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The main function of energy storage system in microgrid
- Jul 27, 2018 -

Energy storage is an important part of the power system and the basis for building a new energy microgrid. New energy sources such as wind power and photovoltaics are intermittent energy sources with obvious instability. Buffering energy through an energy storage system optimizes power quality and improves the stability of the new energy microgrid. So, what role does the energy storage system play in the microgrid?

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Microgrid definition: Microgrid is an important part of smart grid implementation. It can realize the integrated operation of internal power supply and load, and can coordinate control with the main grid, smoothly access the main grid or operate independently, and can meet or even improve. User requirements for power quality, power reliability and safety.

There are two typical modes of operation between the microgrid and the main grid: the grid-connected operating mode and the islanded operating mode. In the case that both the main power grid and the micro grid are normal, the micro grid and the main grid are connected to the grid, and the power generated by the micro grid preferentially meets the demand for the local user load. If the power is surplus or insufficient, it is dispatched with the main grid. When the microgrid system detects a main power grid failure or a serious problem with the power quality, the microgrid will actively disconnect from the main grid and operate independently to ensure the normal operation of the main load.

Main functions of energy storage in micro grid:

1. Improve the stability of distributed energy. Distributed energy sources, such as solar, wind and biomass energy, are easily affected by factors such as lighting, temperature, wind power and climate, etc., and their electricity generation is characterized by randomness and instability. Under the condition that the micro grid is disconnected from the power grid and operates independently, the output power of distributed energy in the micro grid changes with the change of environmental factors, which cannot provide stable output for the load. Energy storage system is applied in micro grid. By means of energy management system (EMS), distributed energy can be controlled in cooperation with energy storage system and main power grid, which can reduce the fluctuation of distributed energy, stabilize the output, and provide the local utilization rate of distributed energy, so as to avoid the transmission pressure and power loss of remote transmission to the main power grid. In addition, the energy storage system can also continuously provide part of the power supply to the main load at night or during distributed energy maintenance, reducing the power outage time.

2. Improve the power quality of the user's electricity. When the microgrid is connected with the main power grid, the power quality must conform to the relevant national standards, that is, the parameters of the power factor, the voltage asymmetry, the current harmonic distortion and the voltage flicker are required to reach the corresponding values. According to the above point, the micro grid, under the condition of no energy storage system, is affected by its own energy characteristics, and can not guarantee the power quality, especially the voltage stability. The application of energy storage system can play an important role in the improvement of the power quality of the microgrid. Through the control of PCS in the energy storage system, the system regulates the active / reactive power of the energy storage system to the micro grid while stabilizing the output of the electric energy, and solves the voltage drop / fall problem. In the face of the sudden and sudden drop in the voltage of the main power grid, the energy storage system can provide fast power buffering, fast absorption / supplement of power, providing active / reactive power support and stabilizing voltage fluctuation. The energy storage system can also provide partial harmonic control function for the microgrid.

3. In the micro grid, the peak energy storage system can store the excess power generated by distributed energy at the low load, release the power at the peak load and adjust the load demand. As an energy buffer link in micro grid, energy storage system is indispensable in micro grid system. The energy storage system can reduce the capacity of generator set or transformer while meeting the peak load.