Microgrids and smart grids are both highly relevant technologies important in the development of a stable, sustainable, decentralized grid. These terms are often mentioned in articles and in the news, but they’re rarely given concrete definitions. I believe it would be beneficial to delve a little deeper into each of these systems to understand what they are separately and how they work together.
Broadly, a microgrid is any system that can act independently of the main electric grid. It should be able to manage multiple loads and act in parallel with the broader grid. Microgrids are beneficial because they increase the reliability and efficiency of power by decreasing transmission lengths and they can be more easily integrated with renewable energy sources.
In general, microgrids are made up of five subsystems: energy storage, distributed generation, power distribution lines, local loads, and control systems. The first two elements allow for a microgrid to generate and store electricity on its own. This stored energy can then be used when there is a blackout or the cost of electricity on the main grid is too expensive. This is only possible because of the control structure within a microgrid, with all devices communicating with a central Microgrid Central Controller(MGCC). The MGCC also facilitates the two way communication between each device on the microgrid and the broader grid. The diagram below shows an example microgrid setup.
As mentioned earlier, these systems can also be integrated with renewable energy systems like wind turbines and photovoltaic(PV) panels more easily. The key component here is the energy storage system(ESS). Any excess voltage generated by solar or wind generators can be saved as energy in the storage system. It will then be used when winds are slow or the sun isn’t shining to keep the power on. ESS is not common on the broader grid though. Any power generated by a utility has to be used at the moment it’s produced. This allows microgrids to be much more sustainable than the larger utility grid.
Microgrids have the potential to be much more efficient than the broader electric grid. For example, imagine if we could optimize the energy usage of every load on the grid, only powering devices actually need power at a given moment in time and always making sure electricity costs are minimized by switching between ESS and the broader grid. This would not only save a significant amount of money on electricity costs, but it would also leave a much smaller carbon footprint by preventing the wastage of energy.
This is where smart grids come in. A smart grid is a system with advancing metering infrastructure that connects with each device in a system through a central controller. For example, if the air conditioning unit inside a large factory is running in the middle of the night when the facility is empty, a smart grid system would allow the grid to cut power to the air conditioner to avoid unwanted energy expenditure.
When smart grid technology is used in a microgrid, connected to the central controller, it gives the entire system more flexibility to make better optimizations. The two way communication between each device in the microgrid provides the smart grid power usage data from each device. This lets the smart grid make optimizations based on the specific use cases of each device, accounting for the time in the day when a device is used, the state of the battery system, and electricity costs pulling from the broader grid. For example, because demand on the broader power grid is usually at its peak in the evening when most people return home, electricity costs are often much higher than normal. If a family runs their washing machine at this time, a smart grid would notice that it could supply the washing machine power from the home’s battery – which would have been charged during the day from the distributed generation system like solar panels or fuel cells – to reduce electricity costs. Such optimizations would drastically decrease the utility bill the family would receive at the end of the month.
Therefore, these two systems are best implemented in conjunction with each other to maximize their effectiveness. Microgrids are subsets of the larger grid that can operate on their own. Smart grids refers to technology that can optimize the power supply to different loads on the grid. Microgrids are an older technology than smart grids. Today, nearly all microgrids use smart grid technology. Together, microgrids and smart grids are making a more reliable, sustainable, and efficient electric grid.
Sources:
https://www.researchgate.net/figure/Schematic-diagram-of-a-Microgrid_fig3_277022435
https://www.powermag.com/the-smart-grid-and-distributed-generation-better-together/
https://www.veckta.com/2020/09/29/microgrid-vs-der-vs-smart-grid/
Further Reading on Grid Controllers:
Electric Grid Gossip 