Battery Energy Storage Systems (BESS) can be connected to the grid or load either on the AC side or the DC side. Both configurations have their own advantages and disadvantages. Here are some advantages of AC side parallel connection compared to DC side parallel connection:
1. Flexibility: AC side parallel connection allows for more flexibility in terms of system design and operation. It can be easily integrated with other AC loads or sources.
2. Safety: AC side parallel connection can be safer because it does not require high DC bus voltages, which can be dangerous. Also, there will be a current circulation in DC side parallel, which requires all battery racks in more closely voltage level.
3. Efficiency: While DC side connection can be more efficient in some cases, AC side connection can also be efficient, especially when the BESS is used for load leveling or peak shaving. This is because the energy is stored and discharged directly at the AC level, reducing conversion losses.
4. Independence: Each BESS in an AC side parallel connection operates independently. This means that if one system fails, the others can continue to operate without any disruption.
5. Scalability: AC side parallel connection allows for easier scalability. Additional BESS units can be added or removed without affecting the operation of the existing units. This is more challenging with DC side parallel connection, where changes can affect the balance of the system.
6. Cost: Normally DC side parallel need 3-level BMS control, but AC side parallel just need 2-level, so the total cost will be less.
DC side parallel / Centralized
AC side parallel / Distributed
