A microgrid, that is, a distributed energy island system, systematically combines generators, loads, energy storage devices, and control devices to form a single controllable unit that supplies electricity and heat to users at the same time. Most of the power sources in the microgrid are micro power sources, that is, small units (less than 100kW) with power electronic interfaces, including micro gas turbines, fuel cells, photovoltaic cells, and energy storage devices such as supercapacitors, flywheels, and batteries. The microgrid is connected to the user side and has the characteristics of low cost, low voltage, and low pollution. The microgrid can be connected to the large grid, and can also be disconnected from the main grid when the grid fails or needs to be run independently.

Microgrids have a dual role. For the power grid, the microgrid, as an intelligent load that can be changed in size, provides a dispatchable load for the local power system, can respond within a few seconds to meet the needs of the system, and provide strong support to the large power grid in a timely manner; it can maintain the system at the same time. Affect the load of customers; it can reduce (extend) the upgrading of distribution network, adopt IEEE1547.4 standard, guide the island operation of distributed power supply, and can eliminate the technical obstacles caused by some special operation requirements. For users, as a customizable power source, the microgrid can meet the diverse needs of users, for example, to enhance the reliability of local power supply, reduce feeder loss, support local voltage, improve efficiency by utilizing waste heat, provide correction of voltage sag, or As an uninterruptible power service, etc.

Microgrids have several benefits:

1. Provide efficient, low-cost and clean energy

2. Improve operability and stability Regional power grid

3. Increased critical infrastructure reliability and resilience

4. Reduce grid congestion and peak load

5. Realize efficient combined heat and power generation, reduce fuel consumption, line loss and carbon footprint

6. Integration of combined heat and power, renewable energy, heat and power storage, advanced systems and building controls

7. Make the RTO market more competitive Provide grid services, including: energy, capacity, and ancillary services

Support shelters and first responders in regional crises

8. Take advantage of local energy resources and employment opportunities

9. Diversification rather than concentration risk

Using electricity and thermal storage capacity, microgrids can provide local management of variable renewable energy generation, especially on-site solar

If properly designed, regional grids can be built combining large central plants and distributed microgrids with lower total capital costs, less installed generation, higher capacity factors across all assets, and greater reliability.。