How Microgrids Function
Microgrids are localized grids with independent power sources and load points. They usually work in tandem with centralized macro grids but can also be completely disconnected to work autonomously. This is called switching from connected mode to the “island” mode. Whether or not a microgrid is connected to the main grid depends on the physical and economic conditions of the region and the power plant. Microgrids play an important role in the deployment of distributed power generation systems, especially in the case of renewable energy sources. They are useful in supplying emergency power, power control, and protection.
To better understand how a microgrid operates, let us look at power grids in general. The power grid connects homes, offices, and other buildings to a centralized power source. This allows people to use electricity for domestic and commercial purposes. However, this large interconnected grid makes maintenance difficult as everyone is affected during repairs in one area. This is where microgrids come into the picture. Microgrids operate in connection with the main grid, but as mentioned above, can switch to island mode and provide power autonomously when required. This is especially useful in times of crisis like natural disasters, storms, and power outages due to maintenance.
A microgrid has its own power source in the form of generators, batteries or renewable sources such as solar power. The microgrid connects with the main grid at a point where an equal voltage is maintained between the two coupling points. A switch is placed at the coupling point which can automatically or manually separate the microgrid from the main grid. Microgrids are not only an emergency measure but also cut costs by using local resources which may be too small for traditional grid use. Microgrids allow communities to be independent and environmentally friendly.
Microgrids provide us with modularity and safety but they are not without challenges. One of the major issues of DGs employing microgrids is bidirectional current flow which can lead to serious complications and voltage fluctuations. Added to this are issues regarding stability and uncertainty, especially when we compare their energy sources to bulk power producing units.
Parts of a microgrid
A typical microgrid has four major components:
- Local power source: Every microgrid has its own power supply. This is divided into two categories- thermal power supply (diesel generators, coal plants) and renewable supply (solar, wind turbines).
- Load points or consumption: This refers to elements and appliances that consume electricity from the grid. They can vary from electronic devices, home appliances, lightings to factory machinery.
- Power storage: Energy storage methods find multiple utilities in microgrids. They ensure power quality, regulate voltage and frequency, straighten out the output of renewable power sources, provide power-backup, and provide methods of cost saving. Power storage systems come in various types- electrical, pressure, gravitational, flywheel, and heat storage.
- Common coupling points: This is the point where the microgrid is connected to the main grid. Isolated microgrids are grids without such points of coupling. They are not interconnected with other grids and are mostly used for power supply to remote locations.