In microgrid systems, the core role of STS (Static Transfer Switch) is to realize millisecond-level seamless switching between two AC power sources (typically grid power and the microgrid's off-grid power supply, such as power converted by BESS and PCS).
Its key value lies in ensuring zero power interruption for critical loads: when the microgrid switches between grid-connected mode and off-grid island mode (e.g., grid power failure or active off-grid), STS completes the power source switching within ≤4~8ms (even as fast as 1ms), avoiding load downtime caused by power interruption.
In the microgrid system, STS works with ATS, PCS, and EMS: STS is responsible for high-speed seamless switching for key loads, while ATS (mechanical switch) handles general switching scenarios, together supporting the microgrid's flexible and stable operation.