The difference between AC coupling and DC coupling of optical storage systems

introduction

Energy storage technology refers to the process of storing energy through media or equipment and releasing it when needed; photovoltaic + energy storage combines solar photovoltaic power generation with energy storage technology to store the electric energy generated by the photovoltaic system so that it can be used when needed. Ensure stable power supply when needed. Currently, the system solutions for photovoltaic + energy storage on the market mainly include DC coupling and AC coupling. So what is the difference between these two solutions?

The difference between DC coupling and AC coupling

DC coupling means that energy storage cells and photovoltaic modules are connected to the DC side of the integrated photovoltaic and storage machine. The integrated photovoltaic and storage machine is directly connected to the photovoltaic modules, and the energy collection point is on the DC side. AC coupling means that the energy storage system and the photovoltaic system are connected on the AC side. , the energy storage system (battery, energy storage inverter) and the photovoltaic system (photovoltaic modules, photovoltaic inverter) work independently of each other, and the energy collection point is on the AC side. However, due to differences in circuit structures and electrical equipment between the two, there are also major differences in working principles, flexibility, efficiency, etc.

1

Differences in working principles

DC coupling: In this solution, the photovoltaic inverter and the bidirectional converter are integrated into a photovoltaic-storage integrated machine, and are directly connected to photovoltaic modules, power grids, batteries, etc. to form a whole. When the photovoltaic system is running, the electricity generated can charge the battery through the photovoltaic storage integrated machine, supply power to the load, or be input into the power grid.

AC coupling: This solution includes two parts: photovoltaic system and energy storage system. The photovoltaic system consists of photovoltaic arrays and photovoltaic inverters; the energy storage system consists of energy storage inverters and batteries. The two systems can operate independently without interfering with each other, or they can be separated from the power grid to form a microgrid system. When the photovoltaic system is running, the generated power can be used to power the load through the photovoltaic inverter or be input into the grid, or it can be used to charge the battery through the energy storage inverter.

2

flexibility difference

DC coupling: In this solution, photovoltaic modules, photovoltaic storage integrated machines and batteries are in a serial state and are closely connected to each other. The addition and removal of equipment is complicated and the flexibility is average. It is mainly used in new photovoltaic markets, such as newly installed Photovoltaic storage systems, photovoltaic modules, integrated photovoltaic storage machines and batteries need to be designed according to the user's load power and power consumption.

AC coupling: In this solution, the photovoltaic inverter, energy storage inverter and battery are in parallel state. The connection is flexible and it is more convenient to add or remove equipment. It can be applied to photovoltaic stock and new markets. If a new energy storage system is added to the original photovoltaic system, it can be directly integrated into the equipment for use without additional system design adjustments. In addition, the design of the energy storage system is not directly related to the photovoltaic system in principle and can be determined according to needs.

3

Photovoltaic utilization difference

From the perspective of photovoltaic utilization efficiency, the two solutions have their own characteristics: In the DC coupling system, the photovoltaic modules store electric energy into the battery through the controller, and the efficiency can reach more than 95%. The electric energy can be stored for night use. This solution is more It is suitable for situations where the electricity consumption during the day is less than the electricity consumption at night; in the AC coupling system, the photovoltaic modules directly supply power to the load through the photovoltaic inverter, and the efficiency can reach more than 96%. This solution is more suitable for the situation when the electricity consumption during the day is greater than Electricity usage at night.

Yuneng Technology AC Coupling Solution

As a professional provider of photovoltaic storage solutions, Yuneng Technology provides AC-coupled household photovoltaic storage system solutions. Its products include micro-inverters, energy storage inverters and batteries. Among them, the micro-inverter photovoltaic system emits The electricity can be used by household loads, and the excess is charged to the battery; the energy storage system can discharge the battery from the battery for use by household loads. At the same time, the Yuneng optical storage system also provides an off-grid function, which can continuously supply power to the load when the power grid is out of power.

Yuneng Technology's household optical storage system has the characteristics of safety, efficiency and flexibility. Yuneng household energy storage inverter can be compatible with low-voltage batteries, and can be used with micro-inverters to form an AC-coupled micro-inverter system, which can avoid the risk of DC high voltage on the battery side and photovoltaic side and ensure the ultimate safety of the system; the product adopts original The innovative design improves the inverter efficiency of low-voltage batteries up to 96.5%; it is suitable for existing photovoltaic and new markets; it also supports parallel connection, allowing for easy expansion and transformation, improving the flexibility of system configuration and installation.

summary

To sum up, the characteristics and selection of DC coupling and AC coupling are not absolute, and more considerations need to be made based on actual application requirements. Yuneng Technology has been deeply involved in the field of photovoltaic storage for many years, and has realized the innovative layout of micro-inverters, energy storage inverters and other products, and provides AC-coupled micro-inverter system technology solutions with ultra-low voltage operation, high-efficiency inverter, and high flexibility. and other features, which can realize the wide application of products in photovoltaic stock and new markets, and promote the high-quality coordinated development of photovoltaic + energy storage.