Microgrid (Micro Grid): refers to small power system connected with the intelligent distributed power sources, generally includes a micro part of the power, the load, storage, power distribution and control system, with a large power grid or off-grid run. The microgrids are divided into two types of grid-connected and independent types. The independent microgrids do not depend on the external power grid and can themselves realize the balance of internal electric power and electric power. The grid-connected microgrids are usually connected to the upper-level grids in parallel and can be operated under special circumstances Off-grid operation, independent operation of the network can maintain all or part of the important electricity load power supply. Micro-grid can be divided into AC micro-grid, DC micro-grid, AC-DC hybrid micro-grid. Micro-grid and power grid, backup power, UPS, distributed generation, energy storage comparison: Different systems The contrast Microgrid Same point the difference 1 Large power grid 1 ) are all power transmission channels; 2) have power distribution, relay protection, monitoring, metering and communication systems; 3) adjust the energy balance, reliable power supply to meet the load requirements. 1 ) Different scales, microgrid <20MW; 2) Different voltage levels, microgrid <= 35kV; 3) Different power supply targets, microgrids are mainly distributed micro-power access; 4) For different targets, microgrid faces the islands, Remote areas, urban areas; 2 backup power Independent power supply from the grid The backup power supply uses a single diesel generator, while the microgrid supports multiple power supplies to coordinate operation, especially for distributed renewable energy. 3 ups Independent power supply from the grid UPS off-grid through the battery to provide energy for the load power supply, but also access the diesel engine, but the power side, the load side there is a strict distinction, the load side of the UPS can not and power supply; micro-grid can support a variety of power access operation, power Load, energy storage equipment can be connected to the same bus 4 Distributed generation Use of new energy sources, especially renewable energy Distributed generation is grid-connected, or a single power supply; microgrid can be grid, can be isolated, support a variety of power at the same time access. 5 Energy storage Independent power supply from the grid Ordinary energy storage systems are grid-connected; microgrids can be both isolated and unobstructed.