Problems and measures of energy storage technology in microgrids

By solving technical, economic and policy problems, using the flexibility and dispatchability of energy storage technology, as well as integration and integration with other technologies, sustainable development of microgrids, efficient use of energy and improved reliability of power supply can be achieved.

1. Advantages of microgrid energy storage technology

① Power peak shaving

Distributed power generation forms microsources in microgrids, but these microsources are often affected by weather factors, resulting in constantly changing loads.

Due to the small scale of microgrids and their limited self-regulation capabilities, microgrids are often subject to fluctuations in power loads during operation. However, microgrid energy storage systems are able to store excess power during load valleys in practical applications.

It feeds back power to the microgrid during peak loads, thus meeting the power demand of the grid. The energy storage system plays an important role in energy buffering in the microgrid, effectively improving the utilization rate of electric energy and realizing power peak regulation in different states.

② Improve power supply

Green energy, such as tidal energy, wind energy, solar energy, etc., often has uncontrollable and uneven characteristics, resulting in frequent changes in electrical energy output.

However, the output energy of a micropower supply will vary with changes in wind, temperature, light, and other factors. Therefore, we need microgrid energy storage systems to play a transitional role.

For example, when a microgrid needs to be serviced or wind power is generated in the absence of wind, or solar power is generated at night. Energy storage systems can improve the power quality of micropower sources and ensure a continuous and stable power supply.

2. Common modes of operation during operation

• Siloed mode of operation
• Grid-connected operation mode

In general, microgrids and distribution grids remain connected to the grid. However, if there is a problem or failure in the power quality of the grid, the microgrid and the main grid will quickly disconnect and operate independently. During the transition from grid-connected to island operation, there may be some power shortages in the microgrid.

How to solve this problem – energy storage systems can be set up in microgrids. The energy storage system acts as an energy "buffer" that can provide the additional power needed during the mode changeover process, ensuring a smooth transition to the microgrid.

When we use new energy sources for power generation, we are affected by various external factors that may affect the stability of the output of electrical energy. However, with the energy storage system of the microgrid, we can ensure the continuity and stability of the power supply. This means that the power supply will not be affected even in the event of unstable renewable energy generation.

• Improve power quality

In order to meet the various requirements of the power system, the microgrid needs to be connected to the grid and strictly controlled by the number of power outages, power supply frequency, voltage, etc.

Microgrid energy storage technology plays a particularly important role, often controlling grid-connected inverters, which can regulate the load and reactive load and active load transmitted between the grid and the energy storage system, thereby improving power quality.

3. Application of microgrid energy storage technology

• Superconducting technology

The superconducting energy storage system is mainly composed of superconducting coils, which store the excitation energy of the grid power supply in time, and then supply this part of the stored energy to the load or back to the grid if necessary.

This superconducting energy storage technology has a very high energy return efficiency and a very fast energy release rate. Therefore, the reactive power, active power, frequency and voltage of the power grid can be adjusted at any time through the superconducting energy storage system.

• Battery technology

Battery energy storage technology is widely used, and the reactive power compensation device and battery energy storage are combined in the power grid. It can meet the peak load demand of the power grid and effectively suppress voltage flicker and fluctuation.

However, the battery charger must have the functions of limiting current, stabilizing current, limiting voltage and stabilizing voltage, and the charging current and voltage must be controlled within a certain range.

Therefore, the battery charging circuit is very complex, and the charging and discharging times of the 12 volt 200ah lithium battery are limited, the charging time is long, the maintenance cost is relatively high, and the service life is limited.

If the battery is short-circuited or overcharged, it is easy to cause an explosion accident, and its safety is low. At present, battery energy storage technologies mainly include lithium-ion batteries, lead-acid batteries and other batteries.

• Supercapacitor technology

Supercapacitors are made of porous material dielectrics and have a high dielectric constant, large storage capacity, and withstand voltage. Its energy storage principle is divided into electrochemical capacitors and electric double-layer capacitors.

Compared with 12v 100ah lithium ion batteries, supercapacitors have long energy storage time, excellent high and low temperature performance, fast charge and discharge rate, high charge and discharge efficiency, and large power density, and do not require maintenance and repair, and have high reliability.

In microgrid system, the use of supercapacitors for wind and solar power generation has clear advantages, such as a stable and reliable power supply. However, it is still necessary to study the application of supercapacitors to solve the problems of series voltage equalization, large voltage fluctuation and low energy density.

• Flywheel technology

The early research of flywheel energy storage technology has matured with the development of power electronics technology, high-strength carbon fiber, and magnetic levitation technology.

Its stored energy is electrical energy, which is converted into mechanical energy through the flywheel, and when the power supply is required, mechanical energy is converted back into electrical energy, and the power electronic equipment realizes voltage and frequency conversion.

Flywheel energy storage technology has large reserves, long life, short construction periods, high efficiency and no pollution, but it is complex and expensive to maintain and repair. Flywheel energy storage technology can improve the reliability and stability of power supply and improve power quality in microgrids.

4. Conclusion

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