grid. If the micro grid can be integrated with the area’s main power grid, it is often referred to as a hybrid micro grid.
Micro grids are typically supported by generators or renewable wind and solar energy resources and are often used to provide backup power or supplement the main power grid during periods of heavy demand. A micro grid strategy that integrates local wind or solar resources can provide redundancy for essential services and make the main grid less susceptible to localized disaster.
Recent Micro grid
Buildings equipped with electric generation capabilities through solar panels and contingency generators can also generate energy and revenue during downtime. By joining together with smart grid deployments, excess energy can be sold back to local micro grids to create revenue in addition to providing resilience and capacity to local electrical grids.
Difference between conventional grid and micro-grid
The key differences between a Micro-grid and a conventional power plant are as follows:
Micro-sources are of much smaller capacity with respect to the large generators in conventional power plants.
Power generated at distribution voltage can be directly fed to the utility distribution network.
Micro-sources are normally installed close to the customers’ premises so that the electrical/heat loads can be efficiently supplied with satisfactory voltage and frequency profile and negligible line losses.
Difference between smart grid and micro-grid
Smart grids are those electrical systems that includes multiple smart generating systems, smart transmission and distribution systems which are controlled through advanced technology like telecommunication system. .
A micro-grid is an electrical system that includes multiple loads and distributed energy resources that can be operated in parallel with the broader utility grid or small, independent power system. A micro-grid is designed for a small scale usually for a certain community whiles the smart grid is designed for the whole electrical system.
They do not have any difference on the energy sources utilized. Micro-grid increases reliability with distributed generation, increases efficiency with reduced transmission length and easier integration of alternative energy sources while A smart grid is a modernized electrical grid that uses information and communications technology to gather and act on information, such as information about the behaviors of suppliers and consumers, in an automated fashion to improve the efficiency, reliability, economics, and sustainability of the production, transmission and distribution of electricity and operations wide- area monitoring, control and protection.
Need of Micro-grid
1. Enables the use of micro level power generating plants by using Renewable and alternative fuels and thereby conserves the fossil fuels.
2. Optimum and efficient use of distribution energy systems.
3. Enables to enhance the use of energy storage systems which raises the reliability factor of the grid.
4. Improves the power quality through the easy frequency and voltage regulation, smoothing the output of renewable energy sources, providing backup power for the system.
5. Playing crucial role in optimization of cost of energy.
6. Minimizes the green gas production by adoption of renewable.
7. Enables to increase the efficiency of energy management system through demand side management, energy conservation measures.
8. Enhances the power balance in the grid and improves the stability of the grid.
9. Micro-grids provide revenue by selling energy and services back to the grid.
Major Components of Micro-grids
Energy Supply System: For a micro-grid to provide energy supply to its connected loads without help from the utility there must be a source of generation within the micro-grid. This could be solar PV, wind, combustion turbines, reciprocating engines, cogeneration, or any other form of generation. Distributed Generation (like renewable sources, small combustion turbines)
Energy Storage Capacity: Energy storage that allows the micro-grid to absorb and store energy that is produced when supply exceeds demand, and to return that energy when the demand exceeds supply. (E.g. during evening hours when solar production is not available). Like Batteries, thermal storage are used.
Demand Response and Efficiency Measures: More sophisticated micro-grids will incorporate the ability to control end-uses in a manner that allows the generation and storage resources to be optimized. For example, non-critical loads like lighting, hot water heaters, etc. can be automatically shut off or turned down to help maintain energy flow to critical loads (e.g. computer servers, life-support equipment, etc.), especially during times when variable renewable generators are not available. As with storage, load control can also provide arbitrage opportunities in power markets and/or where time-based rates are available.
Energy Management Systems: This system ties all of the components together and maintains the real-time balance of generation and load. In a very simple micro-grid, a control system is typically a governor control on a diesel generator. In more complex micro-grids, control systems are made up of sophisticated software platforms, sensors, metering, and communication paths designed for real-time optimization and control of the generators, energy storage, loads, and utility interchange. During interconnected operation, the control system must be able to manage the utility interface and communicate with the utility’s (or independent system operator’s) system operations center (including demand-response management systems) in near real-time. (Maintain Balance and Stable Systems and Real-time response, Predictive and forecasting analysis).
Utility Grid Interconnection: A key design feature of a micro-grid includes the interface with the utility’s power grid. During interconnected operation the micro-grid-utility interconnection must be designed for safe and reliable parallel operation of the micro grid and the power system. For reliability-based micro-grids where operation in an islanded mode is anticipated, the interconnection must also include equipment that will allow for the seamless disconnection and reconnection of the micro-grid and the power grid. This “re-synchronization” of the two systems is not a trivial undertaking and failure to properly plan and design for this function can result in the instability of both grids. Accordingly, islanding of micro-grids must be addressed at both technical and policy levels.
Operation of micro grid
Micro-grid can operate in two modes:
Grid connected mode: In this mode micro-grid operate synchronously with the main grid. During the grid-connected mode the micro-grid sources will be controlled to provide constant real and reactive power injection. A simple example is a small power system network with distributed generators such as wind, solar and combined heat power (CHP) plants that can operate in conjunction with the grid to supply a fraction of the total load.
Islanded mode: Islanding is the condition in which a distributed generator (DG) continues to power a location even though electrical grid power is no longer present. During the islanded mode the sources will be controlled to provide constant voltage and frequency operation. A simple example of islanding is a distribution feeder that has solar panels attached to it.
A traditional wide area synchronous grid (macro-grid), but can also disconnect to “island mode” — and function autonomously as physical or economic conditions dictate. A micro-grid connects to the grid at a point of common coupling that maintains voltage at the same level as the main grid unless there is some sort of problem on the grid or other reason to disconnect. A switch can separate the micro-grid from the main grid automatically or manually, and it then functions as an island.
