Anti-Islanding vs. Backup Power in ESS
The relationship between Anti-Islanding (AI) protection and Backup Power functions in Energy Storage Systems (ESS) often seems paradoxical. By definition, anti-islanding is a safety mechanism required by grid codes (such as NB/T 11054) that forces an inverter to stop discharging when the utility grid fails. This prevents "islanding," where a distributed resource continues to energize a local circuit, potentially endangering utility workers or damaging equipment when the grid recovers out of phase.
However, many industrial facilities invest in ESS specifically to maintain operations during outages. The "conflict" arises because the system must be smart enough to distinguish between a dangerous grid connection and a protected local load. The solution lies in physical and logical isolation, ensuring that the ESS can power the factory without leaking electricity back into the public grid.
Solution 1: Manual Switching for Emergency Power
In scenarios where a brief interruption is acceptable, Manual Switching offers a cost-effective and highly secure method. The core of this strategy is the installation of a mechanical interlock or a "break-before-make" logic at the grid entry point. By disabling automatic reclosing on the main breaker, the system ensures the ESS never operates in parallel with a dead grid.
This manual transition provides a "hard" air gap between the utility and the load, satisfying safety regulations while allowing the factory to resume production using stored energy until the grid is restored.
Solution 2: Automatic Switching via STS/ATS
For mission-critical facilities where downtime equals significant financial loss, Automatic Switching is the preferred path. The logic mimics that of traditional diesel generator setups but operates at much higher speeds-often within milliseconds when using an STS.
When the grid fails, the STS immediately disconnects the local bus from the utility line. Simultaneously, the ESS controller detects the isolation and commands the PCS to switch modes instantaneously. Because the STS provides a high-speed physical disconnection, the anti-islanding requirement is satisfied-the ESS is no longer "islanding" on the grid; it is operating in a Microgrid or Standalone mode. This seamless transition allows the ESS to provide uninterrupted backup power while remaining fully compliant with national grid-connection standards.