Introduction 

Energy storage technology is a crucial component of renewable energy development. Both string and centralized energy storage systems exhibit unique advantages and suitable application scenarios, playing an indispensable role in the efficient utilization of renewable energy and the stable operation of power systems.

1. Centralized Energy Storage 

Centralized energy storage typically involves large-capacity, large-volume equipment assembled in a containerized manner. Its system structure comprises battery packs connected in series to form battery clusters, with multiple clusters paralleled on the DC side, converging into a single energy storage converter that transforms the power into AC, which is then stepped up via a transformer and fed into the grid. This centralized approach excels in large-scale energy storage applications, such as grid-side storage and supporting large renewable energy plants.

Centralized energy storage enables centralized energy dispatch and optimization, effectively balancing supply and demand within the grid, enhancing grid stability and power quality. Its large-scale storage capacity allows excess energy to be stored during off-peak times and released during peak times, thereby flattening peaks and filling valleys, reducing grid operating costs.

Additionally, centralized energy storage offers cost control advantages. Large-scale procurement and centralized management can reduce equipment and operational costs.

2. String Energy Storage 

String energy storage systems usually consist of multiple smaller-capacity storage units connected in series, with each unit having independent control and management functions. This distributed architecture endows string energy storage with high flexibility and scalability.

In distributed energy systems, such as residential rooftop photovoltaics and small storage stations, string energy storage can be precisely configured based on varying energy generation and consumption patterns. It allows for fine-grained management of individual storage units, improving overall system efficiency and reliability.

Furthermore, string energy storage adapts well to complex terrains and dispersed energy layouts. Even if some storage units fail, the remaining units can continue to operate, reducing the risk of overall system downtime.

3. Advantages and Disadvantages of Centralized Energy Storage Advantages:

1. Simple Control Logic: Centralized energy storage systems have simple control logic as the battery packs are directly connected in series, making them easy to manage.

2. Lower System Cost: Due to their relatively simple structure, centralized systems have lower initial investment and maintenance costs.

Disadvantages:

1. Barrel Effect: Directly paralleled battery modules force voltage balance, meaning the system's overall lifespan depends on the shortest-lived battery.

2. Cluster Circulating Current Issues: Disparities in discharge depth among battery clusters can lead to circulating currents, affecting charge/discharge efficiency.

3. Safety Concerns: Parallel battery clusters can form circulating currents, leading to overcharging and increased safety risks.

4. Complex Maintenance: Field debugging of current cabins is complex and time-consuming; system faults generally require on-site manufacturer maintenance, leading to long downtimes and high maintenance costs.

4. Advantages and Disadvantages of String Energy Storage Advantages:

1. Improved System Efficiency: The string architecture allows for individual cluster management, enhancing battery pack balance and charge/discharge efficiency.

2. High Reliability and Easy Maintenance: String energy storage systems manage each cluster independently, allowing precise fault localization without affecting other cabinets.

3. Higher Safety: Each battery cluster independently controls charge and discharge, avoiding circulating current effects and achieving fault isolation. Efficient thermal management ensures uniform temperature distribution, prolonging battery life and ensuring stable system operation.

4. Strong Flexibility: Small cabinet size facilitates transportation and installation, making it suitable for various applications like commercial and industrial user-side storage, shared energy storage, and renewable energy paired storage. The system supports the use of mixed old and new batteries, allowing flexible capacity expansion or supplementation based on actual needs.

Disadvantages:

1. Complex Integration: Compared to centralized systems, string systems may have more complex integration and debugging processes.

2. Increased System Cost: Due to the use of more optimizers and monitoring devices, string systems may have higher overall costs.

5. Application Scenarios 

Centralized energy storage technology performs well in large-scale applications and cost efficiency, suitable for grid-scale large storage projects. In contrast, string energy storage technology excels in flexibility, scalability, and reliability, making it more suitable for distributed energy systems and applications requiring high flexibility.

In practical applications, the appropriate energy storage technology should be chosen based on specific needs and conditions to achieve the best energy storage and utilization effect.