Main content:
In the context of today's energy transition, photovoltaic energy storage systems are becoming an important part of sustainable energy development with their unique advantages. Due to the strong volatility and randomness of photovoltaic output power, the instability of photovoltaic power limits access and transmission, in order to solve this problem, energy storage technology is born because of transport, which can achieve peak cutting and valley filling, load tracking, power quality management and other functions. The coupling method of photovoltaic energy storage is a key link to achieve efficient energy utilization.
DC coupling method
Dc coupling is a common photovoltaic energy storage coupling method. In this way, the direct current generated by the photovoltaic power generation system is directly connected to the energy storage system. After the direct current generated by the solar panel is integrated by equipment such as the bus box, part of it can be directly supplied to the DC load, and the other part can be charged for the energy storage battery through the DC converter.
When electricity is needed, the energy storage battery releases direct current through the DC converter, and then converts to AC power through the inverter for AC load. The advantage of DC coupling is that the system structure is relatively simple, and the energy conversion link is less, so the energy loss is less.
At the same time, for some application scenarios with high DC load, such as communication base stations, data centers, etc., DC coupling can meet their power needs more efficiently. However, this method also has certain limitations, such as high requirements for energy storage batteries, which need to have good DC charge-discharge performance.
How is AC coupling method implemented?
Ac coupling mode AC coupling mode is another important photovoltaic energy storage coupling mode. In this way, the photovoltaic power generation system and the energy storage system are respectively connected to the AC power grid through the inverter. The direct current generated by the photovoltaic power generation system is first converted into alternating current through the inverter, which is incorporated into the grid or used by the AC load.
When energy storage is needed, the alternating current of the grid is converted into direct current through the energy storage inverter to charge the energy storage battery. In the discharge process, the direct current of the energy storage battery is converted into AC power by the energy storage inverter for AC load use or back to the power grid. For example, in a small factory, a photovoltaic energy storage system was installed using AC coupling.
During the day, solar panels receive sunlight to produce direct current, converted into alternating current through photovoltaic inverters, part of the electricity is directly supplied to the AC load in the factory, such as motors, lighting equipment, etc. A portion of the excess energy is added to the grid. At night or when there is not enough light, the power needs of the plant are provided by the grid.
At the same time, if the electricity price of the grid is high at this time, the energy storage system can play a role. The alternating current of the power grid is converted into direct current through the energy storage inverter to charge the energy storage battery. When the power grid fails or the price of electricity is low, the energy storage battery converts the direct current into alternating current through the energy storage inverter for the AC load of the factory, thus achieving the optimal utilization of energy and reducing the cost.
The advantage of AC coupling is that it has high flexibility and compatibility, and can be well integrated with the existing AC power grid system. At the same time, it can adapt to different types and capacities of photovoltaic power generation systems and energy storage systems. However, there are many energy conversion links in AC coupling mode, and the energy loss is relatively large.
In what situations is the AC coupling be used?
For those users who have already installed photovoltaic systems, if they wish to add energy storage systems at a later stage, but their photovoltaic systems are already equipped with photovoltaic inverters, when the AC coupling method allows users to retain the existing photovoltaic inverters and directly add a separate energy storage inverter. In this way, users do not need to replace the original equipment, the cost is low, and the system integration is simpler.
In addition, the photovoltaic and energy storage system can be allowed to operate independently, if the photovoltaic inverter fails, the energy storage system can still operate, because in the AC coupling, the photovoltaic system and energy storage system can work separately and do not interfere with each other. This independence makes the system more flexible and allows for step-by-step installation and expansion.
Please check AC coupling vs DC coupling for more details.
What is hybrid coupling?
In order to give full play to the advantages of DC coupling and AC coupling, and overcome their limitations, hybrid coupling came into being. The hybrid coupling method combines the characteristics of DC coupling and AC coupling, which can not only realize the direct DC coupling between photovoltaic power generation system and energy storage system, but also interact with the power grid through AC coupling. In the hybrid coupling mode, the photovoltaic power generation system can choose DC or AC output according to the actual situation. When it is necessary to power DC loads or charge energy storage batteries, DC output can be used. AC output can be used when it is necessary to interact with the grid or power an AC load.
The energy storage system can also choose DC or AC charge and discharge mode according to the need to achieve more flexible and efficient energy management. There are a variety of coupling methods for photovoltaic energy storage, each of which has its own unique advantages and application scenarios. In practical applications, it is necessary to choose the appropriate coupling mode according to the specific needs and conditions to achieve the efficient operation and sustainable development of photovoltaic energy storage system.
Conclusion
In the context of today's energy transition, photovoltaic energy storage systems are becoming an important part of sustainable energy development with their unique advantages. Suitable photovoltaic energy storage coupling mode can be selected according to the actual situation, DC coupling is favored because of its simple structure and few energy conversion links, especially for the application scenario with a large DC load. Because of its flexibility and compatibility, AC coupling is suitable for users who have installed photovoltaic systems to add energy storage systems at a later stage, and it is easy to modularize and expand.
The hybrid coupling method combines the advantages of DC and AC coupling to provide a more flexible and efficient energy management method. These coupled ways can not only improve energy efficiency, but also reduce energy costs, promote sustainable energy development, and make important contributions to the realization of a green, low-carbon energy future.
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