Distributed power supply mainly includes small hydropower, wind power, photovoltaic power generation and biomass power generation which are generally affected by external environmental factors, such as season, climate, wind power, light and so on. Therefore, this kind of electrical energy is random and unstable, which will lead to poor stability of microgrid. Because of the large capacity of the main network, this influence can be ignored when the distributed power supply is connected to the main network. However, when the microgrid operates independently, the power supply changes with the environment and cannot provide stable output for the load. Flywheel energy storage system applied in microgrid, especially in independent microgrid, can well stabilize the fluctuation of distributed power supply, maintain stable output and improve power quality.