1, improve the stability of distributed energy Distributed energy, such as solar energy, wind energy, biomass, and other renewable energy, is generally affected by the external environment such as light, temperature, wind, climate, and other factors.
The power generation has the characteristics of randomness and instability. When the microgrid is disconnected from the grid and operates independently, the output power of distributed energy in the microgrid changes with the change of environmental factors, and it cannot provide stable output for the load. The energy storage system is applied to the microgrid. Through the energy management system (EMS), the distributed energy can be controlled jointly with the energy storage system and the main grid, which can stabilize the fluctuation of distributed energy, stabilize the output, and provide the local utilization rate of distributed energy, avoiding the transmission pressure and power loss caused by long-distance transmission to the main grid.
In addition, the energy storage system can also continue to provide partial power to the main load during the night, or distributed energy maintenance, reducing power outages.
2, improve the power quality of the user's electricity when the microgrid is connected to the main grid and connected to the grid, its power quality must meet the relevant national standards, that is, the power factor, voltage asymmetry, current harmonic distortion rate, voltage flash drop, and other parameters need to reach the corresponding value.
As mentioned in the first point above, in the case of no energy storage system, the microgrid cannot guarantee power quality, especially voltage stability, due to the influence of its energy characteristics. The application of the energy storage system can play an important role in improving the power quality of the microgrid. By controlling the PCS in the energy storage system, the system regulates the active and reactive power output of the energy storage system to the microgrid while stabilizing the power output, and at the same time solves the problem of voltage plunge/drop.
In the face of problems such as voltage sudden rise or sudden drop in the main grid, the energy storage system can provide fast power loop shock, quickly absorb/supplement electric energy, provide active and reactive power support, and stabilize voltage fluctuations. The energy storage system can also provide some harmonic control functions for the microgrid.
3. In the microgrid, the peaking energy storage system can store the excess energy emitted by distributed energy sources when the load is low, release the energy at the peak of load consumption, and adjust the load demand. As an energy buffer in a microgrid, the energy storage system is essential in microgrid system.
The energy storage system can reduce the capacity required by the generator set or transformer while meeting the peak load power consumption.
The main application directions of energy storage technology in the microgrid are 1 local area network composed of wind power and photovoltaic power generation complementary system, used for remote areas, factories, and office power supply: 2 communication system as an uninterruptible power supply and emergency power system; 3. Adjustment of grid-connected power quality of wind power generation and photovoltaic power generation systems; 4 As a means of large-scale power storage and load peaking: 5 electric vehicle energy storage device; 6 As a large backup power supply for important national departments.
Microgrid is the main application field of energy storage. As an essential part of microgrids, energy storage plays a crucial role.
Generally speaking, the general structure of the microgrid is composed of energy flow and information flow, which are divided into distributed energy, energy storage device, power conversion device, protection device, and microgrid energy management system, and can also be increased or decreased according to the actual application situation. Compared with the large power grid, the microgrid is a single controlled unit, which can ensure the quality of the user's power and power supply safety and is also an important part of the smart grid and energy Internet.
In microgrid operation, there are two operation modes: grid-connected operation mode and isolated island operation mode. The grid-connected operation mode is when the microgrid is connected to the external power grid when there is no external fault. The lone bird operation mode is that when the external power grid fails or the power quality is poor, the microgrid can cut off the connection with the external power grid through a quick switch and enter the independent operation state to ensure the power supply reliability of important loads inside the microgrid. In the isolated operation mode of microgrid, the energy comes from distributed energy and energy storage batteries. When the output of distributed energy is less than the load demand, there will be a certain power gap. The solution to the power gap is to equip the microgrid system with a certain capacity of energy storage devices.
In new energy power generation, there is often no power output due to changes in external environmental conditions, such as photovoltaic power generation to night with no light source and wind power generation in the case of no wind blowing, this time the energy storage system needs to provide continuous power supply to users in the microgrid system.
The fastest progress in energy storage technology is electrochemical energy storage technology, lithium-ion batteries, lead-carbon batteries, and flow batteries as the leading electrochemical energy storage technology in safety, energy conversion efficiency and economy have made breakthroughs, very industrial application prospects.
With the popularity of global renewable energy and the rapid development of the electric vehicle industry, power batteries will also usher in a huge market. Then there will be many power battery decommissioning recycling problems. In the view of the industry, after retirement, the performance of the power battery can be used as an energy storage battery to continue to serve, this application with the development of China's electric vehicles will bring energy storage development opportunities, which will be a very good application field.
Power security is an important component of national energy security, energy storage is an important technology to ensure a safe, low-carbon, and efficient power supply, is an important technology to support the large-scale development of new energy power, and is also a key support technology within the framework of the future smart grid.
Energy Internet as the future direction of global energy development, the need to fundamentally change the current generation, transmission, change, distribution, and use of the link configuration, which determines the future power flow control, distributed power supply, and microgrid will be widely used, energy storage technology will be a crucial part of the coordination of these applications.
